Abstract. Cholinergic dysfunction is one of the cornerstones of Alzheimer’s disease (AD) pathology. Reviewed here is evidence
evaluating relationships between smoking, nicotine exposure, nicotinic cholinergic signaling, and AD. Epidemiological studies
initially indicating a lower incidence of AD in smokers now suggest conflicting results. Clinicopathological findings also are
mixed as to how smoking behavior affects manifestation of AD markers. Studies that show nicotine-induced increases in nicotinic
acetylcholine receptors (nAChR) and protection against age-related nAChR decline contrast, perhaps in a functionally relevant
way, to losses of nAChR in AD. Although epidemiological, clinicopathological, and functional studies in humans do not present
a cohesive picture, much in vitro data suggests neuroprotective properties of nicotine when used in models of neurodegenerative
disorders. Studies of nicotine and nicotinic agonist effects on cognitive function in the non-demented and in AD are not
compelling. More work is needed to ascertain whether acute or repetitive activation of nAChR with acute or intermittent exposure
to nicotine or the persistent inactivation of nAChR with chronic nicotine exposure is a therapeutic objective and/or explains any
pro-cognitive effects of those drugs. Other studies show complex interactions between nAChR, nicotinic agonists, and agents
implicated in AD etiology. Thus, while controversies still exist, ongoing research is illuminating how nicotinic receptor changes
and functions may be relevant to clinical, pathological and neurochemical changes that occur in AD.