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Extrasynaptic GABA A receptors (GABA A Rs) composed of α4, β, and δ subunits mediate GABAergic tonic inhibition and are potential molecular targets in the modulation of behavioral responses to natural and drug rewards. These GABA A Rs are highly expressed within the nucleus accumbens (NAc), where they influence the excitability of the medium spiny neurons. Here, we explore their role in modulating behavioral responses to food-conditioned cues and the behavior-potentiating effects of cocaine. α4-Subunit constitutive knock-out mice (α4 -/- ) showed higher rates of instrumental responding for reward-paired stimuli in a test of conditioned reinforcement (CRf). A similar effect was seen following viral knockdown of GABA A R α4 subunits within the NAc. Local infusion of the α4βδ-GABA A R-preferring agonist THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol; Gaboxadol) into the NAc had no effect on responding when given alone but reduced cocaine potentiation of responding for conditioned reinforcers in wild-type, but not α4 -/- mice. Finally, specific deletion of α4-subunits from dopamine D2, but not D1, receptor-expressing neurons (DRD2 and DRD1 neurons), mimicked the phenotype of the constitutive knockout, potentiating CRf responding, and blocking intra-accumbal THIP attenuation of cocaine-potentiated CRf responding. These data demonstrate that α4-GABA A R-mediated inhibition of DRD2 neurons reduces instrumental responding for a conditioned reinforcer and its potentiation by cocaine and emphasize the importance of GABAergic signaling within the NAc in mediating the effects of cocaine., Competing Interests: The authors declare no competing financial interests., (Copyright © 2023 Macpherson et al.)

Early-life stress (ELS) is known to exert long-term effects on brain function, with resulting deleterious consequences for several aspects of mental health, including the development of addiction to drugs of abuse. One potential mechanism in humans is suggested by findings that ELS interacts with polymorphisms of the GABRA2 gene, encoding α2 subunits of GABAA receptors, to increase the risk for both post-traumatic stress disorder and vulnerability to cocaine addiction. We used a mouse model, in which the amount of material for nest building was reduced during early postnatal life, to study interactions between ELS and expression of α2-containing GABAA receptors in influencing cocaine-related behaviour. Breeding of parents heterozygous for a deletion of α2 resulted in litters containing homozygous knockout (α2), heterozygous knockout (α2) and wild-type (α2) offspring. Following the ELS procedure, the mice were allowed to develop to adulthood before being tested for the acute effect of cocaine on locomotor stimulation, behavioural sensitization to repeated cocaine and to cocaine-conditioned activity. Exposure to ELS resulted in increased acute locomotor stimulant effects of cocaine across all genotypes, with the most marked effects in α2 mice (which also showed increased activity following vehicle). Repeated cocaine administration to nonstressed mice resulted in sensitization in α2 and α2 mice, but, in keeping with previous findings, not in α2 mice. Previous exposure to ELS reduced sensitization in α2 mice, albeit not significantly, and abolished sensitization in α2 mice. Conditioned activity was elevated following ELS in all animals, independently of genotype. Thus, while the enhanced acute effects of cocaine following ELS being most marked in α2 mice suggests a function of α2-containing GABAA receptors in protecting against stress, the interaction between ELS and genotype in influencing sensitization may be more in keeping with ELS reducing expression of α2-containing GABAA receptors. The ability of ELS to increase cocaine-conditioned locomotor activity appears to be independent of α2-containing GABAA receptors.

Haplotypes of the Gabra2 gene encoding the α2-subunit of the GABA A receptor (GABA A R) are associated with drug abuse, suggesting that α2-GABA A Rs may play an important role in the circuitry underlying drug misuse. The genetic association of Gabra2 haplotypes with cocaine addiction appears to be evident primarily in individuals who had experienced childhood trauma. Given this association of childhood trauma, cocaine abuse and the Gabra2 haplotypes, we have explored in a mouse model of early life adversity (ELA) whether such events influence the behavioral effects of cocaine and if, as suggested by the human studies, α2-GABA A Rs in the nucleus accumbens (NAc) are involved in these perturbed behaviors. In adult mice prior ELA caused a selective decrease of accumbal α2-subunit mRNA, resulting in a selective decrease in the number and size of the α2-subunit (but not the α1-subunit) immunoreactive clusters in NAc core medium spiny neurons (MSNs). Functionally, in adult MSNs ELA decreased the amplitude and frequency of GABA A R-mediated miniature inhibitory postsynaptic currents (mIPSCs), a profile similar to that of α2 "knock-out" (α2 -/- ) mice. Behaviourally, adult male ELA and α2 -/- mice exhibited an enhanced locomotor response to acute cocaine and blunted sensitisation upon repeated cocaine administration, when compared to their appropriate controls. Collectively, these findings reveal a neurobiological mechanism which may relate to the clinical observation that early trauma increases the risk for substance abuse disorder (SAD) in individuals harbouring haplotypic variations in the Gabra2 gene., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Variations in the GABRA2 gene, encoding α2 subunits of GABAA receptors, have been associated with risk for addiction to several drugs, but the mechanisms by which variations in non-coding regions of GABRA2 increase risk for addictions are not understood. Mice with deletion of GABRA2 show deficits in the ability of psychostimulants to facilitate responding for conditioned reinforcers, offering a potential explanation., Methods: We report human and mouse studies investigating a potential endophenotype underlying this association. Healthy human volunteers carrying either cocaine-addiction "risk" or "protective" GABRA2 single nucleotide polymorphism (SNPs) were tested for their subjective responses to methylphenidate, and methylphenidate's ability to facilitate conditioned reinforcement (CRf) for visual stimuli (CS+) associated with monetary reward. In parallel, methylphenidate's ability to facilitate responding for a visual CRf was studied in wildtype and α2 knockout (α2(-/-)) mice., Results: Methylphenidate increased the number of CS+ presentations obtained by human subjects carrying protective, but not risk SNPs. In mice, methylphenidate increased responding for a CS+ in wildtype, but not α2(-/-) mice. Human subjects carrying protective SNPs felt stimulated, aroused and restless following methylphenidate, while individuals carrying risk SNPs did not., Conclusion: Human risk SNP carriers were insensitive to methylphenidate's effects on mood or in facilitating CRf. That mice with the gene deletion were also insensitive to methylphenidate's ability to increase responding for CRf, suggests a potential mechanism whereby low α2-subunit levels increase risk for addictions. Circuits employing GABAA-α2 subunit-containing receptors may protect against risk for addictions.

It is becoming increasingly evident that a variety of factors contribute to smoking behavior. Nicotine is a constituent of tobacco smoke that exerts its psychoactive effects via binding to nicotinic acetylcholine receptors (nAChRs) in brain. Human genetic studies have identified polymorphisms in nAChR genes, which predict vulnerability to risk for tobacco dependence. In vitro studies and animal models have identified the functional relevance of specific polymorphisms. Together with animal behavioral models, which parse behaviors believed to contribute to tobacco use in humans, these studies demonstrate that nicotine action at a diversity of nAChRs is important for expression of independent behavioral phenotypes, which support smoking behavior.

Background: Postoperative cognitive dysfunction (POCD) represents a post-surgical complication that features progressive cognitive impairment and memory loss, often occurring in elderly patients. This study aimed to investigate the potential biological mechanisms underlying POCD. Methods: Male C57BL/6 mice (2 and 17 months old) were randomly assigned to surgery or control groups. The surgery group underwent laparotomy under 1.5% isoflurane anesthesia, while controls received no intervention. Cognitive function was assessed 7–10 days post-surgery using open field, Y-maze, and novel object recognition tests. Hippocampal mRNA expression was analyzed using Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment. A competing endogenous RNA (ceRNA) network was constructed using microRNA (miRNA) target prediction databases (miRanda, miRTarbase, miRcode) and sequencing results. Key findings were validated by RT-qPCR and immunofluorescence. The Connectivity Map (CMap) database was queried to predict potential POCD treatments. Results: Aging significantly affected mice's spontaneous activity in the open field test (F1, 28 = 8.933, P < 0.01) and the proportion of time spent in the center area (F1, 28 = 5.387, P < 0.05). Surgery significantly reduced the rate of spontaneous alternations in the Y-maze (F1, 28 = 16.94, P < 0.001) and the recognition index in novel object recognition test (F1, 28 = 6.839, P < 0.05) in aging mice, but had no effect on young mice. Transcriptome analysis revealed that aging and surgery downregulated multiple neurogenesis-related genes in the hippocampus. Doublecortin (DCX) immunofluorescence staining confirmed reduced hippocampal neurogenesis in aging mice, which was further decreased after surgery. We identified several key lncRNAs and miRNAs implicated in neurogenesis regulation. Additionally, drugs were predicted as potential therapeutic candidates for POCD treatment. Conclusion: Both aging and surgery have complex effects on the hippocampal transcriptome in mice. The significant decrease in neurogenesis may be a potential reason for the increased susceptibility of aging mice to POCD. The identified key regulatory lncRNAs, miRNAs, and drugs provide potential therapeutic targets for POCD prevention and treatment. [ABSTRACT FROM AUTHOR]

Rationale: GABAA receptors containing α2-subunits are highly represented in brain areas that are involved in motivation and reward, and have been associated with addiction to several drugs, including cocaine. We have shown previously that a deletion of the α2-subunit results in an absence of sensitisation to cocaine., Objective: We investigated the reinforcing properties of cocaine in GABAA α2-subunit knockout (KO) mice using an intravenous self-administration procedure., Methods: α2-subunit wildtype (WT), heterozygous (HT) and KO mice were trained to lever press for a 30 % condensed milk solution. After implantation with a jugular catheter, mice were trained to lever press for cocaine (0.5 mg/kg/infusion) during ten daily sessions. Responding was extinguished and the mice tested for cue- and cocaine-primed reinstatement. Separate groups of mice were trained to respond for decreasing doses of cocaine (0.25, 0.125, 0.06 and 0.03 mg/kg)., Results: No differences were found in acquisition of lever pressing for milk. All genotypes acquired self-administration of cocaine and did not differ in rates of self-administration, dose dependency or reinstatement. However, whilst WT and HT mice showed a dose-dependent increase in lever pressing during the cue presentation, KO mice did not., Conclusions: Despite a reported absence of sensitisation, motivation to obtain cocaine remains unchanged in KO and HT mice. Reinstatement of cocaine seeking by cocaine and cocaine-paired cues is also unaffected. We postulate that whilst not directly involved in reward perception, the α2-subunit may be involved in modulating the "energising" aspect of cocaine's effects on reward-seeking.

Within the nucleus accumbens (NAc), synaptic GABAA receptors (GABAARs) mediate phasic inhibition of medium spiny neurons (MSNs) and influence behavioral responses to cocaine. We demonstrate that both dopamine D1- and D2-receptor-expressing MSNs (D-MSNs) additionally harbor extrasynaptic GABAARs incorporating α4, β, and δ subunits that mediate tonic inhibition, thereby influencing neuronal excitability. Both the selective δ-GABAAR agonist THIP and DS2, a selective positive allosteric modulator, greatly increased the tonic current of all MSNs from wild-type (WT), but not from δ(-/-) or α4(-/-) mice. Coupling dopamine and tonic inhibition, the acute activation of D1 receptors (by a selective agonist or indirectly by amphetamine) greatly enhanced tonic inhibition in D1-MSNs but not D2-MSNs. In contrast, prolonged D2 receptor activation modestly reduced the tonic conductance of D2-MSNs. Behaviorally, WT and constitutive α4(-/-) mice did not differ in their expression of cocaine-conditioned place preference (CPP). Importantly, however, mice with the α4 deletion specific to D1-expressing neurons (α4(D1-/-)) showed increased CPP. Furthermore, THIP administered systemically or directly into the NAc of WT, but not α4(-/-) or α4(D1-/-) mice, blocked cocaine enhancement of CPP. In comparison, α4(D2-/-) mice exhibited normal CPP, but no cocaine enhancement. In conclusion, dopamine modulation of GABAergic tonic inhibition of D1- and D2-MSNs provides an intrinsic mechanism to differentially affect their excitability in response to psychostimulants and thereby influence their ability to potentiate conditioned reward. Therefore, α4βδ GABAARs may represent a viable target for the development of novel therapeutics to better understand and influence addictive behaviors.

Alcohol dependence is a common, complex and debilitating disorder with genetic and environmental influences. Here we show that alcohol consumption increases following mutations to the γ-aminobutyric acidA receptor (GABAAR) β1 subunit gene (Gabrb1). Using N-ethyl-N-nitrosourea mutagenesis on an alcohol-averse background (F1 BALB/cAnN x C3H/HeH), we develop a mouse model exhibiting strong heritable preference for ethanol resulting from a dominant mutation (L285R) in Gabrb1. The mutation causes spontaneous GABA ion channel opening and increases GABA sensitivity of recombinant GABAARs, coupled to increased tonic currents in the nucleus accumbens, a region long-associated with alcohol reward. Mutant mice work harder to obtain ethanol, and are more sensitive to alcohol intoxication. Another spontaneous mutation (P228H) in Gabrb1 also causes high ethanol consumption accompanied by spontaneous GABA ion channel opening and increased accumbal tonic current. Our results provide a new and important link between GABAAR function and increased alcohol consumption that could underlie some forms of alcohol abuse.

Human genetic studies have suggested that polymorphisms of the GABRA2 gene encoding the GABA(A) α2-subunit are associated with ethanol dependence. Variations in this gene also convey sensitivity to the subjective effects of ethanol, indicating a role in mediating ethanol-related behaviours. We therefore investigated the consequences of deleting the α2-subunit on the ataxic and rewarding properties of ethanol in mice. Ataxic and sedative effects of ethanol were explored in GABA(A) α2-subunit wildtype (WT) and knockout (KO) mice using a Rotarod apparatus, wire hang and the duration of loss of righting reflex. Following training, KO mice showed shorter latencies to fall than WT littermates under ethanol (2 g/kg i.p.) in both Rotarod and wire hang tests. After administration of ethanol (3.5 g/kg i.p.), KO mice took longer to regain the righting reflex than WT mice. To ensure the acute effects are not due to the gabra2 deletion affecting pharmacokinetics, blood ethanol concentrations were measured at 20 minute intervals after acute administration (2 g/kg i.p.), and did not differ between genotypes. To investigate ethanol's rewarding properties, WT and KO mice were trained to lever press to receive increasing concentrations of ethanol on an FR4 schedule of reinforcement. Both WT and KO mice self-administered ethanol at similar rates, with no differences in the numbers of reinforcers earned. These data indicate a protective role for α2-subunits, against the acute sedative and ataxic effects of ethanol. However, no change was observed in ethanol self administration, suggesting the rewarding effects of ethanol remain unchanged.

A clear interrelationship between biological rhythms and addiction has emerged from recent preclinical and clinical studies. In particular, the manipulation of the so-called 'clock genes' interferes with the manifestation of drug-related responses. For instance, Period 1 (Per1(Brdm1)) mutant mice do not display behavioural sensitization in response to repeated cocaine administration and do not express cocaine conditioned place preference, in contrast to control littermates. To assess the involvement of the mPer1 gene in a robust model of cocaine reinforcement and relapse-like behaviour, we tested Per1(Brdm1) mutant mice and their littermates for self-administration of several doses (0.06-0.75 mg/kg/infusion) of cocaine, and for reinstatement of an extinguished cocaine-seeking response. Per1(Brdm1) mutant mice did not differ from control littermates in their propensity to self-administer cocaine or to reinstate an extinguished cocaine-seeking behaviour in response to drug-associated cues or cocaine priming. In contrast to our earlier data on Per1(Brdm1) mutant mice in cocaine sensitization and conditioned place preference, this finding does not suggest a relationship between the circadian clock gene mPer1 in cocaine self-administration and reinstatement of cocaine-seeking behaviour. This study adds one further example to the notion that various behavioural tests usually used in addiction research rely on different neurobiological substrates.

Because GABA(A) receptors containing alpha2 subunits are highly represented in areas of the brain, such as nucleus accumbens (NAcc), frontal cortex, and amygdala, regions intimately involved in signaling motivation and reward, we hypothesized that manipulations of this receptor subtype would influence processing of rewards. Voltage-clamp recordings from NAcc medium spiny neurons of mice with alpha2 gene deletion showed reduced synaptic GABA(A) receptor-mediated responses. Behaviorally, the deletion abolished cocaine's ability to potentiate behaviors conditioned to rewards (conditioned reinforcement), and to support behavioral sensitization. In mice with a point mutation in the benzodiazepine binding pocket of alpha2-GABA(A) receptors (alpha2H101R), GABAergic neurotransmission in medium spiny neurons was identical to that of WT (i.e., the mutation was silent), but importantly, receptor function was now facilitated by the atypical benzodiazepine Ro 15-4513 (ethyl 8-amido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo [1,5-a] [1,4] benzodiazepine-3-carboxylate). In alpha2H101R, but not WT mice, Ro 15-4513 administered directly into the NAcc-stimulated locomotor activity, and when given systemically and repeatedly, induced behavioral sensitization. These data indicate that activation of alpha2-GABA(A) receptors (most likely in NAcc) is both necessary and sufficient for behavioral sensitization. Consistent with a role of these receptors in addiction, we found specific markers and haplotypes of the GABRA2 gene to be associated with human cocaine addiction.

Benzodiazepines increase food intake, an effect attributed to their ability to enhance palatability. We investigated which GABA(A) receptor subtypes may be involved in mediating benzodiazepine-induced hyperphagia. The role of the alpha2 subtype was investigated by observing the effects of midazolam, on the behavioural satiety sequence in mice with targeted deletion of the alpha2 gene (alpha2 knockout). Midazolam (0.125, 0.25 and 0.5mg/kg) increased food intake and the amount of time spent feeding in alpha2 knockout mice, suggesting that BZ-induced hyperphagia does not involve alpha2-containing GABA(A) receptors. We further investigated the roles of alpha1- and alpha3-containing GABA(A) receptors in mediating BZ-induced hyperphagia. We treated alpha2(H101R) mice, in which alpha2-containing receptors are rendered benzodiazepine insensitive, with L-838417, a compound which acts as a partial agonist at alpha2-, alpha3- and alpha5-receptors but is inactive at alpha1-containing receptors. L-838417 (10 and 30 mg/kg) increased food intake and the time spent feeding in both wildtype and alpha2(H101R) mice, demonstrating that benzodiazepine-induced hyperphagia does not require alpha1- and alpha2-containing GABA(A) receptors. These observations, together with evidence against the involvement of alpha5-containing GABA(A) receptors, suggest that alpha3-containing receptors mediate BZ-induced hyperphagia in the mouse.

Mice with point-mutated alpha2 GABA(A) receptor subunits (rendering them diazepam insensitive) are resistant to the anxiolytic-like effects of benzodiazepines (BZs) in the conditioned emotional response (CER) test, but show normal anxiolytic effects of a barbiturate. We investigated the consequence of deleting the alpha2-subunit on acquisition of the CER with increasing intensity of footshock, and on the anxiolytic efficacy of a benzodiazepine, diazepam, and a barbiturate, pentobarbital. alpha2 knockout (KO) and wildtype (WT) mice were trained in a conditioned emotional response (CER) task, in which lever pressing for food on a variable interval (VI) schedule was suppressed during the presentation of a compound light/tone conditioned stimulus (CS+) that predicted footshock. The ability of diazepam and of pentobarbital to reduce suppression during the CS+ was interpreted as an anxiolytic response. There were no differences between the genotypes in shock sensitivity, as assessed by their flinch responses to increasing levels of shock. However, alpha2 KO mice showed a greater suppression of lever pressing than WT littermates in the presence of a compound cue signalling footshock. Diazepam (0, 0.5, 1 and 2 mg/kg) induced a dose-dependent anxiolytic-like effect in WT mice but no such effect was seen in KO mice. Similarly, although pentobarbital (20 mg/kg) reduced the ability of the CS+ to reduce lever pressing rates in WT mice, this effect was not seen in the KO. These findings suggest that alpha2-containing GABA(A) receptors mediate the anxiolytic effects of barbiturates, as well as benzodiazepines, and that they may be involved in neuronal circuits underlying conditioned anxiety.

E-cigarettes gained popularity globally through the promotion of e-cigarettes as a risk-free way to stop traditional smoking. However, new evidence suggests that they may have a detrimental effect on the nervous system and ultimately adverse neurological manifestations. Seizures have been reported among both new and experienced e-cigarette users. In several cases, the seizure presented immediately after its use, while others reported continuous use for weeks before seizures occurred. This review presents a deeper insight into the clinical management, implications, and public health considerations of seizure susceptibility in e-cigarette users. Using recent case reports, epidemiological studies, and experimental research, we highlight the role of likely etiological mechanisms such as how nicotine's convulsive effects are linked to α7- nicotinic acetylcholine receptors (nAChRs), the varied clinical presentations, and the potential nicotine toxicity linked to seizures. Furthermore, we discuss the existing debates and controversies, diagnostic directions, and potential role in individual susceptibility to e-cigarette-associated seizures. Importantly, we address how seizures may be accompanied by both physical and psychological sequelae, which may impair the quality of life for individuals presenting for emergency care. We also address the limitations and challenges in the etiology of e-cigarette-associated seizures and the non-criteria for defining seizures caused by e-cigarettes. The review concludes with an insight into public health considerations and policy recommendations by highlighting the importance of mass awareness and clinical considerations that could guide patient management. [ABSTRACT FROM AUTHOR]

Clinically, inflammatory pain is far more persistent than that typically modelled pre-clinically, with the majority of animal models focussing on short-term effects of the inflammatory pain response. The large attrition rate of compounds in the clinic which show pre-clinical efficacy suggests the need for novel models of, or approaches to, chronic inflammatory pain if novel mechanisms are to make it to the market. A model in which a more chronic inflammatory hypersensitivity phenotype is profiled may allow for a more clinically predictive tool. The aims of these studies were to characterise and validate a chronic model of inflammatory pain. We have shown that injection of a large volume of adjuvant to the intra-articular space of the rat knee results in a prolonged inflammatory pain response, compared to the response in an acute adjuvant model. Additionally, this model also results in a hypersensitive state in the presence and absence of inflammation. A range of clinically effective analgesics demonstrate activity in this chronic model, including morphine (3mg/kg, t.i.d.), dexamethasone (1mg/kg, b.i.d.), ibuprofen (30mg/kg, t.i.d.), etoricoxib (5mg/kg, b.i.d.) and rofecoxib (0.3-10mg/kg, b.i.d.). A further aim was to exemplify the utility of this chronic model over the more acute intra-plantar adjuvant model using two novel therapeutic approaches; NR2B selective NMDA receptor antagonism and iNOS inhibition. Our data shows that different effects were observed with these therapies when comparing the acute model with the model of chronic inflammatory joint pain. These data suggest that the chronic model may be more relevant to identifying mechanisms for the treatment of chronic inflammatory pain states in the clinic.

Deletions of gria1 or gria2 genes encoding alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic-acid-receptor subunits differ in their effects on appetitive conditioning. The authors investigated whether similar differences would occur in an aversive conditioning test. The ability of a discrete stimulus paired with footshock to subsequently inhibit food-maintained operant responding (conditioned emotional response) was examined in mice with deletions of gria1 or gria2 genes. Whereas gria1 knockout (KO) mice performed normally compared with wild-type (WT) controls, gria2 KO mice displayed no reduction in response rates when the shock-paired stimulus was presented. Nevertheless, gria2 KOs displayed evidence of freezing in a footshock-paired context, indicating that aversive learning could occur. In addition, gria1 KO mice showed some evidence of increased anxiety, and gria2 KOs showed reduced anxiety, in the elevated plus-maze., (((c) 2006 APA, all rights reserved).)

Background: Accumulating evidence supports that the Western diet (WD), a diet high in saturated fat and sugary drinks, contributes to the pathogenesis of anxiety disorders, which are the most prevalent mental disorders worldwide. However, the underlying mechanisms by which WD causes anxiety remain unclear. Abundant expression of taste receptor type 1 member 3 (TAS1R3) has been identified in the hypothalamus, a key brain area involved in sensing peripheral nutritional signals and regulating anxiety. Thus, we investigated the influence of excessive WD intake on anxiety and mechanisms by which WD intake affects anxiety development using wild-type (WT) and Tas1r3 deficient (Tas1r3−/−) mice fed a normal diet (ND) or WD for 12 weeks. Results: WD increased anxiety in male WT mice, whereas male Tas1r3−/− mice were protected from WD-induced anxiety, as assessed by open field (OF), elevated plus maze (EPM), light–dark box (LDB), and novelty-suppressed feeding (NSF) tests. Analyzing the hypothalamic transcriptome of WD-fed WT and Tas1r3−/− mice, we found 1,432 genes significantly up- or down-regulated as a result of Tas1r3 deficiency. Furthermore, bioinformatic analysis revealed that the CREB/BDNF signaling-mediated maintenance of neuronal regeneration, which can prevent anxiety development, was enhanced in WD-fed Tas1r3−/− mice compared with WD-fed WT mice. Additionally, in vitro studies further confirmed that Tas1r3 knockdown prevents the suppression of Creb1 and of CREB-mediated BDNF expression caused by high levels of glucose, fructose, and palmitic acid in hypothalamic neuronal cells. Conclusions: Our results imply that TAS1R3 may play a key role in WD-induced alterations in hypothalamic functions, and that inhibition of TAS1R3 overactivation in the hypothalamus could offer therapeutic targets to alleviate the effects of WD on anxiety. [ABSTRACT FROM AUTHOR]

Central nervous system stimulants of various levels of effectiveness are commonly used among students worldwide. These stimulants are a group of drugs that increase vigilance, alertness, and excitation. In the present study, three stimulants; caffeine, methylphenidate, and modafinil are compared in terms of their mechanisms of action, effects on memory, and addiction, especially in the younger population. Caffeine is the most widely used stimulant after methylphenidate and modafinil. Although the possibility of addiction due to caffeine is highly dose-dependent, there is a potential for abuse of methylphenidate and modafinil. These stimulants are used for a variety of reasons, such as staying awake to study, increasing alertness to complete assignments, or for recreational purposes among students. Also, since many stimulants are readily accessible to many individuals, such substances may be misused. The aim of the study is to show different aspects of caffeine, methylphenidate, and modafinil use on epidemiology, mechanism, addiction, and effect on electroencephalogram and long-term memory. [ABSTRACT FROM AUTHOR]

Introduction: Medications which target benzodiazepine (BZD) binding sites of GABAA receptors (GABAARs) have been in widespread use since the nineteen-sixties. They carry labels as anxiolytics, hypnotics or antiepileptics. All benzodiazepines and several nonbenzodiazepine Z-drugs share high affinity binding sites on certain subtypes of GABAA receptors, from which they can be displaced by the clinically used antagonist flumazenil. Additional binding sites exist and overlap in part with sites used by some general anaesthetics and barbiturates. Despite substantial preclinical efforts, it remains unclear which receptor subtypes and ligand features mediate individual drug effects. There is a paucity of literature comparing clinically observed adverse effect liabilities across substances in methodologically coherent ways. Methods: In order to examine heterogeneity in clinical outcome, we screened the publicly available U.S. FDA adverse event reporting system (FAERS) database for reports of individual compounds and analyzed them for each sex individually with the use of disproportionality analysis. The complementary use of physico-chemical descriptors provides a molecular basis for the analysis of clinical observations of wanted and unwanted drug effects. Results and Discussion: We found a multifaceted FAERS picture, and suggest that more thorough clinical and pharmacoepidemiologic investigations of the heterogenous side effect profiles for benzodiazepines and Z-drugs are needed. This may lead to more differentiated safety profiles and prescription practice for particular compounds, which in turn could potentially ease side effect burden in everyday clinical practice considerably. From both preclinical literature and pharmacovigilance data, there is converging evidence that this very large class of psychoactive molecules displays a broad range of distinctive unwanted effect profiles - too broad to be explained by the four canonical, so-called "diazepam-sensitive high-affinity interaction sites". The substance-specific signatures of compound effects may partly be mediated by phenomena such as occupancy of additional binding sites, and/or synergistic interactions with endogenous substances like steroids and endocannabinoids. These in turn drive the wanted and unwanted effects and sex differences of individual compounds. [ABSTRACT FROM AUTHOR]

The use of animal models continues to be essential for carrying out research into clinical phenomena, including addiction. However, the complexity of the clinical condition inevitably means that even the best animal models are inadequate, and this may go some way to account for the apparent failures of discoveries from animal models, including the identification of potential novel therapies, to translate to the clinic. We argue here that it is overambitious and misguided in the first place to attempt to model complex, multifacetted human disorders such as addiction in animals, and especially in rodents, and that all too frequently "validity" of such models is limited to superficial similarities, referred to as "face validity", that reflect quite different underlying phenomena and biological processes from the clinical situation. Instead, a more profitable approach is to identify (a) well-defined intermediate human behavioural phenotypes that reflect defined, limited aspects of, or contributors to, the human clinical disorder, and (b) to develop animal models that are homologous with those discrete human behavioural phenotypes in terms of psychological processes, and underlying neurobiological mechanisms. Examples of past and continuing weaknesses and suggestions for more limited approaches that may allow better homology between the test animal and human condition are made., (© 2024. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

Background: Current approaches for managing benzodiazepine (BZD) withdrawal symptoms are daunting for clinicians and patients, warranting novel treatment and management strategies. This review discusses the pharmacodynamic properties of BZDs, gabapentinoids (GBPs), endozepines, and novel GABAergic compounds associated with potential clinical benefits for BZD-dependent patients. The objective of this study was to review the complex neuromolecular changes occurring within the GABAergic and glutamatergic systems during the BZD tolerance and withdrawal periods while also examining the mechanism by which GBPs and alternative pharmacological therapies may attenuate withdrawal symptoms. Methods and Results: An elaborative literature review was conducted using multiple platforms, including the National Center for Biotechnology (NCBI), AccessMedicine, ScienceDirect, pharmacology textbooks, clinical trial data, case reports, and PubChem. Our literature analysis revealed that many distinctive neuroadaptive mechanisms are involved in the GABAergic and glutamatergic systems during BZD tolerance and withdrawal. Based on this data, we hypothesize that GBPs may attenuate the overactive glutamatergic system during the withdrawal phase by an indirect presynaptic glutamatergic mechanism dependent on the α2δ1 subunit expression. Conclusions: GBPs may benefit individuals undergoing BZD withdrawal, given that the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor current significantly increases during abrupt BZD withdrawal in animal studies. This may be a conceivable explanation for the effectiveness of GBPs in treating both alcohol withdrawal symptoms and BZD withdrawal symptoms in some recent studies. Finally, natural and synthetic GABAergic compounds with unique pharmacodynamic properties were found to exert potential clinical benefits as BZD substitutes in animal studies, though human studies are lacking. [ABSTRACT FROM AUTHOR]

Benzodiazepines have been in use for over half a century. While they remain highly prescribed, their unfavorable side-effect profile and abuse liability motivated a search for alternatives. Most of these efforts focused on the development of benzodiazepine-like drugs that are selective for specific GABAA receptor subtypes. While there is ample evidence that subtype-selective GABAA receptor ligands have great potential for providing symptom relief without typical benzodiazepine side-effects, it is less clear whether subtype-selective targeting strategies can also reduce misuse and abuse potential. This review focuses on the three benzodiazepine properties that are relevant to the DSM-5-TR criteria for Sedative, Hypnotic, or Anxiolytic Use Disorder, namely, reinforcing properties of benzodiazepines, maladaptive behaviors related to benzodiazepine use, and benzodiazepine tolerance and dependence. We review existing evidence regarding the involvement of different GABAA receptor subtypes in each of these areas. The reviewed studies suggest that a1-containing GABAA receptors play an integral role in benzodiazepine-induced plasticity in reward-related brain areas and might be involved in the development of tolerance and dependence to benzodiazepines. However, a systematic comparison of the contributions of all benzodiazepine-sensitive GABAA receptors to these processes, a mechanistic understanding of how the positive modulation of each receptor subtype might contribute to the brain mechanisms underlying each of these processes, and a definitive answer to the question of whether specific chronicmodulation of any given subtype would result in some or all of the benzodiazepine effects are currently lacking from the literature. Moreover, how non-selective benzodiazepines might lead to the maladaptive behaviors listed in DSM and how different GABAA receptor subtypes might be involved in the development of these behaviors remains unexplored. Considering the increasing burden of benzodiazepine abuse, the common practice of benzodiazepine misuse that leads to severe dependence, and the current efforts to generate side-effect free benzodiazepine alternatives, there is an urgent need for systematic, mechanistic research that provides a better understanding of the brain mechanisms of benzodiazepine misuse and abuse, including the involvement of specific GABAA receptor subtypes in these processes, to establish an informed foundation for preclinical and clinical efforts. [ABSTRACT FROM AUTHOR]

Arthritis-induced adjuvant (AIA) is an established animal model reflecting several clinical manifestations of human arthritis. It provides more understanding of pathogenesis and pathways involved in arthritic development and for testing various treatment modalities. Complete Freund's adjuvant (CFA) is one of the most known algogenic agents used to develop AIA rodent model. Its wide application increases understanding of CFA effects locally and systemically following adjuvant-containing mycobacterium exposure in-vivo. This study aims to review possible factors involved in producing a successful CFAinduced arthritic rat model. We conducted a review of previous studies to determine critical factors to be emphasized. Since arthritis can be classified as gout, osteoarthritis, and rheumatoid arthritis, among others, factors that should be assessed include different dosage and volume, injection site, remission, arthritic and animal gender, and strain selections to successfully develop an arthritic rat model. [ABSTRACT FROM AUTHOR]

Traumatic Brain Injury (TBI) and tobacco smoking are both serious public health problems. Many people with TBI also smoke. Nicotine, a component of tobacco smoke, has been identified as a premorbid neuroprotectant in other neurological disorders. This study aims to provide better understanding of relationships between tobacco smoking and nicotine use and effect on outcome/recovery from TBI. PubMed database, SCOPUS, and PTSDpub were searched for relevant English-language papers. Twenty-nine human clinical studies and nine animal studies were included. No nicotine-replacement product use in human TBI clinical studies were identified. While smoking tobacco prior to injury can be harmful primarily due to systemic effects that can compromise brain function, animal studies suggest that nicotine as a pharmacological agent may augment recovery of cognitive deficits caused by TBI. While tobacco smoking before or after TBI has been associated with potential harms, many clinical studies downplay correlations for most expected domains. On the other hand, nicotine could provide potential treatment for cognitive deficits following TBI by reversing impaired signaling pathways in the brain including those involving nAChRs, TH, and dopamine. Future studies regarding the impact of cigarette smoking and vaping on patients with TBI are needed. [ABSTRACT FROM AUTHOR]

Psychostimulant (methamphetamine, cocaine) use disorders have a genetic component that remains mostly unknown. We conducted genome‐wide quantitative trait locus (QTL) analysis of methamphetamine stimulant sensitivity. To facilitate gene identification, we employed a Reduced Complexity Cross between closely related C57BL/6 mouse substrains and examined maximum speed and distance traveled over 30 min following methamphetamine (2 mg/kg, i.p.). For maximum methamphetamine‐induced speed following the second and third administration, we identified a single genome‐wide significant QTL on chromosome 11 that peaked near the Cyfip2 locus (LOD = 3.5, 4.2; peak = 21 cM [36 Mb]). For methamphetamine‐induced distance traveled following the first and second administration, we identified a genome‐wide significant QTL on chromosome 5 that peaked near a functional intronic indel in Gabra2 coding for the alpha‐2 subunit of the GABA‐A receptor (LOD = 3.6–5.2; peak = 34–35 cM [66–67 Mb]). Striatal cis‐expression QTL mapping corroborated Gabra2 as a functional candidate gene underlying methamphetamine‐induced distance traveled. CRISPR/Cas9‐mediated correction of the mutant intronic deletion on the C57BL/6J background to the wild‐type C57BL/6NJ allele was sufficient to reduce methamphetamine‐induced locomotor activity toward the wild‐type C57BL/6NJ‐like level, thus validating the quantitative trait variant (QTV). These studies show the power and efficiency of Reduced Complexity Crosses in identifying causal variants underlying complex traits. Functionally restoring Gabra2 expression decreased methamphetamine stimulant sensitivity and supports preclinical and human genetic studies implicating the GABA‐A receptor in psychostimulant addiction‐relevant traits. Importantly, our findings have major implications for studying psychostimulants in the C57BL/6J strain—the gold standard strain in biomedical research. [ABSTRACT FROM AUTHOR]

Background: Food avoidance secondary to disease or stress can lead to weight loss and rapid deterioration of clinical condition in the common marmoset (Callithrix jacchus). Currently, there are no data supporting the use of any pharmaceuticals as an appetite stimulant in this species; however, benzodiazepines are frequently used for this purpose in other species. Methods: Six marmosets were used in a crossover study design to evaluate the benzodiazepine midazolam as an appetite stimulant and anxiolytic. Total food intake (TFI) and latency to eat (LTE) were measured following administration of oral and injectable midazolam in non‐anxious and anxious states. Results: Injectable midazolam increased TFI and decreased LTE in anxious marmosets, but had no effect in non‐anxious animals. Oral midazolam had no effect on appetite in either state. Conclusions: Injectable midazolam may be an effective treatment for anxiety‐induced inappetence in marmosets. Individual response to both oral and injectable midazolam may vary. [ABSTRACT FROM AUTHOR]

Purpose of review: As fields such as neurotoxicity evaluation and neuro-related drug research are increasing in popularity, there is a demand for the expansion of neurotoxicity research. Currently, neurotoxicity is assessed by measuring changes in weight and behavior. However, measurement of such changes does not allow the detection of subtle and inconspicuous neurotoxicity. In this review, methods for advancing neurotoxicity research are divided into molecule-, cell-, circuit-, and animal model-based methods, and the results of previous studies assessing neurotoxicity are provided and discussed. Recent findings: In coming decades, cooperation between universities, national research institutes, industrial research institutes, governments, and the private sector will become necessary when identifying alternative methods for neurotoxicity evaluation, which is a current goal related to improving neurotoxicity assessment and an appropriate approach to neurotoxicity prediction. Many methods for measuring neurotoxicity in the field of neuroscience have recently been reported. This paper classifies the supplementary and complementary experimental measures for evaluating neurotoxicity. [ABSTRACT FROM AUTHOR]

Introduction: Variation in CYP2A6, the primary enzyme responsible for nicotine metabolism, is associated with nicotine dependence, cigarette consumption, and abstinence outcomes in smokers. The impact of CYP2A6 activity on nicotine reinforcement and tobacco cue-reactivity, mechanisms that may contribute to these previous associations, has not been fully evaluated.Aims and Methods: CYP2A6 activity was indexed using 3 genetic approaches in 104 daily smokers completing forced-choice and cue-induced craving tasks assessing nicotine reinforcement and tobacco cue-reactivity, respectively. First, smokers were stratified by the presence or absence of reduced/loss-of-function CYP2A6 gene variants (normal vs. reduced metabolizers). As nicotine metabolite ratio (NMR) is a reliable biomarker of CYP2A6 activity, our second and third approaches used additional genetic variants identified in genome-wide association studies of NMR to create a weighted genetic risk score (wGRS) to stratify smokers (fast vs. slow metabolizers) and calculate a wGRS-derived NMR.Results: Controlling for race and sex, normal metabolizers (vs. reduced) selected a greater proportion of puffs from nicotine-containing cigarettes (vs. denicotinized) on the forced-choice task (p = .031). In confirmatory analyses, wGRS-based stratification (fast vs. slow metabolizers) produced similar findings. Additionally, wGRS-derived NMR, which correlated with actual NMR assessed in a subset of participants (n = 55), was positively associated with the proportion of puffs from nicotine-containing cigarettes controlling for race and sex (p = .015). None of the CYP2A6 indices were associated with tobacco cue-reactivity in minimally deprived smokers.Conclusions: Findings suggest increased nicotine reinforcement is exhibited by smokers with high CYP2A6 activity, which may contribute to heavier smoking and poorer cessation outcomes previously reported in faster metabolizers.Implications: CYP2A6 activity is a key determinant of smoking behavior and outcomes. Therefore, these findings support the targeting of CYP2A6 activity, either therapeutically or as a clinically relevant biomarker in a precision medicine approach, for tobacco use disorder treatment. [ABSTRACT FROM AUTHOR]

As complexities of addictive behaviors cannot be fully captured in laboratory studies, scientists use simple addiction‐associated phenotypes and measure them in laboratory animals. Locomotor sensitization, characterized by an increased behavioral response to the same dose of the drug, has been extensively used to elucidate the genetic basis and molecular mechanisms of neuronal plasticity. However, to what extent it contributes to the development of addiction is not completely clear. We tested if the development of locomotor sensitization to methamphetamine affects voluntary self‐administration, and vice versa, in order to investigate how two drug‐associated phenotypes influence one another. In our study, we used the genetically tractable model organism, Drosophila melanogaster, and quantified locomotor sensitization and voluntary self‐administration to methamphetamine using behavioral tests that were developed and adapted in our laboratory. We show that flies express robust locomotor sensitization to the second dose of volatilized methamphetamine, which significantly lowers preferential self‐administration of methamphetamine. Naive flies preferentially self‐administer food with methamphetamine over plain food. Exposing flies to volatilized methamphetamine after voluntary self‐administration abolishes locomotor sensitization. We tested period null (per01) mutant flies and showed that they do not develop locomotor sensitization, nor do they show preferential self‐administration of methamphetamine. Our results suggest that there may be partially overlapping neural circuitry that regulates the expression of locomotor sensitization and preferential self‐administration to methamphetamine and that this circuitry requires a functional per gene. [ABSTRACT FROM AUTHOR]

Early-life stress (ELS) is associated with negative consequences, including maladaptive long-lasting brain effects. These alterations seem to increase the likelihood of developing substance use disorders. However, the molecular consequences of ELS are poorly understood. In the present study, we tested the impact of ELS induced by maternal separation with early weaning (MSEW) in CD1 male mice at different phases of cocaine self-administration (SA). We also investigated the subsequent alterations on GluR2, GluR1, cAMP response element-binding (CREB), and CREB-phosphorylation (pCREB) in ventral tegmental area (VTA) and nucleus accumbens (NAc) induced by both MSEW and cocaine SA. Our results show that MSEW animals expressed a higher cocaine intake, an increased vulnerability to the acquisition of cocaine SA, and incapacity to extinguish cocaine SA behaviour. MSEW mice showed decreased GluR2 and increased GluR1 and pCREB in NAc. Also, results displayed reduction of basal levels of GluR1 and CREB and an elevation of GluR1/GluR2 ratio in the VTA. Such results hint at an enhanced glutamatergic function in NAc and increased excitability of VTA DA neurons in maternally separated mice. Altogether, our results suggest that MSEW induces molecular alterations in the brain areas related to reward processing, increasing the vulnerability to depression and cocaine-seeking behaviour. [ABSTRACT FROM AUTHOR]

Rationale: Compulsive cocaine use, defined as the continued use despite the dire consequences, is a hallmark of cocaine addiction. Thus, understanding the brain mechanism regulating the compulsive cocaine-seeking and cocaine-taking behaviors is essential to understand cocaine addiction and the key to identification of the molecular targets for the development of medications against this condition. Objective: This study aimed to determine how the GABAa and GABAb receptors of the central nucleus of the amygdala (CeA) regulate the compulsive cocaine-seeking behavior. Methods: Male Wistar outbred rats were trained to self-administer intravenous cocaine (0.4 mg/kg/infusion) under a chained schedule. The compulsive cocaine-seeking behavior was measured as the cocaine-seeking behavior in the face of footshock punishment. The role of the GABA receptors of CeA in the regulation of such behavior was determined by measuring the dose-dependent effects of the GABAa agonist muscimol or the GABAb agonist baclofen bilaterally microinjected into the CeA on the punished cocaine-seeking behavior. Results: The cocaine-seeking behavior was inhibited by footshock punishment in an intensity-dependent manner. Both muscimol and baclofen dose-dependently increased the punished cocaine-seeking behavior. However, the potency of muscimol but not baclofen was negatively correlated with the effects of punishment. Conclusion: These data indicate that the CeA GABAa receptors play a key role in the regulation of the compulsive cocaine-seeking behavior and suggest that an increase in the function of the GABAa receptors possibly induced by cocaine or genetic factors may be an important mechanism involved in the development of or vulnerability to the compulsive cocaine use and addiction. [ABSTRACT FROM AUTHOR]

Impact of reactive oxygen species (ROS) in development of hyperalgesia has recently motivated scientists to focus on ROS as novel target of anti-hyperalgesic interventions. Studies have indicated the usefulness of ROS scavengers and exogenous antioxidants as anti-nociceptive agents in animal models of neuropathic and inflammatory hyperalgesia. In present study, we suggest the anti-hyperalgesic potential of the dietary antioxidant quercetin on chronic inflammatory hyperalgesia induced by Complete Freund's Adjuvant (CFA). Three doses of quercetin (25, 50 and 75 mg/kg body weight) for consecutive 7 days were used for the study. Thermal hyperalgesia was assessed by paw withdrawal latency (PWL) test and inflammation was checked in terms of changes in paw edema. The insight of molecular signaling during chronic hyperalgesia was analyzed by TNF-α–TNFR1–ERK1/2 pathway in relation to change in ROS level in DRG and spinal cord. CFA-induced hyperalgesia was confirmed by decreased PWL and increased c-Fos activity in dorsal horn of spinal cord, determined by immunohistochemical analysis. It was characterized with elevated level of ROS and TNF-α estimated by ELISA. The activation of ERK1/2 and NF-κB in DRG and spinal cord and over-expression of TNFR1 in DRG were analyzed by Western blotting. Up-regulation of Iba1 and GFAP indicates glial activation in spinal cord. Expression of GFAP and its co-localization with NF-κB were examined by immunofluorescence. All the molecular modulators of hyperalgesia were brought towards normal after quercetin treatment showing its anti-hyperalgesic activity, indicating that repeated quercetin treatment is able to alleviate chronic inflammatory hyperalgesia by attenuating TNF-α-TNFR1–ERK1/2 signaling pathway via modulation of ROS and by suppression of central sensitization via inhibition of spinal glial activation. [ABSTRACT FROM AUTHOR]

Deficits in the gating of sensory stimuli, i.e., the ability to suppress the processing of irrelevant sensory input, are considered to play an important role in the pathogenesis of several neuropsychiatric disorders, in particular schizophrenia. Gating is disrupted both in schizophrenia patients and their unaffected relatives, suggesting that gating deficit may represent a biomarker associated with a genetic liability to the disorder. To assess the strength of the evidence for the etiopathogenetic links between genetic variation, gating efficiency, and schizophrenia, we carried out a systematic review of human genetic association studies of sensory gating (suppression of the P50 component of the auditory event-related brain potential) and sensorimotor gating (prepulse inhibition of the acoustic startle response). Sixty-three full-text articles met the eligibility criteria for inclusion in the review. In total, 117 genetic variants were reported to be associated with gating functions: 33 variants for sensory gating, 80 variants for sensorimotor gating, and four variants for both sensory and sensorimotor gating. However, only five of these associations (four for prepulse inhibition—CHRNA3 rs1317286, COMT rs4680, HTR2A rs6311, and TCF4 rs9960767, and one for P50 suppression—CHRNA7 rs67158670) were consistently replicated in independent samples. Although these variants and genes were all implicated in schizophrenia in research studies, only two polymorphisms (HTR2A rs6311 and TCF4 rs9960767) were also reported to be associated with schizophrenia at a meta-analytic or genome-wide level of evidence. Thus, although gating is widely considered as an important endophenotype of schizophrenia, these findings demonstrate that evidence for a common genetic etiology of impaired gating functions and schizophrenia is yet unsatisfactory, warranting further studies in this field. [ABSTRACT FROM AUTHOR]

Recurrent relapse is a major problem in treating opiate addiction. Pavlovian conditioning plays a role in recurrent relapse whereby exposure to cues learned during drug intake can precipitate relapse to drug taking. α7 nicotinic acetylcholine receptors (nAChRs) have been implicated in attentional aspects of cognition and mechanisms of learning and memory. In this study we have investigated the role of α7 nAChRs in morphine-conditioned place preference (morphine-CPP). CPP provides a model of associative learning that is pertinent to associative aspects of drug dependence. The α7 nAChR antagonist methyllycaconitine (MLA; 4 mg/kg s.c.) had no effect on the acquisition, maintenance, reconsolidation or extinction of morphine-CPP but selectively attenuated morphine-primed reinstatement of CPP, in both mice and rats. Reinstatement of morphine-CPP in mice was accompanied by a selective increase in [3 H]-AMPA binding (but not in [3 H]-MK801 binding) in the ventral hippocampus that was prevented by prior treatment with MLA. Administration of MLA (6.7 μg) directly into the ventral hippocampus of rats prior to a systemic priming dose of morphine abolished reinstatement of morphine-CPP, whereas MLA delivered into the dorsal hippocampus or prefrontal cortex was without effect. These results suggest that α7 nAChRs in the ventral hippocampus play a specific role in the retrieval of associative drug memories following a period of extinction, making them potential targets for the prevention of relapse. [ABSTRACT FROM AUTHOR]

Tobacco use leads to 6 million deaths every year due to severe long-lasting diseases. The main component of tobacco, nicotine, is recognized as one of the most addictive drugs, making smoking cessation difficult, even when 70 percent of smokers wish to do so. Clinical and preclinical studies have demonstrated consistently that nicotine seeking is a complex behavior involving various psychopharmacological mechanisms. Evidence supports that the population of smokers is heterogeneous, particularly as regards the breadth of motives that determine the urge to smoke. Here, we review converging psychological, genetic and neurobiological data from clinical and preclinical studies supporting that the mechanisms controlling nicotine seeking may vary from individual to individual. It appears timely that basic neuroscience integrates this heterogeneity to refine our understanding of the neurobiology of nicotine seeking, as tremendous progress has been made in modeling the various psychopharmacological mechanisms driving nicotine seeking in rodents. For a better understanding of the mechanisms that drive nicotine seeking, we emphasize the need for individual-based research strategies in which nicotine seeking, and eventually treatment efficacy, are determined while taking into account individual variations in the mechanisms of nicotine seeking. [ABSTRACT FROM AUTHOR]

Spastic cerebral palsy (CP), despite the name, is not consistently identifiable by specific brain lesions. CP animal models focus on risk factors for development of CP, yet few reproduce the diagnostic symptoms. Animal models of CP must advance beyond risk factors to etiologies, including both the brain and spinal cord. [ABSTRACT FROM AUTHOR]

Pain is a growing health problem with an increasing prevalence, and represents a large burden worldwide. Pain control can be achieved through pharmacological and non-pharmacological (such as exercise) interventions. The prolonged use of analgesics, such as non-steroidal anti-inflammatory drugs (NSAIDs), is accompanied by numerous side effects. No previous studies have examined whether exercise may enhance the analgesic effect of NSAIDs. In the present study, the effect of ibuprofen and swimming exercise on nociception threshold were investigated using a rat model of inflammatory pain. A prophylactic swimming protocol and a treatment swimming protocol were used. In the two protocols, nociception was induced by intraplantar injection of Complete Freund's Adjuvant. The authors hypothesized that swimming exercise may enhance ibuprofen-induced antinociception. In the control group, nociception lasted for 17 days, and ibuprofen produced an antinociceptive effect at a dose of 32 mg/kg. However, swimming exercise enhanced ibuprofen-induced antinociception in the two swimming protocols. Notably, ibuprofen produced a significant increase in the nociception threshold at a dose of 10 mg/kg in the prophylactic swimming group. In addition, the duration of inflammation did not exceed 8 days under either swimming protocol. In conclusion, the combination of ibuprofen and swimming exercise was effective in controlling nociception in a rat model of inflammatory pain. Based on these observations, the combined use of exercise and ibuprofen may be a viable intervention for the control of chronic pain, and may decrease the potential for drug-induced side effects. [ABSTRACT FROM AUTHOR]

Background: Previous studies have investigated α1GABAA and α5GABAA receptor mechanisms in the behavioral effects of ethanol (EtOH) in monkeys. However, genetic studies in humans and preclinical studies with mutant mice suggest a role for α2GABAA and/or α3GABAA receptors in the effects of EtOH. The development of novel positive allosteric modulators (PAMs) with functional selectivity (i.e., selective efficacy) at α2GABAA and α3GABAA receptors allows for probing of these subtypes in preclinical models of the discriminative stimulus and reinforcing effects of EtOH in rhesus macaques. Methods: In discrimination studies, subjects were trained to discriminate EtOH (2 g/kg, intragastrically) from water under a fixed‐ratio (FR) schedule of food delivery. In oral self‐administration studies, subjects were trained to self‐administer EtOH (2% w/v) or sucrose (0.3 to 1% w/v) under an FR schedule of solution availability. Results: In discrimination studies, functionally selective PAMs at α2GABAA and α3GABAA (HZ‐166) or α3GABAA (YT‐III‐31) receptors substituted fully (maximum percentage of EtOH‐lever responding ≥80%) for the discriminative stimulus effects of EtOH without altering response rates. Full substitution for EtOH also was engendered by a nonselective PAM (triazolam), an α5GABAA‐preferring PAM (QH‐ii‐066) and a PAM at α2GABAA, α3GABAA, and α5GABAA receptors (L‐838417). A partial (MRK‐696) or an α1GABAA‐preferring (zolpidem) PAM only engendered partial substitution (i.e., ~50 to 60% EtOH‐lever responding). In self‐administration studies, pretreatments with the functionally selective PAMs at α2GABAA and α3GABAA (XHe‐II‐053 and HZ‐166) or α3GABAA (YT‐III‐31 and YT‐III‐271) receptors increased EtOH, but not sucrose, drinking at doses that had few, or no, observable sedative‐motor effects. Conclusions: Our results confirm prior findings regarding the respective roles of α1GABAA and α5GABAA receptors in the discriminative stimulus effects of EtOH and, further, suggest a key facilitatory role for α3GABAA and potentially α2GABAA receptors in several abuse‐related effects of EtOH in monkeys. Moreover, they reveal a potential role for these latter subtypes in EtOH's sedative effects. [ABSTRACT FROM AUTHOR]

Extrasynaptic δ subunit‐containing γ‐aminobutyric acid type A receptors (δ‐GABAARs) are emerging as targets for a number of neuropsychopharmacological drugs, including the direct GABA site agonist gaboxadol and neuroactive steroids. Among other regions, these δ‐GABAARs are functionally expressed in the ventral tegmental area (VTA), the cell body region of mesocorticolimbic dopamine (DA) system important for motivated behaviours, and in the target region, the nucleus accumbens. Gaboxadol and neurosteroids induce VTA DA neuron plasticity ex vivo, by inhibiting the VTA GABA neurons, and aversive place conditioning, which are absent in the δ‐GABAAR knockout mice (δ‐KO). It is not known whether δ‐GABAARs are important for the effects of other drugs, such as opioids (that also inhibit GABA neurons) and stimulants (that primarily elevate monoamine levels). Here, we used δ‐KO mice and conditioned place preference (CPP) test to study the rewarding effects of morphine (20 mg/kg), methamphetamine (1 mg/kg) and mephedrone (5 mg/kg). Morphine‐induced nociception was also assessed using tail‐flick and hot‐plate tests. We found that the δ‐KO mice failed to express morphine‐induced CPP, but that they were more sensitive to morphine‐induced analgesia in the tail‐flick test. In contrast, stimulant‐induced CPP in the δ‐KO mice was similar to that in the wild‐type controls. Thus, the conditioned rewarding effect by opioids, but not that of stimulants, was impaired in the absence of δ‐GABAARs. Further studies are warranted to assess the potential of δ‐GABAAR antagonists as possible targets for reducing morphine reward and potentiating morphine analgesia. [ABSTRACT FROM AUTHOR]

Rationale and objective: Two mechanisms underlie smoking cessation efficacies of α4β2* nicotinic acetylcholine receptor (nAChR) agonists: a “nicotine-like” agonist activity reduces craving by substituting for nicotine during a quit attempt, and a “nicotine-blocking” antagonist activity attenuates reinforcement by competing with inhaled nicotine during a relapse. To evaluate the contribution of each mechanism to clinical efficacy, we estimated the degree of agonist and antagonist activities of nicotine replacement therapy (NRT), varenicline, cytisine, and the discontinued nAChR agonists dianicline, ABT-418, ABT-089, CP-601927, and CP-601932, relative to the functional effects of nicotine from smoking.Methods: Functional activities that occur in vivo with clinical doses were predicted from literature data on binding and functional potencies at the target α4β2 nAChR, as well as at α6β2* nAChRs, and from estimates of free drug exposures in human brain. Agonist activity is comprised of nAChR activation and desensitization, which were expressed as percentages of desensitization and activation by nicotine from smoking. Antagonist activity was expressed as the reduction in nAChR occupancy by nicotine during smoking in the presence of an agonist.Results: Comparisons with odds ratios at end of treatment suggest that extensive α4β2 and α6β2* nAChR desensitization combined with α6β2* nAChR activation at similar levels as nicotine from smoking is associated with clinical efficacy (NRT, varenicline, cytisine, ABT-418). Effective competition with inhaled nicotine for α4β2 and α6β2* nAChRs further improves clinical efficacy (varenicline). Other discontinued nAChR agonists have lower agonist and antagonist activities at α4β2 nAChRs and are inactive or less efficacious than NRT (dianicline, ABT-089, CP-601927, CP-601932).Conclusion: Three pharmacological effects appear to be key factors underlying smoking cessation efficacy: the degree of activation of α6β2* nAChRs, desensitization of α4β2 and α6β2* nAChRs (agonist activity), and the reduction of nicotine occupancy at α4β2 and α6β2* nAChRs (antagonist activity). No single activity is dominant, and the level of smoking cessation efficacy depends on the profile of these activities achieved at clinical doses. While adequate agonist activity alone seems sufficient for a clinical effect (e.g., NRT, cytisine), clinical efficacy is improved with substantial competitive antagonism of α4β2 nAChRs, i.e., if the drug has a dual agonist-antagonist mechanism of action (e.g., varenicline). [ABSTRACT FROM AUTHOR]

Valproic acid (VPA)-exposed rat offspring have demonstrated autism spectrum disorder (ASD) phenotypes and impaired N-methyl-D-aspartate receptor (NMDAR)-dependent long-term depression (LTD) in the lateral nucleus of the amygdala. NMDAR partial agonist D-cycloserine (DCS) has been reported to act as a cognitive enhancer by increasing the NMDAR response to improve autistic-like phenotypes in animals. However, the mechanism of DCS in alleviating the ASD is still unknown. Using combined behavioral, electrophysiological, and molecular approaches, we found that DCS administration rescued social interaction deficits and anxiety/repetitive-like behaviors observed in VPA-exposed offspring. In the amygdala synapses, DCS treatment reversed the decreased paired pulse ratio (PPR) and the impaired NMDAR-dependent LTD, increased the frequency and amplitude of miniature excitatory post-synaptic currents (mEPSCs), and resulted in a higher dendritic spine density at the amygdala synapses in the VPA-exposed offspring. Moreover, we found that DCS facilitated the removal of GluA2-containing α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (GluA2/AMPARs) by inducing NMDAR-dependent LTD in the VPA-exposed offspring. We further established that the effects of DCS treatment, including increased GluA2/AMPAR removal and rescues of impaired social behavior, were blocked by Tat-GluA23Y, a GluA2-derived peptide that disrupted regulation of AMPAR endocytosis. These results provided the first evidence that rescue of the ASD-like phenotype by DCS is mediated by the mechanism of GluA2/AMPAR removal in VPA-exposed rat offspring. [ABSTRACT FROM AUTHOR]

A critical brain area implicated in nicotine dependence is the interpeduncular nucleus (IPN) located in the ventral midbrain and consisting primarily of GABAergic neurons. Previous studies indicate that IPN GABAergic neurons contribute to expression of somatic symptoms of nicotine withdrawal; however, whether IPN neurons are dynamically regulated during withdrawal in vivo and how this may contribute to both somatic and affective withdrawal behavior is unknown. To bridge this gap in knowledge, we expressed GCaMP in IPN GABAergic neurons and used in vivo fiber photometry to record changes in fluorescence, as a proxy for neuronal activity, in male mice during nicotine withdrawal. Mecamylamine-precipitated withdrawal significantly increased activity of IPN GABAergic neurons in nicotine-dependent, but not nicotine-naive mice. Analysis of GCaMP signals time-locked with somatic symptoms including grooming and scratching revealed reduced IPN GABAergic activity during these behaviors, specifically in mice undergoing withdrawal. In the elevated plus maze, used to measure anxiety-like behavior, an affective withdrawal symptom, IPN GABAergic neuron activity was increased during open-arm versus closed-arm exploration in nicotine-withdrawn, but not non-withdrawn mice. Optogenetic silencing IPN GABAergic neurons during withdrawal significantly reduced withdrawal-induced increases in somatic behavior and increased open-arm exploration. Together, our data indicate that IPN GABAergic neurons are dynamically regulated during nicotine withdrawal, leading to increased anxiety-like symptoms and somatic behavior, which inherently decrease IPN GABAergic neuron activity as a withdrawal-coping mechanism. These results provide a neuronal basis underlying the role of the IPN in the expression of somatic and affective behaviors of nicotine withdrawal., (© 2021. The Author(s), under exclusive licence to American College of Neuropsychopharmacology.)

α-asarone (ASR) is a major bioactive compound isolated from the rhizome of Acorus tatarinowii Schott and it has extensive biological effects. Clinically, anxiety disorder is a common comorbidity of chronic pain. However, limited information is available regarding the effects of ASR on chronic pain-related anxiety. This study aims to evaluate the anxiolytic effects of ASR in chronic pain mice. Chronic inflammatory pain was induced by hind-paw injection of complete Freund's adjuvant (CFA). Behavioral tests, western-blot analysis and whole-cell patch recordings were performed to evaluate the subsequent events. We found that ASR induced anxiolytic activities in CFA-injected mice but did not affect the nociceptive threshold. ASR administration reversed the up-regulation of GluR1-containing α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, NR2A-containing N-methyl-D-aspartate (NMDA) receptors and down-regulation of γ-aminobutyric acid A (GABA) receptors in the basolateral amygdala (BLA) of CFA-injected mice. Electrophysiological data revealed that ASR treatment restored the balance between excitatory and inhibitory neurotransmissions, which was disturbed in the BLA of CFA-injected mice. Moreover, ASR prevented the hyper-excitability of pyramidal neurons in the BLA of chronic pain mice. Our results suggested that the anxiolytic effects of ASR were partially due to maintaining the balance between excitatory/inhibitory transmissions and attenuating neuronal hyper-excitability of excitatory neurons in the BLA. [ABSTRACT FROM AUTHOR]

Withdrawal from extended-access cocaine self-administration leads to progressive intensification ('incubation') of cocaine craving. After prolonged withdrawal (1-2 months), when craving is high, expression of incubation depends on strengthening of excitatory inputs to medium spiny neurons (MSN) of the nucleus accumbens (NAc). These excitatory inputs interact with the intra-NAc GABAergic 'microcircuit', composed of MSN axon collaterals and GABAergic interneurons. Here, we investigated whether the increased glutamatergic neurotransmission observed after prolonged withdrawal is accompanied by altered GABAergic neurotransmission, focusing on NAc core. Rats self-administered cocaine or saline (6 hours/day) and then underwent >40 days of withdrawal. First, we investigated parvalbumin positive (PV+) interneurons, GABAergic fast-spiking interneurons that regulate MSN activity. Immunohistochemical studies revealed no significant change in PV signal intensity or the number of PV+ cells in cocaine rats versus saline controls. We then screened PV and other interneuron markers using immunoblotting. We detected no changes in levels of PV, calretinin, calbindin or neuronal nitric oxide synthase. Because expression of these markers is activity dependent, our results suggest no marked changes in interneuron activity. Finally, we utilized local field potential recording, which can detect GABA-mediated alterations at the circuit level, to investigate potential changes in two circuits implicated in cocaine craving: prelimbic prefrontal cortex to NAc core and basolateral amygdala to NAc core. We detected differential adaptations in these circuits, some of which may involve GABA. Overall, our results suggest that alterations in GABA transmission may accompany incubation of cocaine craving, but they are circuit specific and less pronounced than alterations in glutamate transmission. [ABSTRACT FROM AUTHOR]