Bisnorcymserine in Healthy Adult Volunteers

Background: \- Alzheimer s disease (AD) is a brain disease that impairs memory, cognitive abilities and the ability to function independently. It is the most common cause of dementia in older people. It is caused by abnormal proteins in the brain that affect how neurons communicate with each other. Researchers are looking for drugs that can slow down the disease or treat its symptoms. One drug, called bisnorcymserine (BNC), may help improve brain function and symptoms in people with AD. BNC is designed to block a chemical that affects how neurons communicate with each other. Researchers want to see how BNC works in healthy older volunteers. Objectives: \- To look at how the body processes bisnorcymserine taken by mouth and how safe it is for healthy older volunteers. Eligibility: \- Healthy volunteers at least 55 years of age. Design: * Participants will be screened with a physical exam, medical history, and blood and urine tests. * Within 3 weeks from the screening visit, participants will come to the National Institute on Aging clinical unit for a 2-night stay. On the morning of the second day, they will take either a BNC capsule or a placebo. They will not know which tablet they are taking. * Blood samples will be collected frequently throughout the second and third days of the study visit. The last blood sample will be collected about 32 hours after taking the study capsule. Participants will have heart function tests and other exams during the visit. Once the tests are done, they will leave the clinical center. * Participants will have a final follow-up visit about 1 week after leaving the clinical center.