Serotonin, cortisol, and DHEA-S levels in anxious and depressive pregnant women living with HIV.

Pregnancy in women living with human immunodeficiency virus (WLWH) represents an important challenge for maternal-fetal health. Besides, they can also present anxiety (Anx) and depression (Dep). Imbalances in serotonin (5-HT), dehydroepiandrosterone sulfate (DHEA-S), and cortisol (CORT) levels can contribute to Anx and Dep manifestations. Currently, there is not enough data about the neuroendocrine and neurochemical changes in pregnant WLWH with affective disorders. This study aimed to characterize 5-HT, DHEA-S, and CORT plasma levels in Mexican pregnant WLWH presenting Anx/Dep. Forty-two adult pregnant women were recruited during the third trimester of gestation at the National Institute of Perinatology in Mexico during 2019-2022. These patients were divided into three groups: (1) pregnant WLWH with Anx/Dep (n = 16), (2) pregnant without HIV but with Anx/Dep (n = 12), and (3) healthy pregnant women without Anx/Dep (n = 14). WLWH presented a marked reduction in 5-HT (41.33 ± 39.37 ng/dL) compared to non-infected pregnant women with Anx/Dep (220.2 ± 151.8 ng/dL) and the healthy group (370.0 ± 145.3 ng/dL). Anx/Dep infected and uninfected pregnant women showed a significant reduction in DHEA-S levels (86.58 ± 30.59 and 76.9 ± 36.7 µg/dL, respectively) compared to healthy subjects (149.7 ± 44.6 µg/dL). Anx and Dep symptoms were inversely correlated with 5-HT and DHEA-S levels. No significant differences were observed in CORT levels among the three groups (p = 0.094). Our results suggest the presence of a disbalance in 5-HT and DHEA-S levels in pregnant WLWH with affective symptoms.

Circulating sex hormones in women with severe anxiety during pregnancy / Hormonas sexuales circulantes en mujeres con ansiedad severa durante el embarazo

Abstract Introduction Anxiety, mood- and stress-related behaviors are regulated by sex hormones in pregnant and non-pregnant women. Very scarce information exists about the role of sex steroids in pregnant women displaying high levels of anxiety. Objective To determine sex hormones serum levels in pregnant women exhibiting high levels of anxiety symptoms. Method The Hamilton Anxiety Rating Scale (HARS/ HAM-A) was used to assess the intensity of anxiety symptoms in third-trimester pregnant women. Two groups were included in the study, pregnant women exhibiting severe anxiety (ANX; HARS scores ≥ 25; n = 101) and healthy control subjects (CTRL; n = 40) displaying lower scores for anxiety (HARS scores ≤ 7). Estradiol (E2), progesterone (P4), and testosterone (T) serum levels were measured using a standard chemiluminescent immunoassay. Bivariate and partial correlations were performed to detect significant associations between groups, clinical measures, biochemical data, and HARS scores. Results The anxiety group (ANX) showed an increase in E2 and T serum levels (p < .001) compared to CTRL. Conversely, significantly lower P4 levels were found in the symptomatic group (p < .001) as compared to the CTRL hormone values. The P4:E2 index was significantly reduced in pregnant women with high levels of anxiety (p < .001). Negative correlations between anxiety (HARS) scores, P4 serum levels (p = .02), and P4:E2 ratio (p = .04) were found in the symptomatic group. Conversely, T serum levels displayed a positive association (p = .001) with high levels of anxiety symptoms in the same group, after adjusting our data by clinical confounders. Discussion and conclusion Serum levels of sex-steroid hormones are altered in pregnant women exhibiting severe anxiety.

Resumen Introducción La ansiedad, el estado de ánimo y el estrés están regulados por diversos esteroides sexuales. Existe poca información sobre el papel que juegan estos esteroides en mujeres embarazadas con niveles elevados de ansiedad. Objetivo Determinar los niveles séricos de hormonas sexuales en mujeres embarazadas con altos índices de síntomas de ansiedad con respecto a mujeres gestantes sanas. Método Determinación de la intensidad de síntomas ansiosos empleando la escala de Hamilton de Ansiedad (HAM-A) en 141 mujeres embarazadas en el tercer trimestre de gestación. Cuantificación de los niveles séricos de estradiol (E2), progesterona (P4) y testosterona (T) por inmunoensayo estándar. Aplicación de las correlaciones de Pearson para detectar asociaciones entre parámetros clínicos y valores hormonales entre los grupos de estudio. Resultados Las mujeres con ansiedad severa (ANX; n = 101; HAM-A ≥ 25) mostraron niveles séricos más altos de E2 y T (p < .001), así como niveles más bajos de P4 (p < .001) en relación con el grupo control (CTRL, n = 40, HAM-A < 7). Se detectó una disminución significativa en el índice P4:E2 en el grupo de ANX (p < .001) y se observaron correlaciones negativas y positivas entre los puntajes elevados de ansiedad con los niveles circulantes de P4 (p = .02), en la taza P4:E2 (p = .04) y en los niveles séricos de T (p = .001) respectivamente, al ajustar nuestros datos con variables confusoras. Discusión y conclusión Los niveles circulantes de los esteroides sexuales se encontraron alterados en mujeres con ansiedad severa.

Cellular senescence in normal and adverse pregnancy.

Cellular senescence (CS) is defined as a state of terminal proliferation arrest accompanied by morphological alterations, pro-inflammatory phenotype, and metabolic changes. In recent years, the implications of senescence in numerous physiological and pathological conditions such as development, tissue repair, aging, or cancer have been evident. Some inductors of senescence are tissue repair pathways, telomere shortening, DNA damage, degenerative disorders, and wound healing. Lately, it has been demonstrated that CS plays a decisive role in the development and progression of healthy pregnancy and labor. Premature maternal-fetal tissues senescence (placenta, choriamniotic membranes, and endothelium) is implicated in many adverse pregnancy outcomes, including fetal growth restriction, preeclampsia, preterm birth, and intrauterine fetal death. Here we discuss cellular senescence and its association with normal pregnancy development and adverse pregnancy outcomes. Current evidence allows us to establish the relevance of CS in processes associated with the appropriate development of placentation, the progression of pregnancy, and the onset of labor; likewise, it allows us to understand the undeniable participation of CS deregulation in pathological processes associated with pregnancy.

Cortisol and DHEA-S levels in pregnant women with severe anxiety.

BACKGROUND: A complex interaction between cortisol and dehydroepiandrosterone-sulphate (DHEA-S) is crucial in the stress system balance; several studies have reported increased cortisol levels during chronic stress and a weak counter-regulation by DHEA-S. During pregnancy, scarce information about this system is available, although cortisol and DHEA-S play an important role in the initiation and acceleration of labor. We conducted the present study in order to determine both cortisol and DHEA-S levels during the last trimester of pregnancy in patients exhibiting severe anxiety. METHODS: Pregnant women during the 3rd trimester of pregnancy were evaluated by using the self-reported version of the Hamilton Anxiety Rating Scale (HARS). According to the scores obtained from the psychometric scale, participants were divided into two groups: 1) patients exhibiting a cutoff score > 15 were considered with severe anxiety (ANX) (n = 101), and control pregnant subjects (CTRL) (n = 44) with a cutoff score < 5. Morning cortisol, DHEA-S and Cortisol/DHEA-S index were measured in all participants. Comparisons between groups were performed; additionally, correlations between clinical variables, biochemical data and HARS were calculated. RESULTS: Cortisol levels were significantly higher in the ANX group (p < 0.001), whereas those of DHEA-S were significantly lower in the same group (p < 0.01) when compared to healthy pregnant subjects. An increased cortisol/DHEA-S index was observed in the ANX group (p < 0.05). A significant association between cortisol and HARS scores (p = 0.03), was observed even after adjusting by gestational weeks (p = 0.004). CONCLUSIONS: Our data support that the cortisol/DHEA-S index is higher in pregnant women with high anxiety levels as compared with healthy pregnant women.

Depressive symptoms in pregnant women with high trait and state anxiety during pregnancy and postpartum.

Background: Depression and anxiety are frequent during pregnancy, and epidemiological studies demonstrate high rates of co-morbidity. Aims: To evaluate the association between the trait and state anxiety and depressive symptoms in women during the perinatal period. Method: A transversal study was conducted at the National Institute of Perinatology (INPer, Mexico City) from 2012 and 2015. Pregnant women diagnosed with Major Depressive Disorder (MDD) were included (N=128). Depressive and anxiety symptoms were evaluated using CES-D and STAI, respectively. Patients were sub-classified according to percentile 75 for Low and High Trait Anxiety (LTA, HTA) and Low and High State Anxiety (LSA, HSA); depressive symptoms were compared between pregnant women and women in the postpartum, by state and trait levels. Results: CES-D scores differed according to state and trait anxiety levels: while we observed that depressive scores (CES-D) were higher in HTA patients compared to LTA prenatally (35.9±9,5 vs 21.2±10,8 respectively; p=0.001), this finding was not observed in the postpartum period. In the case of state anxiety depressive scores were elevated among HSA versus LSA groups before delivery (33.0±11.3 vs 14.0±6.7 respectively; p=0.008) and after partum (35.1±8.06 vs 10.0±6.0; p=0.005). Conclusions: Patients showed higher scores of depressive symptoms when high trait or state anxiety comorbidity is present during the perinatal period. In the postpartum period, even low trait anxiety scores were associated with high depressive scores.

Mexneurin is a novel precursor of peptides in the central nervous system of rodents.

Endomorphins (EMs) have been proposed as the endogenous ligand agonists of the µ-opioid receptor; however, no propeptide precursor protein for EMs has been identified. Here, to identify the presumed precursor of EMs, we designed an immunoscreening assay using specific affinity-purified rabbit antisera raised against synthetic EMs in a whole-mouse brain cDNA library. Following this approach, we identify a DNA sequence encoding a protein precursor, which we name proMexneurin, that contains three different peptide sequences: Mexneurin-1 (an EM-like peptide), Mexneurin-2, and Mexneurin-3, a peptide which appears to be unrelated to EMs. RT-PCR analysis and in situ hybridization reveal a widespread distribution of proMexneurin mRNA throughout the mouse brain. Both Mexneurin-1 and Mexneurin-3 peptides display biological activities in the mouse CNS.

The Immune System and the Role of Inflammation in Perinatal Depression.

Major depression during pregnancy is a common psychiatric disorder that arises from a complex and multifactorial etiology. Psychosocial stress, sex, hormones, and genetic vulnerability increase the risk for triggering mood disorders. Microglia and toll-like receptor 4 play a crucial role in triggering wide and varied stress-induced responses mediated through activation of the inflammasome; this leads to the secretion of inflammatory cytokines, increased serotonin metabolism, and reduction of neurotransmitter availability along with hypothalamic-pituitary-adrenal axis hyperactivity. Dysregulation of this intricate neuroimmune communication network during pregnancy modifies the maternal milieu, enhancing the emergence of depressive symptoms and negative obstetric and neuropsychiatric outcomes. Although several studies have clearly demonstrated the role of the innate immune system in major depression, it is still unclear how the placenta, the brain, and the monoaminergic and neuroendocrine systems interact during perinatal depression. Thus, in the present review we describe the cellular and molecular interactions between these systems in major depression during pregnancy, proposing that the same stress-related mechanisms involved in the activation of the NLRP3 inflammasome in microglia and peripheral myeloid cells in depressed patients operate in a similar fashion in the neuroimmune placenta during perinatal depression. Thus, activation of Toll-like receptor 2 and 4 signaling and the NLRP3 inflammasome in placental immune cells may promote a shift of the Th1/Th2 bias towards a predominant Th1/Th17 inflammatory response, associated with increased secretion of pro-inflammatory cytokines, among other secreted autocrine and paracrine mediators, which play a crucial role in triggering and/or exacerbating depressive symptoms during pregnancy.

Generation of a novel monoclonal antibody that recognizes the alpha (α)-amidated isoform of a valine residue.

BACKGROUND: Alpha (α)-amidation of peptides is a mechanism required for the conversion of prohormones into functional peptide sequences that display biological activities, receptor recognition and signal transduction on target cells. Alpha (α)-amidation occurs in almost all species and amino acids identified in nature. C-terminal valine amide neuropeptides constitute the smallest group of functional peptide compounds identified in neurosecretory structures in vertebrate and invertebrate species. METHODS: The α-amidated isoform of valine residue (Val-CONH2) was conjugated to KLH-protein carrier and used to immunize mice. Hyperimmune animals displaying high titers of valine amide antisera were used to generate stable hybridoma-secreting mAbs. Three productive hybridoma (P15A4, P17C11, and P18C5) were tested against peptides antigens containing both the C-terminal α-amidated (-CONH2) and free α-carboxylic acid (-COO(-)) isovariant of the valine residue. RESULTS: P18C5 mAb displayed the highest specificity and selectivity against C-terminal valine amidated peptide antigens in different immunoassays. P18C5 mAb-immunoreactivity exhibited a wide distribution along the neuroaxis of the rat brain, particularly in brain areas that did not cross-match with the neuronal distribution of known valine amide neuropeptides (α-MSH, adrenorphin, secretin, UCN1-2). These brain regions varied in the relative amount of putative novel valine amide peptide immunoreactive material (nmol/µg protein) estimated through a fmol-sensitive solid-phase radioimmunoassay (RIA) raised for P18C5 mAb. CONCLUSIONS: Our results demonstrate the versatility of a single mAb able to differentiate between two structural subdomains of a single amino acid. This mAb offers a wide spectrum of potential applications in research and medicine, whose uses may extend from a biological reagent (used to detect valine amidated peptide substances in fluids and tissues) to a detoxifying reagent (used to neutralize exogenous toxic amide peptide compounds) or as a specific immunoreagent in immunotherapy settings (used to reduce tumor growth and tumorigenesis) among many others.

Las adicciones, hallazgos genómicos / Addictions, genomic findings

The phrase "X is a gene for Y" and the preformationist concept of gene action that underlies it are inappropriate for psychiatric disorders such as depression, aggression, sexual orientation, obesity, infidelity, alcoholism, or schizophrenia. Drug addictions are complex, chronic, and mental diseases. Genetic studies of twins and families have suggested that genetic factors might account for 40 to 60% of the overall factors in the risk to the development of drug addictions. In addition, numerous studies aiming to discover genetic variants or candidate genes, including genome-wide linkage scans, candidate gene association studies, gene expression, and genome-wide association studies, have also suggested that multiple genes and genomic regions or markers might play important roles in the development of addictions. A primary behavioral pathology in drug addiction is the overpowering motivational strength and decreased ability to control the desire to obtain drugs. Among the most insidious characteristics of drug addiction is the recurring desire to take drugs even after many years of abstinence. Equally sinister is the compromised ability of addicts to suppress drug seeking in response to that desire even when confronted with seriously adverse consequences. The enduring vulnerability to relapse is a primary feature of the addiction disorder and has been identified as a point were pharmacotherapeutic intervention may be most effectively employed. In order to fashion rationale pharmacotherapy it is necessary to understand the neurobiological underpinnings of craving, relapse, choice, and control, and the last decade has seen significant advances, toward achieving this goal. The fact that the vulnerability to relapse in addicts can persist after years of abstinence implies that addiction is caused by long-lasting changes in brain function as a result of repeated drug use, genetic disposition, and environmental associations made with drugs use. Therefore, understanding neurobiological aspects of drug addiction requires the comprehension of the physiological mechanisms that convey to the enduring neuroplasticity. The goal of this review is to explore how the advances in ge-nomics and proteomics may unleash the understanding of the cellular underpinnings of drug addiction and how the recent advances in functional genomics and proteomics may be expected to improve dramatically the treatment of addictive disorders. Applying genomics and proteomics to drug addiction studies will lead to the identification of genes and their protein products that control the brain reward pathways of the brain and their adaptations to drugs of abuse, as well as variations in these genes and proteins that confer genetic risk for addiction and related disorders. Additionally, this review describes recent findings of addictive drugs-inducing altered changes in gene regulation which produce significant cellular modifications on neuronal function in both human and animal brains as detected in animal models of drug abuse. A major goal of drug abuse research is to identify and understand drug-induced changes in brain function that are common to most if not all drugs of abuse, as well as these may underlie drug dependence and addiction. This work describes recent studies whose purpose is to examine the drugs of abuse effect changes in gene and protein expression that converge in common molecular pathways. One of this recent reports using microarrays analysis to assay brain gene expression in the anterior prefrontal cortex (aPFC) of post mortem brains of 42 cocaine, cannabis and/or phencyclidine human cases compared to 30 individual cases, which were characterized by toxicology and drug abuse history. Another study depicted herewith is focused on how the use of drugs frequently begins and escalates during adolescence, with long-term adverse consequences. The study designed a rodent model of adolescence to mirror cocaine use patterns in teenagers. Microarrays analysis was employed to assay brain gene expression in post mortem PFC of rodents treated with cocaine during adolescence. Results from the study revealed that treatment caused acute alterations in the expression of genes encoding cell adhesion molecules and transcription factors within the PFC. Cocaine alters gene expression patterns and histone modification in the PFC. Furthermore observed decreases in histone metylation, which may indicate a role of chromatin remodeling in the observed changes in gene expression patterns. Chromatin remodeling is an important regulatory mechanism for cocaine-induced neural and behavioral plasticity in the striatum. Most of the gene expression changes induced by cocaine were transient. However, if early cocaine exposure triggered changes in cell structure/adhesion, the impact of those alterations could be long-lasting. It is important to consider that the PFC in humans is involved in a large range of different functions, including working memory, action planning, response inhibition, decision-making, reward processes, and social behavior. Any lasting impact cocaine has on these functions could be detrimental, particularly in adolescents. Findings suggest that exposure to cocaine during adolescence has far-reaching molecular and behavioral consequences in the rat PFC that develop over time and endure long after drug administration has ceased. These neuroadaptations could have serious implications, particularly in the developing brain. However, only a causal relationship between these cocaine-induced molecular and behavioral adaptations can be inferred at this time. Therefore, humans who abused cocaine, cannabis and/or phen-cyclidine share a decrease in transcription of calmoduline-related genes and increased transcription related to lipid/colesterol and Gol-gi/ER function. Acute exposure to drugs of abuse initiates molecular and cellular alterations in the central nervous system that lead to an increased overall vulnerability to addiction with subsequent drug exposures. These drug-induced alterations enhance molecular changes in gene transcription that result in the synthesis of new proteins. Therefore, one of the important goals of addiction research is to identify the drug-induced gene expression changes in specific brain structures shown to be vulnerable to the addictive properties of drugs of abuse. These changes represent common molecular features of drug abuse, which may underlie changes in synaptic function and plasticity that could have important ramification for decision-making capabilities in drug addiction. Eventually, all of these discoveries can be exploited for clinical applications as diverse as improved treatments diagnostic tests, and ultimately disease prevention and cure.

Una frase empleada en el argot científico en los primeros años de la era de la genética dictaba que "X es un gen para Y", en donde X representaba a un gen particular del genoma humano y Y correspondía a uno de los complejos trastornos de la conducta humana como la depresión, la agresión, la orientación sexual, la obesidad, la infidelidad, la esquizofrenia y la adicción. Sin embargo, ahora se sabe que la contribución genética a los trastornos psiquiátricos se debe a la acción conjunta de grupos de genes que de manera individual causarían sólo un pequeño impacto incapaz de desencadenar alteraciones conduc-tuales. La contribución de los grupos de genes aunada a un sinnúmero de factores ambientales y sociales es la causa de la amplia variedad de perturbaciones conductuales en el humano. De esta manera, la frase "X es un gen para Y", es inapropiado para los cuadros psiquiátricos. La conducta patológica más importante en la adicción es la búsqueda compulsiva de la droga y la pérdida del control en el deseo de obtenerla. Otra de las graves consecuencias de la adicción es el riesgo de recaídas de los individuos a pesar de tener varios años de abstinencia. Esta última característica ha sido el punto de elección para implementar medidas terapéuticas más eficientes. Para lograr que las terapias sean exitosas es necesario entender los mecanismos neurobiológicos que intervienen en los procesos de adquisición y consolidación del síndrome adictivo. Uno de los puntos que ha llamado la atención es el hecho de que el riesgo de las recaídas puede persistir durante varios años y ha permitido implicar la generación de cambios en la fisiología del cerebro que se mantienen por largos periodos. Así, es de suma relevancia comprender las bases neuro-biológicas de los procesos adictivos que ocasionan cambios en la plasticidad neural. La finalidad de esta revisión es analizar algunos ejemplos representativos de los recientes avances en el campo de las ciencias genó-micas que permiten ampliar el conocimiento de las implicaciones a nivel celular de los procesos adictivos y la importancia que tendrán dichos avances para mejorar la práctica psiquiátrica en general y, de manera específica, el tratamiento de las conductas adictivas. Se describen algunos de los trabajos recientes en los que se ha estudiado la modificación de la expresión génica como consecuencia de la administración de drogas de abuso en diferentes paradigmas de estudio, incluyendo estudios en los que se evalúa la similitud de los efectos ocasionado por tres drogas de abuso diferentes: cocaína, marihuana y fenilciclina. Finalmente se describen las implicaciones moleculares de las modificaciones en la expresión génica de proteínas que participan en diferentes procesos celulares, como el metabolismo del colesterol y los lípidos, las funciones del aparato de Golgi y el retículo endoplásmico, el tráfico intracelular en el citoesqueleto. Todos estos cambios representan modificaciones importantes en la función sináptica y la plasticidad neuronal. Esta información permitirá el desarrollo de aplicaciones clínicas que permitan implementar tratamientos efectivos, métodos de diagnóstico y en última instancia podrá ser de utilidad para prevenir, evitar o curar las adicciones.

Las adicciones, la genómica y la proteómica / Addictions, genomics and proteomics

Drug addiction is a chronically relapsing disorder that has been characterized by (1) compulsion to seek and take the drug, (2) loss of control in limiting intake, and (3) emergence of a negative emotional state (e.g, dysphoria, anxiety, irritability) reflecting a motivational withdrawal syndrome when access to the drug is prevented (defined as Substance Dependence by the Diagnostic and Statistical Manual of Mental Disorders [DSM] of the American Psychiatric Association). Acute exposure to drugs of abuse initiates molecular and cellular alterations in the Central Nervous System that lead to an increased overall vulnerability to addiction with subsequent drug exposures. These drug-induced alterations employ changes in gene transcription that result in the synthesis of new proteins. Therefore, one of the important goals of addiction research is to identify the drug-induced gene expression changes in the specific brain structures related to the addictive properties of various drugs. The molecular and genomic mechanisms by which drugs of abuse induce neuroplastic changes related to addiction remain largely unknown. Several studies have evaluated changes in gene and protein expression profiles in the brain after administration of drugs of abuse. Exposure to psychostimulants induces the activity-dependent gene expression of several transcription activators and repressors. Genomic research strategies have recently transitioned from the search for unknown genes to the identification and evaluation of coordinated gene networks and transcriptional signatures. New opportunities arising from the analysis of these networks include identifying novel relationships between genes and signaling pathways, connecting biological processes with the regulation of gene transcription, and associating genes and gene expression with diseases. The identification of gene networks requires large gene expression data sets with multiple data points. Functional genomics methods, studying the steady-state levels of these mRNA species, such as quantitative RT-PCR (qRT-PCR), whole-genome microarray analysis, and next generation sequencing methods, provide sensitive and high-throughput approaches to quantitatively examining mRNA (and miRNA) species present within the cells of the Nervous System. Functional genomics studies can help to illuminate genes involved in the development of behaviors related to drug abuse and relapse liability, but cannot provide insight into post-translational modifications (e.g., phosphorylation and glycosylation of proteins after translation has occurred) or subcellular localization of the protein product. Therefore, using proteomic techniques presents the opportunity to assess the totality of gene expression, translation, modification, and localization. Unfortunately, the sensitivity of proteomic tools lags behind those of functional genomics. Moreover, examining the mRNA provides a restricted view of primarily the cell body. Indeed, from a systems biology standpoint, analysis of both mRNA and protein levels (as well as miRNA and epigenetic changes) will ultimately provide a more integrated view of the molecular underpinnings of addiction. When applying proteomic technologies to addiction research, an understanding of the power of proteomic analysis is essential. After genetic information is transcribed into mRNA, a template is provided to the cell from which proteins will be synthesized. Neuroproteomic studies offer great promise for increasing understanding of the biochemical basis of addiction. While proteomics is still an evolving field, proteomic approaches have proven useful for elucidating the molecular effects of several drugs of abuse. With a number of ongoing research programs in addiction proteomics and a growing number of investigators taking advantage of these tools, the addiction research field will benefit from a consideration of the capabilities and limitations of proteomic studies. As with other biomedical research fields, drug abuse research is making use of new proteomic capabilities to examine changes in protein expression and modification on a large scale. To obtain the maximum benefit and scientific advancement from these new technologies, a clear understanding of the power and limitations of neuroproteomics is necessary. With the main limitation of neuroproteomic studies being the complexity of the proteome, approaches that focus these studies need to be employed. The salient message is that there is not a single best technical approach for all studies and that the main driver for the choice of proteomic technology and experimental design should be the advancement of the understanding and treatment of drug abuse. An important area that has heretofore received limited attention is the experimental design and interpretation specific to neuro-proteomic studies of drug abuse. These challenges include choice of animal model, ensuring sample quality, the complexity of brain tissue, confirming discovery findings, data analysis strategies, and integration of large data sets with the existing literature. Epigenetics is the study of heritable changes other than those in the DNA sequence and encompasses two major modifications of DNA or chromatin: DNA methylation and post-translational modification of histones. In this context, now it is known that regulation of gene expression contribute to the long-term adaptations underlying the effects of drugs of abuse. The precise molecular events that are required for modification of chromatin and that underlie gene repression or activation have not been elucidated. Recent reports have addressed this question and demonstrated that drugs of abuse modify specific methyl-CpG-binding proteins that control histone acetylation and gene expression. Further elucidation of the wide-range of histone modifications and the ensuing consequences on gene expression will be necessarily before the potential for drug development can be realized. It is important to characterize the molecular alterations underlying chromatin remodeling and the regulation of the epigenetics events by drugs of abuse. It is clear that modification in gene expression by drugs of abuse promote cellular changes. This review is intended to provide guidance on recent advances in the field of drug addiction. This review also presents a number of experimental design and sample approaches that have been applied to genomic, proteomic and epigenetic studies of addiction. Coupled with new technologies for data collection, analysis, and reporting, these approaches represent the future of the addiction field and hold the key to unlocking the complex of profile of drug abuse disorders.

La adicción a las drogas es una enfermedad mental que se caracteriza por ocasionar graves implicaciones sociales, económicas y de salud de los individuos que la padecen. La exposición aguda a las drogas de abuso provoca alteraciones moleculares y celulares en el Sistema Nervioso Central que ocasionan una vulnerabilidad para sufrir adicción a subsecuentes exposiciones a sustancias de abuso diferentes. Las alteraciones inducidas por las drogas producen cambios en la transcripción de genes que resultan en la síntesis de nuevas proteínas. Uno de los objetivos importantes en la investigación en el campo de las adicciones es identificar los cambios en la expresión de genes inducidos por las drogas en estructuras específicas del cerebro que están relacionadas con las propiedades adictivas de diferentes sustancias. El campo de la genómica y la proteómica, aplicada al estudio de las adicciones, tiene como objetivo identificar a los genes y las proteínas candidatos involucrados en la regulación de los procesos adictivos. Se han logrado progresos considerables en la identificación de genes y proteínas que regulan las conductas complejas presentes en los procesos adictivos en modelos de animales y modelos de estudio en humanos con material obtenido post-mortem. Estos descubrimientos se han sumado a los esfuerzos por identificar los circuitos neurales implicados en las manifestaciones conductuales relacionadas con las adicciones. También han permitido la identificación de genes candidatos que podrán ser blancos de futuras estrategias terapéuticas desarrolladas para tratar los procesos adictivos. Los estudios de genómica funcional han permitido identificar algunos de los genes involucrados en el desarrollo de las conductas adictivas, pero no tienen la capacidad de proporcionar información sobre las modificaciones post-traduccionales ni de la localización sub-celular de las proteínas para las que codifican los genes. Por lo tanto, la incorporación de estudios proteómicos ofrece la oportunidad de lograr evaluar, en su totalidad, la expresión, la traducción, las modificaciones y la localización de los genes y sus productos de expresión. Para obtener los máximos beneficios y avances con el empleo de estas nuevas tecnologías, deben comprenderse en su totalidad los alcances y limitaciones de la neuroproteómica. En este sentido, se debe tener especial cuidado en la elección del modelo de estudio, asegurar la calidad de la muestra, la complejidad de la estructura en estudio, confirmar los resultados obtenidos, las estrategias de análisis de resultados y la integración de los datos obtenidos con los ya reportados en la literatura científica. Los estudios recientes sobre los mecanismos moleculares que controlan los cambios inducidos por las drogas de abuso sobre la función transcipcional, la conducta y la plasticidad sináptica han identificado el importante papel que desempeña la remodelación de cromatina en la regulación y estabilidad de los programas genéticos neuronales mediados por las drogas y la subsecuente manifestación de las conductas adictivas. Se han identificado alteraciones epigenéticas sobre el genoma, tales como metilación del DNA y modificaciones en la función de las proteínas histonas. Estos importantes mecanismos se ven afectados como una respuesta neurobiológica a la administración de sustancias de abuso. Esta revisión pretende mostrar algunos de los avances recientes en el campo de las adicciones, presentando una breve descripción de los hallazgos que emplean aproximaciones genómicas, proteómicas y epigenéticas. Las implicaciones de estos estudios moleculares ponen de manifiesto nuevos conocimientos sobre el probable desarrollo de intervenciones terapéuticas en el futuro.

Endomorphin peptides: pharmacological and functional implications of these opioid peptides in the brain of mammals. Part two / Las endorfinas: implicaciones farmacológicas y funcionales de estos péptidos opioides en el cerebro de los mamíferos. Segunda parte

Endomorphin-1 (EM1) and Endomorphin-2 (EM2) represent the two endogenous C-terminal amide tetrapeptides shown to display a high binding affinity and selectivity for the µ-opioid receptor as reported previously (see previous paper, Part I). Endomorphins injected into the VTA were shown to enhance the development of behavioral sensitization responses to amphetamine (AMPH), besides of inducing an increase of locomotion (horizontal) activity in animals. These studies showed that EM2 was significantly more potent than EM1 in modulating the increased opioid-mediated ambulatory responses by altering the dopamine (DA) projecting system in the globus pallidus in tested animals. Several transmission systems (e.g., GABA) have been shown to participate in the endormorphin-induced locomotor responses. EM1 injected into the VTA produced potent rewarding effects in rodents, similar to the rewarding responses produced by distinct opiate compounds. The opioid rewarding responses induced by EM1-2 were shown to be mediated via the activation of both GABAergic and the dopamine (VTA-NAc-PFCx) transmission systems in the brain. Moreover, EM1-2 peptides injected into the VTA, but not in the NAc, produced similar related-rewarding responses induced by low doses of morphine. However, ICV administration of EM1 was shown to enhance a significant conditioned-place preference (CPP); whereas EM2 displayed a place aversion in tested animals. With regard to stress-related behaviors and physiological responses in mammals, endomorphin peptides have been proposed to modulate the HPA axis function via activation of the NTS-projecting neural system impinging on hypothalamic neurons, and/or via activation of the PAG (ventrolateral area) mediating analgesic responses-induced by stress. EM1-2 peptides have been shown to induce mood-related behaviors. For instance, administration of EM1 induced an increased anxiolytic response in mice when tested in elevated plus maze paradigms, results that showed that the µ-opioid receptor modulates mood-related responses in animals and humans, as well. Interesting enough is the recent observation that EM1-2 peptides may induce antidepressant-like behaviors in animals models of stress and depression, whereby EM1-2 peptides have been shown to up-regulate in a dose-dependent manner the neuronal expression of the BDNF mRNA in rat limbic areas involved in stress and depressive-like behaviors. Thus, these studies led to the proposition that endomorphin peptides may play crucial roles in psychiatric disorders (e.g., depression, schizophrenia). Furthermore, over the past years, it has been shown that µ-opioid receptor agonists (e.g., morphine, DAMGO; morphine-6β-glucuronide) displayed potent orexigenic activities in the CNS of mammals, similar to that displayed by EM1-2 peptides, whose dose-dependent orexigenic activity appears to be mediated by the endogenous opioid peptide, Dynorphin A, acting on its cognate κ-opioid receptor at the hypothalamus. Extensive studies revealed the activity of the EOS (e.g., β-endorphin) on the regulation of gonadal hormones and sexually-induced behaviors (e.g., lordosis) in female rats. β-endorphin or morphiceptin have been shown to facilitate lordosis behaviors in estrogen- and/or estrogen/progesterone primed rats, whereas EM1-2 peptides injected into third ventricle or into the diagonal band (DB) produced dose- and time-dependent, naloxone-reversible lordosis responses in female rats. These results posit that EM1-2 peptides produce their sexual behaviors and mating responses via modulating the cell release of LHRH and modulating GABA transmission system in the brain. Endomorphins have been shown to impair short- and long-term memory processing in mice when exposed to different learning paradigms. These opioid mediated effects appear to be regulated through the interaction of both cholinergic and dopaminergic transmissions in the brain. In addition, endomorphins have been shown to modulate cardiovascular and respiratory bioactivities, acting on several rostrocaudal areas of the CNS of mammals. Administration of EM1-2 peptides induced a significant reduction of heart rate and blood pressure in normotensive and hypertensive rats, via regulation of GABA and glutamate transmission systems. Although the exact endogenous mechanisms by which EM1-2 peptides produce their vasoactive responses are still unclear, several studies suggested that the peptide activity depends on the synthesis and release of nitric oxide (NO) from endothelial cells enhanced by activation of µ-opioid receptors. Studies on respiratory function showed that EM1-2 peptides attenuate and produce significant respiratory depression in tested animals. Finally, EM1-2 peptides have been shown to induce important inhibitory gastrointestinal effects via the activation of µ-opioid receptors localized in myenteric-plexus neurons that innervate smooth-muscle cells producing a dose-dependent- and CTOP-reversible inhibition of electrically-induced twitch ileum contractions, probably mediated through a reduced release response of several peptide and non-peptide transmitters.

La endomorfina-1 (EM1) y la endomorfina-2 (EM2) son dos péptidos bioactivos que poseen la más alta afinidad de unión selectiva por el receptor opioide µ en comparación con la unión de distintos ligandos agonistas a este subtipo de receptor opioide (véase resumen y texto del capítulo anterior, parte I). Estudios farmacológicos y conductuales han demostrado que la inyección de las EM1-2 en el área ventrotegmental (AVT) genera respuestas conductuales de sensibilización locomotora a la anfetamina (AMPH), además de incrementar la actividad locomotora de tipo horizontal en los roedores tratados. Estos estudios mostraron que la EM2 fue significativamente más potente que la EM1 en inducir las respuestas locomotoras detectadas, mediadas a través de la alteración de la actividad sináptica de dopamina (DA) y en el globus pallidus de los animales tratados. Asimismo, estudios fármaco-conductuales similares demostraron que otros sistemas de transmisión participan conjuntamente con el sistema dopaminérgico en la generación de los efectos locomotores inducidos por las EM1-2, como es el caso del sistema gabaérgico (GABA). Más aún, la inyección de EM1 en la región AVT del cerebro de roedores mostró generar respuestas potentes de recompensa placentera, similares a las reportadas por distintos alcaloides opiáceos de alto potencial adictivo, posterior a su administración sistémica. Más aún, la inyección de endomorfinas en la región AVT del cerebro del roedor, mas no en el núcleo accumbens (NAc), mostró generar respuestas de recompensa paralela a la generada posteriormente a la administración de dosis bajas de morfina. En línea con los efectos farmacológicos inducidos por las EM1-2, estudios fármaco-conductuales demostraron que la administración ICV de la EM1 fue capaz de generar respuestas de preferencia de lugar en roedores tratados CPP, por sus siglas en inglés, conditioned place preference, en tanto que la administración de EM2 generó respuestas opuestas, esto es, respuestas de aversión al lugar. Estudios conductuales relacionados con el fenómeno de estrés mostraron que las EM1-2 son capaces de modular la actividad funcional del eje HHA (eje hipotálamo/hipófisis/glándula adrenal) a través de la activación del sistema de proyección neuronal del tracto solitario (NTS, por sus siglas en inglés), al hipotálamo y/o a través de la activación del área ventrolateral de la sustancia gris periacueductal (PAG, por sus siglas en inglés); componente importante del sistema opioide endógeno, que median respuestas analgésicas (antinociceptivas) inducidas por estímulos estresantes. Asimismo, la administración de endomorfinas (v.g., EM1) mostró generar incrementos de conductas de naturaleza ansiolítica en ratones expuestos a paradigmas experimentales de generación de conductas estresantes (v.g., laberinto elevado). Estos estudios sugieren que la generación de conductas de estrés-emocional inducidas por las endomorfinas es mediada a través de la activación del receptor opioide µ en neuronas del hipotálamo responsables de regular la secreción de factores liberadores de distintas hormonas hipofisiarias (v.g., CRH, LHRH). Más aún, resulta interesante que las endomorfinas sean capaces de inducir conductas antidepresivas o de tipo antidepresivos como se ha reportado recientemente en modelos animales de estrés y depresión. Estos estudios mostraron que las respuestas conductuales de reacción al estrés y las conductas antidepresivas mediadas por las EM1-2 están ligadas con la expresión neuronal del mensajero de RNA que codifica para el factor trófico (BDNF, por sus siglas en inglés, brain derived neurotrophic factor), en áreas del sistema limbico, y que es inducida en forma dosis-dependiente por las endomorfinas, posterior a su administración ICV. Por lo tanto, estos estudios han permitido proponer que las endomorfinas cumplen un papel relevante durante el curso o desarrollo de las enfermedades mentales (v.g., esquizofrenia y depresión). En extensión a estos estudios conductuales, estudios recientes han demostrado la actividad orexigénica de las endomorfinas en forma similar a lo previamente detectado con distintos ligandos agonistas del receptor opioide µ (v.g., morfina, DAMGO; morfina-6β-glucurónido). Si bien estos estudios mostraron que tanto las EM1-2 como diversos agonistas del receptor opioide µ exhiben potentes actividades orexigénicas en el SNC de roedores, la actividad de las EM1-2 parece depender de la actividad de la dinorfina A y su unión sobre su receptor opioide K en neuronas hipotalámicas. Más aún, diversos estudios han mostrado que el sistema opioide endógeno (a través de la β-endorfina) regula conductas de naturaleza sexual y apareamiento (v.g., lordosis), además de modular la secreción y/o actividad de hormonas de origen gonadal (estrógenos, progesterona). Estudios similares en roedores hembras mostraron que la microinyección de EM1-2 en áreas específicas del sistema límbico y/ o la administración IT de ambos péptidos era capaz de generar respuestas sexuales de apareamiento, similares a las detectadas por la p-endorfina y morficeptina en la misma especie de animal, siendo bloqueados los efectos por la administración de naloxona. Estas respuestas conductuales inducidas por las EM1-2 mostraron estar ligadas a la liberación neuronal de LHRH, como de la activación y modulación del sistema de transmisión gabaérgico. En cuanto a las funciones de memoria y aprendizaje, diferentes estudios han demostrado que la administración ICV de EM1-2 en ratones expuestos a diferentes paradigmas de aprendizaje experimental, los péptidos opioides alteran significativamente los mecanismos de procesamiento y consolidación de memoria a corto y largo plazo en los animales tratados. Estos efectos parecen depender de la modulación del sistema opioide (v.g., el receptor opioide µ) sobre los sistemas de transmisión colinérgica y dopaminérgica en el cerebro de los mamíferos. Asímismo, diversos estudios han demostrado que tanto las EM1-2 como los alcaloides opiáceos y opioides endógenos modulan funciones cardiovasculares y respiratorias. En este contexto, diversos estudios mostraron que la administración de EM1-2 en ratas normotensas e hipertensas produce cambios fisiológicos significativos en la presión sanguínea y la frecuencia cardiaca. Si bien no están del todo esclarecidos los mecanismos por los cuales las endomorfinas producen sus respuestas cardiovasculares, diversos estudios sugieren que la actividad de estos péptidos está en función de la actividad e interacción de los sistemas de transmisión gabaérgico y glutamatérgico, respectivamente. Más aún, otros estudios sugieren que las respuestas fisiológicas de estos péptidos dependen de la actividad del óxido nitroso (NO, por sus siglas en inglés) liberado de los vasos sanguíneos, en respuesta de la activación del receptor opioide µ. Finalmente, diversos estudios han mostrado que las EM1-2 y la activación del receptor opioide µ producen efectos inhibitorios sobre la contracción del músculo liso del tracto gastrointestinal, generados a través de una reducción sostenida en la liberación de neurotransmisores de terminales sinápticas del plexo mientérico, mismas que inervan el tejido muscular liso del tracto gastrointestinal.

Endomorphin peptides: pharmacological and functional implications of these opioid peptides in the brain of mammals. Part one / Las endomorfinas: Implicaciones farmacológicas y funcionales de estos péptidos opioides en el cerebro de los mamíferos

The present paper describes several aspects of the biological activities, physiological and behavioral responses displayed by the most recent discovered opioid peptides: endomorphins. Endormorphins comprise two endogenous C-terminal amide tetrapeptides, named as endomorphin-1 (EM1; Tyr-Pro-Trp-Phe-NH2) and endomorphin-2 (EM2; Tyr-Pro-Phe-Phe-NH2), which were discovered a decade ago (1997) by Zadina's group. Initially, they reported the identification of two endogenous opioid peptides that displayed high binding affinities and selectivities for the µ-opioid receptor among other identified and cloned opioid receptors. These led authors to support the hypothesis that endomorphin peptides represent the endogenous ligand agonists for the µ-opioid receptor. Both peptides were identified and isolated from bovine and human brains. They consist of four amino acids that share a 75% structural homology among amino acids, and which display the structural α-amidated form of C-terminal -Phe- residue, as demonstrated for many other bioactive neuropeptides. These peptides are structurally distinct from other endogenous opioid substances identified in the brain of mammals, although they share some similarities with other amide terapeptides such as Tyr-W-MIF-1, found also in the mammalian brain. Here, we review the structure-relationship activity of both endomorphin molecules comparing their binding properties to different opioid receptors. Both EM1/EM2 peptides appear to be vulnerable to enzymatic degradation when exposed to the activities of different proteolytic enzymes, as occurs with many other neuroactive peptides found in the SNC of mammals. Immunohistochemical studies showed the wide and asymmetric distribution of both EM1-2 peptides in the brain, leading to the extensive pharmacological, cellular, and physiological studies that demonstrated the wide and varied bioactivities displayed by these peptides at both central and peripheral tissues. These studies led several authors to suggest the potential endogenous role of these peptides in major physiological processes (e.g. analgesia or antinociception). Based on the generation of specific (rabbit) polyclonal antibodies and the use of combined radioimmunoassay (RIA) techniques and immunohistochemical procedures, it was shown the wide distribution of EM1-2-LI (endomorphin1-2-like immunoreactivities) throughout the brain of different species (e.g. rat, primate, human), particularly co-localized in specific areas where µ-opioid receptor has been shown to be expressed. IHC mapping of endomorphin material in the CNS showed a parallelism with the neuroanatomical distribution of other endogenous opioid peptides (e.g. Met/Leu-enk, Dynorphin A, β-endorphin) previously reported. These studies showed for instance that, whereas EM1-LI was shown to be widely and densely distributed throughout the brain, particularly in forebrain structures (e.g. nucleus accumbens [NAc]; cortex [Cx]; amygdale [AMG]; thalamus [Th], the hypothalamus [Hyp], the striatum [CPu]), including the upper brainstem (BS); and dorsal root ganglia (DRG); EM2-LI is highly expressed in spinal cord and lower brainstem. Interesting enough is the demonstration of the expression of EM1-2-LI outside the CNS (e.g. spleen, thymus and blood), and detected in immune cells (e.g. macrophages/monocytes, lymphocytes, and polymophonuclear leucocytes) surrounding inflammatory foci. Pharmacological studies showed that these peptides displace with high potency several µ-opioid receptor ligands agonists in a concentration-dependent manner. Moreover, EM1-2 peptides have been shown to modulate the release of several conventional transmitters from neurons (e.g. DA, NA, 5-HT, ACh) besides on active neurohormones. Additionally, in vitro and in vivo studies showed that both EM-1/EM-2 peptides produce their pharmacological and biological effects by stimulating either µ1 or µ2-opioid receptors, which mediate the distinct pharmacological activities detected for each peptide. Cellular studies showed that both EM-1/EM-2 peptides induce a potent granule/vesicle endocytosis and trafficking of µ-opioid receptor in cells transfected with the µ-opioid receptor cDNA; following some endocytosis responses and µ-opioid receptor trafficking mechanisms shown in enteric neurons; cells previously reported to express naturally µ-opioid binding sites on cells. Endomorphins have been shown to induce potent antinociceptive responses after ICV or IT administration into mice; to modulate nociceptive transmission and pain sensation into the brain after stimulating peripheral nociceptors on primary neuronal afferents; and to generate cross-tolerance between endomorphin peptides and between EM1 and opiate compounds, such as morphine.

Este artículo resume varios aspectos de las múltiples actividades biológicas, celulares, efectos farmacológicos, respuestas fisiológicas y conductuales de dos nuevas sustancias peptídicas de naturaleza opioide, descubiertas recientemente y denominadas endomorfinas. Las endomorfinas son dos péptidos opioides, clasificados como endomorfina-1 (EM1, Tyr-Pro-Trp-Phe-NH2) y endomorfina-2 (EM2, Tyr-Pro-Phe-Phe-NH2), cuyas secuencias peptídicas fueron identificadas y aisladas del cerebro de bovino y humano por el grupo de Zadina en 1997. Estudios de unión radioligando-receptor demostraron que estos péptidos se unen con alta afinidad de unión al receptor opioide µ en relación con su capacidad de unión a otros subtipos de receptores opioides (kappa [κ], delta [δ] ), previamente identificados en el SNC de mamíferos. Ambos péptidos están compuestos por cuatro aminoácidos y son estructuralmente distintos de las demás sustancias opioides endógenas conocidas. Esta revisión detalla con precisión diversos aspectos de la farmacología y actividades celulares de estos opioides y sus implicaciones en la modulación de distintas circuitos o vías neurales y funcionamiento del SNC de los mamíferos, respectivamente. Los estudios relacionados con la función estructura-actividad de estos péptidos han mostrado que, al igual que la mayoría de los péptidos bioactivos endógenos de naturaleza opioide y no opioide, son vulnerables a la escisión peptídica por cortes enzimáticos mediante la exposición a distintas enzimas proteolíticas que pudiesen participar en la degradación endógena de las endomorfinas, y la obtención de diversos productos de degradación. Asimismo, este artículo menciona la amplia distribución neuroanatómica que poseen las endomorfinas en distintas regiones del cerebro, particularmente en aquellas que regulan el procesamiento y la transmisión de la información nociceptiva y que, por tanto, reflejan el papel potencial de estos péptidos en procesos fisiológicos de analgesia, entre muchos otros (memoria y otro aprendizaje). En este contexto, diferentes estudios basados en el empleo de ensayos inmunológicos (radioinmunoensayos [RIA] y técnicas de inmunohistoquímica [IHC]) que requieren el uso de anticuerpos específicos generados contra las secuencias consenso de las endomorfinas mostraron una amplia distribución de material inmunoreactivo a endomorfina (vg., EM1-LI, EM2-LI) en tejidos neurales de humano, bovino y roedores. Por ejemplo, la EM1-LI mostró una distribución relativamente abundante en una gran mayoría de las regiones del SNC de mamíferos estudiados, particularmente en la región rostral y superior del tallo cerebral, así como en el núcleo accumbens (NAc), la corteza prefrontal y frontal (PFCx), la amígdala (AMG), el tálamo (TH), el hipotálamo (HPT), el estriado (CPu) y fibras nerviosas de la raíz del ganglio dorsal (DRG). En contraste, la expresión de EMZ mostró ser muy abundante en la región de la médula espinal y en la región caudal del tallo cerebral. La distribución de material inmunoreactivo a EM1-2 en el SNC de mamíferos mostró similitudes en cuanto a la distribución neuroanatómica reportada para otros péptidos opioides endógenos, previamente identificados (vg., encefalinas, dinorfinas, endorfinas). Así mismo, estudios paralelos lograron identificar la presencia de EM1-2-LI en órganos periféricos (vg., bazo, timo, células inflamatorias del tipo de macrófagos-monocitos, linfocitos y leucocitos PMN) y en plasma. Más aún, diversos estudios farmacológicos han mostrado que las actividades biológicas y respuestas fisiológicas de las EM1-2 están mediadas a través de la estimulación de los subtipos de receptores opioides µ1 y µ2. Estudios de inmunohistoquímica (IHC) demostraron la colocalización del receptor opioide µ y las EM1-2 en diversas regiones del SNC de mamiferos. Esto ha permitido proponer que las EM1-2 representan una nueva familia de péptidos opioides con funciones neuromoduladoras relevantes en el SNC, las cuales intervienen en la regulación de los procesos biológicos de percepción del dolor; respuestas de estrés; funciones límbicas de placer y recompensa inducidas por incentivos naturales y/o sustancias psicotrópicas; funciones de estado de alerta y vigilia, funciones cognitivas (de aprendizaje y memoria) y actividades de regulación neuroendócrina. Además, diversos estudios celulares han mostrado que ambos péptidos opioides son capaces de inducir la internalización aguda o endocitosis del receptor opioide µ en células somáticas transfectadas con el ADN (ADNc) que codifica este mismo receptor opioide. Al igual que otros péptidos opioides (v.g., encefalinas), diversos estudios mostraron el catabolismo enzimático de estos péptidos amidados mediante la actividad de enzimas proteolíticas (v.g., carboxipeptidasa Y, aminopeptidasa M), lo que ha permitido sugerir que estos péptidos opioides son degradados por rutas de degradación enzimática similares que rigen para múltiples péptidos bioactivos moduladores en el SNC de los mamíferos. Al igual que otros péptidos endógenos, ambas endomorfinas mostraron la capacidad de modular la liberación neuronal de neurotransmisores (DA, NA, 5-HT, ACh) y hormonas peptídicas en áreas específicas del cerebro de los mamíferos. Asimismo, ambos péptidos mostraron una capacidad de generar efectos antinociceptivos potentes en forma dosis-dependiente posterior a su administración ICV o IT en animales experimentales, además de generar respuestas de tolerancia cruzada entre ambas endomorfinas y/o entre la EM1 y alcaloides opiáceos del tipo de la morfina.