Raclopride, but not SCH 23,390, induces maldirected jumping in rats trained to perform a run-climb-run behavioral task.

In order to explore further the putative differential behavioral consequences of D1 dopamine and D2 dopamine receptor antagonism, SCH 23,390 (0.01-0.12 mg/kg) and raclopride (0.12-1.0 mg/kg) were administered to two separate groups of rats that had been trained in an eight-trial-per-day format to run down an alleyway, climb a vertical rope, and run across a horizontal board to access sweetened milk. Although both drugs dose-dependently reduced the speed of task completion, only raclopride produced vigorous, maldirected jumping behavior in the floor segment of the apparatus. The number of such jumps increased with dose. This raclopride-specific jumping phenomenon may provide a new behavioral arena for investigating the functional differences between D1 and D2 receptor antagonism.