This is a request for a Research Career Development Award Level II. The long-term objectives of this research are to study the effect of chronic ethanol exposure and withdrawal from this exposure on neuronal plasticity. Because neuronal plasticity allows for adaptation to any stimuli and conditions the nervous system is exposed to, it represents one of the most important properties of the nervous system. Animal experiments suggest that chronic ethanol consumption affects neuronal plasticity which could reduce the capacity of the brain to adjust adequately to afferent stimuli. Such deficiencies could be in turn responsible for pathological brain changes observed in chronic alcoholics. Our previous work suggests that the neuronal cytoskeleton, because of its versatility, is well suited to being involved in the mechanism of neuronal plasticity. In addition, the neuronal cytoskeleton is also likely to be involved in ethanol-induced morphological changes in neurons. Therefore, this proposal is designed to study the mechanism underlying morphological changes after chronic ethanol exposure and withdrawal from this exposure . Ethanol-induced morphological changes were shown prevailingly in dendrites, dendritic spines, and synaptic contacts. Since microtubules are responsible for maintaining dendritic and axonal arborization and actin filaments for maintaining dendritic spines and synaptic contacts, it is possible that alcohol-induced alteration of these cytoskeletal components constitutes the mechanism of morphological changes observed following chronic ethanol exposure and withdrawal. To establish the nature of these changes, we shill determine possible modifications in the composition of microtubules and actin filaments. I. With quantitative immunoblotting, relative levels of actin and tubulin polymerization will be established in whole brain preparations together with posttranslational modifications of alpha-tubulin. II. With immunoelectron microscopy, the microtubule associated proteins (MAP 2 and MAP tau) and posttranslational modifications of tubulin will be studied in dendrites and axons together with the organization of actin filaments. III[. With conventional electron microscopy, the density of microtubules in dendrites and axons and the microtubule spacing in dendrites will be determined with conventional electron microscopy in selected brain regions. Alcohol-sensitive (LS-IBG ) mice will be used in these experiments. Although the proposed experiments deal with basic question of the chronic effect of ethanol on the molecular composition of the neuronal cytoskeleton, the results could be of practical importance, leading ultimately to improvements in therapeutic interventions.