BDNF is a negative modulator of morphine action

BACLOFEN PREVENTS MORPHINE REWARDING EFFECTS AND ASSOCIATED BIOCHEMICAL ALTERATIONS IN MALE AND FEMALE MICE

Previous studies from our laboratory have shown sex differences in the behavioral, molecular, and neurochemical manifestations of morphine withdrawal and they were related to an increased sensitivity to morphine effects in males. In addition, we observed an interaction between the GABAergic and opioid systems that could also be sex-dependent. Baclofen, a GABAB receptor agonist, prevented the somatic expression and the molecular and neurochemical changes induced by morphine withdrawal syndrome in mice. On the contrary, little is known about baclofen effects in the rewarding properties of morphine in male and female mice. The present study aimed to explore the effect of baclofen (1, 2 and 3 mg/kg, i.p.) pretreatment in the rewarding effects induced by morphine (7 mg/kg, s.c.) and its effect on c-Fos and brain-derived neurotrophic factor (BDNF) expression induced by the rewarding properties of morphine in prepubertal male and female mice. Baclofen (2 mg/kg) pretreatment prevented the rewarding effects of morphine only in male mice, while baclofen (3 mg/kg) reduced these effects in both sexes. Moreover, the rewarding effects of morphine were associated with a decrease of BDNF and c-Fos expression cingulate cortex, nucleus accumbens shell, cornu ammonis 1 (CA1), and cornu ammonis 3 (CA3) areas of the hippocampus only in male mice. In addition, baclofen pretreatment prevented these changes in BDNF, but not in c-Fos expression. In conclusion, our results show that GABAB receptors have a regulatory role in the rewarding effects of morphine that could be of interest for a potential future therapeutic application in opioid use disorders.

The single-cell opioid responses in the context of HIV (SCORCH) consortium

Substance use disorders (SUD) and drug addiction are major threats to public health, impacting not only the millions of individuals struggling with SUD, but also surrounding families and communities. One of the seminal challenges in treating and studying addiction in human populations is the high prevalence of co-morbid conditions, including an increased risk of contracting a human immunodeficiency virus (HIV) infection. Of the ~15 million people who inject drugs globally, 17% are persons with HIV. Conversely, HIV is a risk factor for SUD because chronic pain syndromes, often encountered in persons with HIV, can lead to an increased use of opioid pain medications that in turn can increase the risk for opioid addiction. We hypothesize that SUD and HIV exert shared effects on brain cell types, including adaptations related to neuroplasticity, neurodegeneration, and neuroinflammation. Basic research is needed to refine our understanding of these affected cell types and adaptations. Studying the effects of SUD in the context of HIV at the single-cell level represents a compelling strategy to understand the reciprocal interactions among both conditions, made feasible by the availability of large, extensively-phenotyped human brain tissue collections that have been amassed by the Neuro-HIV research community. In addition, sophisticated animal models that have been developed for both conditions provide a means to precisely evaluate specific exposures and stages of disease. We propose that single-cell genomics is a uniquely powerful technology to characterize the effects of SUD and HIV in the brain, integrating data from human cohorts and animal models. We have formed the Single-Cell Opioid Responses in the Context of HIV (SCORCH) consortium to carry out this strategy.

Transcriptional signatures of fentanyl use in the mouse ventral tegmental area

Synthetic opioids such as fentanyl contribute to the vast majority of opioid-related overdose deaths, but fentanyl use remains broadly understudied. Like other substances with misuse potential, opioids cause lasting molecular adaptations to brain reward circuits, including neurons in the ventral tegmental area (VTA). The VTA contains numerous cell types that play diverse roles in opioid use and relapse; however, it is unknown how fentanyl experience alters the transcriptional landscape in specific subtypes. Here, we performed single nuclei RNA sequencing to study transcriptional programs in fentanyl-experienced mice. Male and female C57/BL6 mice self-administered intravenous fentanyl (1.5 μg/kg/infusion) or saline for 10 days. After 24 h abstinence, VTA nuclei were isolated and prepared for sequencing on the 10× platform. We identified different patterns of gene expression across cell types. In dopamine neurons, we found enrichment of genes involved in growth hormone signalling. In dopamine-glutamate-GABA combinatorial neurons, and some GABA neurons, we found enrichment of genes involved in Pi3k-Akt signalling. In glutamate neurons, we found enrichment of genes involved in cholinergic signalling. We identified transcriptional regulators for the differentially expressed genes in each neuron cluster, including downregulated transcriptional repressor Bcl6, and upregulated transcription factor Tcf4. We also compared the fentanyl-induced gene expression changes identified in mouse VTA with a published rat dataset in bulk VTA, and found overlap in genes related to GABAergic signalling and extracellular matrix interaction. Together, we provide a comprehensive picture of how fentanyl self-administration alters the transcriptional landscape of the mouse VTA that serves as the foundation for future mechanistic studies.

Transcriptional signatures of fentanyl use in the mouse ventral tegmental area

Synthetic opioids such as fentanyl contribute to the vast majority of opioid-related overdose deaths, but fentanyl use remains broadly understudied. Like other substances with misuse potential, opioids cause lasting molecular adaptations to brain reward circuits, including neurons in the ventral tegmental area (VTA). The VTA contains numerous cell types that play diverse roles in opioid use and relapse, however it is unknown how fentanyl experience alters the transcriptional landscape in specific subtypes. Here, we performed single nuclei RNA sequencing to study transcriptional programs in fentanyl experienced mice. Male and female C57/BL6 mice self-administered intravenous fentanyl (1.5 µg/kg/infusion) or saline for 10 days. After 24 hr abstinence, VTA nuclei were isolated and prepared for sequencing on the 10X platform. We identified different patterns of gene expression across cell types. In dopamine neurons, we found enrichment of genes involved in growth hormone signaling. In dopamine-glutamate-GABA combinatorial neurons, and some GABA neurons, we found enrichment of genes involved in Pi3k-Akt signaling. In glutamate neurons, we found enrichment of genes involved in cholinergic signaling. We identified transcriptional regulators for the differentially expressed genes in each neuron cluster, including downregulation of transcriptional repressor Bcl6, and upregulation of Wnt signaling partner Tcf4. We also compared the fentanyl-induced gene expression changes identified in mouse VTA with a published rat dataset in bulk VTA, and found overlap in genes related to GABAergic signaling and extracellular matrix interaction. Together, we provide a comprehensive picture of how fentanyl self-administration alters the transcriptional landscape of the mouse VTA, that serves for the foundation for future mechanistic studies.

Main targets of ibogaine and noribogaine associated with its putative anti-addictive effects: A mechanistic overview

BACKGROUND

There is a growing interest in studying ibogaine (IBO) as a potential treatment for substance use disorders (SUDs). However, its clinical use has been hindered for mainly two reasons: First, the lack of randomized, controlled studies informing about its safety and efficacy. And second, IBO's mechanisms of action remain obscure. It has been challenging to elucidate a predominant mechanism of action responsible for its anti-addictive effects.

OBJECTIVE

To describe the main targets of IBO and its main metabolite, noribogaine (NOR), in relation to their putative anti-addictive effects, reviewing the updated literature available.

METHODS

A comprehensive search involving MEDLINE and Google Scholar was undertaken, selecting papers published until July 2022. The inclusion criteria were both theoretical and experimental studies about the pharmacology of IBO. Additional publications were identified in the references of the initial papers.

RESULTS

IBO and its main metabolite, NOR, can modulate several targets associated with SUDs. Instead of identifying key targets, the action of IBO should be understood as a complex modulation of multiple receptor systems, leading to potential synergies. The elucidation of IBO's pharmacology could be enhanced through the application of methodologies rooted in the polypharmacology paradigm. Such approaches possess the capability to describe multifaceted patterns within multi-target drugs.

CONCLUSION

IBO displays complex effects through multiple targets. The information detailed here should guide future research on both mechanistic and therapeutic studies.

Addictive drugs modify neurogenesis, synaptogenesis and synaptic plasticity to impair memory formation through neurotransmitter imbalances and signaling dysfunction

Drug abuse changes neurophysiological functions at multiple cellular and molecular levels in the addicted brain. Well-supported scientific evidence suggests that drugs negatively affect memory formation, decision-making and inhibition, and emotional and cognitive behaviors. The mesocorticolimbic brain regions are involved in reward-related learning and habitual drug-seeking/taking behaviors to develop physiological and psychological dependence on the drugs. This review highlights the importance of specific drug-induced chemical imbalances resulting in memory impairment through various neurotransmitter receptor-mediated signaling pathways. The mesocorticolimbic modifications in the expression levels of brain-derived neurotrophic factor (BDNF) and the cAMP-response element binding protein (CREB) impair reward-related memory formation following drug abuse. The contributions of protein kinases and microRNAs (miRNAs), along with the transcriptional and epigenetic regulation have also been considered in memory impairment underlying drug addiction. Overall, we integrate the research on various types of drug-induced memory impairment in distinguished brain regions and provide a comprehensive review with clinical implications addressing the upcoming studies.

HCN channel inhibitor induces ketamine-like rapid and sustained antidepressant effects in chronic social defeat stress model

Repeated, long-term (weeks to months) exposure to standard antidepressant medications is required to achieve treatment efficacy. In contrast, acute ketamine quickly improves mood for an extended time. Recent work implicates that hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are involved in mediating ketamine's antidepressant effects. In this study, we directly targeted HCN channels and achieved ketamine-like rapid and sustained antidepressant efficacy. Our in vitro electrophysiological recordings first showed that HCN inhibitor DK-AH 269 (also called cilobradine) decreased the pathological HCN-mediated current (Ih) and abnormal hyperactivity of ventral tegmental area (VTA) dopamine (DA) neurons in a depressive-like model produced by chronic social defeat stress (CSDS). Our in vivo studies further showed that acute intra-VTA or acute systemic administration of DK-AH 269 normalized social behavior and rescued sucrose preference in CSDS-susceptible mice. The single-dose of DK-AH 269, both by intra-VTA microinfusion and intraperitoneal (ip) approaches, could produce an extended 13-day duration of antidepressant-like efficacy. Animals treated with acute DK-AH 269 spent less time immobile than vehicle-treated mice during forced swim test. A social behavioral reversal lasted up to 13 days following the acute DK-AH 269 ip injection, and this rapid and sustained antidepressant-like response is paralleled with a single-dose treatment of ketamine. This study provides a novel ion channel target for acutely acting, long-lasting antidepressant-like effects.

Effects of brain-derived neurotrophic factor and adeno-associated viral vector on morphine-induced condition through target concentration changes in the ventral tegmental area and nucleus accumbens

Morphine remains the standard analgesic for severe pain. However, the clinical use of morphine is limited by the innate tendency of opiates to become addictive. Brain-derived neurotrophic factor (BDNF) is a growth factor that is protective against many mental disorders. This study aimed to evaluate the protective function of BDNF on morphine addiction based on the behavioural sensitisation (BS) model and assess potential changes in downstream molecular tropomyosin-related kinase receptor B (TrkB) and cyclic adenosine monophosphate response element binding protein (CREB) expression caused by overexpression of BDNF. We divided 64 male C57BL/6 J mice into saline, morphine, morphine plus adeno-associated viral vector (AAV), and morphine plus BDNF groups. After administering the treatments, behavioural tests were conducted during the development and expression phases of BS, followed by a western blot analysis. All data were analysed by one- or two-way analysis of variance. The overexpression of BDNF in the ventral tegmental area (VTA) caused by BDNF-AAV injection decreased the total distance of locomotion in mice who underwent morphine-induced BS and increased the concentrations of BDNF, TrkB, and CREB in the VTA and nucleus accumbens (NAc). BDNF exerts protective effects against morphine-induced BS by altering target gene expression in the VTA and NAc.

Several reasons why ketamine as a neuroplastic agent may have failed to prevent postoperative delirium: Implications for future protocols

Ketamine exerts anti-inflammatory, neuroprotective and neuroplastic activity, therefore it may counteract the neurotoxic processes underlying postoperative delirium. However, the majority of studies in this field failed. We identified several pharmacological reasons why these studies may have failed, together with suggestions of how to remediate them. Among them, the interaction with intravenous general anesthetics exerting the opposite effect on GABA interneurons than ketamine may be of principal importance. We suggest biomarkers which may elucidate the influence of this interaction on the different steps of neuroplastic pathways. We hypothesize that administering ketamine before or after general anesthesia could both prevent the interactions and strengthen the effect of ketamine by timing surgery within the climax of ketamine-induced neuroplastic changes or by stabilizing AMPA receptors. It is vital to deal with these questions because the protocols of ongoing studies are based again on the administration of ketamine during general anesthesia (the major identified pitfall).

Mu-opioid receptor and receptor tyrosine kinase crosstalk: Implications in mechanisms of opioid tolerance, reduced analgesia to neuropathic pain, dependence, and reward

Despite the prevalence of opioid misuse, opioids remain the frontline treatment regimen for severe pain. However, opioid safety is hampered by side-effects such as analgesic tolerance, reduced analgesia to neuropathic pain, physical dependence, or reward. These side effects promote development of opioid use disorders and ultimately cause overdose deaths due to opioid-induced respiratory depression. The intertwined nature of signaling via μ-opioid receptors (MOR), the primary target of prescription opioids, with signaling pathways responsible for opioid side-effects presents important challenges. Therefore, a critical objective is to uncouple cellular and molecular mechanisms that selectively modulate analgesia from those that mediate side-effects. One such mechanism could be the transactivation of receptor tyrosine kinases (RTKs) via MOR. Notably, MOR-mediated side-effects can be uncoupled from analgesia signaling via targeting RTK family receptors, highlighting physiological relevance of MOR-RTKs crosstalk. This review focuses on the current state of knowledge surrounding the basic pharmacology of RTKs and bidirectional regulation of MOR signaling, as well as how MOR-RTK signaling may modulate undesirable effects of chronic opioid use, including opioid analgesic tolerance, reduced analgesia to neuropathic pain, physical dependence, and reward. Further research is needed to better understand RTK-MOR transactivation signaling pathways, and to determine if RTKs are a plausible therapeutic target for mitigating opioid side effects.

Hippocampal and amygdalar increased BDNF expression in the extinction of opioid-induced place preference

The opioid crisis was exacerbated during the COVID-19 pandemic in the United States with alarming statistics about overdose-related deaths. Current treatment options, such as medication assisted treatments, have been unable to prevent relapse in many patients, whereas cue-based exposure therapy have had mixed results in human trials. To improve patient outcomes, it is imperative to develop animal models of addiction to understand molecular mechanisms and identify potential therapeutic targets. We previously found increased brain derived neurotrophic factor (bdnf) transcript in the ventral striatum/nucleus accumbens (VS/NAc) of rats that extinguished morphine-induced place preference. Here, we expand our study to determine whether BDNF protein expression was modulated in mesolimbic brain regions of the reward system in animals exposed to extinction training. Drug conditioning and extinction sessions were followed by Western blots for BDNF in the hippocampus (HPC), amygdala (AMY) and VS/NAc. Rears, as a measure of withdrawal-induced anxiety were also measured to determine their impact on extinction. Results showed that animals who received extinction training and successfully extinguished morphine CPP significantly increased BDNF in the HPC when compared to animals deprived of extinction training (sham-extinction). This increase was not significant in animals who failed to extinguish (extinction-resistant). In AMY, all extinction-trained animals showed increased BDNF, regardless of behavior phenotype. No BDNF modulation was observed in the VS/NAc. Finally, extinction-trained animals showed no difference in rears regardless of extinction outcome, suggesting that anxiety elicited by drug withdrawal did not significantly impact extinction of morphine CPP. Our results suggest that BDNF expression in brain regions of the mesolimbic reward system could play a key role in extinction of opioid-induced maladaptive behaviors and represents a potential therapeutic target for future combined pharmacological and extinction-based therapies.

Anterior cingulate cortex and its projections to the ventral tegmental area regulate opioid withdrawal, the formation of opioid context associations and context-induced drug seeking

Clinical evidence suggests that there are correlations between activity within the anterior cingulate cortex (ACC) following re-exposure to drug-associated contexts and drug craving. However, there are limited data contributing to our understanding of ACC function at the cellular level during re-exposure to drug-context associations as well as whether the ACC is directly related to context-induced drug seeking. Here, we addressed this issue by employing our novel behavioral procedure capable of measuring the formation of drug-context associations as well as context-induced drug-seeking behavior in male mice (8–12 weeks of age) that orally self-administered oxycodone. We found that mice escalated oxycodone intake during the long-access training sessions and that conditioning with oxycodone was sufficient to evoke conditioned place preference (CPP) and drug-seeking behaviors. Additionally, we found that thick-tufted, but not thin-tufted pyramidal neurons (PyNs) in the ACC as well as ventral tegmental area (VTA)-projecting ACC neurons had increased intrinsic membrane excitability in mice that self-administered oxycodone compared to controls. Moreover, we found that global inhibition of the ACC or inhibition of VTA-projecting ACC neurons was sufficient to significantly reduce oxycodone-induced CPP, drug seeking, and spontaneous opioid withdrawal. These results demonstrate a direct role of ACC activity in mediating context-induced opioid seeking among other behaviors, including withdrawal, that are associated with the DSM-V criteria of opioid use disorder.

BDNF-AAV has protective effects on morphine-induced conditioned place preference through BDNF, TrkB, and CREB concentration changes in the VTA and NAc

Brain-derived neurotrophic factor (BDNF) is one of the neurotrophic factors that promotes the survival and protection of neurons in many disorders. The potential protective effect of BDNF and its mechanisms on morphine addiction are unclear. In this study, morphine-induced conditioned place preference (CPP) in mice was used to show the effect of BDNF on rewarding behavior. Western blot assays were used to determine the changes caused by BDNF, for example, changes in total BDNF, tropomyosin-related kinase receptor B (TrkB), and cAMP response element binding protein (CREB) in the ventral tegmental area (VTA) and nucleus accumbens (NAc). The results showed that the BDNF-adeno-associated viral vector (BDNF-AAV) injected in the VTA, attenuated morphine-induced CPP with synergistic changes in BDNF/TrkB/CREB concentrations in the VTA and NAc in the CPP acquisition and recurrence phases; however, the attenuation was lower in the extinction phase, with different changes in molecules downstream of the BDNF.

Blood biomarkers of post-stroke depression after minor stroke at three months in males and females

BACKGROUND

Post-stroke depression (PSD) is one of the most common neuropsychiatric complications after stroke. Studies on the underlying mechanisms and biological markers of sex differences in PSD are of great significance, but there are still few such studies. Therefore, the main objective of this study was to investigate the association of biomarkers with PSD at 3 months after minor stroke in men and women.

METHODS

This was a prospective multicenter cohort study that enrolled 530 patients with minor stroke (males, 415; females, 115). Demographic information and blood samples of patients were collected within 24 h of admission, and followed up at 3 months after stroke onset. PSD was defined as a depressive disorder due to another medical condition with depressive features, major depressive-like episode, or mixed-mood features according to the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-V). Univariate analysis was performed using the chi-square test, Mann-Whitney U test, or t-test. Partial least-squares discriminant analysis (PLS-DA) was used to distinguish between patients with and without PSD. Factors with variable importance for projection (VIP) > 1.0 were classified as the most important factors in the model segregation.

RESULTS

The PLS-DA model mainly included component 1 and component 2 for males and females. For males, the model could explain 13% and 16.9% of the variables, respectively, and 29.9% of the variables in total; the most meaningful predictors were exercise habit and fibrinogen level. For females, the model could explain 15.7% and 10.5% of the variables, respectively, and 26.2% of the variables in total; the most meaningful predictors in the model were brain-derived neurotrophic factor (BDNF), magnesium and free T3. Fibrinogen was positively correlated with the Hamilton Depression Scale-17 items (HAMD-17) score. BDNF, magnesium, and free T3 levels were negatively correlated with the HAMD-17 score.

CONCLUSIONS

This was a prospective cohort study. The most important markers found to be affecting PSD at 3 months were fibrinogen in males, and free T3, magnesium, and BDNF in females.

TRIAL REGISTRATION

ChiCTR-ROC-17013993 .

JQ1 attenuates psychostimulant- but not opioid-induced conditioned place preference

Epigenetic mechanisms play important roles in the neurobiology of substance use disorder. In particular, bromodomain and extra-terminal domain (BET) proteins, a class of histone acetylation readers, have been found to regulate cocaine conditioned behaviors, but their role in the behavioral response to other drugs of abuse remains unclear. To address this knowledge gap, we examined the effects of the BET inhibitor, JQ1, on nicotine, amphetamine, morphine, and oxycodone conditioned place preference (CPP). Similar to previous cocaine studies, systemic administration of JQ1 caused a dose-dependent reduction in the acquisition of amphetamine and nicotine CPP in male mice. However, in opioid studies, JQ1 did not alter morphine or oxycodone CPP. Investigating the effects of JQ1 on other types of learning and memory, we found that JQ1 did not alter the acquisition of contextual fear conditioning. Together, these results indicate that BET proteins play an important role in the acquisition of psychostimulant-induced CPP but not the acquisition of opioid-induced CPP nor contextual fear conditioning.

Aerobic exercise as a promising nonpharmacological therapy for the treatment of substance use disorders

Despite the prevalence and public health impact of substance use disorders (SUDs), effective long-term treatments remain elusive. Aerobic exercise is a promising, nonpharmacological treatment currently under investigation as a strategy for preventing drug relapse. Aerobic exercise could be incorporated into the comprehensive treatment regimens for people with substance abuse disorders. Preclinical studies of SUD with animal models have shown that aerobic exercise diminishes drug-seeking behavior, which leads to relapse, in both male and female rats. Nevertheless, little is known regarding the effects of substance abuse-induced cellular and physiological adaptations believed to be responsible for drug-seeking behavior. Accordingly, the overall goal of this review is to provide a summary and an assessment of findings to date, highlighting evidence of the molecular and neurological effects of exercise on adaptations associated with SUD.

A role of anterior cingulate cortex in the emergence of worker-parasite relationship

We studied the brain mechanisms underlying action selection in a social dilemma setting in which individuals' effortful gains are unfairly distributed among group members. A stable "worker-parasite" relationship developed when three individually operant-conditioned rats were placed together in a Skinner box equipped with response lever and food dispenser on opposite sides. Specifically, one rat, the "worker," engaged in lever-pressing while the other two "parasitic" rats profited from the worker's effort by crowding the feeder in anticipation of food. Anatomically, c-Fos expression in the anterior cingulate cortex (ACC) was significantly higher in worker rats than in parasite rats. Functionally, ACC inactivation suppressed the worker's lever-press behavior drastically under social, but only mildly under individual, settings. Transcriptionally, GABA_A receptor- and potassium channel-related messenger RNA expressions were reliably lower in the worker's, relative to parasite's, ACC. These findings indicate the requirement of ACC activation for the expression of exploitable, effortful behavior, which could be mediated by molecular pathways involving GABA_A receptor/potassium channel proteins.

Melatonin Blocks Morphine-Induced Place Preference: Involvement of GLT-1, NF-κB, BDNF, and CREB in the Nucleus Accumbens

Opioid addiction remains a widespread issue despite continuous attempts by the FDA to help maintain abstinence. Melatonin is a neurohormone considered to be involved only in the neuroendocrine and reproductive systems; however, recent reports have demonstrated its potential to attenuate drug addiction and dependence. Cumulative studies have suggested that melatonin can attenuate the rewarding effects of several drugs of abuse, including opioids. This study aimed to investigate the effect of melatonin (50 mg/kg) on morphine (5 mg/kg) to produce place preference. We also investigated the effect of melatonin and morphine on the expression of GLT-1, BDNF, NF-κB, and CREB within the nucleus accumbens. Male Wistar rats were divided into control, morphine, melatonin, and the morphine + melatonin groups. The study involved a two-phase habituation phase from day 1 to day 3 and an acquisition phase from day 5 to day 14. The conditioned place preference (CPP) score, distance traveled, resting time, ambulatory count, and total activity count were measured for all animals. Rats that received morphine showed a significant increase in CPP score compared to those in the control group. Morphine treatment reduced the mRNA expression of GLT-1, BDNF, and CREB and increased that of NF-κB. However, melatonin treatment administered 30 min before morphine treatment attenuated morphine place preference and reversed GLT-1, BDNF, NF-κB, and CREB expression levels. In conclusion, the study results indicate, for the first time, the new potential targets of melatonin in modulating morphine-induced CPP.

Impact of Early Life Stress on Reward Circuit Function and Regulation

Early life stress - including experience of child maltreatment, neglect, separation from or loss of a parent, and other forms of adversity - increases lifetime risk of mood, anxiety, and substance use disorders. A major component of this risk may be early life stress-induced alterations in motivation and reward processing, mediated by changes in the nucleus accumbens (NAc) and ventral tegmental area (VTA). Here, we review evidence of the impact of early life stress on reward circuit structure and function from human and animal models, with a focus on the NAc. We then connect these results to emerging theoretical models about the indirect and direct impacts of early life stress on reward circuit development. Through this review and synthesis, we aim to highlight open research questions and suggest avenues of future study in service of basic science, as well as applied insights. Understanding how early life stress alters reward circuit development, function, and motivated behaviors is a critical first step toward developing the ability to predict, prevent, and treat stress-related psychopathology spanning mood, anxiety, and substance use disorders.

Brain-derived neurotrophic factor predominantly regulates the expression of synapse-related genes in the striatum: Insights from in vitro transcriptomics

Aim

The striatum, a main component of the basal ganglia, is a critical part of the motor and reward systems of the brain. It consists of GABAergic and cholinergic neurons and receives projections of dopaminergic, glutamatergic, and serotonergic neurons from other brain regions. Brain‐derived neurotrophic factor (BDNF) plays multiple roles in the central nervous system, and striatal BDNF has been suggested to be involved in psychiatric and neurodegenerative disorders. However, the transcriptomic impact of BDNF on the striatum remains largely unknown. In the present study, we performed transcriptomic profiling of striatal cells stimulated with BDNF to identify enriched gene sets (GSs) and their novel target genes in vitro.

Methods

We carried out RNA sequencing (RNA‐Seq) of messenger RNA extracted from primary dissociated cultures of rat striatum stimulated with BDNF and conducted Generally Applicable Gene‐set Enrichment (GAGE) analysis on 10599 genes. Significant differentially expressed genes (DEGs) were determined by differential expression analysis for sequence count data 2 (DESeq2).

Results

GAGE analysis identified significantly enriched GSs that included GSs related to regulation and dysregulation of synaptic functions, such as synaptic vesicle cycle and addiction to nicotine and morphine, respectively. It also detected GSs related to various types of synapses, including not only GABAergic and cholinergic synapses but also dopaminergic and glutamatergic synapses. DESeq2 revealed 72 significant DEGs, among which the highest significance was observed in the apolipoprotein L domain containing 1 (Apold1).

Conclusions

The present study indicates that BDNF predominantly regulates the expression of synaptic‐function‐related genes and that BDNF promotes synaptogenesis in various subtypes of neurons in the developing striatum. Apold1 may represent a unique target gene of BDNF in the striatum.

In the present study, we performed transcriptomic profiling of striatal cells stimulated with BDNF to identify enriched gene sets (GSs) in vitro. Generally Applicable Gene‐set Enrichment (GAGE) analysis followed by differential expression analysis for sequence count data 2 (DESeq2) suggested that BDNF predominantly regulates the expression of synaptic‐function‐related genes and that BDNF promotes synaptogenesis in various subtypes of neurons in the developing striatum.

Effects of Compound 511 on BDNF-TrkB Signaling in the Mice Ventral Tegmental Area in Morphine-Induced Conditioned Place Preference

Compound 511 (511) is specially developed for opioid addiction treatment based on the Ancient Chinese drug rehabilitation literature, and its composition has profound effects in the treatment of drug addiction in various clinical trials and animal experiments. The effect of 511 on the rewarding properties of morphine and craving responses and its potential mechanisms remain unclear. Here, we have applied a conditioned place preference (CPP) paradigm in mice to measure morphine-induced rewarding effects under the treatment of 511. Then we used the RNA sequencing strategy to screen its potential mechanisms. In our research, firstly, we found 511 could decrease CPP score, locomotor activity, self-administration, jumping behavior, weight loss, wet-dog shakes, and stereotyped behavior. Then the brain VTA region tissues were performed mRNA sequencing to detect potential mechanisms. We found the brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB) were downregulated in morphine-induced CPP, whereas the decreased BDNF and TrkB were reversed after 511 treatment. We retested the levels of BDNF and TrkB using qRT-PCR and Western blot and found the similar results to mRNA sequencing. It has been widely reported that BDNF-TrkB signaling in the VTA is involved in multiple facets of addiction, including reward and motivation, so we focused on the BDNF-TrkB signaling to investigate the anti-addiction mechanisms of 511 in morphine addiction mice. We studied the downstream pathway of BDNF-TrkB and the soma size of dopaminergic neurons. The results showed 511 could increase the phosphorylation levels of PI3K and AKT, which were decreased in morphine-induced CPP. Simultaneously, 511 could decrease the level of PLCγ1 and the phosphorylation levels of ERK and S6K, which were increased in morphine-induced CPP. In addition, 511 also enlarged the soma size of VTA dopaminergic neurons, which was reduced in morphine-induced CPP. Hence, our research indicated 511 maybe mediate the BDNF-TrkB signaling in VTA to improve morphine addiction behavior.

Elevation of DNA Methylation in the Promoter Regions of the Brain-Derived Neurotrophic Factor Gene is Associated with Heroin Addiction

To study the potential role of brain-derived neurotrophic factor (BDNF) methylation in heroin addiction, we first detected the methylation level of seven CpG islands that included 106 CpG sites in the promoter regions of BDNF from 120 people addicted to heroin and 113 controls. Methylation quantitative trait locus (mQTL) analysis was then employed to determine the association between the single-nucleotide polymorphism rs6265, a well-known locus shown to be correlated with heroin addiction, and the methylation levels of these CpG sites. Finally, we used the JASPAR database to predict whether transcription factors could bind to these CpG sites. We found that the methylation levels of CpG islands 6 and 7 and the methylation levels of BDNF_45 and BDNF_80 were significantly higher in the heroin addiction group than in the control group. We also found that rs6265 was an mQTL and was associated with the methylation level of BDNF_58. Using the JASPAR database, we found that ALX homeobox 3 (ALX3), achaete-scute family bHLH transcription factor 1 (ASCL1) and aryl hydrocarbon receptor nuclear translocator 2 (ARNT2) could bind to CpG island 6, and ALX3 could bind to CpG island 7. In summary, we showed that increased DNA methylation in the promoter regions of the BDNF gene was associated with heroin addiction in Han Chinese.

The Ameliorative Effects of Isorhynchophylline on Morphine Dependence Are Mediated Through the Microbiota-Gut-Brain Axis

Morphine abuse is a global public health problem. Increasing evidence has shown that gut microbiota dysbiosis plays an important role in several central nervous system diseases. However, whether there is an association between gut microbiota and morphine dependence remains unclear. In this study, the effects of isorhynchophylline on morphine dependence were evaluated based on the microbiota-gut-brain axis (MGBA). The results showed that isorhynchophylline could reverse the changes in alpha and beta diversity, composition, and richness of the intestinal flora occurring in morphine-dependent zebrafish, as well as the morphine-induced changes in the expression of MGBA-related genes in BV2 cells and the brain and intestine of zebrafish. Based on the results, we then used antibiotics to evaluate whether disrupting the gut microbiota would affect morphine addiction in zebrafish. The results showed that the antibiotic-induced intestinal floral imbalance changed the behavior of morphine-dependent zebrafish, the characteristics of the zebrafish intestinal flora, and the expression of MGBA-related genes in the zebrafish brain and intestine. Importantly, we also show that, following antibiotic administration, the ameliorative effects of isorhynchophylline on morphine addiction were lost. Together, our results indicate that the gut microbiota interacts with the brain, and dysbiosis of the intestinal flora may affect the efficacy of isorhynchophylline in the body. Our findings provide a novel framework for understanding the mechanisms of morphine addiction through the MGBA and may provide new therapeutic strategies for the use of Chinese medicines in the prevention of drug addiction.

Alterations in neurotransmitter levels and transcription factor expression following intranasal buprenorphine administration

Buprenorphine is an opioid drug used in the management of pain and the treatment opioid addiction. Like other opioids, it is believed that it achieves these effects by altering functional neurotransmitter pathways and the expression of important transcription factors; cyclic AMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) in the brain. However, there is a lack of scientific evidence to support these theories. This study investigated the pharmacodynamic effects of BUP administration by assessing neurotransmitter and molecular changes in the healthy rodent brain. Sprague-Dawley rats (150-200 g) were intranasally administered buprenorphine (0.3 mg/mL) and sacrificed at different time points: 0.25, 0.5, 1, 2, 4, 6, 8 and 24 h post drug administration. LC-MS was used to quantify BUP and neurotransmitters (GABA, GLUT, DA, NE and 5-HT) in the brain, while CREB and BDNF gene expression was determined using qPCR. Results showed that BUP reached a Cmax of 1.21 ± 0.0523 ng/mL after 2 h, with all neurotransmitters showing an increase in their concentration over time, with GABA, GLUT and NE reaching their maximum concentration after 8 h. DA and 5-HT reached their maximum concentrations at 1 h and 24 h, respectively post drug administration. Treatment with BUP resulted in significant upregulation in BDNF expression throughout the treatment period while CREB showed patterns of significant upregulation at 2 and 8 h, and downregulation at 1 and 6 h. This study contributes to the understanding of the pharmacodynamic effects of BUP in opioid addiction by proving that the drug significantly influences NT pathways that are implicated in opioid addiction.

Effects of Morphine and Maternal Care on Behaviors and Protein Expression of Male Offspring

Genes and environment interact during development to alter gene expression and behavior. Parental morphine exposure before conception has devastating effects on the offspring. In the present study, we evaluated the role of maternal care in the intergenerational effect of maternal morphine exposure. Female rats received morphine or saline for ten days and were drugfree for another ten days. Thereafter, they were allowed to mate with drug-naïve male rats. When pups were born, they were cross-fostered to assess the contribution of maternal care versus morphine effects on the offspring. Adult male offspring were examined for anxiety-like behavior, spatial memory, and obsessive-compulsive-like behavior. To determine the mechanisms underlying the observed behavioral changes, protein levels of acetylated histone H3, BDNF, Trk-B, NMDA subunits, p-CREB, and 5-HT₃R were measured in the brain. Our results indicate that maternal caregiving is impaired in morphine-abstinent mothers. Interestingly, maternal care behaviors were also affected in drug-naïve mothers that raised offspring of morphine-exposed mothers. In addition, the offspring of morphine abstinent and non-drug dependent mothers, when raised by morphine abstinent mothers, exhibited more anxiety, obsessive-compulsive behaviors and impaired spatial memory. These altered behaviors were associated with alterations in the levels of the above-mentioned proteins. These data illustrate the intergenerational effects of maternal morphine exposure on offspring behaviors. Moreover, exposure to morphine before gestation not only affects maternal care and offspring behavior, but also has negative consequences on behaviors and protein expression in adoptive mothers of affected offspring.

Intermediation of perceived stress between early trauma and plasma M/P ratio levels in obsessive-compulsive disorder patients

OBJECTIVES

This study is to find the correlation among BDNF metabolism, early trauma, and current stress status of OCD patients. As well as to study the BDNF metabolism-stress related pathological mechanism in OCD development.

METHODS

A total of 140 participants were recruited in this study, including 64 drug-naïve OCD patients (OCDs) and 76 healthy controls (HCs). The clinical data of the subjects were measured using YBOCS, CTQ, and PSS. The plasma mBDNF and proBDNF values were measured by ELISA while the M/P ratio was calculated.

RESULTS

The mBDNF, proBDNF plasma levels, and M/P ratio of unmedicated OCD individuals decreased evidently comparing with HCs. Also, positive associations were found between PSS and CTQ and between CTQ and M/P ratio. The negative correlation included proBDNF and PSS as well as proBDNF and CTQ. Intermediary analysis generated by SPSS has showed that the perceived stress played a complete mediating role between early trauma and plasma M/P ratio levels, and the mediating effect was 0.043 in non-medication OCD patients.

CONCLUSIONS

Findings from this study suggested that early trauma experience and stress state work together in regulating BDNF metabolism level in OCD patients. The nucleus accumbens and reward loop are also pivotal in the pathogenesis of OCD.

Energy sensors in drug addiction: A potential therapeutic target

Addiction is defined as the repeated exposure and compulsive seek of psychotropic drugs that, despite the harmful effects, generate relapse after the abstinence period. The psychophysiological processes associated with drug addiction (acquisition/expression, withdrawal, and relapse) imply important alterations in neurotransmission and changes in presynaptic and postsynaptic plasticity and cellular structure (neuroadaptations) in neurons of the reward circuits (dopaminergic neuronal activity) and other corticolimbic regions. These neuroadaptation mechanisms imply important changes in neuronal energy balance and protein synthesis machinery. Scientific literature links drug-induced stimulation of dopaminergic and glutamatergic pathways along with presence of neurotrophic factors with alterations in synaptic plasticity and membrane excitability driven by metabolic sensors. Here, we provide current knowledge of the role of molecular targets that constitute true metabolic/energy sensors such as AMPK, mTOR, ERK, or K_ATP in the development of the different phases of addiction standing out the main brain regions (ventral tegmental area, nucleus accumbens, hippocampus, and amygdala) constituting the hubs in the development of addiction. Because the available treatments show very limited effectiveness, evaluating the drug efficacy of AMPK and mTOR specific modulators opens up the possibility of testing novel pharmacotherapies for an individualized approach in drug abuse.

Glutamatergic Systems and Memory Mechanisms Underlying Opioid Addiction

Glutamate is the main excitatory neurotransmitter in the brain and is of critical importance for the synaptic and circuit mechanisms that underlie opioid addiction. Opioid memories formed over the course of repeated drug use and withdrawal can become powerful stimuli that trigger craving and relapse, and glutamatergic neurotransmission is essential for the formation and maintenance of these memories. In this review, we discuss the mechanisms by which glutamate, dopamine, and opioid signaling interact to mediate the primary rewarding effects of opioids, and cover the glutamatergic systems and circuits that mediate the expression, extinction, and reinstatement of opioid seeking over the course of opioid addiction.

Opioid-Induced Molecular and Cellular Plasticity of Ventral Tegmental Area Dopamine Neurons

Opioid drugs are highly valued as potent analgesics; however, there are significant risks associated with long-term use because of their abuse liability. Opioids cause changes in ventral tegmental area (VTA) gene expression and cell activity that have been linked to addiction-related behaviors in rodent models. Here, we focus on VTA dopamine (DA) neurons and review the cellular, structural, and synaptic plasticity changes induced by acute and chronic opioid exposure. We also discuss many avenues for future research including determination of whether opioid neuroadaptations are specific for subpopulations of VTA DA neurons. A better understanding of the molecular adaptations within the cells and circuits that drive opioid abuse is crucial for the development of better treatments for substance use disorders and to create novel, safer pain-relieving therapeutics.

Microinjection of the BDNF receptor antagonist ANA-12 into the nucleus accumbens and medial-prefrontal cortex attenuates morphine-induced reward memory, and alterations of BDNF levels and apoptotic cells in rats

This study was designed to examine the effects of intra- nucleus accumbens (NAc) of BDNF receptor antagonist ANA-12 on the acquisition and expression and intra- medial-prefrontal cortex (mPFC) of ANA-12 on the extinction and reinstatement of morphine-induced conditioned place preference (CPP) and also BDNF levels and apoptotic neurons in the NAc and mPFC of rats. In this study, adult male Wistar rats (200-250 g) were used. Two separate cannulas were inserted bilaterally into the NAc and/or mPFC. ANA-12 (3 μg/0.5 μl/side) was injected into the NAc and/or mPFC to evaluate the rewarding effects of morphine using a CPP paradigm. Then, the levels of BDNF and apoptotic in the NAc and mPFC were assessed at the end of each treatment phase using ELISA and TUNEL methods, respectively. All of vehicle-treated rats following morphine CPP showed the increase of BDNF levels and apoptotic neurons in the NAc and mPFC. ANA-12 significantly attenuated the acquisition and expression of morphine-induced CPP, BDNF levels and apoptotic neurons in the NAc during the acquisition, but not the expression phase. Also, ANA-12 significantly facilitated the extinction, but no effect on reinstatement of morphine CPP, and decreased BDNF levels and apoptotic neurons in the mPFC during the extinction, but not the reinstatement. We conclude that blocking TrkB with ANA-12 showed therapeutic effects on morphine-associated reward memory and neuronal death in the NAc and mPFC induced by morphine CPP. Thus, the BDNF-TrkB signaling may be important in the acquisition, expression, extinction, but not the reinstatement of morphine CPP.

Morphine produces better thermal analgesia in young Huntington mice and are associated with less neuroinflammation in spinal cord

BACKGROUND

Huntington's disease (HD) is an inherited disease characterized by both mental and motor dysfunctions. Our previous studies showed that HD mice demonstrate a diminished pain response. However, few studies have focused on the relationship between HD and morphine analgesia. The purpose of this study is to investigate and compare the analgesic effects of morphine in HD and wild-type (WT) mice.

METHODS

We used clinically similar transgenic HD mice (7-10 weeks of age with motor dysfunction at 8-9 mo of age) carrying a mutant Huntington CAG trinucleotide repeats to evaluate morphine analgesia. The morphine (10 mg/kg subcutaneously) analgesia was evaluated with a tail-flick in hot water (52°C). Mice spinal cords were harvested at the end of the analgesia studies. An immunofluorescence assay and western blotting were used to identify changes in the cells and cytokines.

RESULTS

Our data demonstrate that preonset young HD mice exhibited a better analgesic response to morphine than the WT mice. Western blotting and an immunohistological examination of the lumbar spinal cord tissue indicated less activation of glial cells and astrocytes in the HD mice compared with the WT mice. The production levels of tumor necrosis factor α and interleukine-1β were also lower in the young HD mice.

CONCLUSION

Our data demonstrate better morphine analgesic and less pain-related cytokine responses at the spinal cord level for HD mice. Further studies are needed to determine the morphine analgesia mechanism in HD.

CRHCeA→VTA inputs inhibit the positive ensembles to induce negative effect of opiate withdrawal

Plasticity of neurons in the ventral tegmental area (VTA) is critical for establishment of drug dependence. However, the remodeling of the circuits mediating the transition between positive and negative effect remains unclear. Here, we used neuronal activity-dependent labeling technique to characterize and temporarily control the VTA neuronal ensembles recruited by the initial morphine exposure (morphine-positive ensembles, Mor-Ens). Mor-Ens preferentially projected to NAc, and induced dopamine-dependent positive reinforcement. Electrophysiology and rabies viral tracing revealed the preferential connections between the VTA-projective corticotrophin-releasing hormone (CRH) neurons of central amygdala (CRH^CeA→VTA) and Mor-Ens, which was enhanced after escalating morphine exposure and mediated the negative effect during opiate withdrawal. Pharmacologic intervention or CRISPR-mediated repression of CRHR1 in Mor-Ens weakened the inhibitory CRH^CeA→VTA inputs, and alleviated the negative effect during opiate withdrawal. These data suggest that neurons encoding opioid reward experience are inhibited by enhanced CRH^CeA→VTA inputs induced by chronic morphine exposure, leading to negative effect during opiate withdrawal, and provide new insight into the pathological changes in VTA plasticity after drug abuse and mechanism of opiate dependence.

Peptide Mimetic of BDNF Loop 4 Blocks Behavioral Signs of Morphine Withdrawal Syndrome and Prevents the Increase in ΔFosB Level in the Striatum of Rats

Activity of compound GSB-106, a low-molecular mimetic of loop 4 of the brain neurotrophic factor (BDNF), was studied in experimental morphine withdrawal syndrome simulated in outbred rats. Single and subchronic (5 intraperitoneal injections) administration of GSB-106 in a dose of 0.1 mg/kg significantly reduced the total index of morphine withdrawal syndrome by 55.2 and 45.6%, respectively. GSB-106 reduced the severity of some behavioral signs (piloerection, gnashing of teeth, wet-dog shaking, and runaway attempts), but had no effect on mechanical allodynia formed in the rats with dependence. Subchronic treatment with GSB-106 prevented the increase in the content of ΔFosB (product of early response gene) in the striatum induced by morphine withdrawal. The results confirmed the concept on the involvement of neurotrophins, specifically BDNF and its analogs, in the mechanisms associated with the formation of opiate dependence.

BDNF receptor antagonism during the induction of morphine dependence exacerbates the severity of physical dependence and ameliorates psychological dependence in rats

This study examined the effects of systemic administration of the TrkB receptor antagonist (ANA-12) during induction of morphine dependence on the severity of physical and psychological dependence and the cerebrospinal fluid (CSF) BDNF levels in morphine-dependent and withdrawn rats. Rats became morphine-dependent by increasing daily doses of morphine for 7 days, along with ANA-12 injection. 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) behaviors after spontaneous morphine withdrawal. Also, the CSF BDNF levels were assessed 2 h after the last dose of morphine and day 13 after morphine withdrawal in morphine-dependent and withdrawn rats. We found that the morphine withdrawal signs were significantly higher in morphine dependent rats receiving ANA-12 on days of 5-7 after morphine withdrawal, also ANA-12 exacerbated overall dependence severity. While, the percentage of time spent in the open arms and sucrose preference were higher in morphine-dependent rats receiving ANA-12 than morphine-dependent rats receiving saline. Also, the ANA-12 injection decreased the CSF BDNF levels following morphine dependence, while increased it after morphine withdrawal. We conclude that the ANA-12 exacerbated the severity of physical morphine dependence but attenuated the anxiety/depressive-like behaviors in morphine-dependent and withdrawn rats. Also, ANA-12 injection was able to reverse the changes in the CSF BDNF levels. Therefore, ANA-12 is not more likely to complete treatment for opiate addiction.

Interruption of continuous opioid exposure exacerbates drug-evoked adaptations in the mesolimbic dopamine system

Drug-evoked adaptations in the mesolimbic dopamine system are postulated to drive opioid abuse and addiction. These adaptations vary in magnitude and direction following different patterns of opioid exposure, but few studies have systematically manipulated the pattern of opioid administration while measuring neurobiological and behavioral impact. We exposed male and female mice to morphine for one week, with administration patterns that were either intermittent (daily injections) or continuous (osmotic minipump infusion). We then interrupted continuous morphine exposure with either naloxone-precipitated or spontaneous withdrawal. Continuous morphine exposure caused tolerance to the psychomotor-activating effects of morphine, whereas both intermittent and interrupted morphine exposure caused long-lasting psychomotor sensitization. Given links between locomotor sensitization and mesolimbic dopamine signaling, we used fiber photometry and a genetically encoded dopamine sensor to conduct longitudinal measurements of dopamine dynamics in the nucleus accumbens. Locomotor sensitization caused by interrupted morphine exposure was accompanied by enhanced dopamine signaling in the nucleus accumbens. To further assess downstream consequences on striatal gene expression, we used next-generation RNA sequencing to perform genome-wide transcriptional profiling in the nucleus accumbens and dorsal striatum. The interruption of continuous morphine exposure exacerbated drug-evoked transcriptional changes in both nucleus accumbens and dorsal striatum, dramatically increasing differential gene expression and engaging unique signaling pathways. Our study indicates that opioid-evoked adaptations in brain function and behavior are critically dependent on the pattern of drug administration, and exacerbated by interruption of continuous exposure. Maintaining continuity of chronic opioid administration may, therefore, represent a strategy to minimize iatrogenic effects on brain reward circuits.

Drug-Induced Conditioned Place Preference and Its Practical Use in Substance Use Disorder Research

The conditioned place preference (CPP) paradigm is a well-established model utilized to study the role of context associations in reward-related behaviors, including both natural rewards and drugs of abuse. In this review article, we discuss the basic history, various uses, and considerations that are tied to this technique. There are many potential takeaway implications of this model, including negative affective states, conditioned drug effects, memory, and motivation, which are all considered here. We also discuss the neurobiology of CPP including relevant brain regions, molecular signaling cascades, and neuromodulatory systems. We further examine some of our prior findings and how they integrate CPP with self-administration paradigms. Overall, by describing the fundamentals of CPP, findings from the past few decades, and implications of using CPP as a research paradigm, we have endeavored to support the case that the CPP method is specifically advantageous for studying the role of a form of Pavlovian learning that associates drug use with the surrounding environment.

Chronic morphine intoxication reduces binding of HuD to BDNF long 3'-UTR, while morphine withdrawal stimulates BDNF expression in the frontal cortex of male Wistar rats

BACKGROUND

Brain-derived neurotrophic factor (BDNF) mediates opiate dependence phenomenon. In the brain of morphine dependent animals BDNF level is controlled transcriptionally, however, post-transcriptional mechanisms of BDNF regulation in this context remain unknown. Regulation of mRNA by binding of specific proteins to the 3'-untranslated region (3'-UTR) is one of such mechanisms. Among RNA-binding proteins neuronal Hu antigen D (HuD) is the best characterized positive regulator of BDNF, however its involvement in opiate dependence remains obscure. We suggested that HuD binding to the BDNF 3'-UTR may be linked to changes in BDNF expression induced by morphine. The aim of this study was to investigate potential association of HuD with BDNF 3'-UTR in relation to BDNF expression (Exon- and 3'-UTR-specific mRNA variants and protein level) in the frontal cortex and midbrain of male Wistar rats after chronic morphine intoxication and spontaneous withdrawal in dependent animals.

RESULTS

After chronic morphine intoxication but not during morphine withdrawal HuD binding to the long BDNF 3'-UTR in the frontal cortex decreased as compared with the corresponding control group, however after intoxication BDNF expression did not change. The level of BDNF Exon I as well as mature BDNF polypeptide increased in the frontal cortex upon morphine withdrawal, while no changes in HuD binding could be detected.

CONCLUSION

Thus, contrary to the assumption, HuD-BDNF 3'-UTR interaction and BDNF expression in the frontal cortex differentially change in a manner dependent on the context of morphine action.

Genomics testing and personalized medicine in the preoperative setting: Can it change outcomes in postoperative pain management?

Postoperative pain and opioid use are major challenges in perioperative medicine. Pain perception and its response to opioid use are multi-faceted and include pharmacological, psychological, and genetic components. Precision medicine is a unique approach to individualized health care in which decisions in management are based on genetics, lifestyle, and environment of each person. Genetic variations can have an impact on the perception of pain and response to treatment. This can have an effect on pain management in both acute and chronic settings. Although there is currently not enough evidence for making recommendations about genetic testing to guide pain management in the acute care setting, there are some known polymorphisms that play a role in surgical pain and opioid-related postoperative adverse outcomes. In this review, we describe the potential use of pharmacogenomics (PGx) for improving perioperative pain management. We first review a number of genotypes that have shown correlations with pain and opioid use and then describe the importance of PGx-guided analgesic protocols and implementation of screening in a preoperative evaluation clinical setting.

Sex Differences and the Role of Estradiol in Mesolimbic Reward Circuits and Vulnerability to Cocaine and Opiate Addiction

Although both men and women become addicted to drugs of abuse, women transition to addiction faster, experience greater difficulties remaining abstinent, and relapse more often than men. In both humans and rodents, hormonal cycles are associated with females' faster progression to addiction. Higher concentrations and fluctuating levels of ovarian hormones in females modulate the mesolimbic reward system and influence reward-directed behavior. For example, in female rodents, estradiol (E2) influences dopamine activity within the mesolimbic reward system such that drug-directed behaviors that are normally rewarding and reinforcing become enhanced when circulating levels of E2 are high. Therefore, neuroendocrine interactions, in part, explain sex differences in behaviors motivated by drug reward. Here, we review sex differences in the physiology and function of the mesolimbic reward system in order to explore the notion that sex differences in response to drugs of abuse, specifically cocaine and opiates, are the result of molecular neuroadaptations that differentially develop depending upon the hormonal state of the animal. We also reconsider the notion that ovarian hormones, specifically estrogen/estradiol, sensitize target neurons thereby increasing responsivity when under the influence of either cocaine or opiates or in response to exposure to drug-associated cues. These adaptations may ultimately serve to guide the motivational behaviors that underlie the factors that cause women to be more vulnerable to cocaine and opiate addiction than men.

Impairment of cost-benefit decision making in morphine-dependent rats is partly mediated via the alteration of BDNF and p-CREB levels in the nucleus accumbens

The ability to choose goals based on decision usefulness or the time required to reach the goals chosen are important aspects of decision making. There is considerable evidence in the literature indicating the fact that drug abuse affects different aspects of cognition. In the current study, we assessed the effects of morphine dependence and its withdrawal on cost-benefit decision making and furthermore the involvement of BDNF and p-CREB in the nucleus accumbens, a key brain area involved in decision making was measured. Different groups of male Wistar rats were trained in an effort-based and/or delay-based form of cost-benefit T-maze decision-making task. Thereafter, the animals were morphine dependent and the percentage of the high reward preference was evaluated. After behavioral tests, the BDNF level, and p-CREB/CREB ratio were measured by Western blot analysis. The results showed that during effort-based but not delay-based decision making, BDNF and p-CREB levels increased. During effort-based decision making in morphine dependent rats, BDNF decreased but there was no significant change in p-CREB. Besides, during delay-based decision making in the morphine dependent group, both BDNF and p-CREB did not show any significant change. These findings revealed that BDNF and p-CREB/CREB ratio in the NAc are essential factors for effort-based but not delay-based decision making. In addition, impairment of effort-based decision making in morphine dependent rats is related to the decrease of BDNF level but not p-CREB/CREB ratio in the NAc. However, delay-based decision making defects in morphine dependent rats did not associate with the change in BDNF and p-CREB levels in the NAc.

Dexmedetomidine Activation of Dopamine Neurons in the Ventral Tegmental Area Attenuates the Depth of Sedation in Mice

Background

Dexmedetomidine induces a sedative response that is associated with rapid arousal. To elucidate the underlying mechanisms, the authors hypothesized that dexmedetomidine increases the activity of dopaminergic neurons in the ventral tegmental area, and that this action contributes to the unique sedative properties of dexmedetomidine.

Methods

Only male mice were used. The activity of ventral tegmental area dopamine neurons was measured by a genetically encoded Ca2+ indicator and patch-clamp recording. Dopamine neurotransmitter dynamics in the medial prefrontal cortex and nucleus accumbens were measured by a genetically encoded dopamine sensor. Ventral tegmental area dopamine neurons were inhibited or activated by a chemogenetic approach, and the depth of sedation was estimated by electroencephalography.

Results

Ca2+ signals in dopamine neurons in the ventral tegmental area increased after intraperitoneal injection of dexmedetomidine (40 μg/kg; dexmedetomidine, 16.917 [14.882; 21.748], median [25%; 75%], vs. saline, –0.745 [–1.547; 0.359], normalized data, P = 0.001; n = 6 mice). Dopamine transmission increased in the medial prefrontal cortex after intraperitoneal injection of dexmedetomidine (40 μg/kg; dexmedetomidine, 10.812 [9.713; 15.104], median [25%; 75%], vs. saline, –0.498 [–0.664; –0.355], normalized data, P = 0.001; n = 6 mice) and in the nucleus accumbens (dexmedetomidine, 8.543 [7.135; 11.828], median [25%; 75%], vs. saline, –0.329 [–1.220; –0.047], normalized data, P = 0.001; n = 6 mice). Chemogenetic inhibition or activation of ventral tegmental area dopamine neurons increased or decreased slow waves, respectively, after intraperitoneal injection of dexmedetomidine (40 μg/kg; delta wave: two-way repeated measures ANOVA, F[2, 33] = 8.016, P = 0.002; n = 12 mice; theta wave: two-way repeated measures ANOVA, F[2, 33] = 22.800, P < 0.0001; n = 12 mice).

Conclusions

Dexmedetomidine activates dopamine neurons in the ventral tegmental area and increases dopamine concentrations in the related forebrain projection areas. This mechanism may explain rapid arousability upon dexmedetomidine sedation.

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m-Trifluoromethyl-diphenyl diselenide (m-CF3-PhSe)2 modulates the hippocampal neurotoxic adaptations and abolishes a depressive-like phenotype in a short-term morphine withdrawal in mice

The opioid withdrawal syndrome is defined as a complex phenomenon involving multiple cellular adaptations, which leads to the emergence of aversive physical and affective signs. The m-trifluoromethyl-diphenyl diselenide (m-CF₃-PhSe)₂ elicits an antidepressant-like effect by modulating the opioid system in different animal models of mood disorders. Notably, repeated exposure to (m-CF₃-PhSe)₂ developed neither tolerance nor withdrawal signs in mice. The aim of the present study was to investigate whether (m-CF₃-PhSe)₂ attenuates the physical signs and the depressive-like phenotype during morphine withdrawal through its neuroprotective effects on oxidative stress, the NMDA receptor and the proBDNF/mBDNF signaling in the hippocampus of mice. Adult Swiss mice received saline solution or escalating doses (20-100 mg/kg, sc) of morphine for six days. For the next three days, the animals were treated with canola oil, (m-CF₃-PhSe)₂ (5 and 10 mg/kg, ig) or methadone (5 mg/kg, sc) whereas morphine injections were discontinued. On day 9, physical withdrawal signs and depressive-like behavior were assessed 30 min after the last administration of (m-CF₃-PhSe)_2. Although short-term treatment with (m-CF₃-PhSe)₂ at both doses suppressed the aversive physical and affective signs in morphine withdrawn-mice, the highest dose of (m-CF₃-PhSe)₂ per se increased the teeth chattering manifestation. The intrinsic antioxidant property of (m-CF₃-PhSe)₂ modulated oxidative stress, it also restored the NMDA receptor levels in the hippocampus of morphine withdrawn-mice. Besides, (m-CF₃-PhSe)₂ downregulated the proBDNF/p-75^NTR/JNK pro-apoptotic pathway without affecting the mBDNF/TrkB/ERK/CREB pro-survival signaling in the hippocampus of morphine withdrawn-mice. The results show that (m-CF₃-PhSe)₂ treatment modulated the hippocampal neurotoxic adaptations and abolished the depressive-like phenotype following morphine withdrawal in mice.

Opioid-Induced Adaptations of cAMP Dynamics in the Nucleus Accumbens

To investigate how opioid exposure alters dopamine (DA) responses in medium spiny neurons (MSNs), Muntean et al. used a novel cAMP sensor to track cAMP dynamics and report a coordinated effort of adaptations in D1- and D2-MSNs to integrate DA inputs and shift signaling strengths in various states of opioid dependence.

Dopamine D1 and Glutamate Receptors Co-operate With Brain-Derived Neurotrophic Factor (BDNF) and TrkB to Modulate ERK Signaling in Adult Striatal Slices

In the striatum, the input nucleus of the basal ganglia, the extracellular-signal-regulated kinase (ERK) pathway, necessary for various forms of behavioral plasticity, is triggered by the combined engagement of dopamine D1 and ionotropic glutamate receptors. In this study, we investigated the potential crosstalk between glutamatergic, dopaminergic, and brain-derived neurotrophic factor (BDNF)-TrkB inputs to ERK cascade by using an ex vivo model of mouse striatal slices. Our results confirmed that the concomitant stimulation of D1 and glutamate receptors is necessary to activate ERK in striatal medium spiny neurons (MSNs). Moreover, we found that ERK activation is significantly enhanced when BDNF is co-applied either with glutamate or the D1 agonist SKF38393, supporting the idea of possible integration between BDNF, glutamate, and D1R-mediated signaling. Interestingly, ERK activation via BDNF-TrkB is upregulated upon blockade of either AMPAR/NMDAR or D1 receptors, suggesting a negative regulatory action of these two neurotransmitter systems on BDNF-mediated signaling. However, the observed enhancement of ERK1/2 phosphorylation does not result in corresponding downstream signaling changes at the nuclear level. Conversely, the TrkB antagonist cyclotraxin B partially prevents glutamate- and D1-mediated ERK activation. Altogether, these results suggest a complex and unexpected interaction among dopaminergic, glutamatergic, and BDNF receptor systems to modulate the ERK pathway in striatal neurons.

Role of Mesolimbic Brain-Derived Neurotrophic Factor in Depression

Brain-derived neurotrophic factor (BDNF) is widely accepted as being critical for neural and synaptic plasticity throughout the nervous system. Recent work has shown that BDNF in the mesolimbic dopamine (DA) circuit, originating in ventral tegmental area DA neurons that project to the nucleus accumbens, is crucial in the development of depressive-like behaviors following exposure to chronic social defeat stress in mice. Whereas BDNF modulates DA signaling in encoding responses to acute defeat stress, BDNF signaling alone appears to be responsible for the behavioral effects after chronic social defeat stress. Very different patterns are seen with another widely used chronic stress paradigm in mice, chronic mild stress (also known as chronic variable or unpredictable stress), where DA signaling, but not BDNF signaling, is primarily responsible for the behavioral effects observed. This review discusses the molecular, cellular, and circuit basis of this dramatic discrepancy, which appears to involve the nature of the stress, its severity and duration, and its effects on distinct cell types within the ventral tegmental area-to-nucleus accumbens mesolimbic circuit.

Parental morphine exposure affects repetitive grooming actions and marble burying behavior in the offspring: Potential relevance for obsessive-compulsive like behavior

Family, adoption and twin studies have highlighted the significant role of heritable influences on individual differences in opioid addiction. Meanwhile, obsessive-compulsive disorder (OCD) is a disorder wherein the individual experiences recurring thoughts that cause irrational fears and anxiety. In the present study, adult male and female rats received morphine solution for 21 days and were drug-free for 10 days. Offspring were used in 4 distinct groups; (1) paternal morphine-exposed, (2) maternal morphine-exposed, (3) maternal and paternal morphine-exposed, and (4) drug-naïve subjects. We assessed the grooming behavior and marble burying test as an indicator of obsessive-compulsive behavior. To clarify the mechanisms underlying these changes, the mRNA level of BDNF, the phosphorylation level of CREB and the protein level of D2 dopamine receptor (DR) were evaluated in the nucleus accumbens (NAc). The grooming behavior in male offspring with one or two morphine-abstinent parent(s) increased compared with the offspring of drug naïve rats. In addition, the offspring of morphine-exposed parents buried more marbles when compared with the offspring of drug-naïve parents. Also, the BDNF mRNA was down-regulated in the NAC. However, the levels of phospho-CREB and D2 DR were elevated. Previous studies indicated that exposure to morphine in adulthood enhances the risk of psychiatric disorders in offspring. OCD is one the comorbid disorders with addiction and increases the risk of substance abuse disorder in patients. In this survey, we found that morphine exposure in parents before gestation can encourage obsessive-compulsive behavior in offspring.