A quantitative study of cholinergic-dopaminergic interactions in the central nervous system.

The effects of cholinergic (Ach) and anti-Ach drugs on stereotyped behavior induced by apomorphine administration were studied quantitatively. Dose-response curves were constructed to apomorphine and the horizontal shifts of the experimental curves induced by the different treatments were measured at the level of ED50 of apomorphine. Treatment with both atropine sulfate and scopolamine hydrobromide induced a leftward displacement of the dose-response curve; physostigmine and oxotremorine displaced the curve to the right. Changes in stereotypy were not observed after atropine methyl nitrate. It is concluded that the activity of acetylcholine-containing neurons may exert a modulatory influence on dopaminergic systems.