- Central nicotinic acetylcholine receptors (nAChRs) are the primary target for the action of nicotine. In addition to being involved in tobacco dependence, they are also involved in a variety of brain disorders, including Alzheimer's and Parkinson's diseases. Researchers are interested in developing better ways to study the action of nAChRs to improve treatments for smoking cessation and other problems affected by these receptors. These new study methods may involve different radiotracers, which are drugs that can help show brain activity during positron emission tomography (PET) scanning.