Elsevier

Neuroscience

Volume 199, 29 December 2011, Pages 333-345
Neuroscience

Neurodegeneration, Neuroprotection, and Disease-Oriented Neuroscience
Research Paper
Periadolescent ethanol exposure reduces adult forebrain ChAT+IR neurons: correlation with behavioral pathology

https://doi.org/10.1016/j.neuroscience.2011.10.011Get rights and content

Abstract

Substance abuse typically begins in adolescence; therefore, the impact of alcohol during this critical time in brain development is of particular importance. Epidemiological data indicate that excessive alcohol consumption is prevalent among adolescents and may have lasting neurobehavioral consequences. Loss of cholinergic input to the forebrain has been demonstrated following fetal alcohol exposure and in adults with Wernicke–Korsakoff syndrome. In the present study, immunohistochemistry for choline acetyltransferase (ChAT) was determined to assess forebrain cholinergic neurons (Ch1-4), and behavioral changes following periadolescent alcohol exposure. Wistar rats were exposed to intermittent ethanol vapor (14 h on/10 h off/day) for 35 days from postnatal day (PD) 22 to PD 57 (average blood alcohol concentration (BAC): 163 mg%). Rats were withdrawn from vapor and assessed for locomotor activity, startle response, conflict behavior in the open field, and immobility in the forced swim test, as adults. Rats were then sacrificed at day 71/72 and perfused for histochemical analyses. Ethanol vapor–exposed rats displayed: increased locomotor activity 8 h after the termination of vapor delivery for that 24 h period at day 10 and day 20 of alcohol vapor exposure, significant reductions in the amplitude of their responses to prepulse stimuli during the startle paradigm at 24 h withdrawal, and at 2 weeks following withdrawal, less anxiety-like and/or more “disinhibitory” behavior in the open field conflict, and more immobility in the forced swim test. Quantitative analyses of ChAT immunoreactivity revealed a significant reduction in cell counts in the Ch1-2 and Ch3-4 regions of the basal forebrain in ethanol vapor–exposed rats. This reduction in cell counts was significantly correlated with less anxiety-like and/or more “disinhibitory” behavior in the open field conflict test. These studies demonstrate that behavioral measures of arousal, affective state, disinhibitory behavior, and ChAT+IR, are all significantly impacted by periadolescent ethanol exposure and withdrawal in Wistar rats.

Highlights

▶Adolescence ethanol exposure produces disinhibitory behavior at 2 weeks withdrawal. ▶Adolescence ethanol exposure produces depressive-like behavior at 2 weeks withdrawal. ▶Adolescent ethanol exposure reduced cholinergic neurons in basal forebrain. ▶Reduced cholinergic neurons were correlated with more disinhibitory behavior.

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Section snippets

Subjects

Male Wistar rats who were received at postnatal day (PD) 23 (n=42; 36 juveniles, six dams, Charles River, USA) were used in this study. The adolescent animals (PD 23) were housed three per cage respectively in standard cages for the duration of the experiment. Animals were kept in a light/dark (12 h light/12 h dark, lights on at 6:00 am) and temperature-controlled environment. Food and water were available ad libitum throughout the experiment, except where noted. All experimental protocols were

Body weight and BACs

As seen in Fig. 1, all rats gained weight over the course of the experiment. Rats grew in both groups from about 50 g at PD 22 to about 360 g being 373.6 (±9.4) and 352.1 (±6.8) for control and ethanol at PD 72 respectively. Ethanol vapor–exposed rats showed parallel increases in weight gain to controls, although ethanol vapor rats had slightly reduced body weights at 3 of the 27 weightings, for example, at ages PD 48, PD 52, and PD 55 (P<0.05) as seen in Fig. 1. Both groups had similar body

Discussion

In the present study, rats were exposed to ethanol vapors during the periadolescent period in order to examine ethanol's effects on cholinergic neurons in the basal forebrain and correlated behavioral changes. Ethanol vapor–exposed rats displayed increased locomotor activity 8 h after the termination of vapor delivery for that 24 h period at day 10 and day 20 of alcohol vapor exposure, significant reductions in the amplitude of their responses to prepulse stimuli during the startle paradigm at

Conclusions

Our data suggest that rats exposed to daily ethanol vapor for 5 weeks over the adolescent period display increased locomotor activity 8 h after the termination of vapor delivery for that 24 h period at day 10 and day 20 of alcohol vapor exposure, significant reductions in the amplitude of their responses to prepulse stimuli during the startle paradigm at 24 h withdrawal, and at 2 weeks following withdrawal, less anxiety-like and/or more “disinhibitory” behavior in the open field conflict, and

Acknowledgments

This study was supported in part by the NADIA Initiative Project of the NIH National Institute on Alcoholism and Alcohol Abuse grants AA019969 (C.L.E.) and AA020022, AA020023 and AA020024 (F.T.C.) and the UNC Bowles Center for Alcohol Studies. The authors thank Greta Berg for her assistance in data collection and Shirley Sanchez for editing the manuscript.

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