Differential effects of quinpirole in the nucleus accumbens depending on the initial level of locomotor activity.

Effects of dopamine D1 and D2 receptor agonists (SKF 38393 and quinpirole, respectively) on locomotion were studied in two behavioural situations characterized by low and high level of exploratory locomotor activity. Administration of quinpirole bilaterally into the nucleus accumbens increased locomotor activity at the low initial level of activity and decreased locomotor activity at the high activity level, while the administration of SKF 38393 increased locomotor activity in both behavioural situations. It was concluded that quinpirole has differential effects on locomotion, depending on the initial level of activity.