Adolescent intermittent ethanol exposure enhances adult stress effects in male rats

Differential effects of chronic and intermittent administration of taurine on alcohol binge drinking in male rats

Episodic consumption of high doses of alcohol in a short period (binge drinking - BD) among adolescents is known to be harmful to their brain development. Chronic use of taurine increases voluntary alcohol consumption and shows an anxiolytic-like effect in rats. In this study, we evaluated the differential effects of chronic and intermittent taurine administration on alcohol consumption and behavioral changes in adolescent and young adult rats subjected to the BD model. Male Wistar rats (35 days old) were divided into 4 groups for daily intraperitoneal administration of saline (SAL); taurine, 100mg/kg (TAU); taurine on BD days and saline on intervals (TAU/SAL); and saline on BD days and taurine on intervals (SAL/TAU). They were exposed to 4 cycles of BD, with free access to alcoholic solution (20% w/v), for 2h, 3 days per week. At the end of the 3rd cycle, anxiety-like behaviors were assessed using the light-dark task. After euthanasia, plasma and prefrontal cortex samples were collected to measure corticosterone and BDNF levels, respectively. Chronic taurine treatment did not alter alcohol consumption in rats, whereas intermittent administration increased alcohol intake after 4 BD exposures (TAU/SAL: +19.4% and SAL/TAU: +21.6%). No anxiolytic-like effects were found by taurine administration, nor were there changes in serum corticosterone or BDNF levels in the frontal cortex of young adult rats. Intermittent taurine, but not chronic treatment, increased alcohol intake among rats after the second week of exposure. The translation of these results to humans is concerning since the combination of alcohol and drinks containing taurine is common among adolescent and young adult individuals.

Adolescent alcohol exposure modifies adult anxiety-like behavior and amygdala sensitivity to alcohol in rats: Increased c-Fos activity and sex-dependent microRNA-182 expression

Adolescent binge alcohol drinking is a serious health concern contributing to adult alcohol abuse often associated with anxiety disorders. We have used adolescent intermittent ethanol (AIE) administration as a model of binge drinking in rats in order to explore its long-term effect on the basolateral amygdala (BLA) responsiveness to alcohol and anxiety-like behavior. AIE increased the number of BLA c-Fos positive cells in adult Wistar rats and anxiety-like behavior assessed by the open field test (OFT). Additionally, in adult female rats receiving AIE BLA over expression of miR-182 was found. Therefore, our results indicate that alcohol consumption during adolescence can lead to enduring changes in anxiety-like behavior and BLA susceptibility to alcohol that may be mediated by sex-dependent epigenetic changes. These results contribute to understanding the mechanisms involved in the development of alcohol use disorders (AUD) and anxiety-related disorders.

Adolescent intermittent ethanol exposure alters adult exploratory and affective behaviors, and cerebellar Grin2b expression in C57BL/6J mice

Binge drinking is one of the most common patterns (more than 90%) of alcohol consumption by young people. During adolescence, the brain undergoes maturational changes that influence behavioral control and affective behaviors, such as cerebellar brain volume and function in adulthood. We investigated long-term impacts of adolescent binge ethanol exposure on affective and exploratory behaviors and cerebellar gene expression in adult male and female mice. Further, the cerebellum is increasingly recognized as a brain region integrating a multitude of behaviors that span from the traditional primary sensory-motor to affective functions, such as anxiety and stress reactivity. Therefore, we investigated the persistent effects of adolescent intermittent ethanol (AIE) on exploratory and affective behaviors and began to elucidate the role of the cerebellum in these behaviors through excitatory signaling gene expression. We exposed C57BL/6J mice to AIE or air (control) vapor inhalation from postnatal day 28-42. After prolonged abstinence (>34 days), in young adulthood (PND 77+) we assessed behavior in the open field, light/dark, tail suspension, and forced swim stress tests to determine changes in affective behaviors including anxiety-like, depressive-like, and stress reactivity behavior. Excitatory signaling gene mRNA levels of fragile X messenger ribonucleoprotein (FMR1), glutamate receptors (Grin2a, Grin2b and Grm5) and excitatory synaptic markers (PSD-95 and Eaat1) were measured in the cerebellum of adult control and AIE-exposed mice. AIE-exposed mice showed decreased exploratory behaviors in the open field test (OFT) where both sexes show reduced ambulation, however only females exhibited a reduction in rearing. Additionally, in the OFT, AIE-exposed females also exhibited increased anxiety-like behavior (entries to center zone). In the forced swim stress test, AIE-exposed male mice, but not females, spent less time immobile compared to their same-sex controls, indicative of sex-specific changes in stress reactivity. Male and female AIE-exposed mice showed increased Grin2b (Glutamate Ionotropic Receptor NMDA Type Subunit 2B) mRNA levels in the cerebellum compared to their same-sex controls. Together, these data show that adolescent binge-like ethanol exposure altered both exploratory and affective behaviors in a sex-specific manner and modified cerebellar Grin2b expression in adult mice. This indicates the cerebellum may serve as an important brain region that is susceptible to long-term molecular changes after AIE.

Sargassum horneri Extract Attenuates Depressive-like Behaviors in Mice Treated with Stress Hormone

Sargassum horneri, a brown seaweed, is known for its various health benefits; however, there are no reports on its effects on depression. This study aimed to investigate the antidepressant effects of S. horneri ethanol extract (SHE) in mice injected with corticosterone (CORT) and to elucidate the underlying molecular mechanisms. Behavioral tests were conducted, and corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), and CORT levels were measured. A fluorometric monoamine oxidase (MAO) enzyme inhibition assay was performed. Neurotransmitters like serotonin, dopamine, and norepinephrine levels were determined. Moreover, the ERK-CREB-BDNF signaling pathway in the prefrontal cortex and hippocampus was evaluated. Behavioral tests revealed that SHE has antidepressant effects by reducing immobility time and increasing time spent in open arms. Serum CRH, ACTH, and CORT levels decreased in the mice treated with SHE, as did the glucocorticoid-receptor expression in their brain tissues. SHE inhibited MAO-A and MAO-B activities. In addition, SHE increased levels of neurotransmitters. Furthermore, SHE activated the ERK-CREB-BDNF pathway in the prefrontal cortex and hippocampus. These findings suggest that SHE has antidepressant effects in CORT-injected mice, via the regulation of the hypothalamic-pituitary-adrenal axis and monoaminergic pathway, and through activation of the ERK-CREB-BDNF signaling pathway. Thus, our study suggests that SHE may act as a natural antidepressant.

Adolescent Intermittent Ethanol Exposure Alters Adult Exploratory and Affective Behaviors, and Cerebellar Grin2B Expression in C57BL/6J Mice

Binge drinking is one of the most common patterns (more than 90%) of alcohol consumption by young people. During adolescence, the brain undergoes maturational changes that influence behavioral control and affective behaviors, such as cerebellar brain volume and function in adulthood. We investigated long-term impacts of adolescent binge ethanol exposure on affective and exploratory behaviors and cerebellar gene expression in adult male and female mice. Further, the cerebellum is increasingly recognized as a brain region integrating a multitude of behaviors that span from the traditional primary sensory-motor to affective functions, such as anxiety and stress reactivity. Therefore, we investigated the persistent effects of adolescent intermittent ethanol (AIE) on exploratory and affective behaviors and began to elucidate the role of the cerebellum in these behaviors through excitatory signaling gene expression. We exposed C57BL/6J mice to AIE or air (control) vapor inhalation from postnatal day 28-42. After prolonged abstinence (>34 days), in young adulthood (PND 77+) we assessed behavior in the open field, light/dark, tail suspension, and forced swim stress tests to determine changes in affective behaviors including anxiety-like, depressive-like, and stress reactivity behavior. Excitatory signaling gene mRNA levels of fragile X messenger ribonucleoprotein ( FMR1) , glutamate receptors ( Grin2a , Grin2B and Grm5 ) and excitatory synaptic markers (PSD-95 and Eaat1) were measured in the cerebellum of adult control and AIE-exposed mice. AIE-exposed mice showed decreased exploratory behaviors in the open field test (OFT) where both sexes show reduced ambulation, however only females exhibited a reduction in rearing. Additionally, in the OFT, AIE-exposed females also exhibited increased anxiety-like behavior (entries to center zone). In the forced swim stress test, AIE-exposed male mice, but not females, spent less time immobile compared to their same-sex controls, indicative of sex-specific changes in stress reactivity. Male and female AIE-exposed mice showed increased Grin2B (Glutamate Ionotropic Receptor NMDA Type Subunit 2B) mRNA levels in the cerebellum compared to their same-sex controls. Together, these data show that adolescent binge-like ethanol exposure altered both exploratory and affective behaviors in a sex-specific manner and modified cerebellar Grin2B expression in adult mice. This indicates the cerebellum may serve as an important brain region that is susceptible to long-term molecular changes after AIE.

Highlights

Adolescent intermittent ethanol (AIE) exposure decreased exploratory behavior in adult male and female mice.In females, but not males, AIE increased anxiety-like behavior.In males, but not females, AIE reduced stress reactivity in adulthood.These findings indicate sex differences in the enduring effects of AIE on exploratory and affective behaviors. Cerebellar Grin2B mRNA levels were increased in adulthood in both male and female AIE-exposed mice. These findings add to the small, but growing literature on behavioral AIE effects in mice, and establish cerebellar excitatory synaptic gene expression as an enduring effect of adolescent ethanol exposure.

Neuroactive Steroid-Gut Microbiota Interaction in T2DM Diabetic Encephalopathy

The pathological consequences of type 2 diabetes mellitus (T2DM) also involve the central nervous system; indeed, T2DM patients suffer from learning and memory disabilities with a higher risk of developing dementia. Although several factors have been proposed as possible contributors, how neuroactive steroids and the gut microbiome impact brain pathophysiology in T2DM remain unexplored. On this basis, in male Zucker diabetic fatty (ZDF) rats, we studied whether T2DM alters memory abilities using the novel object recognition test, neuroactive steroid levels by liquid chromatography-tandem mass spectrometry, hippocampal parameters using molecular assessments, and gut microbiome composition using 16S next-generation sequencing. Results obtained reveal that T2DM worsens memory abilities and that these are correlated with increased levels of corticosterone in plasma and with a decrease in allopregnanolone in the hippocampus, where neuroinflammation, oxidative stress, and mitochondrial dysfunction were reported. Interestingly, our analysis highlighted a small group of taxa strictly related to both memory impairment and neuroactive steroid levels. Overall, the data underline an interesting role for allopregnanolone and microbiota that may represent candidates for the development of therapeutic strategies.