A full repetitive jaw movement response after 70% depletion of caudate D1 receptors.

Repetitive jaw movements (RJM in the rat can be produced in a dose-dependent manner with the selective D1 agonist, SKF 38393. Administration of the protein coupling agent, N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) to rats pretreated with a D2 receptor blocker resulted in a 70-30% reduction of D1 dopamine receptors, but only a 10% reduction of D2 receptors in the rat caudate. Twenty-four hours following EEDQ, the RJM response to SKF 38393 was assessed. The massive selective reduction of the D1 receptor density was found not to modify the rate of RJM induced by SKF 38393 in that dose response curves in control and EEDQ-treated rats were essentially identical. These data provide evidence to indicate that there is a functional D1 receptor reserve for D1-mediated RJM behavior.