Differential behavioral effects of sulpiride in the rat and squirrel monkey

Despite its clinical efficacy as an antipsychotic agent, sulpiride differs from other neuroleptics in that it has been reported to exert erratic effects in several animal models. The effects of sulpiride were investigated on Sidman avoidance responding by the rat and squirrel monkey. At 100 mg/kg i. p. or orally, sulpiride failed to impair rat Sidman avoidance responding appreciably while exerting marginally toxic effects, but at 30 mg/kg orally, this drug strongly impaired Sidman avoidance responding by the squirrel monkey. This effect, which manifested delayed onset, was reversed by benztropine, indicating that dopamine receptor blockade was most likely responsible for the impairment of responding. The gross behavioral effects of sulpiride in the squirrel monkey resembled those of haloperidol, and dyskinetic postures induced by haloperidol could be mimicked by sulpiride in some instances. It is concluded that the behavioral effects of sulpiride in the rat may not be representative of its action in primates or in the clinic.