Abstract: Amyloid precursor protein (APP) processing which is activated by cell-surface neurotransmitter receptors, is described. An assay for testing an agent for the capacity to regulate, and particularly to stimulate, secretion of amyloid precursor protein (APP), a description of the characteristics of agents identified by the assay, and a method of altering APP processing in an individual are also disclosed. The assay, agents, and method of altering APP processing are particularly useful for the treatment and prevention of diseases involving APP processing, such as Alzheimer's disease.