Leslie L. Devaud - US grants

The objective of this proposal for a Scientist Development Award is for the candidate to retrain in the field of alcohol research utilizing molecular genetic approaches to investigate the potential role of gender and endogenous steroid modulation of GABAA receptors in the development and manifestation of ethanol dependence. Increasing evidence suggests that alterations in GABAergic neurotransmission underlie some of the pathophysiological effects of ethanol. The purpose of the present proposal is to examine the influence of gender on regulation of GABAA receptor gene expression in ethanol-dependent rats. Gonadal hormones have been shown to produce an altered profile of GABAergic regulation in female rats compared to their male counterparts. Gender differences in seizure susceptibility, anxiety and sedation have been observed. The first goal will be to ascertain whether gender influences ethanol-induced alterations in seizure susceptibility. Prior investigations have shown that female rats have decreased seizure sensitivity compared to male rats, as well as variations in seizure sensitivity across estrous (rat) and the menstrual cycle (human). The proposed studies will determine whether female gender effects the proconvulsant activity of chronic ethanol consumption. The second goal of this proposal will be to determine if ethanol-dependence produces different effects on GABAA receptor subunit mRNA levels in female as compared to male rats. Our lab has shown that ethanol selectively alters several GABAA receptor alpha subunit mRNA levels in the male rat cortex and cerebellum. The proposed studies will show whether the effects of ethanol on GABAA receptor subunit expression are gender-specific. The final goal will be to determine whether the endogenous neurosteroid, 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha-THP) influences alterations seen in GABAA receptor subunit composition following chronic ethanol exposure. A major metabolite of progesterone, 3alpha-THP binds stereoselectively and with high affinity to GABAA receptors and is the most potent endogenous GABAergic ligand known. Taken together, these experiments will test the hypothesis that gender influences ethanol- induced alterations in GABAA receptor gene expression related to the acquisition and maintenance of ethanol dependence. Investigation of the role of endogenous neuroactive steroids in imparting these effects may afford insight into mechanisms which underlie or protect against the pathophysiological effects of ethanol. These findings should have important implications for the treatment of alcoholism in males as well as females.

The goal of this proposal is to characterize the molecular basis for gender differences underlying ethanol dependence. The objective is to test the hypothesis that gender influences neuroadaptations of GABA and glutamatergic systems elicited by chronic ethanol exposure. GABAA and NMDA receptors are key sites in the brain mediating the effects of ethanol. Ethanol dependence results in subunit selective alterations in gene expression and function for both GABAA and NMDA receptors. We have recently found profound gender differences in the effects of chronic ethanol consumption on GABAA receptor alpha and NMDA NR1 subunit expression. This shows that gender impacts the effects of ethanol dependence on gene expression for these two key neurotransmitter systems. This suggests that neuroadaptations associated with ethanol dependence and withdrawal may be dependent on the hormonal context of the ethanol exposure. However, there is little evidence showing a direct association between ethanol dependence and withdrawal behaviors and the molecular changes observed for GABAA and NMDA receptors. The proposed studies will investigate the molecular basis for gender differences in the effects of ethanol dependence and withdrawal by correlating the development of and recovery from ethanol dependence with changes in gene expression and receptor regulation. This proposal will test the hypothesis that ethanol dependence induces gender-selective alterations in 1) GABAA receptor regulation, function and gene expression, 2) NMDA receptor regulation, function and gene expression, and 3) levels of several key neuroactive steroids. We will determine whether these alterations show a temporal correlation with behavioral manifestations of ethanol dependence and withdrawal. These studies are particularly important as the expression of neuroadaptations to chronic ethanol consumption varies according to gender, even though both genders display similar behavioral signs of dependence and withdrawal. It is critical to ascertain whether the timing of functional or molecular changes in GABAA or NMDA receptors are associated with physiological manifestations of dependence and withdrawal, including the influence of differing endogenous regulation. These investigations are important for understanding the neurobiological basis of ethanol dependence and withdrawal in both males and females.

DESCRIPTION (provided by applicant): This proposal is the second submission of a competing renewal to continue our investigations into the neurobiological basis for sex differences in ethanol dependence and withdrawal. To date, we have identified important differences between male and female rats in adaptations of GABA-A and NMDA receptors during ethanol dependence and early withdrawal across several brain sites. We recently found significant and robust behavioral sex differences in the timing for recovery from ethanol withdrawal. Whereas both males and females showed significant withdrawal signs at 24 hr, females, but not males, appeared to have recovered by 3 days. Therefore, the overall goal of this project is to elucidate the mechanistic underpinnings for behavioral expressions of ethanol withdrawal at 24 hr and 3 days. We hypothesize that differences in recovery from ethanol withdrawal involve sex-selective changes in GABAergic and glutamatergic neurotransmission that occur as a result of the differing hormonal milieu between males and females. To test this hypothesis we will compare and contrast findings in young adult male, cycling diestrus female and ovariectomized female rats. The proposed studies will allow us to delineate the importance of hormonal modulation in conferring sex differences in recovery from ethanol withdrawal. This project will test the hypothesis by these aims: 1. assessment of several ethanol withdrawal behaviors, including responses to drug treatments, at early (24 hr) and later (3 days) withdrawal, 2. identification of concomitant sex differences in brain activation with analysis of modulation of GABA-A and NMDA receptors at these same times of withdrawal, and 3. analysis of ethanol withdrawal-induced changes in GABA, glutamate and steroid levels. We expect to find that the differing hormonal milieu between males and cycling females regulates adaptations of GABAergic and glutamatergic neurotransmission that confers recovery from ethanol withdrawal. Findings resulting from these proposed studies should show that inherent, neurobiological regulation due to hormonal status is an important factor influencing actions of ethanol, with adaptations being different for recovery than development of dependence. Increasing our understanding of sex-selective mechanism underlying withdrawal should help guide us towards improving treatments for alcohol withdrawal in both women and men.