Mixing energy drinks and alcohol during adolescence impairs brain function: A study of rat hippocampal plasticity.

In the last decades, the consumption of energy drinks has risen dramatically, especially among young people, adolescents and athletes, driven by the constant search for ergogenic effects, such as the increase in physical and cognitive performance. In parallel, mixed consumption of energy drinks and ethanol, under a binge drinking modality, under a binge drinking modality, has similarly grown among adolescents. However, little is known whether the combined consumption of these drinks, during adolescence, may have long-term effects on central function, raising the question of the risks of this habit on brain maturation. Our study was designed to evaluate, by behavioral, electrophysiological and molecular approaches, the long-term effects on hippocampal plasticity of ethanol (EtOH), energy drinks (EDs), or alcohol mixed with energy drinks (AMED) in a rat model of binge-like drinking adolescent administration. The results show that AMED binge-like administration produces adaptive hippocampal changes at the molecular level, associated with electrophysiological and behavioral alterations, which develop during the adolescence and are still detectable in adult animals. Overall, the study indicates that binge-like drinking AMED adolescent exposure represents a habit that may affect permanently hippocampal plasticity.

Parental Social Isolation during Adolescence Alters Gut Microbiome in Rat Male Offspring.

Previous work from our laboratory demonstrated that parental stress, induced by social isolation starting at puberty, leads to behavioral, endocrine, and biochemical changes in the male, but not female, offspring (ISO-O) of Sprague-Dawley rats. Here, we report alterations in the gut microbiota composition of ISO-O vs. grouped-housed offspring (GH-O), although all animals received the same diet and were housed in the same conditions. Analysis of bacterial communities by next-generation sequencing (NGS) of 16S rRNA gene revealed alterations at family and order levels within the main phyla of Bacteroides, Proteobacteria, and Firmicutes, including an almost total deficit in Limosilactobacillus reuteri (formerly Lactobacillus reuteri) and a significant increase in Ligilactobacillus murinus (formerly Lactobacillus murinus). In addition, we found an increase in the relative abundance of Rhodospirillales and Clostridiales in the families of Lachnospiraceae and Ruminococcaceae, and Bacteroidales in the family of Prevotellaceae. Furthermore, we examined plasma levels of the proinflammatory cytokines interleukin-1-beta and tumor necrosis factor-alpha, which did not differ between the two groups, while corticosterone concentrations were significantly increased in ISO-O rats. Our findings suggest that adverse environmental conditions experienced by parents may have an impact on the likelihood of disease development in the subsequent generations.

Identification of metabolic biomarkers of chronic vagus nerve stimulation (VNS) in subjects with drug-resistant epilepsy (DRE).

Neuromodulation by means of vagus nerve stimulation (VNS) therapy, reduces seizure frequency and improves quality of life in subjects with drug-resistant epilepsy (DRE), yet its molecular mechanism remains unclear. This study investigates the impact of chronic VNS on lipid bioactive metabolites and fatty acids (FA) in the plasma and red blood cells of seven subjects with DRE. By measuring expression levels of peroxisome proliferator-activated receptor α (PPARα) and sirtuin1 (SIRT1) genes-key regulators in energy and lipid metabolism-and lipid profiles before and after various stages of VNS, this study identifies potential mechanisms by which VNS may reduce seizure frequency. Blood samples collected before VNS device implantation, after acute VNS stimulus, and following gradual intensity increments up to therapeutic levels revealed that VNS increases SIRT1 and PPARα expression and erythrocyte concentrations of PPARα ligands. Additionally, we observe reduced de novo lipogenesis biomarkers in erythrocytes, indicating that VNS may influence systemic lipid and energy metabolism. Our findings suggest that VNS could enhance neuronal function by modulating energy metabolism, thus potentially reducing seizure frequency in subjects with DRE. Future research targeting SIRT1 and PPARα may provide innovative therapeutic strategies for managing DRE. Plain Language Summary: The exact mechanism of VNS is still unknown. This study investigated the effects of VNS Therapy on energetic metabolism, suggesting possible novel biomarkers for DRE subjects and neuromodulation therapies.

Effects of Chronic Bifidobacteria Administration in Adult Male Rats on Plasma Metabolites: A Preliminary Metabolomic Study.

Probiotics are live microorganisms distributed in the gastrointestinal tract that confer health benefits to the host when administered in adequate amounts. Bifidobacteria have been widely tested as a therapeutic strategy in the prevention and treatment of a broad spectrum of gastrointestinal disorders as well as in the regulation of the "microbiota-gut-brain axis". Metabolomic techniques can provide details in the study of molecular metabolic mechanisms involved in Bifidobacteria function through the analysis of metabolites that positively contribute to human health. This study was focused on the effects of the chronic assumption of a mixture of Bifidobacteria in adult male rats using a metabolomic approach. Plasma samples were collected at the end of treatment and analyzed with a gas chromatography-mass spectrometry (GC-MS) platform. Partial least square discriminant analysis (PLS-DA) was performed to compare the metabolic pattern in control and probiotic-treated rats. Our results show, in probiotic-treated animals, an increase in metabolites involved in the energetic cycle, such as glucose, erythrose, creatinine, taurine and glycolic acid, as well as 3-hydroxybutyric acid. This is an important metabolite of short-chain fatty acids (SCFA) with multitasking roles in energy circuit balance, and it has also been proposed to have a key role in the prevention and treatment of neurodegenerative diseases.

Increased Voluntary Alcohol Consumption in Mice Lacking GABAB(1) Is Associated With Functional Changes in Hippocampal GABAA Receptors.

Gamma-aminobutyric acid type B receptor (GABABR) has been extensively involved in alcohol use disorders; however, the mechanisms by which this receptor modulates alcohol drinking behavior remain murky. In this study, we investigate alcohol consumption and preference in mice lacking functional GABABR using the 2-bottle choice paradigm. We found that GABAB(1), knockout (KO), and heterozygous (HZ) mice drank higher amounts of an alcoholic solution, preferred alcohol to water, and reached higher blood alcohol concentrations (BACs) compared to wild-type (WT) littermates. The GABABR agonist GHB significantly reduced alcohol consumption in the GABAB(1) HZ and WT but not in the KO mice. Next, because of a functional crosstalk between GABABR and δ-containing GABAA receptor (δ-GABA A R), we profiled δ subunit mRNA expression levels in brain regions in which the crosstalk was characterized. We found a loss of the alcohol-sensitive GABAAR δ subunit in the hippocampus of the GABAB(1) KO alcohol-naïve mice that was associated with increased É£2 subunit abundance. Electrophysiological recordings revealed that these molecular changes were associated with increased phasic inhibition, suggesting a potential gain of synaptic GABAAR responsiveness to alcohol that has been previously described in an animal model of excessive alcohol drinking. Interestingly, voluntary alcohol consumption did not revert the dramatic loss of hippocampal δ-GABAAR occurring in the GABAB(1) KO mice but rather exacerbated this condition. Finally, we profiled hippocampal neuroactive steroids levels following acute alcohols administration in the GABAB(1) KO and WT mice because of previous involvement of GABABR in the regulation of cerebral levels of these compounds. We found that systemic administration of alcohol (1.5 g/kg) did not produce alcohol-induced neurosteroid response in the GABAB(1) KO mice but elicited an expected increase in the hippocampal level of progesterone and 3α,5α-THP in the WT controls. In conclusion, we show that genetic ablation of the GABAB(1) subunit results in increased alcohol consumption and preference that were associated with functional changes in hippocampal GABAAR, suggesting a potential mechanism by which preference for alcohol consumption is maintained in the GABAB(1) KO mice. In addition, we documented that GABAB(1) deficiency results in lack of alcohol-induced neurosteroids, and we discussed the potential implications of this finding in the context of alcohol drinking and dependence.

Therapeutic Use of Cerebellar Intermittent Theta Burst Stimulation (iTBS) in a Sardinian Family Affected by Spinocerebellar Ataxia 38 (SCA 38).

Spinocerebellar ataxia 38 (SCA 38) is an autosomal dominant disorder caused by conventional mutations in the ELOVL5 gene which encodes an enzyme involved in the synthesis of very long fatty acids, with a specific expression in cerebellar Purkinje cells. Three Italian families carrying the mutation, one of which is of Sardinian descent, have been identified and characterized. One session of cerebellar intermittent theta burst stimulation (iTBS) was applied to 6 affected members of the Sardinian family to probe motor cortex excitability measured by motor-evoked potentials (MEPs). Afterwards, patients were exposed to ten sessions of cerebellar real and sham iTBS in a cross-over study and clinical symptoms were evaluated before and after treatment by Modified International Cooperative Ataxia Rating Scale (MICARS). Moreover, serum BDNF levels were evaluated before and after real and sham cerebellar iTBS and the role of BDNF Val66Met polymorphism in influencing iTBS effect was explored. Present data show that one session of cerebellar iTBS was able to increase MEPs in all tested patients, suggesting an enhancement of the cerebello-thalamo-cortical pathway in SCA 38. MICARS scores were reduced after ten sessions of real cerebellar iTBS showing an improvement in clinical symptoms. Finally, although serum BDNF levels were not affected by cerebellar iTBS when considering all samples, segregating for genotype a difference was found between Val66Val and Val66Met carriers. These preliminary data suggest a potential therapeutic use of cerebellar iTBS in improving motor symptoms of SCA38.

Metabolomic Analysis of Plasma from GABAB(1) Knock-Out Mice Reveals Decreased Levels of Elaidic Trans-Fatty Acid.

Mice lacking the GABAB(1) subunit of gamma-aminobutyric acid (GABA) type B receptors exhibit spontaneous seizures, hyperalgesia, hyperlocomotor activity, and memory impairment. Although mice lacking the GABAB(1) subunit are viable, they are sterile, and to generate knockout (KO) mice, it is necessary to cross heterozygous (HZ) mice. The aim of our study was to detect the metabolic differences between the three genotypes of GABAB(1) KO mice in order to further characterize this experimental animal model. Plasma samples were collected from wild-type (WT), HZ, and KO mice. Samples were analyzed by means of a gas chromatography-mass spectrometry (GC-MS) platform. Univariate t-test, and partial least square discriminant analysis (PLS-DA) were performed to compare the metabolic pattern of different genotypes. The metabolomic analysis highlighted differences between the three genotypes and identified some metabolites less abundant in KO mice, namely elaidic acid and other fatty acids, and chiro-inositol.

Cerebellar continuous theta burst stimulation reduces levodopa-induced dyskinesias and decreases serum BDNF levels.

Patients with Parkinson's Disease (PD) experience bothersome motor fluctuations and Levodopa-induced Dyskinesias (LIDs). Cerebellar continuous theta burst stimulation (cTBS) was used as an inhibitory protocol of repetitive transcranial magnetic stimulation (rTMS) to reduce LIDs in PD patients. The influence of Val66Met polymorphism of Brain Derived Neurotrophic Factor (BDNF) gene on the therapeutic response to cTBS was investigated and the serum levels of BDNF were measured before and after treatment. Eleven patients were exposed to a session of cTBS and sham stimulation (one week apart) after the administration of 125 % of their usual morning dose of Levodopa and LIDs were video-recorded and evaluated at different time points (0, 15, 30, 45, 60, 90 min after Levodopa). Cerebellar cTBS significantly reduced LIDs with respect to sham stimulation and decreased serum BDNF levels. These effects were evident in the Val66Val group (7 subjects) but not in the Val66Met group (4 subjects). These data confirm the efficacy of cerebellar cTBS in reducing LIDs in PD patients and show that the clinical effect is accompanied by a decrease in serum BDNF levels. Moreover, they suggest that BDNF Val66Met polymorphism may influence the clinical and biological response to cTBS.

Are preconceptional stressful experiences crucial elements for the aetiology of autism spectrum disorder? Insights from an animal model.

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders characterized by changes in social interactions, impaired language and communication, fear responses and presence of repetitive behaviours. Although the genetic bases of ASD are well documented, the recent increase in clinical cases of idiopathic ASD indicates that several environmental risk factors could play a role in ASD aetiology. Among these, maternal exposure to psychosocial stressors during pregnancy has been hypothesized to affect the risk for ASD in offspring. Here, we tested the hypothesis that preconceptional stressful experiences might also represent crucial elements in the aetiology of ASD. We previously showed that social isolation stress during adolescence results in a marked decrease in the brain and plasma concentrations of progesterone and in the quality of maternal care that these female rats later provide to their young. Here we report that male offspring of socially isolated parents showed decreased agonistic behaviour and social transmission of flavour preference, impairment in reversal learning, increased seizure susceptibility, reduced plasma oxytocin levels, and increased plasma and brain levels of BDNF, all features resembling an ASD-like phenotype. These alterations came with no change in spatial learning, aggression, anxiety and testosterone plasma levels, and were sex-dependent. Altogether, the results suggest that preconceptional stressful experiences should be considered as crucial elements for the aetiology of ASD, and indicate that male offspring of socially isolated parents may be a useful animal model to further study the neurobiological bases of ASD, avoiding the adaptations that may occur in other genetic or pharmacologic experimental models of these disorders.

Impaired glucocorticoid-mediated HPA axis negative feedback induced by juvenile social isolation in male rats.

We previously demonstrated that socially isolated rats at weaning showed a significant decrease in corticosterone and adrenocorticotropic hormone (ACTH) levels, associated with an enhanced response to acute stressful stimuli. Here we shown that social isolation decreased levels of total corticosterone and of its carrier corticosteroid-binding globulin, but did not influence the availability of the free active fraction of corticosterone, both under basal conditions and after acute stress exposure. Under basal conditions, social isolation increased the abundance of glucocorticoid receptors, while it decreased that of mineralocorticoid receptors. After acute stress exposure, socially isolated rats showed long-lasting corticosterone, ACTH and corticotrophin releasing hormone responses. Moreover, while in the hippocampus and hypothalamus of group-housed rats glucocorticoid receptors expression increased with time and reached a peak when corticosterone levels returned to basal values, in socially isolated rats expression of glucocorticoid receptors did not change. Finally, social isolation also affected the hypothalamic endocannabinoid system: compared to group-housed rats, basal levels of anandamide and cannabinoid receptor type 1 were increased, while basal levels of 2-arachidonoylglycerol were decreased in socially isolated rats and did not change after acute stress exposure. The present results show that social isolation in male rats alters basal HPA axis activity and impairs glucocorticoid-mediated negative feedback after acute stress. Given that social isolation is considered an animal model of several neuropsychiatric disorders, such as generalized anxiety disorder, depression, post-traumatic stress disorder and schizophrenia, these data could contribute to better understand the alterations in HPA axis activity observed in these disorders.

Trigeminal nerve stimulation induces Fos immunoreactivity in selected brain regions, increases hippocampal cell proliferation and reduces seizure severity in rats.

Sites and mechanisms by which trigeminal nerve stimulation (TNS) exerts beneficial effects on symptoms of drug-resistant epilepsy and depression are still unknown. Effects of short-term TNS on brain regions involved in the physiopathology of these disorders were investigated in this study. Forty male rats were assigned to three groups: TNS (undergoing electrical stimulation of the left infraorbitary nerve via surgically implanted cuff electrodes); Sham (undergoing surgical procedure but without a stimulation); Naïve rats. The effects of TNS (3-hour session; 30-s ON, 5-min OFF; 30Hz; 500µs; 2mA) were evaluated on: (i) behavioral pattern of pentylenetetrazole (PTZ)-induced seizures as measured by the Racine scale; (ii) c-Fos-like immunoreactivity in discrete brain areas; (iii) hippocampal cell proliferation by bromodeoxyuridine (BrdU)-like immunoreactivity. In comparison with Sham groups, TNS significantly decreased the duration of PTZ-induced seizures (p<0.05) and promoted a faster recovery (p<0.001) by reducing the most severe seizure types. In the TNS group the number of c-Fos-labeled cells was significantly increased (p<0.001) in the trigeminal nuclear complex, nucleus of the solitary tract, locus coeruleus, dorsal raphe nucleus, hippocampus, amygdala, endopiriform nucleus, entorhinal cortex and sensorimotor cortex. In the TNS group the number of BrdU-positive cells in the dentate gyrus was significantly greater with respect to both Naïve and Sham groups. Data show that acute TNS effectively counteracted PTZ-induced seizures and boosted hippocampal cell proliferation in rats. TNS increased c-Fos-like immunoreactivity in brainstem and forebrain structures which play a pivotal role in the physiopathology of epilepsy and depression.

Regulatory Role of Circular RNAs and Neurological Disorders.

Circular RNAs (circRNAs) are a class of long noncoding RNAs that are characterized by the presence of covalently linked ends and have been found in all life kingdoms. Exciting studies in regulatory roles of circRNAs are emerging. Here, we summarize classification, characteristics, biogenesis, and regulatory functions of circRNAs. CircRNAs are found to be preferentially expressed along neural genes and in neural tissues. We thus highlight the association of circRNA dysregulation with neurodegenerative diseases such as Alzheimer's disease. Investigation of regulatory role of circRNAs will shed novel light in gene expression mechanisms during development and under disease conditions and may identify circRNAs as new biomarkers for aging and neurodegenerative disorders.

Transcutaneous trigeminal nerve stimulation induces a long-term depression-like plasticity of the human blink reflex.

The beneficial effects of trigeminal nerve stimulation (TNS) on several neurological disorders are increasingly acknowledged. Hypothesized mechanisms include the modulation of excitability in networks involved by the disease, and its main site of action has been recently reported at brain stem level. Aim of this work was to test whether acute TNS modulates brain stem plasticity using the blink reflex (BR) as a model. The BR was recorded from 20 healthy volunteers before and after 20 min of cyclic transcutaneous TNS delivered bilaterally to the infraorbital nerve. Eleven subjects underwent sham-TNS administration and were compared to the real-TNS group. In 12 subjects, effects of unilateral TNS were tested. The areas of the R1 and R2 components of the BR were recorded before and after 0 (T0), 15 (T15), 30 (T30), and 45 (T45) min from TNS. In three subjects, T60 and T90 time points were also evaluated. Ipsi- and contralateral R2 areas were significantly suppressed after bilateral real-TNS at T15 (p = 0.013), T30 (p = 0.002), and T45 (p = 0.001), while R1 response appeared unaffected. The TNS-induced inhibitory effect on R2 responses lasted up to 60 min. Real- and sham-TNS protocols produced significantly different effects (p = 0.005), with sham-TNS being ineffective at any time point tested. Bilateral TNS was more effective (p = 0.009) than unilateral TNS. Acute TNS induced a bilateral long-lasting inhibition of the R2 component of the BR, which resembles a long-term depression-like effect, providing evidence of brain stem plasticity produced by transcutaneous TNS. These findings add new insight into mechanisms of TNS neuromodulation and into physiopathology of those neurological disorders where clinical benefits of TNS are recognized.

Chronic Intermittent Ethanol Regulates Hippocampal GABA(A) Receptor Delta Subunit Gene Expression.

Chronic ethanol consumption causes structural and functional reorganization in the hippocampus and induces alterations in the gene expression of gamma-aminobutyric acid type A receptors (GABAARs). Distinct forced intermittent exposure models have been used previously to investigate changes in GABAAR expression, with contrasting results. Here, we used repeated cycles of a Chronic Intermittent Ethanol paradigm to examine the relationship between voluntary, dependence-associated ethanol consumption, and GABAAR gene expression in mouse hippocampus. Adult male C57BL/6J mice were exposed to four 16-h ethanol vapor (or air) cycles in inhalation chambers alternated with limited-access two-bottle choice between ethanol (15%) and water consumption. The mice exposed to ethanol vapor showed significant increases in ethanol consumption compared to their air-matched controls. GABAAR alpha4 and delta subunit gene expression were measured by qRT-PCR at different stages. There were significant changes in GABAAR delta subunit transcript levels at different time points in ethanol-vapor exposed mice, while the alpha4 subunit levels remained unchanged. Correlated concurrent blood ethanol concentrations suggested that GABAAR delta subunit mRNA levels fluctuate depending on ethanol intoxication, dependence, and withdrawal state. Using a vapor-based Chronic Intermittent Ethanol procedure with combined two-bottle choice consumption, we corroborated previous evidences showing that discontinuous ethanol exposure affects GABAAR delta subunit expression but we did not observe changes in alpha4 subunit. These findings indicate that hippocampal GABAAR delta subunit expression changes transiently over the course of a Chronic Intermittent Ethanol paradigm associated with voluntary intake, in response to ethanol-mediated disturbance of GABAergic neurotransmission.

The mTOR signaling pathway and neuronal stem/progenitor cell proliferation in the hippocampus are altered during the development of absence epilepsy in a genetic animal model.

Hyperactivation of mammalian target of rapamycin (mTOR) signaling pathway occurs after an epileptogenic insult and, its inhibition prevents the development of spontaneous seizures. We have recently demonstrated that mTOR's inhibition by rapamycin (started before seizure onset), permanently reduces the development of spontaneous absence seizures in WAG/Rij rats, an animal model of absence epilepsy; furthermore, mTOR phosphorylation was increased in adult WAG/Rij rats' cortex, but not other brain areas. However, it was not clear whether this hyperphosphorylation was a cause or a consequence of absence seizure. Here, we have addressed this issue by analyzing immunohistochemically: (1) the brain levels of total and phosphorylated mTOR in young (before seizures) and adult WAG/Rij rats; (2) the proliferation of hippocampal neuronal stem/progenitor cells assessed by BrdU analysis at different ages. WAG/Rij rats have higher levels of total mTOR in several brain areas than Wistar rats; phospho-mTOR staining is higher in young WAG/Rij rats than control and adult WAG/Rij rats. Finally, the age-related decline in hippocampal neural progenitor cell proliferation rate was slower in WAG/Rij than Wistar rats. Our results support a role for persistent mTOR activation and consequent change in hippocampal progenitor cell proliferation during the epileptogenic process leading to the development of absence seizures in WAG/Rij rats.

Increased voluntary ethanol consumption and changes in hippocampal synaptic plasticity in isolated C57BL/6J mice.

Social isolation (SI) is a notable model of prolonged mild stress, characterized by multiple neurochemical and behavioral alterations, that appears particularly suitable for studying different aspects of the interplay between stress and ethanol (EtOH) consumption in order to characterize potential molecular mechanisms, including changes in the function of inhibitory GABAergic synapses, underlying such interaction. In C57BL/6J mice, SI is associated with an altered hippocampal concentration of the neuroactive steroids 3α-hydroxy-5α-pregnan-20-one (3α-5α-THP), an increased expression of the α4 and δ subunit of γ-aminobutyric acid type A receptors (GABAARs) in the dentate gyrus (DG), and a parallel enhancement of the stimulatory action of 4,5,6,7-tetrahydroisoxazolo[5,4-c] pyridin-3-ol (THIP) on GABAergic tonic currents recorded in voltage-clamped DG granule cells (DGGCs). In addition, SI in C57BL/6J mice determines an increase in voluntary EtOH consumption and EtOH preference when compared to group-housed (GH) control animals. Furthermore, in hippocampal slices of SI mice we also observed a marked reduction of both cellular excitability and long term potentiation (LTP) in pyramidal neurons of the CA1 hippocampal sub-region, effects that were prevented by the long term treatment of SI mice with the neuroactive steroid precursor progesterone. In this article, we summarize some of our recent findings on the effects of SI in C57BL/6J mice on voluntary EtOH intake, regulation of GABAARs gene expression and function and hippocampal long term synaptic plasticity.

Vagus nerve stimulation reduces body weight and fat mass in rats.

Among the manifold effects of vagus nerve stimulation (VNS) delivered as an add-on treatment to patients with drug-resistant epilepsy, a moderate loss of body weight has been observed in some individuals. We have now investigated this effect in rats. Exposure of rats to VNS for 4 weeks reduced feed conversion efficiency as well as body weight gain (by ∼25%) and the amount of mesenteric adipose tissue (by ∼45%) in comparison with those in sham-operated control animals. A pair-fed experiment showed that both lower dietary intake and increase energy expenditure independently contributed to the reduction of body weight and mesenteric adipose tissue. Moreover, VNS increased the level of non-esterified fatty acids in plasma and mesenteric adipose tissue by ∼50 and 80%, respectively, without affecting that in the liver. In addition, VNS reduced the amounts of endocannabinoids and increased N-palmitoylethanolamide, an endogenous ligand of the transcription factor PPARα (peroxisome proliferator-activated receptor α) in mesenteric adipose tissue but not in the hypothalamus. These effects were accompanied by increased expression of the gene for brain-derived neurotrophic factor (BDNF) in the hypothalamus and up-regulation of the abundance of PPARα in the liver. Our results suggest that the reduction in body fat induced by VNS in rats may result from the action of both central and peripheral mediators. The reduced feed conversion efficiency associated with VNS may be mediated by hypothalamic BDNF, down-regulation of endocannabinoid tone in mesenteric adipose tissue and a PPARα-dependent increase in fatty acid oxidation in the liver, which in concerted action may account for the anorexic effect and increased energy expenditure.

Voluntary Ethanol Consumption Induced by Social Isolation Reverses the Increase of α(4)/δ GABA(A) Receptor Gene Expression and Function in the Hippocampus of C57BL/6J Mice.

Post-weaning social isolation (SI) is a model of prolonged mild stress characterized by behavioral and neurochemical alterations. We used SI in C57BL/6J mice to investigate the effects of ethanol (EtOH) in the free-choice drinking paradigm on gene expression and function of γ-aminobutyric acid type A receptors (GABA(A)Rs) and the role of neuroactive steroids in the actions of EtOH in the hippocampus. SI stress induced a marked reduction in hippocampal 3α-hydroxy-5α-pregnan-20-one (3α,5α-TH PROG) and was associated with molecular and functional changes of the GABA(A)R. The gene expression of the α(4) and δ subunits was increased in the hippocampus of SI C57BL/6J mice; the expression of the γ(2) subunit was decreased whereas that of the α(1) did not change. Patch-clamp recordings in dentate gyrus (DG) granule cells obtained from SI C57BL/6J mice revealed a greater enhancement of tonic currents induced by α-(4,5,6,7-tetrahydroisoxazolo[5,4-c] pyridin-3-ol (THIP) compared to that in control C57BL/6J mice. These neurochemical, molecular and functional changes observed in SI C57BL/6J mice were associated with an increased EtOH intake and EtOH preference. Nevertheless, the increase in EtOH consumption did not restore the reduction in hippocampal 3α,5α-TH PROG induced by SI. EtOH self-administration blocked the changes in gene expression of the α(4) subunit but not those of the δ and γ(2) subunits induced by SI. In addition, EtOH self-administration did not block the SI-induced changes in GABA(A)R-mediated tonic inhibition in hippocampal granule cells but increased the frequency of basal GABAergic sIPSCs in DG granule cells. We conclude that self-administration of EtOH selectively abolishes the increase of α(4) subunit but not other neurochemical, molecular, and functional modifications induced by SI prolonged mild stress.

GABA(A) receptor function and gene expression during pregnancy and postpartum.

Neuroactive steroids such as 3alpha,5alpha-THP are reduced metabolites of progesterone and are considered to play an important physiological role to locally modulate neuronal excitability by "fine-tuning" the action of GABA acting at GABA(A) receptors (GABA(A)-Rs). In different brain regions, such as the hippocampus, different subpopulations of nerve cells exhibit two components of inhibitory GABAergic transmission: a phasic component mediated by synaptic GABA(A)-Rs, and a tonic component mediated by "ambient" GABA acting at extrasynaptic GABA(A)-Rs mainly containing the delta subunit and endowed with a higher sensitivity to neuroactive steroids compared to synaptic receptors. It is also well accepted that fluctuations in brain neuroactive steroid levels may result in plastic changes of GABA(A)-Rs. In this article we review some of our results obtained with the model of pregnancy in rats. Pregnancy, in fact, is characterized by a marked and progressive increase in plasma and brain levels of neuroactive steroids which could contribute to changes in mood, anxiety as well as other psychiatric conditions. Such elevation in brain neuroactive steroid concentrations during pregnancy, in turn, is accompanied by alterations in both gene expression and function of synaptic and extrasynaptic GABA(A)-Rs in the hippocampus as well as other areas.

Plasticity and function of extrasynaptic GABA(A) receptors during pregnancy and after delivery.

Neuroactive steroids such as 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-THP) are reduced metabolites of progesterone and are thought to play an important physiological role in local modulation of neuronal excitability by "fine-tuning" the action of gamma-aminobutyric acid (GABA) at GABA(A) receptors. Fluctuations in the concentrations of neuroactive steroids in the brain are also thought to contribute to GABA(A) receptor plasticity. We here review results from our laboratory related to the regulation of GABA(A) receptor function and plasticity by changes in the levels of neuroactive steroids during pregnancy and after delivery in rats. Pregnancy is characterized by marked and progressive increases in the plasma and brain concentrations of neuroactive steroids, which are implicated in the changes in mood, anxiety, and other psychiatric states associated with this condition. We have shown that the increases in the brain levels of neuroactive steroids during pregnancy are causally related to changes in the expression of specific GABA(A) receptor subunits and the function of extrasynaptic GABA(A) receptors in the hippocampus.