Effects of (-)3-PPP on acquisition and retention of a conditioned avoidance response in the rat.

The administration of (-)3-(3-hydroxyphenyl)-N-n-propylpiperidine (3-PPP) was found to partially, but significantly, suppress the acquisition (4-8 mg/kg IP) and performance (8-16 mg/kg IP) of a conditioned avoidance response (CAR) in male Sprague-Dawley rats. All statistically significant effects were observed within 2 h of injection. Furthermore, using a situation in which the CAR was dependent on a visual successive discrimination, it was shown that discriminative performance was unaffected, and that (-)3-PPP (12.5-25 mg/kg IP) but not (+)3-PPP, suppressed the CAR. When (-)3-PPP (6.25 mg/kg IP) was combined with haloperidol (0.1-0.4 mg/kg IP), additive effects on the CAR performance were observed. Considering these effects, and the doses of (-)3-PPP required to suppress the CAR performance, it is concluded that the effects obtained in the present experiments are primarily due to a blockade of postsynaptic DA receptors.