The use of conditioned defensive burying to test the effects of pimozide on associative learning.

Rats shocked by a wire-wrapped prod mounted on the wall of the experimental chamber buried the prod with available bedding material when they were tested 24 hr later. Injection of the neuroleptic, pimozide (1.0 mg/kg) before conditioning and again before testing disrupted this conditioned defensive burying; however, a concomitant reduction in general activity suggested that this deficit in conditioned burying may have reflected a general motor impairment instead of a learning deficit. The observation that rats conditioned under the influence of pimozide but tested 24 hr later while undrugged did not display deficits in conditioned burying confirmed this view. Thus, neuroleptics appear to disrupt learned behavior by interfering with the performance of conditioned responses rather than by disrupting associative learning per se.