The effect of the enantiomers of 3-PPP on conditioned avoidance responding in the rat.

The effects of the enantiomers of 3-PPP on the maintenance of conditioned avoidance responding (CAR) were studied. The weak classical dopamine (DA) agonist (+)-3-PPP failed to interfere with CAR at any dose tested (0.8-13.6 mg/kg). Low doses of the drug produced sedation, while high doses produced behavioural stimulation. (-)-3-PPP, which acts as an antagonist on postsynaptic and as an agonist on autoreceptor DA sites, reduced avoidance with no effect on escape behaviour (6.8-13.6 mg/kg). However, this reduction of CAR occurred at doses much higher than those previously demonstrated to inhibit locomotor activity. This profile is discussed in relation to the behavioural effects of classical postsynaptic DA receptor antagonists.