The discriminant dopamine antagonist property of benzamides is observed at various times after their systemic or intracerebroventricular administration.

The cataleptogenic effect or the antagonism of apormorphine-induced behaviour (climbing, sniffing, licking and yawning) shown by haloperidol, (+/-)sulpiride and (+/-)amisulpride were determined at different times after their intraperitoneal or intraventricular administration. After intraperitoneal injection, the ED50 or ID50 of haloperidol was similar for all the behavioural responses. On the other hand, sulpiride and amisulpride were effective on climbing and yawning in smaller doses than on sniffing, licking and catalepsy. The property of amisulpride to antagonize climbing at smaller doses than sniffing was still found whether this benzamide derivative was injected 30, 90, 150 or 240 min before testing. After the intraventricular administration of neuroleptics, a dissociated antagonist efficacy appeared for haloperidol, but that of sulpiride and amisulpride became much more marked than after their intraperitoneal injection. Amisulpride antagonized climbing in smaller doses than sniffing, whether administered intraventricularly 15, 30 or 120 min before testing. These results indicate that the dissociated dopamine antagonist efficacy of benzamides is long lasting and is observed even when the passage across the blood-brain barrier is avoided (i.c.v. route).