This protein involves an examination of adaptation at the synaptic level. Attention is currently being focused on the synapse between dopamine-containing nigrostriatal neurons and acetylcholine-containing interneurons in the rat striatum. Neural activity at this synapse is being altered in vivo by acute and chronic changes in the internal and external environments and by drug treatment, and in vitro by depolarization. Measurements include tyrosine hydroxylase activity, dopamine synthesis, adenylate cyclase and high affinity choline uptake. The object of the study is to examine the short- and long-term adaptive response of the synapse to changes in synaptic input and then to determine the functional significance of those adapations.