Date of Award

12-2011

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Arts (MA)

Department

Psychology

Advisor

Alan M. Rosenwasser

Second Committee Member

Leslie L. Devaud

Third Committee Member

Thane E. Fremouw

Abstract

Chronic ethanol consumption is known to cause physiological tolerance and dependence in both alcoholics and experimental animals. In the absence of alcohol, an alcoholic will experience multiple withdrawal symptoms, believed to arise from a general hyper-excitation of the central nervous system, anxiety, tremors and sleep and neuroendocrine disruption. Several investigations have found differences in expression and recovery from ethanol withdrawal (EW) in people and across various animal models. There is increasing evidence that some of these differences are sexually dimorphic in nature. The overall goal of this project was to indentify sex differences in male and female rats in response to ethanol withdrawal. We used multiple behavioral and molecular methods to achieve this end. In the first set of experiments, male and female rats were made ethanol-dependent through a 14 day administration of 6% ethanol diet. We used a repeated measures design to assess loss of righting reflex (LORR] in control, 1day [1d] and 3day (3d) EW males, females and ovariectomized (OVX) rats following a bolus injection of ethanol to induce hypnosis. Time to loss and regain was recorded for each animal and tail blood analyzed upon the animal's loss of righting and upon regain. Next, in a different set of animals using the same diet and EW paradigm, we used immunohistochemistry (IHC) techniques to assess the effects of ethanol withdrawal on levels of Arc (activity-regulated cytoskeletal protein) in select brain regions. Arc has been implicated in regulation of glutamatergic transmission and in glutamate-induced neural plasticity. For the next study, we obtained organotypic hippocampal slice cultures from 8 day old male and female rats. We exposed these cultures to ethanol on a chronic intermittent cycle (CIE). Various concentrations of PTZ (pentylenetetrazol) or CORT (corticosterone) were added to the cultures for the last 24 hours. We used Propidium iodide (PI), to visualize cell damage and Hoechst 33342 (Ho), to visualize cell viability. Overall, the results of these experiments indicated that sex differences play a significant role in ethanol withdrawal. At the behavioral level, tolerance to the hypnotic effects of ethanol was lost more rapidly in EW females than males. However, at the molecular level, EW females and males expressed similiar neuroadaptations in Arc expression. Finally, we noted a number of sex- and brain region-selective differences in the sensitivity of hippocampal slice cultures to the neurotoxic effects of CIE and/or CORT and PTZ. These findings add to the growing evidence of important neurobiological sex differences in response to chronic ethanol exposure and withdrawal.

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