The Effects of Adolescent Alcohol Exposure on Stress Circuitry and Behaviors
Publication Date
July 2019
Location
LSU Health Medical Education Building
Document Type
Abstract
Start Date
26-7-2019 9:00 AM
End Date
26-7-2019 12:00 PM
Description
Individuals who consume alcohol as adolescents are known to have an increased risk of developing an alcohol use disorder. However, the mechanisms leading to this increased vulnerability are unknown. To help uncover these mechanisms, we utilize a mouse model of adolescent intermittent alcohol vapor exposure (AIE) and examine its effects on the adolescent brain. One brain region of particular interest is the bed nucleus of the stria terminalis (BNST) because of its role in stress and negative affect induced alcohol relapse. Previous work in the lab has demonstrated that adolescent alcohol enhances glutamate release and plasticity in the BNST. The current work set out to test the hypothesis that adolescent alcohol exposure activates BNST inputs involved in stress/fear-related circuitry and produces long-term changes in contextual-fear conditioning, a behavior that is in part mediated by the BNST. To do this, male C57BL/6J mice were exposed to two four-day cycles of 16hr in ethanol vapor chambers with 8hr of withdrawal, separated by three undisturbed days. A subset of mice were injected with Green Retrobeads into the BNST prior to AIE, which tags neurons in brain regions that project to the BNST. These injected mice were then perfused 4-6hrs after acute withdrawal from AIE. Immunohistochemistry was then performed to identify co-labeling of the immediate early gene cfos and cells labeled with tracer. Specifically, we quantified c-fos and tracer co-labeling in the locus coeruleus, paraventricular nucleus, dorsal raphe nucleus, and central and basolateral amygdala to identify stress sensitive regions that project to the BNST and are activated by AIE withdrawal. A separate cohort of mice were also exposed to AIE and then allowed to voluntarily consume alcohol in an intermittent two bottle choice paradigm (escalating to 20% ethanol for 4 weeks). After a 6-7 day water only withdrawal period, mice were tested in contextual fear conditioning. Mice receive 6 low-intensity (0.4 mA, 1 sec) electric shocks paired with a context. The amount of time spent freezing before and after the shocks, as well as anxiety-like activity in the center of the open field prior to shock, is recorded. Although we have previously found that an AIE history increases post-shock freezing compared to air vapor in adult mice, our mice exposed to AIE in conjunction with voluntary alcohol drinking did not demonstrate increased freezing compared to air vapor-alcohol drinking mice (p > 0.05). However, we did find that alcohol drinking increased anxiety-like behavior regardless of adolescent vapor exposure when compared to mice exposed to vapor without drinking history (p = 0.013). Average alcohol intake over the four weeks was not correlated with fear or anxiety-like activity (p’s > 0.05). Voluntary alcohol consumption attenuated the enhancement in fear conditioning previously seen in AIEexposed mice, but increased anxiety-like activity. These data suggest that altered activation of stress circuitry by adolescent alcohol promotes an altered fear and anxiety-like behavioral state that is sensitive to voluntary alcohol intake.
Recommended Citation
Collins, Taylor K., "The Effects of Adolescent Alcohol Exposure on Stress Circuitry and Behaviors" (2019). Summer Research Internship Program. 6.
https://digitalscholar.lsuhsc.edu/srip/2019/undergrad/6
The Effects of Adolescent Alcohol Exposure on Stress Circuitry and Behaviors
LSU Health Medical Education Building
Individuals who consume alcohol as adolescents are known to have an increased risk of developing an alcohol use disorder. However, the mechanisms leading to this increased vulnerability are unknown. To help uncover these mechanisms, we utilize a mouse model of adolescent intermittent alcohol vapor exposure (AIE) and examine its effects on the adolescent brain. One brain region of particular interest is the bed nucleus of the stria terminalis (BNST) because of its role in stress and negative affect induced alcohol relapse. Previous work in the lab has demonstrated that adolescent alcohol enhances glutamate release and plasticity in the BNST. The current work set out to test the hypothesis that adolescent alcohol exposure activates BNST inputs involved in stress/fear-related circuitry and produces long-term changes in contextual-fear conditioning, a behavior that is in part mediated by the BNST. To do this, male C57BL/6J mice were exposed to two four-day cycles of 16hr in ethanol vapor chambers with 8hr of withdrawal, separated by three undisturbed days. A subset of mice were injected with Green Retrobeads into the BNST prior to AIE, which tags neurons in brain regions that project to the BNST. These injected mice were then perfused 4-6hrs after acute withdrawal from AIE. Immunohistochemistry was then performed to identify co-labeling of the immediate early gene cfos and cells labeled with tracer. Specifically, we quantified c-fos and tracer co-labeling in the locus coeruleus, paraventricular nucleus, dorsal raphe nucleus, and central and basolateral amygdala to identify stress sensitive regions that project to the BNST and are activated by AIE withdrawal. A separate cohort of mice were also exposed to AIE and then allowed to voluntarily consume alcohol in an intermittent two bottle choice paradigm (escalating to 20% ethanol for 4 weeks). After a 6-7 day water only withdrawal period, mice were tested in contextual fear conditioning. Mice receive 6 low-intensity (0.4 mA, 1 sec) electric shocks paired with a context. The amount of time spent freezing before and after the shocks, as well as anxiety-like activity in the center of the open field prior to shock, is recorded. Although we have previously found that an AIE history increases post-shock freezing compared to air vapor in adult mice, our mice exposed to AIE in conjunction with voluntary alcohol drinking did not demonstrate increased freezing compared to air vapor-alcohol drinking mice (p > 0.05). However, we did find that alcohol drinking increased anxiety-like behavior regardless of adolescent vapor exposure when compared to mice exposed to vapor without drinking history (p = 0.013). Average alcohol intake over the four weeks was not correlated with fear or anxiety-like activity (p’s > 0.05). Voluntary alcohol consumption attenuated the enhancement in fear conditioning previously seen in AIEexposed mice, but increased anxiety-like activity. These data suggest that altered activation of stress circuitry by adolescent alcohol promotes an altered fear and anxiety-like behavioral state that is sensitive to voluntary alcohol intake.
Comments
Mentor: Dr. Tiffany Wills, PhD, Department of Cell Biology and Anatomy