The endogenous opioid system in the medial prefrontal cortex mediates ketamine's antidepressant-like actions.

Recent studies have implicated the endogenous opioid system in the antidepressant actions of ketamine, but the underlying mechanisms remain unclear. We used a combination of pharmacological, behavioral, and molecular approaches in rats to test the contribution of the prefrontal endogenous opioid system to the antidepressant-like effects of a single dose of ketamine. Both the behavioral actions of ketamine and their molecular correlates in the medial prefrontal cortex (mPFC) are blocked by acute systemic administration of naltrexone, a competitive opioid receptor antagonist. Naltrexone delivered directly into the mPFC similarly disrupts the behavioral effects of ketamine. Ketamine treatment rapidly increases levels of ß-endorphin and the expression of the µ-opioid receptor gene (Oprm1) in the mPFC, and the expression of gene that encodes proopiomelanocortin, the precursor of ß-endorphin, in the hypothalamus, in vivo. Finally, neutralization of ß-endorphin in the mPFC using a specific antibody prior to ketamine treatment abolishes both behavioral and molecular effects. Together, these findings indicate that presence of ß-endorphin and activation of opioid receptors in the mPFC are required for the antidepressant-like actions of ketamine.

The opioid peptide ß-endorphin interferes with the pituitary-testis axis in the Mozambique tilapia Oreochromis mossambicus.

Although the involvement of ß-endorphin (ß-ERP) in vertebrate reproduction has been suggested, its role in testicular activity is not clear in fish. We describe the influence of ß-ERP on spermatogenesis in a cichlid fish in the present paper. In comparison to the control group, the administration of ß-ERP (3 µg) caused a significant increase in the number of spermatogonia-A and spermatids. Following treatment with ß-ERP (6 µg), a significant increase in the number of spermatogonia-A was observed, whereas the numbers of all the other germ cells, excluding spermatogonia-B, significantly decreased in comparison to those in the control group. In addition, treatment of fish with 6 µg ß-ERP resulted in a significant reduction in the dimensions of the lumen and seminiferous lobules, the level of immunopositive androgen receptor (AR) expression in Sertoli cells, and the percentage of luteinizing hormone (LH) immunolabeled in the pituitary compared to those in the control group or the group treated with 3 µg ß-ERP. In contrast, the intensity of AR immunoreactivity and the percentage of LH immunolabeling were substantially increased in fish treated with 3 µg ß-ERP compared to those in the control group. These findings reveal for the first time that a low dose of ß-ERP stimulates the recruitment of spermatogonia as well as spermateleosis, whereas a high concentration affects the recruitment of germ cells prior to meiotic division in tilapia. These results suggest that ß-ERP exerts modulatory effects at the testicular and hypophysial levels through alterations in AR expression and LH secretory activity, respectively, in teleosts.

ß-endorphin suppresses ultraviolet B irradiation-induced epidermal barrier damage by regulating inflammation-dependent mTORC1 signaling.

Solar ultraviolet B (UVB) radiation triggers excessive inflammation, disrupting the epidermal barrier, and can eventually cause skin cancer. A previous study reported that under UVB irradiation, epidermal keratinocytes synthesize the proopiomelanocortin-derived peptide ß-endorphin, which is known for its analgesic effect. However, little is known about the role of ß-endorphin in UVB-exposed skin. Therefore, in this study, we aimed to explore the protective role of ß-endorphin against UVB irradiation-induced damage to the skin barrier in normal human keratinocytes (NHKs) and on a human skin equivalent model. Treatment with ß-endorphin reduced inflammatory responses in UVB-irradiated NHKs by inactivating the NF-κB signaling pathway. Additionally, we found that ß-endorphin treatment reversed UVB-induced abnormal epidermal proliferation and differentiation in NHKs and, thus, repaired the skin barrier in UVB-treated skin equivalents. The observed effects of ß-endorphin on UVB-irradiated NHKs were mediated via blockade of the Akt/mTOR signaling pathway. These results reveal that ß-endorphin might be useful against UVB-induced skin injury, including the disruption of the skin barrier function.

Epigenetic regulation of beta-endorphin synthesis in hypothalamic arcuate nucleus neurons modulates neuropathic pain in a rodent pain model.

Although beta-endorphinergic neurons in the hypothalamic arcuate nucleus (ARC) synthesize beta-endorphin (ß-EP) to alleviate nociceptive behaviors, the underlying regulatory mechanisms remain unknown. Here, we elucidated an epigenetic pathway driven by microRNA regulation of ß-EP synthesis in ARC neurons to control neuropathic pain. In pain-injured rats miR-203a-3p was the most highly upregulated miRNA in the ARC. A similar increase was identified in the cerebrospinal fluid of trigeminal neuralgia patients. Mechanistically, we found histone deacetylase 9 was downregulated following nerve injury, which decreased deacetylation of histone H3 lysine-18, facilitating the binding of NR4A2 transcription factor to the miR-203a-3p gene promoter, thereby upregulating miR-203a-3p expression. Further, increased miR-203a-3p was found to maintain neuropathic pain by targeting proprotein convertase 1, an endopeptidase necessary for the cleavage of proopiomelanocortin, the precursor of ß-EP. The identified mechanism may provide an avenue for the development of new therapeutic targets for neuropathic pain treatment.

ß-Endorphin (an endogenous opioid) inhibits inflammation, oxidative stress and apoptosis via Nrf-2 in asthmatic murine model.

Asthma, a chronic respiratory disease is characterized by airway inflammation, remodelling, airflow limitation and hyperresponsiveness. At present, it is considered as an umbrella diagnosis consisting several variable clinical presentations (phenotypes) and distinct pathophysiological mechanisms (endotypes). Recent evidence suggests that oxidative stress participates in airway inflammation and remodelling in chronic asthma. Opioids resembled by group of regulatory peptides have proven to act as an immunomodulator. ß-Endorphin a natural and potent endogenous morphine produced in the anterior pituitary gland play role in pain modulation. Therapeutic strategy of many opioids including ß-Endorphin as an anti­inflammatory and antioxidative agent has not been yet explored despite its promising analgesic effects. This is the first study to reveal the role of ß-Endorphin in regulating airway inflammation, cellular apoptosis, and oxidative stress via Nrf-2 in an experimental asthmatic model. Asthma was generated in balb/c mice by sensitizing with 1% Toulene Diisocyanate on day 0, 7, 14 and 21 and challenging with 2.5% Toulene Diisocyanate from day 22 to 51 (on every alternate day) through intranasal route. ß-Endorphin (5 µg/kg) was administered through the nasal route 1 h prior to sensitization and challenge. The effect of ß-Endorphin on pulmonary inflammation and redox status along with parameters of oxidative stress were evaluated. We found that pre-treatment of ß-Endorphin significantly reduced inflammatory infiltration in lung tissue and cell counts in bronchoalveolar lavage fluid. Also, pre-treatment of ß-Endorphin reduced reactive oxygen species, Myeloperoxidase, Nitric Oxide, Protein and protein carbonylation, Glutathione Reductase, Malondialdehyde, IFN-γ, and TNF-α. Reversely, ß-Endorphin significantly increased Superoxide dismutase, Catalase, glutathione, Glutathione-S-Transferase, and activation of NF-E2-related factor 2 (Nrf-2) via Kelch-like ECH-associated protein 1 (Keap1), independent pathway in the lung restoring architectural alveolar and bronchial changes. The present findings reveal the therapeutic potency of ß-END in regulating asthma by Keap-1 independent regulation of Nrf-2 activity. The present findings reveal the therapeutic potency of ß-Endorphin in regulating asthma.

Cell apoptosis in the testis of male rats is elevated by intervention with ß-endorphin and the mu opioid receptor.

ß-endorphin (ß-EP) is involved in the regulation of male germ cells; however, little is known about the effect of ß-EP on primary germ cells via opioid receptors. In this study, we first revealed significant cell apoptosis in the testis of male rats after ß-EP intervention. Subsequently, the expression of the mu opioid receptor (MOR) was detected in both Leydig cells (LCs) and spermatogonia (SGs) by fluorescence colocalization; overlapping signals were also detected in apoptotic cells. In addition, LCs and SGs were separated from the testis of male rats and primary cells were treated with ß-EP; this increased the mRNA levels of MOR and was accompanied by acute cell apoptosis. Our findings provide a foundation for the further study of apoptosis in reproductive cells regulated by ß-EP and the MOR receptor.

Heme-Induced Macrophage Phenotype Switching and Impaired Endogenous Opioid Homeostasis Correlate with Chronic Widespread Pain in HIV.

Chronic widespread pain (CWP) is associated with a high rate of disability and decreased quality of life in people with HIV-1 (PWH). We previously showed that PWH with CWP have increased hemolysis and elevated plasma levels of cell-free heme, which correlate with low endogenous opioid levels in leukocytes. Further, we demonstrated that cell-free heme impairs ß-endorphin synthesis/release from leukocytes. However, the cellular mechanisms by which heme dampens ß-endorphin production are inconclusive. The current hypothesis is that heme-dependent TLR4 activation and macrophage polarization to the M1 phenotype mediate this phenomenon. Our novel findings showed that PWH with CWP have elevated M1-specific macrophage chemokines (ENA-78, GRO-α, and IP-10) in plasma. In vitro, hemin-induced polarization of M0 and M2 macrophages to the M1 phenotype with low ß-endorphins was mitigated by treating cells with the TLR4 inhibitor, TAK-242. Similarly, in vivo phenylhydrazine hydrochloride (PHZ), an inducer of hemolysis, injected into C57Bl/6 mice increased the M1/M2 cell ratio and reduced ß-endorphin levels. However, treating these animals with the heme-scavenging protein hemopexin (Hx) or TAK-242 reduced the M1/M2 ratio and increased ß-endorphins. Furthermore, Hx attenuated heme-induced mechanical, heat, and cold hypersensitivity, while TAK-242 abrogated hypersensitivity to mechanical and heat stimuli. Overall, these results suggest that heme-mediated TLR4 activation and M1 polarization of macrophages correlate with impaired endogenous opioid homeostasis and hypersensitivity in people with HIV.

Systemic and Peripheral Mechanisms of Cortical Stimulation-Induced Analgesia and Refractoriness in a Rat Model of Neuropathic Pain.

Epidural motor cortex stimulation (MCS) is an effective treatment for refractory neuropathic pain; however, some individuals are unresponsive. In this study, we correlated the effectiveness of MCS and refractoriness with the expression of cytokines, neurotrophins, and nociceptive mediators in the dorsal root ganglion (DRG), sciatic nerve, and plasma of rats with sciatic neuropathy. MCS inhibited hyperalgesia and allodynia in two-thirds of the animals (responsive group), and one-third did not respond (refractory group). Chronic constriction injury (CCI) increased IL-1ß in the nerve and DRG, inhibited IL-4, IL-10, and IL-17A in the nerve, decreased ß-endorphin, and enhanced substance P in the plasma, compared to the control. Responsive animals showed decreased NGF and increased IL-6 in the nerve, accompanied by restoration of local IL-10 and IL-17A and systemic ß-endorphin. Refractory animals showed increased TNF-α and decreased IFNγ in the nerve, along with decreased TNF-α and IL-17A in the DRG, maintaining low levels of systemic ß-endorphin. Our findings suggest that the effectiveness of MCS depends on local control of inflammatory and neurotrophic changes, accompanied by recovery of the opioidergic system observed in neuropathic conditions. So, understanding the refractoriness to MCS may guide an improvement in the efficacy of the technique, thus benefiting patients with persistent neuropathic pain.

Local analgesia of electroacupuncture is mediated by the recruitment of neutrophils and released ß-endorphins.

ABSTRACT: The efficacy of acupuncture in treating pain diseases has been recognized in clinical practice, and its mechanism of action has been a hot topic in academic acupuncture research. Previous basic research on acupuncture analgesia has focused mostly on the nervous system, with few studies addressing the immune system as a potential pathway of acupuncture analgesia. In this study, we investigated the effect of electroacupuncture (EA) on the ß-endorphins (ß-END) content, END-containing leukocyte type and number, sympathetic neurotransmitter norepinephrine (NE), and chemokine gene expression in inflamed tissues. To induce inflammatory pain, about 200 µL of complete Frester adjuvant (CFA) was injected into the unilateral medial femoral muscle of adult Wistar rats. Electroacupuncture treatment was performed for 3 days beginning on day 4 after CFA injection, with parameters of 2/100 Hz, 2 mA, and 30 minutes per treatment. The weight-bearing experiment and enzyme-linked immunosorbent assay showed that EA treatment significantly relieved spontaneous pain-like behaviors and increased the level of ß-END in inflamed tissue. Injection of anti-END antibody in inflamed tissue blocked this analgesic effect. Flow cytometry and immunofluorescence staining revealed that the EA-induced increase in ß-END was derived from opioid-containing ICAM-1 + /CD11b + immune cells in inflamed tissue. In addition, EA treatment increased the NE content and expression of ß2 adrenergic receptor (ADR-ß2) in inflammatory tissues and upregulated Cxcl1 and Cxcl6 gene expression levels. These findings provide new evidence for the peripheral analgesic effect of acupuncture treatment by recruiting ß-END-containing ICAM-1 + /CD11b + immune cells and increasing the ß-END content at the site of inflammation.

Interactions between ß-endorphin and kisspeptin neurons of the ewe arcuate nucleus are modulated by photoperiod.

Opioid peptides are well-known modulators of the central control of reproduction. Among them, dynorphin coexpressed in kisspeptin (KP) neurons of the arcuate nucleus (ARC) has been thoroughly studied for its autocrine effect on KP release through κ opioid receptors. Other studies have suggested a role for ß-endorphin (BEND), a peptide cleaved from the pro-opiomelanocortin precursor, on food intake and central control of reproduction. Similar to KP, BEND content in the ARC of sheep is modulated by day length and BEND modulates food intake in a dose-dependent manner. Because KP levels in the ARC vary with photoperiodic and metabolic status, a photoperiod-driven influence of BEND neurons on neighboring KP neurons is plausible. The present study aimed to investigate a possible modulatory action of BEND on KP neurons located in the ovine ARC. Using confocal microscopy, numerous KP appositions on BEND neurons were found but there was no photoperiodic variation of the number of these interactions in ovariectomized, estradiol-replaced ewes. By contrast, BEND terminals on KP neurons were twice as numerous under short days, in ewes having an activated gonadotropic axis, compared to anestrus ewes under long days. Injection of 5 µg BEND into the third ventricle of short-day ewes induced a significant and specific increase of activated KP neurons (16% vs. 9% in controls), whereas the percentage of overall activated (c-Fos positive) neurons, was similar between both groups. These data suggest a photoperiod-dependent influence of BEND on KP neurons of the ARC, which may influence gonadotropin-releasing hormone pulsatile secretion and inform KP neurons about metabolic status.

Crotalphine Modulates Microglia M1/M2 Phenotypes and Induces Spinal Analgesia Mediated by Opioid-Cannabinoid Systems.

Pain is a worldwide public health problem and its treatment is still a challenge since clinically available drugs do not completely reverse chronic painful states or induce undesirable effects. Crotalphine is a 14 amino acids synthetic peptide that induces a potent and long-lasting analgesic effect on acute and chronic pain models, peripherally mediated by the endogenous release of dynorphin A and the desensitization of the transient receptor potential ankyrin 1 (TRPA1) receptor. However, the effects of crotalphine on the central nervous system (CNS) and the signaling pathway have not been investigated. Thus, the central effect of crotalphine was evaluated on the partial sciatic nerve ligation (PSNL)-induced chronic neuropathic pain model. Crotalphine (100 µg/kg, p.o.)-induced analgesia on the 14th day after surgery lasting up to 24 h after administration. This effect was prevented by intrathecal administration of CB1 (AM251) or CB2 (AM630) cannabinoid receptor antagonists. Besides that, crotalphine-induced analgesia was reversed by CTOP, nor-BNI, and naltrindole, antagonists of mu, kappa, and delta-opioid receptors, respectively, and also by the specific antibodies for ß-endorphin, dynorphin-A, and met-enkephalin. Likewise, the analgesic effect of crotalphine was blocked by the intrathecal administration of minocycline, an inhibitor of microglial activation and proliferation. Additionally, crotalphine decreased the PSNL-induced IL-6 release in the spinal cord. Importantly, in vitro, crotalphine inhibited LPS-induced CD86 expression and upregulated CD206 expression in BV-2 cells, demonstrating a polarization of microglial cells towards the M2 phenotype. These results demonstrated that crotalphine, besides activating opioid and cannabinoid analgesic systems, impairs central neuroinflammation, confirming the neuromodulatory mechanism involved in the crotalphine analgesic effect.

Evaluation of the Influence of Biological Factors during the Course of Treatment in Patients with Ovarian Cancer.

The aim of this study was to evaluate the influence of ß-endorphins and serotonin on the course of treatment, disease-free time, and overall survival of patients with ovarian cancer. This study may contribute to the identification of modifiable factors that may influence the treatment of ovarian cancer. The research was carried out in a group of 162 patients of which 139 respondents were included in the research; ovarian cancer was diagnosed in 78 of these patients. The study consisted of three stages. In the first stage of diagnostics, a survey among the patients was carried out. In the second stage-5 mL of blood was collected from each patient (n = 139) in the preoperative period to determine the concentration of ß-endorphin and serotonin. In the third stage-blood samples were collected from those patients who had completed chemotherapy treatment or had surgery. Concentrations of ß-endorphin and serotonin were measured by the Luminex method, using the commercial Luminex Human Discovery Assay kit. The average age of the patients was 62.99 years. The level of ß-endorphin significantly differs among patients diagnosed with ovarian cancer and among patients in the control group (202.86; SD-15.78 vs. 302.00; SD-24.49). A lower level of ß-endorphins was found in the patients with a recurrence of the neoplastic process compared to those without recurrence (178.84; SD-12.98 vs. 205.66; SD-13.37). On the other hand, the level of serotonin before chemotherapy was higher in the group of people with disease recurrence compared to those without recurrence (141.53; SD-15.33 vs. 134.99; SD-10.08). Statistically significantly positive correlations were found between the level of ß-endorphin and both disease-free time (ß-endorphin levels before chemotherapy: rho Spearman 0.379, p < 0.027; ß-endorphin levels after chemotherapy: rho Spearman 0.734 p < 0.001) and survival time (ß-endorphin levels before chemotherapy: rho Spearman 0.267, p < 0.018; ß-endorphin levels after chemotherapy: rho Spearman 0.654 p < 0.001). 1. The levels of serotonin and ß-endorphin levels are significantly related to ovarian cancer and change during treatment. 2. High mean preoperative concentrations of ß-endorphins were significantly related to overall survival and disease-free time.

Evidence of alterations of Beta-endorphin levels and Mu-opioid receptor gene expression in bipolar disorder.

Despite the well-recognized effects of endogenous opioids on mood and behavior, research on its role in bipolar disorder (BD) is still limited to small or anecdotal reports. Considering that Beta-endorphins (ß-END) and Mu-opioid receptors (MOR), in particular, have a crucial activity in affective modulation, we hypothesized their alteration in BD. A cross-sectional study was conducted. We compared: (1) BD type I (BD-I) patients (n = 50) vs healthy controls (n = 27), (2) two BD-I subject subgroups: manic (MAN; n = 25) vs depressed (DEP; n = 25) subjects. Plasma levels of ß-END and MOR gene expression in peripheral blood mononuclear cells were analyzed using ELISA Immunoassay qRT-PCR. We found that subjects with BD exhibited a significant upregulation of MOR gene expression and a decrease of ß-END (p<0.0001 for both). MAN display higher MOR levels than DEP (p<0.001) and HC (p<0.0001). Plasma levels of ß-END were lower in DEP compared to MAN (p<0.05) and HC (p<0.0001). The main limitations are the cross-sectional design and the lack of a group of euthymic subjects. Although preliminary, our results suggest a dysregulation of the endogenous opioid systems in BD. In particular, both MAN and DEP showed a reduction of ß-END levels, whereas MAN was associated with MOR gene overexpression.

The Clash of Two Epidemics: the Relationship Between Opioids and Glucose Metabolism.

PURPOSE OF REVIEW: We are currently in the midst of a global opioid epidemic. Opioids affect many physiological processes, but one side effect that is not often taken into consideration is the opioid-induced alteration in blood glucose levels. RECENT FINDINGS: This review shows that the vast majority of studies report that opioid stimulation increases blood glucose levels. In addition, plasma levels of the endogenous opioid ß-endorphin rise in response to low blood glucose. In contrast, in hyperglycaemic baseline conditions such as in patients with type 2 diabetes mellitus (T2DM), opioid stimulation lowers blood glucose levels. Furthermore, obesity itself alters sensitivity to opioids, changes opioid receptor expression and increases plasma ß-endorphin levels. Thus, opioid stimulation can have various side effects on glycaemia that should be taken into consideration upon prescribing opioid-based medication, and more research is needed to unravel the interaction between obesity, glycaemia and opioid use.

Sex differences and the lack of effects of chemogenetic manipulation of pro-opiomelanocortin (POMC) neurons on alcohol consumption in male and female mice.

The endogenous opioid system has been implicated in the rewarding and reinforcing effects of alcohol. Pro-opiomelanocortin (POMC) neurons located within the arcuate nucleus of the hypothalamus (ArcN) secrete multiple peptides associated with alcohol consumption, including ß-endorphin (ß-END), α-melanocyte stimulating hormone (α-MSH), and adrenocorticotropic hormone (ACTH). In this study, we utilized chemogenetics to bidirectionally modulate ArcN POMC neurons to determine their role in alcohol and saccharin consumption and regional levels of POMC-derived peptides. Male and female POMC-cre mice were infused with viral vectors designed for cre-dependent expression of either excitatory and inhibitory DREADDs or a control vector into the ArcN. Following recovery, animals were allowed to consume alcohol or saccharin using the drinking-in-the-dark (DID) paradigm of binge-like intake for 4 consecutive days. Prior to the final test session, animals were injected with clozapine-N-oxide (2.5 mg/kg, i.p.) for DREADD activation. Following the last DID session, animals were euthanized and the ArcN, VTA, amygdala and NAc were dissected and assessed for POMC peptide expression utilizing western blotting. We found that female mice consumed more alcohol than males during DID sessions 2-4, and that chemogenetic activation had no effect on alcohol or saccharin consumption in either sex. We found that ß-END expression within the ArcN positively correlated with alcohol consumption. Given the molecular and functional heterogeneity of ArcN POMC neurons, future studies are needed to assess the effects of modulation of specific subpopulations of these neurons within the ArcN on consumption of rewarding substances such as alcohol and saccharin.

Human Sensory Neuron-like Cells and Glycated Collagen Matrix as a Model for the Screening of Analgesic Compounds.

Increased collagen-derived advanced glycation end-products (AGEs) are consistently related to painful diseases, including osteoarthritis, diabetic neuropathy, and neurodegenerative disorders. We have recently developed a model combining a two-dimensional glycated extracellular matrix (ECM-GC) and primary dorsal root ganglion (DRG) that mimicked a pro-nociceptive microenvironment. However, culturing primary cells is still a challenge for large-scale screening studies. Here, we characterized a new model using ECM-GC as a stimulus for human sensory-like neurons differentiated from SH-SY5Y cell lines to screen for analgesic compounds. First, we confirmed that the differentiation process induces the expression of neuron markers (MAP2, RBFOX3 (NeuN), and TUBB3 (ß-III tubulin), as well as sensory neuron markers critical for pain sensation (TRPV1, SCN9A (Nav1.7), SCN10A (Nav1.8), and SCN11A (Nav1.9). Next, we showed that ECM-GC increased c-Fos expression in human sensory-like neurons, which is suggestive of neuronal activation. In addition, ECM-GC upregulated the expression of critical genes involved in pain, including SCN9A and TACR1. Of interest, ECM-GC induced substance P release, a neuropeptide widely involved in neuroinflammation and pain. Finally, morphine, the prototype opiate, decreased ECM-GC-induced substance P release. Together, our results suggest that we established a functional model that can be useful as a platform for screening candidates for the management of painful conditions.

Inhibition of POMC neurons in mice undergoing activity-based anorexia selectively blunts food anticipatory activity without affecting body weight or food intake.

Anorexia nervosa (AN) is a debilitating eating disorder characterized by severely restricted eating and significant body weight loss. In addition, many individuals also report engaging in excessive exercise. Previous research using the activity-based anorexia (ABA) model has implicated the hypothalamic proopiomelanocortin (POMC) system. Using the ABA model, Pomc mRNA has been shown to be transiently elevated in both male and female rodents undergoing ABA. In addition, the POMC peptide ß-endorphin appears to contribute to food anticipatory activity (FAA), a characteristic of ABA, as both deletion and antagonism of the µ opioid receptor (MOR) that ß-endorphin targets, results in decreased FAA. The role of ß-endorphin in reduced food intake in ABA is unknown and POMC neurons release multiple transmitters in addition to ß-endorphin. In the current study, we set out to determine whether targeted inhibition of POMC neurons themselves rather than their peptide products would lessen the severity of ABA. Inhibition of POMC neurons during ABA via chemogenetic Designer Receptors Exclusively Activated by Designer Drugs (DREADD) technology resulted in reduced FAA in both male and female mice with no significant changes in body weight or food intake. The selective reduction in FAA persisted even in the face of concurrent chemogenetic inhibition of additional cell types in the hypothalamic arcuate nucleus. The results suggest that POMC neurons could be contributing preferentially to excessive exercise habits in patients with AN. Furthermore, the results also suggest that metabolic control during ABA appears to take place via a POMC neuron-independent mechanism.

αN-Acetyl ß-Endorphin Is an Endogenous Ligand of σ1Rs That Regulates Mu-Opioid Receptor Signaling by Exchanging G Proteins for σ2Rs in σ1R Oligomers.

The opioid peptide ß-endorphin coexists in the pituitary and brain in its αN-acetylated form, which does not bind to opioid receptors. We now report that these neuropeptides exhibited opposite effects in in vivo paradigms, in which ligands of the sigma type 1 receptor (σ1R) displayed positive effects. Thus, αN-acetyl ß-Endorphin reduced vascular infarct caused by permanent unilateral middle cerebral artery occlusion and diminished the incidence of N-methyl-D-aspartate acid-promoted convulsive syndrome and mechanical allodynia caused by unilateral chronic constriction of the sciatic nerve. Moreover, αN-acetyl ß-Endorphin reduced the analgesia of morphine, ß-Endorphin and clonidine but enhanced that of DAMGO. All these effects were counteracted by ß-Endorphin and absent in σ1R-/- mice. We observed that σ1Rs negatively regulate mu-opioid receptor (MOR)-mediated morphine analgesia by binding and sequestering G proteins. In this scenario, ß-Endorphin promoted the exchange of σ2Rs by G proteins at σ1R oligomers and increased the regulation of G proteins by MORs. The opposite was observed for the αN-acetyl derivative, as σ1R oligomerization decreased and σ2R binding was favored, which displaced G proteins; thus, MOR-regulated transduction was reduced. Our findings suggest that the pharmacological ß-Endorphin-specific epsilon receptor is a σ1R-regulated MOR and that ß-Endorphin and αN-acetyl ß-Endorphin are endogenous ligands of σ1R.

Β-endorphin-immunoreactive perikarya appear to receive innervation from NPY-immunoreactive fiber varicosities in the human hypothalamus.

Morphological and pharmacological studies indicate that hypothalamic neuropeptide Y (NPY) and proopiomelanocortin (POMC) neurons communicate with each other in rats and regulate a variety of hypothalamic and extrahypothalamic functions. Indeed, electron microscopic studies revealed NPY-immunoreactive (NPI-IR) synapses on ß-endorphin-IR neurons in the hypothalamus. However, no such connections have been reported in humans. Here, we studied the putative NPY-ß-endorphin associations with high-resolution light microscopic double-label immunocytochemistry in the human hypothalamus. The majority of ß-endorphin-IR perikarya appear to be innervated by abutting NPY-IR fibers in the infundibulum/median eminence, receiving more than 6 contacts (38% of the counted neurons) or three to six contacts (42% of the counted neurons). The rest of the ß-endorphin-IR neurons are lightly innervated by NPY fibers (14%, one-three contacts) or do not receive any detectable NPY-IR axon varicosities (6% of the counted neurons). Since ß-endorphin is cleaved from the proopiomelanocortin (POMC) precursor, the NPY-ß-endorphin connections also provide the foundation for NPY-α-MSH and NPY-ACTH connections and their subsequent physiology. The close anatomical connections between NPY-IR nerve terminals and ß-endorphin-IR neurons reported herein may represent functional synapses and provide the foundation for NPY-stimulated ß-endorphin release. By interacting with ß-endorphin, NPY may have a more widespread regulatory capacity than acting alone on different neurotransmitter systems.

Effect of Chaihu-jia-Longgu-Muli decoction on withdrawal symptoms in rats with methamphetamine-induced conditioned place preference.

Traditional Chinese medicine detoxification prescription Chaihu-jia-Longgu-Muli decoction (CLMD) relieves depressive symptoms in patients withdrawing from methamphetamine. In the present study, we assessed the effects of CLMD on methamphetamine withdrawal in rats. A methamphetamine-intoxicated rat model was established. Rats were randomly divided into the control, model, high-dosage, medium-dosage, and low-dosage groups, receiving high, medium, and low doses of CLMD, respectively. Weekly body weight measurements revealed that rats treated with methamphetamine had the lowest body weight. The conditioned place preference (CPP) experiment revealed that methamphetamine-intoxicated rats stayed significantly longer in the drug-paired chamber than the control rats. However, after administering high-dosage CLMD, the amount of time the rats spent in the drug-paired chamber was significantly less than that of the model rats. Our open-field test revealed that the model group had lower crossing and rearing scores than the control group. Additionally, rats that received CLMD treatment exhibited higher crossing and rearing scores than the model rats. Striatal dopamine (DA), 5-hydroxytryptamine (5-HT), and endorphins (ß-EP) and serum interleukin (IL)-1α and IL-2 concentrations were estimated. Rats in the model group had lower striatal DA, 5-HT, and ß-EP and higher serum IL-1α and IL-2 concentrations than those in the control group. High-dosage CLMD administration significantly changed the concentrations of these molecules, such that they approached normal concentrations. In general, CLMD could prevent the development of methamphetamine-induced withdrawal symptoms in rats by increasing the DA, 5-HT, and ß-EP and lowering the IL-1α and IL-2 concentrations.