DOPAMINE D-1 OR D-2 ANTAGONISTS ENHANCE INHIBITION OF CONSUMMATORY INGESTIVE BEHAVIOR BY CCK-8

A dopamine D-1 (SKF-38393, 1 mg)- or D-2 (LY-171555, 0.1 mg)-receptor agonist inhibited intake of an intraorally infused solution of sucrose by male rats, a test of consummatory ingestive behavior. Treatment with a D-1 (SCH-39166, 0.1 mg) or D-2 (raclopride, 0.6 mg) antagonist reversed inhibition by the respective agonist but enhanced the inhibitory effect of cholecystokinin octapeptide (CCK-8; 1.8 mu g). It was not possible to demonstrate specific effects of D-1 and D-2 agonists on intake of pellets, a test that does not discriminate consummatory ingestive behavior from appetitive ingestive behavior, i.e., behavior used to obtain food. The results demonstrate specific involvement of dopamine D-1 and D-2 receptors inhibition of consummatory ingestive behavior.