Effects of raclopride on exploratory locomotor activity, treadmill locomotion, conditioned avoidance behaviour and catalepsy in rats: behavioural profile comparisons between raclopride, haloperidol and preclamol.

Raclopride, a new potential antipsychotic agent blocking central dopamine (D2) receptors, was found to suppress exploratory locomotor activity, treadmill locomotion and conditioned avoidance response in rats. The threshold dose for effects in these test situations was about 0.5 mg/kg intraperitoneally. A considerably higher dose, 16 mg/kg intraperitoneally, was needed to produce maximal catalepsy. Maximal effects were obtained within 1-2 hrs and the duration of the effect was 2-8 hrs, depending on the test situation. The behavioural profile of raclopride is different from the classic antipsychotic haloperidol, blocking central dopamine (DA) receptors, as well as from the partial DA agonist preclamol, which inhibits central DA neurotransmission by activating DA autoreceptors. Thus, although similar to haloperidol in other respects, comparatively high doses of raclopride are needed to produce catalepsy, indicating less propensity to produce severe extrapyramidal side effects. Raclopride and preclamol are about equipotent in suppressing exploratory locomotor activity. However, raclopride is more potent than preclamol in suppressing treadmill locomotion, conditioned avoidance behaviour and catalepsy.