NICOTINIC CHOLINERGIC SYSTEMS IN MUTANT MICE

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Tobacco use is a major health problem in the United States, where over 400,00 deaths and $50 billion in medical costs yearly are directly attributed to smoking (Epping-Jordan et al., 1998). Teenagers smoke 1.1 billion packs of cigarettes annually and will account for more than $200 billion in future health care costs (Woolf, 1997). Nicotine is the major component of tobacco that leads to addiction, but the underlying mechanisms remain unclear. This Program Project application takes a multi-level approach to understand nicotinic cholinergic systems and nicotine's effect on synaptic events, cardiovascular function, and behavior. Overall the Program will investigate the hypothesis that different nicotinic acetylcholine receptor (nAChR) subunits have special importance in the individual properties that contribute to nicotinic cholinergic functions in the nervous system. Three Projects have arisen from the production of mutant mice for nAChR subunits. The Mouse Core, headed by Dr. Beaudet, has already produced null mice lacking alpha3, alpha5, alpha7, beta3, or beta 4, and a mouse expressing in alpha7 L247T mutation that diminishes desensitization. The Morphology Core, headed by Dr. Armstrong, will do a systematic anatomical and histological screen of each mutant mouse, and will pursue further morphological investigations as warranted. The three Projects could not exist without the mutant mice, which are the fundamental tool used in each investigation. The Dani Project will directly study the altered nAChRs and the synaptic basis for nicotine's actions. The work is intended to provide basic biophysical and synaptic information that will be helpful when interpreting the results from all of the Projects. The De Biasi Project will use radio-telemetry to examine the effects of nicotine on the autonomic nervous system and cardiovascular functions. Among the specific goals is to understand how tolerance to nicotine develops more rapidly for increases in blood pressure than for increases in heart rate. The Paylor Project will use a battery of behavioral tests to examine the mutant mice with the aim of understanding how nAChR subunits regulate the sensitivity to nicotine and the development of tolerance.