Differential effects of acute and prolonged morphine withdrawal on motivational and goal-directed control over reward-seeking behaviour.

Opioid addiction is a relapsing disorder marked by uncontrolled drug use and reduced interest in normally rewarding activities. The current study investigated the impact of spontaneous withdrawal from chronic morphine exposure on emotional, motivational and cognitive processes involved in regulating the pursuit and consumption of food rewards in male rats. In Experiment 1, rats experiencing acute morphine withdrawal lost weight and displayed somatic signs of drug dependence. However, hedonically driven sucrose consumption was significantly elevated, suggesting intact and potentially heightened reward processing. In Experiment 2, rats undergoing acute morphine withdrawal displayed reduced motivation when performing an effortful response for palatable food reward. Subsequent reward devaluation testing revealed that acute withdrawal disrupted their ability to exert flexible goal-directed control over reward seeking. Specifically, morphine-withdrawn rats were impaired in using current reward value to select actions both when relying on prior action-outcome learning and when given direct feedback about the consequences of their actions. In Experiment 3, rats tested after prolonged morphine withdrawal displayed heightened rather than diminished motivation for food rewards and retained their ability to engage in flexible goal-directed action selection. However, brief re-exposure to morphine was sufficient to impair motivation and disrupt goal-directed action selection, though in this case, rats were only impaired in using reward value to select actions in the presence of morphine-paired context cues and in the absence of response-contingent feedback. We suggest that these opioid-withdrawal induced deficits in motivation and goal-directed control may contribute to addiction by interfering with the pursuit of adaptive alternatives to drug use.

Model of negative affect induced by withdrawal from acute and chronic morphine administration in male mice.

Opioid use disorder (OUD) is a chronic relapsing disorder that is a major burden for the lives of affected individuals, and society as a whole. Opioid withdrawal is characterized by strong physical symptoms, along with signs of negative affect. Negative affect due to opioid withdrawal is a major obstacle to recovery and relapse prevention. The mechanisms behind negative affect due to either spontaneous or antagonist-precipitated opioid withdrawal are not well known, and more animal models need be developed. Here, we present behavioral models of negative affect upon naloxone-precipitated morphine withdrawal in adult male mice. Social, anxiety, and despair-like deficits were investigated following naloxone administration in mice receiving morphine under three dosing regimens; acute, chronic constant dose and chronic escalating doses. Social behaviour in the three-chamber social preference test was decreased following withdrawal from chronic and escalating but not acute morphine. Anxiety-like behaviour in the open field was increased for all three treatments. Despair-like behaviour was increased following withdrawal from chronic and escalating but not acute morphine. Altogether, these animal models will contribute to study behavioural and neuronal circuitries involved in the several negative affective signs characterizing OUD.

Deficient mitochondrial respiration in astrocytes impairs trace fear conditioning and increases naloxone-precipitated aversion in morphine-dependent mice.

Mitochondria are abundant in the fine processes of astrocytes, however, potential roles for astrocyte mitochondria remain poorly understood. In the present study, we performed a systematic examination of the effects of abnormal oxidative phosphorylation in astrocytes on several mouse behaviors. Impaired astrocyte oxidative phosphorylation was produced by astrocyte-specific deletion of the nuclear mitochondrial gene, Cox10, that encodes an accessory protein of complex IV, the protoheme:heme-O-farnesyl transferase. As expected, conditional deletion of the Cox10 gene in mice (cKO mice) significantly reduced expression of COX10 and Cytochrome c oxidase subunit I (MTCO1) of Complex IV, resulting in decreased oxidative phosphorylation without significantly affecting glycolysis. No effects of the deletion were observed on locomotor activity, anxiety-like behavior, nociception, or spontaneous alternation. Cox10 cKO female mice exhibited mildly impaired novel object recognition, while Cox10 cKO male mice were moderately deficient in trace fear conditioning. No group-related changes were observed in conditional place preference (CPP) that assessed effects of morphine on reward. In contrast to CPP, Cox10 cKO mice demonstrated significantly increased aversive behaviors produced by naloxone-precipitated withdrawal following chronic exposure to morphine, that is, jumping and avoidance behavior as assessed by conditional place aversion (CPA). Our study suggests that astrocyte oxidative phosphorylation may contribute to behaviors associated with greater cognitive load and/or aversive and stressful conditions.

The role of circTmeff-1 in incubation of context-induced morphine craving.

A progressive increase in drug craving following drug exposure is an important trigger of relapse. CircularRNAs (CircRNAs), key regulators of gene expression, play an important role in neurological diseases. However, the role of circRNAs in drug craving is unclear. In the present study, we trained mice to morphine conditioned place preference (CPP) and collected the nucleus accumbens (NAc) sections on abstinence day 1 (AD1) and day 14 (AD14) for RNA-sequencing. CircTmeff-1, which was highly expressed in the NAc core, was associated with incubation of context-induced morphine craving. The gain- and loss- of function showed that circTmeff-1 was a positive regulator of incubation. Simultaneously, the expression of miR-541-5p and miR-6934-3p were down-regulated in the NAc core during the incubation period. The dual luciferase reporter, RNA pulldown, and fluorescence insitu hybridization assays confirmed that miR-541-5p and miR-6934-3p bind to circTmeff-1 selectively. Furthermore, bioinformatics and western blot analysis suggested that vesicle-associated membrane protein 1 (VAMP1) and neurofascin (NFASC), both overlapping targets of miR-541-5p and miR-6934-3p, were highly expressed during incubation. Lastly, AAV-induced down-regulation of circTmeff-1 decreased VAMP1 and NFASC expression and incubation of morphine craving. These findings suggested that circTmeff-1, a novel circRNA, promotes incubation of context-induced morphine craving by sponging miR-541/miR-6934 in the NAc core. Thus, circTmeff-1 represents a potential therapeutic target for context-induced opioid craving, following prolonged abstinence.

Kratom Alkaloids, Natural and Semi-Synthetic, Show Less Physical Dependence and Ameliorate Opioid Withdrawal.

Chronic administration of opioids produces physical dependence and opioid-induced hyperalgesia. Users claim the Thai traditional tea "kratom" and component alkaloid mitragynine ameliorate opioid withdrawal without increased sensitivity to pain. Testing these claims, we assessed the combined kratom alkaloid extract (KAE) and two individual alkaloids, mitragynine (MG) and the analog mitragynine pseudoindoxyl (MP), evaluating their ability to produce physical dependence and induce hyperalgesia after chronic administration, and as treatments for withdrawal in morphine-dependent subjects. C57BL/6J mice (n = 10/drug) were administered repeated saline, or graded, escalating doses of morphine (intraperitoneal; i.p.), kratom alkaloid extract (orally, p.o.), mitragynine (p.o.), or MP (subcutaneously, s.c.) for 5 days. Mice treated chronically with morphine, KAE, or mitragynine demonstrated significant drug-induced hyperalgesia by day 5 in a 48 °C warm-water tail-withdrawal test. Mice were then administered naloxone (10 mg/kg, s.c.) and tested for opioid withdrawal signs. Kratom alkaloid extract and the two individual alkaloids demonstrated significantly fewer naloxone-precipitated withdrawal signs than morphine-treated mice. Additional C57BL/6J mice made physically dependent on morphine were then used to test the therapeutic potential of combined KAE, mitragynine, or MP given twice daily over the next 3 days at either a fixed dose or in graded, tapering descending doses. When administered naloxone, mice treated with KAE, mitragynine, or MP under either regimen demonstrated significantly fewer signs of precipitated withdrawal than control mice that continued to receive morphine. In conclusion, while retaining some liabilities, kratom, mitragynine, and mitragynine pseudoindoxyl produced significantly less physical dependence and ameliorated precipitated withdrawal in morphine-dependent animals, suggesting some clinical value.

Exogenous SO2 donor treatment impairs reconsolidation of drug reward memory in mice.

Substance-related and addictive disorders (SRADs) are characterized by compulsive drug use and recurrent relapse. The persistence of pathological drug-related memories indisputably contributes to a high propensity to relapse. Hence, strategies to disrupt reconsolidation of drug reward memory are currently being pursued as potential anti-relapse interventions. Sulfur dioxide (SO2), acting as a potential gaseous molecule, endogenously derives from sulfur amino acid and can exert significant neural regulatory effects. However, the role of SO2 in reconsolidation of drug memory has not been determined. In the present study, we used morphine- or cocaine-induced conditioned place preference (CPP) mouse models with retrieval to investigate the effects of exogenous SO2 donor treatment on reconsolidation of drug reward memory. We found that administration of SO2 donor immediately after the retrieval impaired the expression of morphine or cocaine CPP. Furthermore, the exogenous SO2 donor treatment 6 h post-retrieval or in the absence of retrieval had no effect on drug reward memory and the expression of CPP. SO2 itself did not produce aversive effects nor did it acutely block morphine CPP. Our results indicate that exogenous SO2 impairs reconsolidation of drug reward memory rather than inhibits the expression of drug reward memory. As such, SO2 holds potential for the treatment and prevention of SRADs and should be studied further.

Naloxone-induced conditioned place aversion score and extinction period are higher in C57BL/6J morphine-dependent mice than in Swiss: Role of HPA axis.

Intense associative memories develop between drug-paired contextual cues and the drug withdrawal associated aversive feeling. They have been suggested to contribute to the high rate of relapse. Our study was aimed to elucidate the involvement of hypothalamic-pituitary-adrenocortical (HPA) axis activity in the expression and extinction of aversive memory in Swiss and C57BL/6J (B6) mice. The animals were rendered dependent on morphine by i.p. injection of increasing doses of morphine (10-60 mg/kg). The negative state associated with naloxone (1 mg/kg s.c.) precipitated morphine withdrawal was examined by using conditioned place aversion (CPA) paradigm. B6 mice obtained a higher aversion score and took longer to extinguish the aversive memory than Swiss mice. In addition, corticosterone levels were increased after CPA expression. Moreover, corticosterone levels were decreased during CPA extinction in Swiss mice without changes in B6 mice. Pre-treatment with the selective CRF1 receptor antagonist CP-154,526 before naloxone, impaired morphine-withdrawal aversive memory acquisition and decreased the extinction period. CP-154,526 also antagonized the increased levels of corticosterone observed after CPA expression in Swiss mice, without any changes in B6 mice. These results indicate that HPA axis could be a critical factor governing opioid withdrawal memory storage and retrieval, but in a strain or stock-specific manner. The differences observed between Swiss and B6 mice suggest that the treatment of addictive disorders should consider different individual predisposition to associate the aversive learning with the context.

Effects of processed Aconiti tuber on the extinction and reinstatement of morphine-induced conditioned place preference in rats.

AIM OF THE STUDY: To investigate the effect of processed Aconiti tuber (PAT) administered during or after the time of conditioned place preference (CPP) training on the extinction and reinstatement of morphine-priming CPP in rats. The dynorphin level in rats' nucleus accumbens (NAc) is detected as a target of the Dynorphin/Kappa Opioid Receptor (KOR) system for the possible mechanism. MATERIALS AND METHODS: Eight groups of rats were subcutaneously (s.c.) injected with morphine (10mg/kg) (on days 2,4,6,8) or saline (1ml/kg) (on days 3,5,7,9) alternately for 8 days. Five groups, including groups (Mor + Water, Mor + PAT (1.0/3.0g/kg) (S) and Sal + PAT(1.0/3.0g/kg)), were orally given distilled water or PAT 1.0 or 3.0 g/kg daily on days 1-8 during CPP training while other three groups, including groups (Sal + Water and Mor + PAT (1.0/3.0g/kg)(P), were given distilled water or PAT daily from day 10 until CPP was extinct. Morphine 1mg/kg (s.c.) was used to reinstate the extinct CPP and the CPP scores were recorded. The dynorphin concentration in nucleus accumbens (NAc) was assayed by radioimmunoassay after the last CPP measurement. RESULTS: 1) The CPP extinction shortened in Mor + PAT (1.0/3.0 g/kg) (S) groups but extended in Mor + PAT (1.0/3.0 g/kg)(P) groups. 2) Morphine-priming CPP did not change either in Mor + PAT (1.0/3.0 g/kg) (S) or Mor + PAT (1.0/3.0 g/kg)(P) groups. 3) The dynorphin concentration in NAc increased either in Mor + PAT (1.0/3.0 g/kg)(S) or Mor + PAT (1.0/3.0 g/kg)(P) groups. CONCLUSIONS: 1) PAT shortened the extinction from morphine induced CPP when administrated before CPP acquisition, whereas it extended the extinction when administrated after CPP formation. 2) PAT administrated during or after CPP training did not affect morphine-priming reinstatement of morphine induced CPP. 3) Dynorphin/KOR system might be a target to regulate morphine-induced CPP extinction but not reinstatement.

Swimming exercise during morphine abstinence in parents-to-be attenuated morphine-induced conditioned place preference and locomotor sensitization only in male rat offspring.

This study was designed to examine the effects of swimming exercise during morphine abstinence in parents-to-be before mating on morphine-induced conditioned place preference (CPP) and locomotor sensitization in the pubertal male and female rat offspring. Male and female Wistar rats were injected with bi-daily doses (10 mg/kg, 12 h intervals) of morphine for 14 days. The exercising rats exposed to a regular swimming exercise (45 min/d, five days per a week) during 30 days of morphine abstinence before mating. Then, the pubertal male and female rat offspring were tested for morphine-induced CPP and locomotor sensitization (using the open field). The results showed that the pubertal male offspring of the morphine-abstinent parents-to-be exhibited an increase in CPP to morphine and locomotor activity after morphine challenge than the offspring from the control group. While, swimming exercise in morphine-abstinent parents-to-be decreased CPP score and locomotor activity in the pubertal male offspring than control offspring. Thus, exposure to swimming exercise in morphine-abstinent parents-to-be before mating may exert a protective effect against morphine-induced reward and locomotor sensitization in their pubertal offspring which may prevent the vulnerability of the first generation to drug abuse following opiate-addicted parents before mating.

Representações sociais de pessoas com câncer em cuidados paliativos sobre a morfina / Social representations of people with cancer in palliative care on morphine

INTRODUÇÃO: A dor se apresenta como sintoma frequente nas pessoas com câncer, e os opioides são os fármacos de escolha para o seu alívio. Dentre eles tem-se a morfina, que é um dos mais utilizados. OBJETIVOS: Descrever as representações sociais de pessoas com câncer em cuidados paliativos sobre a morfina; Analisar tais representações e suas implicações para a adesão ou não a esse opioide no tratamento/alívio da dor do câncer; Propor estratégias de cuidados afinadas às representações das pessoas com câncer que requerem o uso de morfina. MÉTODO: Pesquisa com abordagem qualitativa, do tipo descritiva e exploratória, realizada em uma instituição pública hospitalar. Os participantes foram pessoas com câncer atendidas no Ambulatório. Critérios de inclusão: maiores de 18 anos, com índice ≥ 50% na Escala de Karnofsky (KPS) e prescrição analgésica de morfina. Critérios de exclusão: presença de dor de moderada a intensa no momento da coleta de dados; e aqueles com comprometimento verbal, cognitivo e/ou psiquiátrico. Os dados foram coletados por questionário e entrevista semiestruturada. Os dados do questionário foram analisados por estatística descritiva simples e percentual, e aos conteúdos verbais aplicou-se a análise de conteúdo do tipo lexical, com o uso do software Alceste. Projeto aprovado pelos Comitês de Ética em Pesquisa da instituição proponente e cooperante, com pareceres no 3.296.128 e no 3.453.968, respectivamente. Todos os participantes assinaram o Termo de Consentimento Livre e Esclarecido. RESULTADOS: A média de idade foi de 54,7 anos; sexo feminino (69,7%); predomínio da religião evangélica (60,6%); 81,8% afirmaram seguir corretamente a prescrição da morfina; na Escala de Karnofsky, 45,5% apresentaram índice de 60%, evidenciando a necessidade de assistência ocasional, mas com capacidade de trabalhar; a intensidade da dor pela escala visual analógica variou entre leve (grau 1) e moderada (grau 4), ambas com 21,2% de respostas. O processamento dos dados no Alceste gerou dois blocos, o primeiro com a Classe 1, que expressa a representação medicamentosa do tratamento com a morfina e os fatores associados a esse tratamento; o segundo foi composto pelas Classes 2 e 3 e expressam as relações sociais envolvidas no contexto do tratamento, o vínculo da pessoa que usa morfina com o mundo que a cerca, bem como a relação estabelecida com esse medicamento, o conhecimento sobre a morfina e as atitudes adotadas diante desse uso. Houve ambiguidade nas representações da morfina, colocando-a entre a dor e o temor, pois a indicam como um importante recurso para alívio/tratamento da dor do câncer, mas sinalizam que também pode trazer repercussões negativas associadas aos seus efeitos. CONSIDERAÇÕES FINAIS: Apesar de haver aderência dos pacientes à morfina, a opiofobia ainda precisa ser combatida por meio de estratégias que façam circular informações que possam reconstruir representações sobre a morfina e seu uso terapêutico. A educação terapêutica por meio da atuação de equipe multidisciplinar se destaca como uma boa estratégia de difusão de informações seguras sobre o uso de opioides.

INTRODUCTION: Pain is a frequent symptom in people with cancer, and opioids are the drug of choice for its relief, including morphine, which is one of the most used. OBJECTIVES: To describe the social representations of people with cancer in palliative care about morphine; To analyze such representations and their implications for adherence or not to this opioid in the cancer pain treatment/relief; To propose care strategies related to the representations of people with cancer that require the use of morphine. METHOD: Descriptive and exploratory research with a qualitative approach, carried out in a public hospital. The participants were people with cancer treated at the clinic. Inclusion criteria: over 18 years old, with an index ≥ 50% on the Karnofsky Scale (KPS) and morphine as an analgesic medication prescribed. Exclusion criteria: presence of moderate to severe pain at the time of data collection; and those with verbal, cognitive and/or psychiatric impairment. Data was collected by questionnaire and semi-structured interview. The questionnaire data were analyzed using simple and percentage descriptive statistics, and the verbal content was analyzed using lexical content with the Alceste software. Project approved by the Research Ethics Committees of the proposing and cooperating institution, with opinions No. 3,296,128 and 3,453,968, respectively. All participants signed the Free and Informed Consent Form. RESULTS: The average age was 54.7 years; female gender (69.7%); prevalence of the evangelical religion (60.6%); 81.8% said they correctly followed the prescription of morphine; on the Karnofsky Scale, 45.5% had an index of 60% showing the need for occasional assistance, but with the ability to work; pain intensity by visual analog scale ranged from mild (grade 1) to moderate (grade 4), both with 21.2% responses. The data processing at Alceste generated two blocks, the first with class 1, which expresses the drug representation of the treatment with morphine and the factors associated with that treatment; the second was composed of Classes 2 and 3 and expresses the social relationships involved in the context of the treatment, the bond of the person who uses morphine with the world around her, as well as the relationship established with this medicine, the knowledge about the morphine and the attitudes towards the use of the medicine. There was ambiguity in the representations of morphine, placing it between pain and fear, as they indicate it as an important resource to relieve/treat cancer pain, but it can also bring negative repercussions associated with its effects. FINAL CONSIDERATIONS: Despite patient adherence to morphine, opiophobia still needs to be fought through strategies that spread information that can reconstruct representations about morphine and its therapeutic use. Therapeutic education through the work of a multidisciplinary team stands out as a good strategy to disseminate safe information about the use of opioids.

INTRODUCCIÓN: El dolor es un síntoma frecuente en las personas con cáncer y los opioides son los fármacos de elección para su alivio; entre ellos está la morfina, que es uno de los más utilizados. OBJETIVOS: Describir las representaciones sociales de las personas con cáncer en cuidados paliativos sobre la morfina; analizar tales representaciones y sus implicaciones para la adherencia o no a este opioide en el tratamiento / alivio del dolor producido por el cáncer; Proponer estrategias de cuidados en sintonía con las representaciones de las personas con cáncer que requieren el uso de morfina. MÉTODO: Investigación con enfoque cualitativo, descriptivo y exploratorio, realizada en un hospital público. Los participantes fueron personas con cáncer tratadas en modalidad ambulatorial. Criterios de inclusión: mayores de 18 años, con índice ≥ 50% en la Escala de Karnofsky (KPS) y prescripción analgésica de morfina. Criterios de exclusión: presencia de dolor de moderado a intenso en el momento de la recogida de datos; y aquellos con comprometimiento verbal, cognitivo y/o psiquiátrico. Datos recogidos mediante cuestionario y entrevista semiestructurada. Los datos del cuestionario se analizaron mediante estadística descriptiva simple y porcentual y el contenido verbal fue sometido a análisis de contenido de tipo lexical, utilizándose el software Alceste. Proyecto aprobado por los Comités de Ética en Investigación de la institución proponente y cooperante, con dictámenes núm. 3.296.128 y 3.453.968, respectivamente. Todos los participantes firmaron una declaración de Consentimiento Libre e Informado. RESULTADOS: La edad promedio fue de 54,7 años; sexo femenino (69,7%); predominio de la religión evangélica (60,6%). El 81,8% afirmó que seguía correctamente la prescripción de morfina. En la Escala de Karnofsky, el 45,5% presentó un índice del 60%, lo que indica la necesidad de asistencia ocasional, pero con capacidad para trabajar. La intensidad del dolor, según la escala visual analógica (EVA), varió de leve (grado 1) a moderado (grado 4), ambos con 21,2% de respuestas. El procesamiento de datos en el software Alceste generó dos bloques: el primero con la Clase 1, que expresa la representación farmacológica del tratamiento con morfina y los factores asociados a ese tratamiento; el segundo estaba compuesto por las Clases 2 y 3 y expresa las relaciones sociales involucradas en el contexto del tratamiento, el vínculo de la persona que usa morfina con el mundo que la rodea, así como la relación que establece con ese medicamento, el conocimiento sobre la morfina y las actitudes adoptadas con respecto a su uso. Hubo ambigüedad en las representaciones de la morfina, pues se la situó entre el dolor y el miedo: los participantes la señalaron como un recurso importante para el alivio/tratamiento del dolor oncológico, pero también mencionaron la posibilidad de repercusiones negativas asociadas a sus efectos. CONSIDERACIONES FINALES: A pesar de la adherencia de los pacientes a la morfina, la opiofobia aún debe combatirse mediante estrategias que hagan circular información que permita la reconstrucción de las representaciones sobre la morfina y su uso terapéutico. La educación terapéutica mediante la actuación de un equipo multidisciplinario descolla como una buena estrategia para difundir información segura sobre el uso de opioides.

Lyophilized Kratom Tea as a Therapeutic Option for Opioid Dependence.

BACKGROUND: Made as a tea, the Thai traditional drug "kratom" reportedly possesses pharmacological actions that include both a coca-like stimulant effect and opium-like depressant effect. Kratom has been used as a substitute for opium in physically-dependent subjects. The objective of this study was to evaluate the antinociception, somatic and physical dependence produced by kratom tea, and then assess if the tea ameliorated withdrawal in opioid physically-dependent subjects. METHODS: Lyophilized kratom tea (LKT) was evaluated in C57BL/6J and opioid receptor knockout mice after oral administration. Antinociceptive activity was measured in the 55 °C warm-water tail-withdrawal assay. Potential locomotor impairment, respiratory depression and locomotor hyperlocomotion, and place preference induced by oral LKT were assessed in the rotarod, Comprehensive Lab Animal Monitoring System, and conditioned place preference assays, respectively. Naloxone-precipitated withdrawal was used to determine potential physical dependence in mice repeatedly treated with saline or escalating doses of morphine or LKT, and LKT amelioration of morphine withdrawal. Data were analyzed using one- and two-way ANOVA. RESULTS: Oral administration of LKT resulted in dose-dependent antinociception (≥1 g/kg, p.o.) absent in mice lacking the mu-opioid receptor (MOR) and reduced in mice lacking the kappa-opioid receptor. These doses of LKT did not alter coordinated locomotion or induce conditioned place preference, and only briefly reduced respiration. Repeated administration of LKT did not produce physical dependence, but significantly decreased naloxone-precipitated withdrawal in morphine dependent mice. CONCLUSIONS: The present study confirms the MOR agonist activity and therapeutic effect of LKT for the treatment of pain and opioid physical dependence.

BDNF and p-GSK3ß in the hippocampus mediate the impairment of delay-based decision making in morphine-dependent rats.

It has been shown that morphine addiction impairs cognitive brain functions. However, there is no document to consider the effect of morphine dependency and its withdrawal on cost-benefit decision making and its molecular pathways. The present study aimed to evaluate the influences of morphine dependency and its withdrawal on delay-based decision making and the BDNF, p-GSK3ß, and p-CREB levels during the decision making in the hippocampus. Different groups of rats were trained in a T-maze with the delay-based cost-benefit decision-making paradigm. After that, the animals were dependent on morphine, and the percentage of the high reward preference was evaluated. After behavioral tests, BDNF level, p-GSK3ß/GSK3ß ratio, and p-CREB/CREB ratio in the hippocampus measured by Western blot analysis. The gathered data showed that level of BDNF enhanced while p-GSK3ß/GSK3ß ratio and p-CREB/CREB ratio in the hippocampus did not change during delay-based decision making. In morphine-dependent rats, the p-GSK3ß/GSK3ß ratio increased, the BDNF level and p-CREB/CREB ratio did not change in the decision making procedure. After withdrawal from morphine, the BDNF level raised while p-GSK3ß/GSK3ß ratio and p-CREB/CREB ratio did not change compared to the addiction group. The data declared that BDNF in the hippocampus has a critical role in delay-based decision making. Change in p-CREB in the hippocampus is not related to decision making in normal and morphine-dependent rats. P-GSK3 in the hippocampus is not involved in the decision making in normal rats, but during decision making in morphine-dependent rats, its level increased.

NPY alterations induced by chronic morphine exposure affect the maintenance and reinstatement of morphine conditioned place preference.

Opioid addiction is a brain disease that severely harms society and personal health. Although the tremendous numbers of patients worldwide and emerged negative events, effective treatments for opioid addiction are still lacking. Neuropeptide Y (NPY) is one of the main orexigenic peptides that play vital roles in food intake and energy metabolism. However, increasing evidence indicates that NPY may have great potential in mediating reward effects and drug dependence. In the present study, we assessed the expression changes of NPY in the nucleus accumbens at different timepoints following morphine conditioned place preference (CPP) and investigated the functional importance of potential NPY changes. Our results showed that NPY expression significantly decreased in the nucleus accumbens shell (AcbSh) immediately after chronic morphine exposure. Subsequently, it increased rapidly at first and then gradually returned to normal levels. Further data indicated that these NPY changes were involved in morphine reward memory, demonstrated by a reduction in the extinction period after blocking of the Y5 receptor by L-152,804 in the AcbSh and a prolonged duration of the extinction period following the application of NPY. More importantly, the additional results revealed that L-152,804 also remarkably suppressed the reinstatement of morphine CPP. Together, our results indicate that a complicated plasticity of the NPY pathway in AcbSh occurs following morphine CPP, and this plasticity plays an important role in modulating morphine reward memory. These findings may enhance our understanding of the role of the NPY system in opioid addiction and indicate a promising target for opioid addiction treatment.

Oleoyl alanine (HU595): a stable monomethylated oleoyl glycine interferes with acute naloxone precipitated morphine withdrawal in male rats.

RATIONALE: Oleoyl glycine, a little studied fatty acid amide similar in structure to anandamide, interferes with nicotine addiction in mice and acute naloxone-precipitated morphine withdrawal (MWD) in rats. Because endogenous oleoyl glycine is subject to rapid enzymatic deactivation, we evaluated the potential of more stable analogs to interfere with opiate withdrawal. OBJECTIVES: The potential of monomethylated oleoyl glycine (oleoyl alanine, HU595) to interfere with somatic and aversive effects of acute naloxone-precipitated MWD, its duration, and mechanism of action was assessed in male Sprague Dawley rats. The potential of dimethylated oleoyl glycine (HU596) to interfere with the aversive effects of naloxone-precipitated MWD was also investigated. RESULTS: Oleoyl alanine (HU595) interfered with somatic and aversive effects produced by naloxone-precipitated MWD at equivalent doses (1 and 5 mg/kg, i.p.) as we have reported for oleoyl glycine; however, oleoyl alanine produced a longer lasting (60 min) interference, yet did not produce rewarding or aversive effects on its own and did not modify locomotor activity. HU596 was not effective. The interference with aversive effects of naloxone-precipitated MWD by oleoyl alanine was prevented by both a PPARα antagonist and a CB1 receptor antagonist. Accordingly, the compound was found to inhibit FAAH and activate PPARα in vitro. Finally, oleoyl alanine also reduced acute naloxone-precipitated MWD anhedonia, as measured by decreased saccharin preference. CONCLUSIONS: Oleoyl alanine (also an endogenous fatty acid) may be a more stable and effective treatment for opiate withdrawal than oleoyl glycine.

Age- and sex-related changes in the severity of physical and psychological dependence in morphine-dependent rats.

Gender- and age-dependent effects on the severity of morphine dependence are still controversial. The aim of this study was to investigate the effects of age and sex on the severity of physical and psychological dependence in morphine-dependent rats. The adult/aged male and female Wistar rats were chronically treated with bi-daily doses (10 mg/kg, at 12 h intervals) of morphine for 14 days. Then, rats were tested for the severity of physical dependence on morphine (spontaneous withdrawal signs), anxiety-like (the elevated plus maze), depressive-like (sucrose preference test) and grooming behaviors after spontaneous morphine withdrawal. We found that the morphine withdrawal signs decreased after 3 and 7 days of withdrawal in female and male rats respectively, while there was no significant difference in overall dependence severity between the two sexes or ages. Also, we found that the withdrawal of morphine led to increased anxiety, depression and obsessive-compulsive behavior in the D (dependent)/Adult male and female rats. Also, the D/aged female and male rats exhibited a reduction in depressive-like behavior than the D/Adult rats. Moreover, the D/female rats exhibited a decreased obsessive-compulsive behavior in both age groups than male rats. We conclude that age has no effect on the duration of withdrawal from morphine and overall dependence severity. While, the duration of withdrawal from morphine was lower in female than male rats. Our results showed a sex difference on the duration of morphine withdrawal and an age difference in the expression of psychological dependence on morphine. Thus, therapeutic strategies may be different for opiate-dependent individuals in physical and psychological dimensions.

Mediterranean X Western based diets: Opposite influences on opioid reinstatement.

Opioids are addictive drugs, whose misuse evoke withdrawal and relapse. Mediterranean-based diet (MBD) is rich in n-3 polyunsaturated fatty acids (PUFA), while Western based diets (WBDs) contain saturated fatty acids including interesterified fat (IF) and palm oil (PO), influencing neural functions. We compared MBD and WBDs on morphine-induced addiction parameters. Rats fed with MBD (chow plus 20% soybean- and fish-oil- n-6/n-3 PUFA 1:1) or WBD (WBD- PO or WBD-IF: chow plus 20% of palm oil or interesterified fat, respectively; high n-6/n-3 PUFA ratio) were exposed to morphine in conditioned place preference (CPP) paradigm. Anxiety-like behavior, locomotion and thermal sensitivity were evaluated during withdrawal. After morphine-CPP extinction, animals were challenged to morphine-reinstatement to induce relapse. All groups showed morphine-CPP, WBDs favored anxiety-like behaviors per se, locomotor sensitization and thermal hipersensitivity during withdrawal, resulting in increased morphine-reinstatement in comparison to MBD, which did not show relapse. WBDs increased glucocorticoid receptor immunoreactivity in the pre-frontal cortex, increasing corticosterone (CORT) and adrenocorticotrophic hormone (ACTH) per se and after morphine-reinstatement. In the nucleus accumbens, WBDs increased dopamine transporter (DAT) and dopamine receptor-2 (D2R) immunoreactivity and decreased dopamine receptor-1 (D1R). These findings indicate that WBDs facilitate morphine-reinstatement, unlike MBD, preserving the DA system mesolimbic neuroplasticity.

Morphine Dependence is Attenuated by Treatment of 3,4,5-Trimethoxy Cinnamic Acid in Mice and Rats.

The effect of 3, 4, 5-trimethoxy cinnamic acid (TMCA) against morphine-induced dependence in mice and rats was investigated. Mice were pretreated with TMCA and then morphine was injected intraperitoneally; whereas rats were treated with TMCA (i.p.) and infused with morphine into the lateral ventricle of brain. Naloxone-induced morphine withdrawal syndrome and conditioned place preference test were performed. Moreover, western blotting and immunohistochemistry were used to measure protein expressions. Number of naloxone-precipitated jumps and conditioned place preference score in mice were attenuated by TMCA. Likewise, TMCA attenuated morphine dependent behavioral patterns such as diarrhea, grooming, penis licking, rearing, teeth chattering, and vocalization in rats. Moreover, the expression levels of pNR1and pERK in the frontal cortex of mice and cultured cortical neurons were diminished by TMCA. In the striatum, pERK expression was attenuated despite unaltered expression of pNR1 and NR1. Interestingly, morphine-induced elevations of FosB/ΔFosB+ cells were suppressed by TMCA (50, 100 mg/kg) in the nucleus accumbens sub-shell region of mice. In conclusion, TMCA could be considered as potential therapeutic agent against morphine-induced dependence.

Selective dopamine D3 receptor antagonist YQA14 inhibits morphine-induced behavioral sensitization in wild type, but not in dopamine D3 receptor knockout mice.

Increasing preclinical evidence demonstrates that dopamine D3 receptor (D3R) antagonists are a potential option for the treatment of drug addiction. The reinstatement of the addiction can be triggered by environmental stimuli that acquire motivational salience through repeated associations with the drug's effects. YQA14 is a novel D3R antagonist that has exhibited pharmacotherapeutic efficacy in reducing cocaine and amphetamine reward and relapse to drug seeking in mice. In this study we investigated the effects of YQA14 on morphine-induced context-specific locomotor sensitization in mice. We showed that repeated injection of YQA14 (6.25-25 mg/kg every day ip) prior to morphine (10 mg/kg every day sc) not only inhibited the acquisition, but also significantly attenuated the expression of morphine-induced locomotor sensitization. Furthermore, in the expression phase, one single injection of YQA14 (6.25-25 mg/kg, ip) dose-dependently inhibited the expression of morphine-induced behavioral sensitization. Moreover, YQA14 inhibited the expression of morphine-induced behavioral sensitization in wild mice (WT), but not in D3R knockout (D3R-/-) mice in the expression phase. In addition, D3R-/- mice also displayed the reduction in the expression phase compared with WT mice. In summary, this study demonstrates that blockade or knockout of the D3R inhibits morphine-induced behavior sensitization, suggesting that D3R plays an important role in the pathogenesis and etiology of morphine addiction, and it might be a potential target for clinical management of opioid addiction.

The gut microbiota mediates reward and sensory responses associated with regimen-selective morphine dependence.

Opioid use for long-term pain management is limited by adverse side effects, such as hyperalgesia and negative affect. Neuroinflammation in the brain and spinal cord is a contributing factor to the development of symptoms associated with chronic opioid use. Recent studies have described a link between neuroinflammation and behavior that is mediated by a gut-brain signaling axis, where alterations in indigenous gut bacteria contribute to several inflammation-related psychopathologies. As opioid receptors are highly expressed within the digestive tract and opioids influence gut motility, we hypothesized that systemic opioid treatment will impact the composition of the gut microbiota. Here, we explored how opioid treatments, and cessation, impacts the mouse gut microbiome and whether opioid-induced changes in the gut microbiota influences inflammation-driven hyperalgesia and impaired reward behavior. Male C57Bl6/J mice were treated with either intermittent or sustained morphine. Using 16S rDNA sequencing, we describe changes in gut microbiota composition following different morphine regimens. Manipulation of the gut microbiome was used to assess the causal relationship between the gut microbiome and opioid-dependent behaviors. Intermittent, but not sustained, morphine treatment was associated with microglial activation, hyperalgesia, and impaired reward response. Depletion of the gut microbiota via antibiotic treatment surprisingly recapitulated neuroinflammation and sequelae, including reduced opioid analgesic potency and impaired cocaine reward following intermittent morphine treatment. Colonization of antibiotic-treated mice with a control microbiota restored microglial activation state and behaviors. Our findings suggest that differing opioid regimens uniquely influence the gut microbiome that is causally related to behaviors associated with opioid dependence.

The effect of amitriptyline administration on pain-related behaviors in morphine-dependent rats: Hypoalgesia or hyperalgesia?

Pain control in opioid-dependent individuals is a clinical complication. The present study investigated the effects of different doses of amitriptyline in the three stages of the formalin test in morphine-dependent rats (MDRs). Morphine dependency was induced using the oral method, and then, amitriptyline-induced antinociceptive effects were measured at 4 doses (2.5, 5, 10, and 20 mg/kg) and compared with the control group in a formalin-based model of pain. There was no observed antinociceptive effect in the MDRs and morphine-naïve rats (MNRs) in phase I. In the interphase, amitriptyline induced pain suppression at doses of 5 and 20 mg/kg. In phase II, at doses of 5, 10, and 20 mg/kg, the hypoalgesic effect on pain-related behaviors was seen in the MNRs. In MDRs, amitriptyline at doses of 2.5 and 5 mg/kg caused the hyperalgesic effect, whereas at 10 and 20 mg/kg doses, it induced a hypoalgesic effect. A significant attenuation was observed in the latency to fall from the accelerating rotarod at doses of 10 and 20 mg/kg in the MDRs, and at a dose of 20 mg/kg in the MNRs. Data showed that amitriptyline dose-dependently induced paradoxical hypo- and hyper-algesic effects in MDRs.