The present invention provides methods for reducing .beta.-amyloid deposition, .beta.-amyloid neurotoxicity and microgliosis in animals or humans afflicted with a cerebral amyloidogenic disease, such as Alzheimer's disease (AD), by administering therapeutically effective amounts of the dihydropyridine calcium channel antagonist, nilvadipine. The present invention also provides methods for diagnosing cerebral amyloidogenic diseases in animals or humans. Further provided are methods for reducing the risk of .beta.-amyloid deposition, .beta.-amyloid neurotoxicity and microgliosis in animals or humans suffering from traumatic brain injury by administering nilvadipine immediately after the traumatic brain injury and continuing treatment for a prescribed period of time thereafter. Finally, methods are provided for treating transplantable neuronal stem cells by administering nilvadipine to the neuronal stem cells prior to transplantation in the central nervous system of an animal or human afflicted with a cerebral amyloidogenic disease, such as AD.