Our goal is to understand the effects of nigrostriatal damage and nicotine treatment on nicotinic receptor (nAChR) subtypes in the basal ganglia, and determine the relationship of any changes to neuroprotection. The rationale for such work is based, in part, on epidemiological studies showing that there is a decreased incidence of Parkinson's disease (PD) in smokers. This apparent neuroprotection may be due to nicotine in tobacco since nicotine protects against nigrostriatal damage in various experimental models. Nicotine exerts its effects by stimulating nAChRs. We hypothesize that nicotine-mediated protection against nigrostriatal damage occurs as a consequence of changes in nAChR subtypes. Our preliminary data show that there are differential changes in nAChRs subtypes and their function after MPTP treatment. In this proposal, we will test the effects of nicotine to modulate nAChRs, study its neuroprotective effects against nigrostriatal degeneration and investigate its mechanism(s) of action. This will be approached through the following Specific Aims. (1) We will test the hypothesis that nicotine administration influences nAChR expression and function in MPTP-treated mice. Although nicotine exposure is well-known to upregulate nAChRs in control animals, studies to determine its effects after nigrostriatal damage remain to be done. Next (2) we will test the hypothesis that nicotine-induced changes in nAChRs correlate with neuroprotection against nigrostriatal damage by measuring various markers of striatal dopaminergic function. These data will be correlated to changes in nAChRs to determine whether receptor alterations are linked to neuroprotection. (3) To determine whether specific nicotinic receptor subtypes are involved we will we will study whether nicotine protects against nigrostriatal damage in nAChR knockout mice. (4) Finally, experiments will be done to study the molecular mechanisms that mediate nicotine-induced neuroprotection. We will investigate the hypothesis that trophic factors such as basic fibroblast growth factor (bFGF) and brain derived neurotrophic factor (BDNF), as well as immune mediators such as interleukin-6, are involved. These studies will enhance our knowledge of the changes in nAChR expression and function with chronic nigrostriatal damage and nicotine treatment. This may allow for the design of neuroprotective strategies for PD, a disorder for which only symptomatic treatment is currently available.
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