Vesicular glutamate transporter 2 expression in the ventral tegmental area of outbred male rats following exposure to nicotine and alcohol.

Background: Initiation of use/co-use of nicotine and alcohol, commonly occurring in an episodic manner during adolescence, can imprint vulnerability to the developing brain and lead to addiction. The ventral tegmental area (VTA) is a key heterogeneous region of the mesocorticolimbic circuit involved in the binge-drinking and intoxication step of the addiction circuit. Higher human post-mortem VTA expression of vesicular glutamate transporter 2 (VGLUT2), a marker of the glutamatergic phenotype also expressed in dopaminergic [Tyrosine Hydroxylase (Th)-positive] neurons, has been associated with chronic nicotine use and co-use with alcohol. Methods: The present study aimed to map and characterize the Vglut2- and Th-expressing neurons in the VTA of adolescent male rats exposed or not to prolonged (six-weeks) episodic (three consecutive days/week) nicotine and/or alcohol administration. Nicotine (0.35 mg/kg free base) was injected subcutaneously, whereas alcohol (2 g/kg 20%) was administrated via gavage. Vglut2 and Th mRNA was assessed in the anterior and posterior VTA by use of in situ hybridization. Results: The profile of neurons varied with substance-exposure among VTA subregions. Th-only expressing neurons were more abundant in the posterior VTA of the group exposed to nicotine-only, compared to controls. The same neurons were, on the contrary, less present in the anterior VTA of animals exposed to alcohol-only, who also displayed a higher number of Vglut2-expressing neurons in the lateral anterior VTA. Conclusions: VTA Vglut2- and Th-only neurons seem differentially involved in the effects of adolescent episodic nicotine and alcohol exposure in the anterior and posterior VTA.

Alcohol consumption habits and associations with anxiety or depressive symptoms postpartum in women with high socioeconomic status in Sweden.

Postpar tum depression and anxiety are common among new mothers. It is well-established that in the general population alcohol use is associated with depression and anxiety. Linking alcohol consumption to symptoms of postpartum depression (PPDS) or postpartum anxiety (PPAS) is presently less established. This study aims to determine if alcohol consumption pre-pregnancy, 6 weeks postpartum, 6 months postpartum, or changes in alcohol consumption are associated with PPDS or PPAS. Longitudinal data on 3849 women from a Swedish perinatal cohort were analyzed using logistic regression analyses for associations between alcohol consumption and symptoms of anxiety or depression, as assessed with the Edinburgh Postnatal Depression Scale. There was no association between pre-pregnancy drinking habits and PPDS (p = 0.588, n = 2479) or PPAS (p = 0.942; n = 2449) at 6 weeks postpartum. Similarly, no associations were observed between concurrent drinking habits at 6 weeks postpartum and PPAS (p = 0.070, n = 3626), 6 months postpartum and PPDS (0.647, n = 3461) or PPAS (p = 0.700, n = 3431). However, there was an association between drinking habits at 6 weeks postpartum and concurrent PPDS (p = 0.047, n = 3659). In conclusion, robust associations were not found between postpartum alcohol consumption and mood symptoms. This lack of association between poor mental health and risk behaviors in new mothers could be interpreted as a result of long-term policy work and high participation in Swedish maternity care. Future studies need to address these research questions in more diverse socio-cultural contexts.

DNA methylation of Vesicular Glutamate Transporters in the mesocorticolimbic brain following early-life stress and adult ethanol exposure-an explorative study.

DNA methylation and gene expression can be altered by early life stress (ELS) and/or ethanol consumption. The present study aimed to investigate whether DNA methylation of the Vesicular Glutamate Transporters (Vglut)1-3 is related to previously observed Vglut1-3 transcriptional differences in the ventral tegmental area (VTA), nucleus accumbens (Acb), dorsal striatum (dStr) and medial prefrontal cortex (mPFC) of adult rats exposed to ELS, modelled by maternal separation, and voluntary ethanol consumption. Targeted next-generation bisulfite sequencing was performed to identify the methylation levels on 61 5'-cytosine-phosphate-guanosine-3' sites (CpGs) in potential regulatory regions of Vglut1, 53 for Vglut2, and 51 for Vglut3. In the VTA, ELS in ethanol-drinking rats was associated with Vglut1-2 CpG-specific hypomethylation, whereas bidirectional Vglut2 methylation differences at single CpGs were associated with ELS alone. Exposure to both ELS and ethanol, in the Acb, was associated with lower promoter and higher intronic Vglut3 methylation; and in the dStr, with higher and lower methylation in 26% and 43% of the analyzed Vglut1 CpGs, respectively. In the mPFC, lower Vglut2 methylation was observed upon exposure to ELS or ethanol. The present findings suggest Vglut1-3 CpG-specific methylation signatures of ELS and ethanol drinking, underlying previously reported Vglut1-3 transcriptional differences in the mesocorticolimbic brain.

Behavioral Profiling in Early Adolescence and Early Adulthood of Male Wistar Rats After Short and Prolonged Maternal Separation.

Early-life stress and its possible correlations to genes, environment, and later health outcomes can only be studied retrospectively in humans. Animal models enable the exploration of such connections with prospective, well-controlled study designs. However, with the recent awareness of replicability issues in preclinical research, the reproducibility of results from animal models has been highlighted. The present study aims to reproduce the behavioral effects of maternal separation (MS) previously observed in the multivariate concentric square fieldTM (MCSF) test. A second objective was to replicate the adolescent behavioral profiles previously described in the MCSF test. Male rats, subjected to short or prolonged MS or standard rearing, were subjected to behavioral testing in early adolescence and early adulthood. As seen in previous studies, the behavioral effects of MS in the MCSF were small at both tested time points. When tested in early adolescence, the animals exhibited a similar behavioral profile as previously seen, and the finding of adolescent behavioral types was also reproduced. The distribution of animals into the behavioral types was different than in the initial study, but in a manner consistent with developmental theories, as the current cohort was younger than the previous. Notably, the Shelter seeker behavioral type persisted through development, while the Explorer type did not. The lack of basal behavioral effect after MS is in line with the literature on this MS paradigm; the working hypothesis is that the prolonged MS gives rise to a phenotype predisposed to negative health outcomes but which is not apparent without additional provocation.

VGLUT2 rs2290045 genotype moderates environmental sensitivity to alcohol-related problems in three samples of youths.

The importance of Vesicular Glutamate Transporter 2 (VGLUT2)-mediated neurotransmission has been highlighted in studies on addiction-related phenotypes. The single nucleotide polymorphism rs2290045 in VGLUT2 has been associated with alcohol dependence, but it is unknown whether or how this association is affected by environmental factors. The present study determined whether the association of alcohol-related problems with the rs2290045 in the VGLUT2 gene was modified by negative and positive environmental factors. Three samples were included: a clinical sample of 131 adolescents followed from age 17 to 22; a general population sample of 1794 young adults; and a general population sample of 1687 adolescents followed from age 14 to 17. DNA was extracted from saliva and the rs2290045 (T/C) was genotyped. Alcohol-related problems were assessed using the Alcohol Use Disorders Identification Test. Stressful life events (SLE) and parenting were assessed by questionnaires. Gene-environment interactions were investigated using a dual statistical approach. In all samples (effect sizes 0.6-6.2%), and consistent with the differential susceptibility framework, T carriers exposed to SLE reported more alcohol-related problems if they had experienced poor parenting, and lower alcohol-related problems if they had received supportive parenting. T carriers not exposed to SLE reported higher alcohol-related problems if they had received supportive parenting and lower alcohol-related problems if they had received poor parenting. Among CC carriers, alcohol-related problems did not vary as a function of negative and positive environmental factors. In conclusion, in three samples of youths, alcohol-related problems were associated with an interaction of VGLUT2 rs2290045, SLE, and parenting.

Constitutive Serotonin Transporter Reduction Resembles Maternal Separation with Regard to Stress-Related Gene Expression.

Interactive effects between allelic variants of the serotonin transporter (5-HTT) promoter-linked polymorphic region (5-HTTLPR) and stressors on depression symptoms have been documented, as well as questioned, by meta-analyses. Translational models of constitutive 5-htt reduction and experimentally controlled stressors often led to inconsistent behavioral and molecular findings and often did not include females. The present study sought to investigate the effect of 5-htt genotype, maternal separation, and sex on the expression of stress-related candidate genes in the rat hippocampus and frontal cortex. The mRNA expression levels of Avp, Pomc, Crh, Crhbp, Crhr1, Bdnf, Ntrk2, Maoa, Maob, and Comt were assessed in the hippocampus and frontal cortex of 5-htt± and 5-htt+/+ male and female adult rats exposed, or not, to daily maternal separation for 180 min during the first 2 postnatal weeks. Gene- and brain region-dependent, but sex-independent, interactions between 5-htt genotype and maternal separation were found. Gene expression levels were higher in 5-htt+/+ rats not exposed to maternal separation compared with the other experimental groups. Maternal separation and 5-htt+/- genotype did not yield additive effects on gene expression. Correlative relationships, mainly positive, were observed within, but not across, brain regions in all groups except in non-maternally separated 5-htt+/+ rats. Gene expression patterns in the hippocampus and frontal cortex of rats exposed to maternal separation resembled the ones observed in rats with reduced 5-htt expression regardless of sex. These results suggest that floor effects of 5-htt reduction and maternal separation might explain inconsistent findings in humans and rodents.

Early life stress and voluntary alcohol consumption in relation to Maoa methylation in male rats.

Early life stress (ELS) or alcohol consumption can influence DNA methylation and affect gene expression. Monoamine oxidase A (Maoa) encodes the enzyme that metabolizes monoaminergic neurotransmitters crucial for the stress response, alcohol reward, and reinforcement. Previously, we reported lower Maoa expression in the nucleus accumbens and dorsal striatum of male rats exposed to ELS during the first three postnatal weeks, and to voluntary alcohol consumption in adulthood, compared with controls. The present study continued to investigate the effect of ELS and alcohol consumption on Maoa methylation, and its relation to Maoa expression in these animals. We selected candidate CpGs after performing next-generation bisulfite sequencing of the Maoa promoter, intron 1-5, and exons 5 and 6, together composed of 107 CpGs (5'-cytosine-phosphate-guanosine-3'), in a subgroup of rats. Pyrosequencing was used to analyze the methylation of 10 candidate CpGs in the promoter and intron 1 in the entire sample. ELS and alcohol displayed an interactive effect on CpG-specific methylation in the dorsal striatum. CpG-specific methylation correlated with Maoa expression, corticosterone levels, and alcohol consumption in a brain region-specific manner. CpG-specific methylation in the Maoa promoter was a potential moderator of the interaction of ELS with alcohol consumption on Maoa expression in the NAc. However, the findings were sparse, did not survive correction for multiple testing, and the magnitude of differences in methylation levels was small. In conclusion, CpG-specific Maoa methylation in the promoter and intron 1 may associate with ELS, alcohol consumption, and Maoa expression in reward-related brain regions.

Episodic Ethanol Exposure in Adolescent Rats Causes Residual Alterations in Endogenous Opioid Peptides.

Adolescent binge drinking is associated with an increased risk of substance use disorder, but how ethanol affects the central levels of endogenous opioid peptides is still not thoroughly investigated. The aim of this study was to examine the effect of repeated episodic ethanol exposure during adolescence on the tissue levels of three different endogenous opioid peptides in rats. Outbred Wistar rats received orogastric (i.e., gavage) ethanol for three consecutive days per week between 4 and 9 weeks of age. At 2 h and 3 weeks, respectively, after the last exposure, beta-endorphin, dynorphin B and Met-enkephalin-Arg6Phe7 (MEAP) were analyzed with radioimmunoassay. Beta-endorphin levels were low in the nucleus accumbens during ethanol intoxication. Remaining effects of adolescent ethanol exposure were found especially for MEAP, with low levels in the amygdala, and high in the substantia nigra and ventral tegmental area three weeks after the last exposure. In the hypothalamus and pituitary, the effects of ethanol on beta-endorphin were dependent on time from the last exposure. An interaction effect was also found in the accumbal levels of MEAP and nigral dynorphin B. These results demonstrate that repeated episodic exposure to ethanol during adolescence affected opioid peptide levels in regions involved in reward and reinforcement as well as stress response. These alterations in opioid networks after adolescent ethanol exposure could explain, in part, the increased risk for high ethanol consumption later in life.

Few long-term consequences after prolonged maternal separation in female Wistar rats.

Environmental factors during the early-life period are known to have long-term consequences for the adult phenotype. An intimate interplay between genes and environment shape the individual and may affect vulnerability for psychopathology in a sex-dependent manner. A rodent maternal separation model was here used to study the long-term effects of different early-life rearing conditions on adult behavior, HPA axis activity and long-term voluntary alcohol intake in female rats. Litters were subjected to 15 min (MS15) or 360 min (MS360) of daily maternal separation during postnatal day 1-21. In adulthood, the behavioral profiles were investigated using the multivariate concentric square field™ (MCSF) test or examined for HPA axis reactivity by cat-odor exposure with subsequent characterization of voluntary alcohol intake and associated changes in HPA axis activity. Adult female MS360 offspring showed mostly no, or only minor, effects on behavior, HPA axis reactivity and long-term alcohol intake relative to MS15. Instead, more pronounced effects were found dependent on changes in the natural hormonal cycle or by the choice of animal supplier. However, changes were revealed in corticosterone load after long-term alcohol access, as females subjected to MS360 had higher concentrations of fecal corticosterone. The present findings are in line with and expand on previous studies on the long-term effects of maternal separation in female rats with regard to behavior, HPA axis activity and voluntary alcohol intake. It can also be a window into further studies detailing how early-life experiences interact with other risk and protective factors to impact the adult phenotype and how possible sex differences play a role.

The expression of opioid genes in non-classical reward areas depends on early life conditions and ethanol intake.

The young brain is highly sensitive to environmental influences that can cause long-term changes in neuronal function, possibly through altered gene expression. The endogenous opioid system continues to mature after birth and because of its involvement in reward, an inadequate maturation of this system could lead to enhanced susceptibility for alcohol use disorder. Recent studies show that the classical reward areas nucleus accumbens and ventral tegmental area are less affected by early life stress whereas endogenous opioids in non-classical areas, e.g. dorsal striatum and amygdala, are highly responsive. The aim was to investigate the interaction between early life conditions and adult voluntary ethanol intake on opioid gene expression. Male Wistar rats were exposed to conventional rearing, 15, or 360min of daily maternal separation (MS) postnatal day 1-21, and randomly assigned to ethanol or water drinking postnatal week 10-16. Rats exposed to early life stress (MS360) had increased opioid receptor gene (Oprm1, Oprd1 and Oprk1) expression in the dorsal striatum. Ethanol drinking was associated with lower striatal Oprd1 and Oprk1 expression solely in rats exposed to early life stress. Furthermore, rats exposed to early life stress had high inherent Pomc expression in the amygdala but low expression after ethanol intake. Thus, adverse events early in life induced changes in opioid gene expression and also influenced the central molecular response to ethanol intake. These long-term consequences of early life stress can contribute to the enhanced risk for excessive ethanol intake and alcohol use disorder seen after exposure to childhood adversity.

Prevalence and influence of cys407* Grm2 mutation in Hannover-derived Wistar rats: mGlu2 receptor loss links to alcohol intake, risk taking and emotional behaviour.

Modulation of metabotropic glutamate 2 (mGlu2) receptor function has huge potential for treating psychiatric and neurological diseases. Development of drugs acting on mGlu2 receptors depends on the development and use of translatable animal models of disease. We report here a stop codon mutation at cysteine 407 in Grm2 (cys407*) that is common in some Wistar rats. Therefore, researchers in this field need to be aware of strains with this mutation. Our genotypic survey found widespread prevalence of the mutation in commercial Wistar strains, particularly those known as Han Wistar. Such Han Wistar rats are ideal for research into the separate roles of mGlu2 and mGlu3 receptors in CNS function. Previous investigations, unknowingly using such mGlu2 receptor-lacking rats, provide insights into the role of mGlu2 receptors in behaviour. The Grm2 mutant rats, which dominate some selectively bred lines, display characteristics of altered emotionality, impulsivity and risk-related behaviours and increased voluntary alcohol intake compared with their mGlu2 receptor-competent counterparts. In addition, the data further emphasize the potential therapeutic role of mGlu2 receptors in psychiatric and neurological disease, and indicate novel methods of studying the role of mGlu2 and mGlu3 receptors. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'.

Evidence for a Link Between Fkbp5/FKBP5, Early Life Social Relations and Alcohol Drinking in Young Adult Rats and Humans.

Alcohol misuse has been linked to dysregulation of stress, emotion, and reward brain circuitries. A candidate key mediator of this association is the FK506-binding protein (FKBP5), a negative regulator of the glucocorticoid receptor. The aim of the present study was to further understand the Fkbp5/FKBP5-related genetic underpinnings underlying the relationship between early life social relations and alcohol drinking. The effect of maternal separation and voluntary alcohol drinking on Fkbp5 expression was investigated in the brain of young adult rats, whereas the interaction effect of the functional FKBP5 single nucleotide polymorphism rs1360780 genotype and parent-child relationship on problematic drinking was examined in young adult humans. In rats, Fkbp5 expression in the nucleus accumbens and ventral tegmental area, core regions of the reward system, was affected in a region-dependent manner and in opposite direction by maternal separation and alcohol drinking. Fkbp5 expression in the cingulate cortex was affected by the combined effect of maternal separation and alcohol drinking. In humans, the TT genotype, in the presence of a poor relationship between the child and parents, was associated with problematic drinking behavior. The present findings suggest that Fkbp5 expression in mesocorticolimbic dopaminergic regions associates with early life stress-mediated sensitivity to alcohol drinking and that FKBP5 genotype interacts with parent-child relationship to influence alcohol drinking. These findings are the first to point to a role of FKBP5 in propensity to alcohol misuse and call for studies of the underlying molecular mechanisms to identify potential drug targets.

Altered corticosterone levels and social play behavior after prolonged maternal separation in adolescent male but not female Wistar rats.

Early-life socio-environmental factors are crucial for normal developmental processes; adverse experiences early in life can therefore lead to detrimental effects in several physiological systems. The aim of this study was to examine short-term effects of early adverse experiences in a maternal separation (MS) rodent model. In this study two separation conditions were used: daily 15- (MS15) or 360-min (MS360) separation of the litter from the dam during postnatal day 1-21. In early adolescence, male and female offspring were subjected to a single-isolation procedure with analysis of corticosterone levels prior to and after isolation. In addition, social play behavior was assessed during mid-adolescence. There was a clear difference between male and female offspring in both tests performed. There was no difference in corticosterone levels between the female MS groups, whereas MS360 males showed higher baseline and recovery corticosterone levels than MS15 males. The amount of pinning, a specific social play behavior, was affected by rearing with MS360 males having a higher frequency than MS15 males, while there was no difference between the female MS groups. The observation that males but not females are affected by MS360 has previously been reported for adult animals, and herein we show that this difference is present already in adolescence. Changes in corticosterone levels and social behavior following early-life adversity have been associated with adult behavioral alterations, and our results confirm that these changes emerge already within adolescence.

Ethanol affects limbic and striatal presynaptic glutamatergic and DNA methylation gene expression in outbred rats exposed to early-life stress.

Alcohol use disorder is the outcome of both genetic and environmental influences and their interaction via epigenetic mechanisms. The neurotransmitter glutamate is an important regulator of reward circuits and implicated in adaptive changes induced by ethanol intake. The present study aimed at investigating corticolimbic and corticostriatal genetic signatures focusing on the glutamatergic phenotype in relation to early-life stress (ELS) and consequent adult ethanol consumption. A rodent maternal separation model was employed to mimic ELS, and a free-choice paradigm was used to assess ethanol intake in adulthood. Gene expression levels of the Vesicular Glutamate Transporters (Vglut) 1, 2 and 3, as well as two key regulators of DNA methylation, DNA (cytosine-5)-methyltransferase 1 (Dnmt1) and methyl-CpG-binding protein 2 (Mecp2), were analyzed. Brain regions of interest were the ventral tegmental area (VTA), nucleus accumbens (Acb), medial prefrontal cortex (mPFC) and dorsal striatum (dStr), all involved in mediating aspects of ethanol reward. Region-specific Vglut, Dnmt1 and Mecp2 expression patterns were observed. ELS was associated with down-regulated expression of Vglut2 in the VTA and mPFC. Rats exposed to ELS were more sensitive to ethanol-induced changes in Vglut expression in the VTA, Acb, and dStr and in Dnmt1 and Mecp2 expression in the striatal regions. These findings suggest long-term glutamatergic and DNA methylation neuroadaptations as a consequence of ELS, and show an association between voluntary drinking in non-preferring, non-dependent, rodents and different Vglut, Dnmt1 and Mecp2 expression depending on early-life history.

qPCR based mRNA quality score show intact mRNA after heat stabilization.

Analysis of multiple analytes from biological samples can be challenging as different analytes require different preservation measures. Heat induced enzymatic inactivation is an efficient way to preserve proteins and their modifications in biological samples but RNA quality, as measured by RIN value, has been a concern in such samples. Here, we investigate the effect of heat stabilization compared with standard snap freezing on RNA quality using two RNA extraction protocols, QiaZol with and without urea pre-solubilization, and two RNA quality measurements: RIN value, as defined by the Agilent Bioanalyzer, and an alternative qPCR based method. DNA extraction from heat stabilized brain samples was also examined. The snap frozen samples had RIN values about 1 unit higher than heat stabilized samples for the direct QiaZol extraction but equal with stabilized samples using urea pre-solubilization. qPCR based RNA quality measurement showed no difference in quality between snap frozen and heat inactivated samples. The probable explanation for this discrepancy is that the RIN value is an indirect measure based on rRNA, while the qPCR score is based on actual measurement of mRNA quality. The DNA yield from heat stabilized brain tissue samples was significantly increased, compared to the snap frozen tissue, without any effects on purity or quality. Hence, heat stabilization of tissues opens up the possibility for a two step preservation protocol, where proteins and their modifications can be preserved in the first heat based step, while in a second step, using standard RNA preservation strategies, mRNA be preserved. This collection strategy will enable biobanking of samples where the ultimate analysis is not determined without loss of sample quality.

Minimizing Postsampling Degradation of Peptides by a Thermal Benchtop Tissue Stabilization Method.

Enzymatic degradation is a major concern in peptide analysis. Postmortem metabolism in biological samples entails considerable risk for measurements misrepresentative of true in vivo concentrations. It is therefore vital to find reliable, reproducible, and easy-to-use procedures to inhibit enzymatic activity in fresh tissues before subjecting them to qualitative and quantitative analyses. The aim of this study was to test a benchtop thermal stabilization method to optimize measurement of endogenous opioids in brain tissue. Endogenous opioid peptides are generated from precursor proteins through multiple enzymatic steps that include conversion of one bioactive peptide to another, often with a different function. Ex vivo metabolism may, therefore, lead to erroneous functional interpretations. The efficacy of heat stabilization was systematically evaluated in a number of postmortem handling procedures. Dynorphin B (DYNB), Leu-enkephalin-Arg(6) (LARG), and Met-enkephalin-Arg(6)-Phe(7) (MEAP) were measured by radioimmunoassay in rat hypothalamus, striatum (STR), and cingulate cortex (CCX). Also, simplified extraction protocols for stabilized tissue were tested. Stabilization affected all peptide levels to varying degrees compared to those prepared by standard dissection and tissue handling procedures. Stabilization increased DYNB in hypothalamus, but not STR or CCX, whereas LARG generally decreased. MEAP increased in hypothalamus after all stabilization procedures, whereas for STR and CCX, the effect was dependent on the time point for stabilization. The efficacy of stabilization allowed samples to be left for 2 hours in room temperature (20°C) without changes in peptide levels. This study shows that conductive heat transfer is an easy-to-use and efficient procedure for the preservation of the molecular composition in biological samples. Region- and peptide-specific critical steps were identified and stabilization enabled the optimization of tissue handling and opioid peptide analysis. The result is improved diagnostic and research value of the samples with great benefits for basic research and clinical work.

A ghrelin receptor (GHS-R1A) antagonist attenuates the rewarding properties of morphine and increases opioid peptide levels in reward areas in mice.

Gut-brain hormones such as ghrelin have recently been suggested to have a role in reward regulation. Ghrelin was traditionally known to regulate food intake and body weight homoeostasis. In addition, recent work has pin-pointed that this peptide has a novel role in drug-induced reward, including morphine-induced increase in the extracellular levels of accumbal dopamine in rats. Herein the effect of the ghrelin receptor (GHS-R1A) antagonist, JMV2959, on morphine-induced activation of the mesolimbic dopamine system was investigated in mice. In addition, the effects of JMV2959 administration on opioid peptide levels in reward related areas were investigated. In the present series of experiment we showed that peripheral JMV2959 administration, at a dose with no effect per se, attenuates the ability of morphine to cause locomotor stimulation, increase the extracellular levels of accumbal dopamine and to condition a place preference in mice. JMV2959 administration significantly increased tissue levels of Met-enkephalin-Arg(6)Phe(7) in the ventral tegmental area, dynorphin B in hippocampus and Leu-enkephalin-Arg(6) in striatum. We therefore hypothesise that JMV2959 prevents morphine-induced reward via stimulation of delta receptor active peptides in striatum and ventral tegmental areas. In addition, hippocampal peptides that activate kappa receptor may be involved in JMV2959׳s ability to regulate memory formation of reward. Given that development of drug addiction depends, at least in part, of the effects of addictive drugs on the mesolimbic dopamine system the present data suggest that GHS-R1A antagonists deserve to be elucidated as novel treatment strategies of opioid addiction.

Αlpha 2a-Adrenoceptor Gene Expression and Early Life Stress-Mediated Propensity to Alcohol Drinking in Outbred Rats.

Stressful events early in life, later high alcohol consumption and vulnerability to alcohol use disorder (AUD) are tightly linked. Norepinephrine is highly involved in the stress response and the α2A-adrenoceptor, which is an important regulator of norepinephrine signalling, is a putative target in pharmacotherapy of AUD. The aim of the present study was to investigate the effects of early-life stress and adult voluntary alcohol drinking on the α2A-adrenoceptor. The relative expression and promoter DNA methylation of the Adra2a gene were measured in the hypothalamus, a key brain region in stress regulation. A well-characterized animal model of early-life stress was used in combination with an episodic voluntary drinking in adulthood. Alcohol drinking rats with a history of early-life stress had lower Adra2a expression than drinking rats not exposed to stress. Alcohol intake and Adra2a gene expression were negatively correlated in high-drinking animals, which were predominantly rats subjected to early-life stress. The results provide support for a link between early-life stress, susceptibility for high alcohol consumption, and low Adra2a expression in the hypothalamus. These findings can increase our understanding of the neurobiological basis for vulnerability to initiate risk alcohol consumption and individual differences in the response to α2A-adrenoceptor agonists.

HPA Axis Gene Expression and DNA Methylation Profiles in Rats Exposed to Early Life Stress, Adult Voluntary Ethanol Drinking and Single Housing.

The neurobiological basis of early life stress (ELS) impact on vulnerability to alcohol use disorder is not fully understood. The effect of ELS, adult ethanol consumption and single housing, on expression of stress and DNA methylation regulatory genes as well as blood corticosterone levels was investigated in the hypothalamus and pituitary of adult out-bred Wistar rats subjected to different rearing conditions. A prolonged maternal separation (MS) of 360 min (MS360) was used to study the effect of ELS, and a short MS of 15 min (MS15) was used as a control. Voluntary ethanol drinking was assessed using a two-bottle free choice paradigm to simulate human episodic drinking. The effects of single housing and ethanol were assessed in conventional animal facility rearing (AFR) conditions. Single housing in adulthood was associated with lower Crhr1 and higher Pomc expression in the pituitary, whereas ethanol drinking was associated with higher expression of Crh in the hypothalamus and Crhr1 in the pituitary, accompanied by lower corticosterone levels. As compared to controls with similar early life handling, rats exposed to ELS displayed lower expression of Pomc in the hypothalamus, and higher Dnmt1 expression in the pituitary. Voluntary ethanol drinking resulted in lower Fkbp5 expression in the pituitary and higher Crh expression in the hypothalamus, independently of rearing conditions. In rats exposed to ELS, water and ethanol drinking was associated with higher and lower corticosterone levels, respectively. The use of conventionally reared rats as control group yielded more significant results than the use of rats exposed to short MS. Positive correlations, restricted to the hypothalamus and ELS group, were observed between the expression of the hypothalamus-pituitary-adrenal receptor and the methylation-related genes. Promoter DNA methylation and expression of respective genes did not correlate suggesting that other loci are involved in transcriptional regulation. Concluding, single housing is a confounding factor to be considered in voluntary ethanol drinking paradigms. ELS and ethanol drinking in adulthood exert independent effects on hypothalamic and pituitary related genes, however, in a manner dependent on the control group used.

Asymmetry of the endogenous opioid system in the human anterior cingulate: a putative molecular basis for lateralization of emotions and pain.

Lateralization of the processing of positive and negative emotions and pain suggests an asymmetric distribution of the neurotransmitter systems regulating these functions between the left and right brain hemispheres. By virtue of their ability to selectively mediate euphoria, dysphoria, and pain, the µ-, δ-, and κ-opioid receptors and their endogenous ligands may subserve these lateralized functions. We addressed this hypothesis by comparing the levels of the opioid receptors and peptides in the left and right anterior cingulate cortex (ACC), a key area for emotion and pain processing. Opioid mRNAs and peptides and 5 "classical" neurotransmitters were analyzed in postmortem tissues from 20 human subjects. Leu-enkephalin-Arg (LER) and Met-enkephalin-Arg-Phe, preferential δ-/µ- and κ-/µ-opioid agonists, demonstrated marked lateralization to the left and right ACC, respectively. Dynorphin B (Dyn B) strongly correlated with LER in the left, but not in the right ACC suggesting different mechanisms of the conversion of this κ-opioid agonist to δ-/µ-opioid ligand in the 2 hemispheres; in the right ACC, Dyn B may be cleaved by PACE4, a proprotein convertase regulating left-right asymmetry formation. These findings suggest that region-specific lateralization of neuronal networks expressing opioid peptides underlies in part lateralization of higher functions, including positive and negative emotions and pain in the human brain.