| Abstract: | Tested a total of 85 male hooded rats in 3 experiments. In 30-min free-operant tests, the dopamine receptor blockers pimozide (.125, .25, and .50 mg/kg) and (+)-butaclamol (.1, .2, and .4 mg/kg) attenuated leverpressing for lateral hypothalamic brain stimulation. When discrete self-stimulation trials were offered in a straight alleyway, pimozide increased start box latencies, slowed running speeds, and reduced leverpressing rates. However, performance early in both lever-pressing and runway sessions was normal; performance deteriorated as testing progressed, following patterns that paralleled those seen when Ss were tested with reductions in the amplitude of stimulating current. Spontaneous recovery was obtained in both situations; experimenter-imposed 10-min timeouts caused renewed leverpressing and running. In contrast, alpha-noradrenergic receptor blockade by phenoxybenzamine (5, 10, and 20 mg/kg) failed to produce extinction-like response patterns. Data support the view that central dopaminergic systems are important components of the neural mechanisms mediating reward. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
