Dopamine D1 and D2 antagonist effects on response likelihood and duration.

Experimentally induced and parkinsonian disruptions in dopamine (DA) transmission are associated with motor abnormalities that include a reduced likelihood of behavioral response initiation and an increased duration of executed responses. Here we investigated the dopamine receptor subtypes involved in regulating these two aspects of behavior. We examined the effects of D1 family (D1/D5) antagonist R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride (SCH23390; 0, 0.

A "good parent" function of dopamine: transient modulation of learning and performance during early stages of training.

While extracellular dopamine (DA) concentrations are increased by a wide category of salient stimuli, there is evidence to suggest that DA responses to primary and conditioned rewards may be distinct from those elicited by other types of salient events. A reward-specific mode of neuronal responding would be necessary if DA acts to strengthen behavioral response tendencies under particular environmental conditions or to set current environmental inputs as goals that direct approach responses. As described in this review, DA critically mediates both the acquisition and expression of learned behaviors during early stages of training, however, during later stages, at least some forms of learned behavior become independent of (or less dependent upon) DA transmission for their expression.