Effects of SKF 38393 and quinpirole on aggressive, motor and schedule-controlled behaviors in mice.

The respective roles of D1 and D2 dopamine receptors in mediating motor functions, aggressive behaviors and reinforcement processes have not been specified. The present experiments examined conditioned and unconditioned behaviors of mice under different demands and reinforcing contingencies. We compared the behavioral effects of the D2 agonist quinpirole and the D1 partial agonist SKF 38393 on motor activities, aggressive behaviors and schedule-controlled responses in male mice that were either pair-housed with a female for 4 weeks or singly-housed. Singly-housed mice were found to be more active than pair-housed mice both when alone in the home cage and in the presence of a male intruder. However, the effects of both quinpirole and SKF 38393 were substantially similar for both singly- and pair-housed mice. Quinpirole decreased motor activity, aggressive behavior, and schedule-controlled responding. In contrast, SKF 38393 decreased schedule-controlled responding at doses that did not affect either motor or aggressive behaviors. The relative behavioral specificity of SKF 38393 suggests that D1 activation alters the temporal patterning of behavior, while D2 activation appears to cause a more general suppression of behavior in mice.