The Role of Dopamine D1 and D3 Receptors in N-Methyl-D-Aspartate (NMDA)/GlycineB Site-Regulated Complex Cognitive Behaviors following Repeated Morphine Administration

Adolescent morphine exposure induced long-term cognitive impairment and prefrontal neurostructural abnormality in adulthood in male mice

Opioids abuse in adolescence is becoming a pressing public health issue. While evidence suggests that exposure to opioids during adolescence leads to lasting alterations in brain development, the long-term cognitive implications in adulthood remain uncertain. We developed a male mouse model of adolescent morphine exposure and used the 5-choice serial reaction time task (5-CSRTT), along with the open field, novel object recognition, Y maze and Barnes maze tests, to assess changes in cognitive behavior. We found that exposure to morphine during adolescence led to deficits in multidimensional cognitive functions in mice, including attention, information processing speed, and behavior inhibition. Notable, these impairments persisted into adulthood. Furthermore, the morphine-exposed mice exhibited decreased learning efficiency and spatial memory. Adolescent morphine exposure also induced significant and persistent morphological changes and synaptic abnormalities in medial prefrontal cortex (mPFC) neurons, which may be responsible for cognitive impairments in adulthood. Together, our study suggests that opioid exposure during adolescence profoundly affects cognitive development and emphasizes that opioid-induced disruption of neurons in adolescence may link mPFC-associated cognitive impairments in adulthood.

Methadone maintenance treatment and impulsivity: premature responding

INTRODUCTION

Previous research showed that methadone maintenance treatment (MMT) is linked to impulsivity, with higher impulsivity levels being associated with for example, increased drug use. One aspect of impulsivity, most commonly studied in rodent research, is premature responding, the failure to wait for a starting signal. Premature responding is of high translational significance since it predicts the development of addiction-like behaviors in rodents.

METHODS

We assessed 45 MMT patients and 46 demographically matched (age, sex, education, and handedness) healthy volunteers (HVs) on premature responding alongside action and inhibition of instructed and intentional trials using the Intentional Hand Task (IHT).

RESULTS

The results showed markedly enhanced premature responses in the MMT vs. the HV group, which correlated positively with methadone dosage in the MMT patients. Throughout the task, MMT patients were faster across all trial parts and less accurate in response to instructed trials compared to HVs.

CONCLUSIONS

The increase in premature motor reactions during variable waiting periods alongside increased motion speed and lower accuracy might reflect a specific motor inhibition deficit in MMT, a subcomponent of impulsivity not previously assessed in MMT. Incorporating an experimentally defined measure of impulsivity, such as premature responding, into existing test batteries used by clinicians might enable more tailored treatments addressing the increased impulsivity levels and associated dysfunctional behaviors in MMT.

Study on correlations of BDNF, PI3K, AKT and CREB levels with depressive emotion and impulsive behaviors in drug-naïve patients with first-episode schizophrenia

BACKGROUND

The pathogenesis of schizophrenia is still unknown. Nearly a half of schizophrenic patients have depressive symptoms and even some impulsive behaviors. The definite diagnosis of schizophrenia is an immense challenge. Molecular biology plays an essential role in the research on the pathogenesis of schizophrenia.

OBJECTIVE

This study aims to analyze the correlations of serum protein factor levels with depressive emotion and impulsive behaviors in drug-naïve patients with first-episode schizophrenia.

METHODS

Seventy drug-naïve patients with first-episode schizophrenia and sixty-nine healthy volunteers from the health check center in the same period participated in this study. In both the patient group and control group, brain-derived neurotrophic factor (BDNF), phosphatidylin-ositol-3-kinase (PI3K), protein kinase B (AKT), and cAMP-response element binding protein (CREB) levels in the peripheral blood were tested by enzyme-linked immunosorbent assay (ELISA). The depressive emotion and impulsive behaviors were evaluated with Chinese versions of the Calgary Depression Scale for Schizophrenia (CDSS) and Short UPPS-P Impulsive Behavior Scale (S-UPPS-P), respectively.

RESULTS

The serum levels of BDNF, PI3K, and CREB in the patient group were lower than those in the control group, while AKT level, total CDSS score and total S-UPPS-P score were all higher. In the patient group, total CDSS score, and total S-UPPS-P score were both correlated negatively with BDNF, PI3K, and CREB levels but positively with AKT level, and the lack-of-premeditation (PR) sub-scale score was not significantly correlated with BDNF, PI3K, AKT, and CREB levels.

CONCLUSION

Our study results showed that the peripheral blood levels of BDNF, PI3K, AKT, and CREB in drug-naïve patients with first-episode schizophrenia were significantly different from those in the control group. The levels of these serum protein factors are promising biomarkers to predict schizophrenic depression and impulsive behaviors.

Effects of glycogen synthase kinase-3β activity inhibition on cognitive, behavioral, and hippocampal ultrastructural deficits in adulthood associated with adolescent methamphetamine exposure

Objective

Glycogen synthase kinase-3β (GSK3β) has been implicated in the maintenance of synaptic plasticity, memory process, and psychostimulant-induced behavioral effects. Hyperactive GSK3β in the Cornu Ammonis 1 (CA1) subregion of the dorsal hippocampus (DHP) was associated with adolescent methamphetamine (METH) exposure-induced behavioral and cognitive deficits in adulthood. This study aimed to evaluate the possible therapeutic effects of GSK3β inhibition in adulthood on adolescent METH exposure-induced long-term neurobiological deficits.

Methods

Adolescent male mice were treated with METH from postnatal day (PND) 45-51. In adulthood, three intervention protocols (acute lithium chloride systemic administration, chronic lithium chloride systemic administration, and chronic SB216763 administration within CA1) were used for GSK3β activity inhibition. The effect of GSK3β intervention on cognition, behavior, and GSK3β activity and synaptic ultrastructure in the DHP CA1 subregion were detected in adulthood.

Results

In adulthood, all three interventions reduced adolescent METH exposure-induced hyperactivity (PND97), while only chronic systemic and chronic within CA1 administration ameliorated the induced impairments in spatial (PND99), social (PND101) and object (PND103) recognition memory. In addition, although three interventions reversed the aberrant GSK3β activity in the DHP CA1 subregion (PND104), only chronic systemic and chronic within CA1 administration rescued adolescent METH exposure-induced synaptic ultrastructure changes in the DHP CA1 subregion (PND104) in adulthood.

Conclusion

Rescuing synaptic ultrastructural abnormalities in the dHIP CA1 subregion by chronic administration of a GSK3β inhibitor may be a suitable therapeutic strategy for the treatment of behavioral and cognitive deficits in adulthood associated with adolescent METH abuse.

Adolescent kratom exposure affects cognitive behaviours and brain metabolite profiles in Sprague-Dawley rats

Adolescence is a critical developmental period during which exposure to psychoactive substances like kratom (Mitragyna speciosa) can cause long-lasting deleterious effects. Here, we evaluated the effects of mitragynine, the main alkaloid of kratom, and lyophilised kratom decoction (LKD) on cognitive behaviours and brain metabolite profiles in adolescent rats. Male Sprague-Dawley rats (Postnatal day, PND31) were given vehicle, morphine (5 mg/kg), mitragynine (3, 10, or 30 mg/kg), or LKD (equivalent dose of 30 mg/kg mitragynine) for 15 consecutive days. Later, a battery of behavioural testing was conducted, brain was extracted and metabolomic analysis was performed using LCMS-QTOF. The results showed that mitragynine did not affect the recognition memory in the novel object recognition task. In the social interaction task, morphine, mitragynine, and LKD caused a marked deficit in social behaviour, while in Morris water maze task, mitragynine and LKD only affected reference memory. Metabolomic analysis revealed distinct metabolite profiles of animals with different treatments. Several pathways that may be involved in the effects of kratom exposure include arachidonic acid, pantothenate and CoA, and tryptophan pathways, with several potential biomarkers identified. These findings suggest that adolescent kratom exposure can cause cognitive behavioural deficits that may be associated with changes in the brain metabolite profiles.

Frequency of the Dopamine Receptor D3 (rs6280) vs. Opioid Receptor µ1 (rs1799971) Polymorphic Risk Alleles in Patients with Opioid Use Disorder: A Preponderance of Dopaminergic Mechanisms?

While opioids are a powerful class of drugs that inhibit transmission of pain signals, their use is tarnished by the current epidemic of opioid use disorder (OUD) and overdose deaths. Notwithstanding published reports, there remain gaps in our knowledge of opioid receptor mechanisms and their role in opioid seeking behavior. Thus, novel insights into molecular, neurogenetic and neuropharmacological bases of OUD are needed. We propose that an addictive endophenotype may not be entirely specific to the drug of choice but rather may be generalizable to altered brain reward circuits impacting net mesocorticolimbic dopamine release. We suggest that genetic or epigenetic alterations across dopaminergic reward systems lead to uncontrollable self-administration of opioids and other drugs. For instance, diminished availability via knockout of dopamine D3 receptor (DRD3) increases vulnerability to opioids. Building upon this concept via the use of a sophisticated polymorphic risk analysis in a human cohort of chronic opioid users, we found evidence for a higher frequency of polymorphic DRD3 risk allele (rs6280) than opioid receptor µ1 (rs1799971). In conclusion, while opioidergic mechanisms are involved in OUD, dopamine-related receptors may have primary influence on opioid-seeking behavior in African Americans. These findings suggest OUD-targeted novel and improved neuropharmacological therapies may require focus on DRD3-mediated regulation of dopaminergic homeostasis.

Identification of the Risk Genes Associated With Vulnerability to Addiction: Major Findings From Transgenic Animals

Understanding risk factors for substance use disorders (SUD) can facilitate medication development for SUD treatment. While a rich literature exists discussing environmental factors that influence SUD, fewer articles have focused on genetic factors that convey vulnerability to drug use. Methods to identify SUD risk genes include Genome-Wide Association Studies (GWAS) and transgenic approaches. GWAS have identified hundreds of gene variants or single nucleotide polymorphisms (SNPs). However, few genes identified by GWAS have been verified by clinical or preclinical studies. In contrast, significant progress has been made in transgenic approaches to identify risk genes for SUD. In this article, we review recent progress in identifying candidate genes contributing to drug use and addiction using transgenic approaches. A central hypothesis is if a particular gene variant (e.g., resulting in reduction or deletion of a protein) is associated with increases in drug self-administration or relapse to drug seeking, this gene variant may be considered a risk factor for drug use and addiction. Accordingly, we identified several candidate genes such as those that encode dopamine D₂ and D₃ receptors, mGluR₂, M₄ muscarinic acetylcholine receptors, and α₅ nicotinic acetylcholine receptors, which appear to meet the risk-gene criteria when their expression is decreased. Here, we describe the role of these receptors in drug reward and addiction, and then summarize major findings from the gene-knockout mice or rats in animal models of addiction. Lastly, we briefly discuss future research directions in identifying addiction-related risk genes and in risk gene-based medication development for the treatment of addiction.

Modafinil rescues repeated morphine-induced synaptic and behavioural impairments via activation of D1R-ERK-CREB pathway in medial prefrontal cortex

Long-term opioid abuse causes a variety of long-lasting cognitive impairments such as attention, impulsivity and working memory. These cognitive impairments undermine behavioural treatment for drug abuse and lead to poor treatment retention and outcomes. Modafinil is a wake-promoting drug that shows potential in improving attention and memory in humans and animals. However, modafinil's effect on opioid-induced cognitive impairments remains unclear, and the underlying mechanism is poorly understood. This study showed that repeated morphine administration significantly impairs attention, increases impulsivity and reduces motivation to natural rewards in mice. Systemic modafinil treatment at low dose efficiently ameliorates morphine-induced attention dysfunction and improves motivation and working memory in mice. High dose of modafinil has adverse effects on impulsive action and attention. Local infusion of D1R antagonist SCH-23390 reverses the morphine-induced synaptic abnormalities and activation of the D1R-ERK-CREB pathway in medial prefrontal cortex (mPFC). This study demonstrated a protective effect of modafinil in mPFC neurons and offered a therapeutic potential for cognitive deficits in opioid abuse.

HCN2 contributes to oxaliplatin-induced neuropathic pain by inducing spinal long-term potentiation via activation of NMDA receptor-mediated CaMKII signaling

Our previous findings indicate that HCN2 contributes to oxaliplatin-induced neuropathic pain, but the mechanisms underlying the development of neuropathic pain are still unclear. Here, we found that the rat HCN2 levels significantly increased after high-frequency stimulation-induced long-term potentiation (LTP). Spinal local application of ZD7288 (a cyclic-nucleotide-gated-channel-specific inhibitor) prevented LTP induction after intraperitoneal injection of oxaliplatin. In addition, oxaliplatin administration induced spinal LTP via activation of the CaMKII-CREB cascade in the rat spinal dorsal horn. Moreover, we found that administration of oxaliplatin significantly increased the amplitude of excitatory postsynaptic currents and the number of action potentials, but these effects were attenuated by pretreatment with either CaMKII inhibitor KN-93 or NR2B antagonist Ro 25-6981. An increase in the phosphorylation of spinal N-methyl-d-aspartate (NMDA) receptor subunit 1 (NR1) after oxaliplatin administration was weakened by ZD7288 pretreatment. Administration of noncompetitive NMDA receptor antagonist MK-801 blocked oxaliplatin-evoked CaMKII-CREB cascade activation and prevented HCN2-mediated spinal-LTP induction in vitro and suppressed neuropathic-pain behaviors of rats. All these data suggest that HCN2 contributes to the development of neuropathic pain by inducing spinal LTP via activation of NMDA receptor-mediated CaMKII signaling.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

The basolateral amygdala regulation of complex cognitive behaviours in the five-choice serial reaction time task

RATIONALE

The basolateral amygdala (BLA) plays important roles in the cognitive control in human and non-human animals. However, inconsistent findings between species have been observed and there have been relatively few detailed investigations of the cognitive properties of BLA, especially in mice.

OBJECTIVE

Our aim was to determine the role of BLA in cognition by using optogenetic manipulations.

METHODS

Male C57BL/six mice were trained and tested on the five-choice serial reaction time task (5-CSRTT), open-field test (OFT), elevated plus maze (EPM), Y-maze, and novel object recognition (NOR) test during optogenetic stimulation and inhibition of the BLA.

RESULTS

Optogenetic activation of the BLA decreased the impulsivity and increased the compulsivity of mice, whereas optogenetic inhibition of BLA had the opposite effect. Similarly, anxiety-like behaviours and spatial working memory were increased in BLA activation mice, whereas BLA inhibition decreased these behaviours. However, both BLA activation and inhibition decreased the motivation of the mice.

CONCLUSIONS

These data demonstrate that the BLA regulates impulsive action and spatial working memory, and plays a critical role in anxiety-like behaviours.

Naloxone reversed cognitive impairments induced by repeated morphine under heavy perceptual load in the 5-choice serial reaction time task

Repeated opioids abuse may produce long-lasting and complicated cognitive deficits in individuals. Naloxone is a typical mu-opioid receptor antagonist widely used in clinical treatment for opioid overdose and opioid abuse. However, it remains unclear whether naloxone affects morphine-induced cognitive deficits. Using the 5-choice serial reaction time task (5-CSRTT), the present study investigated cognitive profiles including attention, impulsivity, compulsivity, and processing speed in repeated morphine-treated mice. Repeated morphine administration (10 mg/kg, i.p.) induced complex cognitive changes including decreased attention and increased impulsivity, compulsivity, processing speed. Systemic naloxone administration (5 mg/kg, i.p.) reversed these cognitive changes under the heavy perceptual load in 5-CSRTT. Using the novel object recognition (NOR), Y-maze and open-field test (OFT), the present study investigated the memory ability and locomotor activity. Naloxone reversed the effect of morphine on recognition memory and locomotion but had no effect on working memory. In addition, repeated morphine administration decreased the expression of postsynaptic density protein 95 (PSD95) and cAMP response element binding protein (CREB) phosphorylation in the prefrontal cortex (PFC) and hippocampus (HIP), and these effects were significantly reversed by naloxone in PFC. Our study suggests that repeated exposure to morphine affects multiple cognitive aspects and impairs synaptic functions. Systemic naloxone treatment reverses the mu-opioids-induced cognitive changes, especially under the heavy perceptual load, possibly by restoring the synaptic dysfunctions.

LiCl Pretreatment Ameliorates Adolescent Methamphetamine Exposure-Induced Long-Term Alterations in Behavior and Hippocampal Ultrastructure in Adulthood in Mice

BACKGROUND

Adolescent methamphetamine exposure causes a broad range of neurobiological deficits in adulthood. Glycogen synthase kinase-3β is involved in various cognitive and behavioral processes associated with methamphetamine exposure. This study aims to investigate the protective effects of the glycogen synthase kinase-3β inhibitor lithium chloride on adolescent methamphetamine exposure-induced long-term alterations in emotion, cognition, behavior, and molecule and hippocampal ultrastructure in adulthood.

METHODS

A behavioral test battery was used to investigate the protective effects of lithium chloride on adolescent methamphetamine exposure-induced long-term emotional, cognitive, and behavioral impairments in mice. Western blotting and immunohistochemistry were used to detect glycogen synthase kinase-3β activity levels in the medial prefrontal cortex and dorsal hippocampus. Electron microscopy was used to analyze changes in synaptic ultrastructure in the dorsal hippocampus. Locomotor sensitization with a methamphetamine (1 mg/kg) challenge was examined 80 days after adolescent methamphetamine exposure.

RESULTS

Adolescent methamphetamine exposure induced long-term alterations in locomotor activity, novel spatial exploration, and social recognition memory; increases in glycogen synthase kinase-3β activity in dorsal hippocampus; and decreases in excitatory synapse density and postsynaptic density thickness in CA1. These changes were ameliorated by lithium chloride pretreatment. Adolescent methamphetamine exposure-induced working memory deficits in Y-maze spontaneous alternation test and anxiety-like behavior in elevated-plus maze test spontaneously recovered after long-term methamphetamine abstinence. No significant locomotor sensitization was observed after long-term methamphetamine abstinence.

CONCLUSIONS

Hyperactive glycogen synthase kinase-3β contributes to adolescent chronic methamphetamine exposure-induced behavioral and hippocampal impairments in adulthood. Our results suggest glycogen synthase kinase-3β may be a potential target for the treatment of deficits in adulthood associated with adolescent methamphetamine abuse.

Brain and Cognition for Addiction Medicine: From Prevention to Recovery Neural Substrates for Treatment of Psychostimulant-Induced Cognitive Deficits

Addiction to psychostimulants like cocaine, methamphetamine, and nicotine poses a continuing medical and social challenge both in the United States and all over the world. Despite a desire to quit drug use, return to drug use after a period of abstinence is a common problem among individuals dependent on psychostimulants. Recovery for psychostimulant drug-dependent individuals is particularly challenging because psychostimulant drugs induce significant changes in brain regions associated with cognitive functions leading to cognitive deficits. These cognitive deficits include impairments in learning/memory, poor decision making, and impaired control of behavioral output. Importantly, these drug-induced cognitive deficits often impact adherence to addiction treatment programs and predispose abstinent addicts to drug use relapse. Additionally, these cognitive deficits impact effective social and professional rehabilitation of abstinent addicts. The goal of this paper is to review neural substrates based on animal studies that could be pharmacologically targeted to reverse psychostimulant-induced cognitive deficits such as impulsivity and impairment in learning and memory. Further, the review will discuss neural substrates that could be used to facilitate extinction learning and thus reduce emotional and behavioral responses to drug-associated cues. Moreover, the review will discuss some non-pharmacological approaches that could be used either alone or in combination with pharmacological compounds to treat the above-mentioned cognitive deficits. Psychostimulant addiction treatment, which includes treatment for cognitive deficits, will help promote abstinence and allow for better rehabilitation and integration of abstinent individuals into society.

Sinomenine Protects Against Morphine Dependence through the NMDAR1/CAMKII/CREB Pathway: A Possible Role of Astrocyte-Derived Exosomes

Sinomenine is a nonaddictive alkaloid used to prevent morphine dependence, even thoughits mechanism isnot fully understood. Astrocytes aggravate the pathological process in their neighboring cellsthrough exosomes in central nervous system diseases. However, the effect of sinomenine on astrocyte-derived exosomes for the amelioration of morphine dependence has not been reported yet. In this study, we found that sinomenine prevented the morphine-induced conditionedplace preference in mice. Sinomenine reduced the levels of cAMP and intracellular Ca2+ in morphine-treated SH-SY5Y cells. Moreover, sinomenine inhibited the expressions of p-NMDAR1/NMDAR1, p-CAMKII/CAMKII, and p-CREB/CREB in the hippocampusof morphine-dependent mice and SH-SY5Y cells. Furthermore, we found that sinomenine inhibitedthe morphine-induced activation of astrocytesin vivo and in vitro. Afterwards, exosomes were isolated from cultured primary astrocytes treated with phosphate buffer saline (PBS, ctl-exo), morphine (mor-exo), or morphine and sinomenine (Sino-exo). Subsequently, morphine-treated SH-SY5Y cells were treated with ctl-exo, mor-exo, and Sino-exo. Results showed that Sino-exo reduced the level of cAMP, intracellular Ca2+, and the expression of p-CAMKII/CAMKII and p-CREB/CREB in morphine-treated SH-SY5Y cells. In conclusion, we demonstrated that sinomenine exhibited protective effects against morphine dependencein vivo and in vitro through theNMDAR1/CAMKII/CREB pathway. Sinomenine-induced alterationof the function of astrocyte-derived exosomes may contribute to the antidependence effects of sinomenine in morphine dependence.