[en] Antipsychotic therapy is frequently associated with several side effects such as hyperprolactinemia. The influence of a putative antipsychotic JL 13 on prolactin release was assessed after intraperitoneal injection in gentled male rats in comparison with clozapine and haloperidol. A total of 30 or 150 min after administration, whole blood was collected for preparing serum samples. Prolactin was quantified by radioimmunoassay method. At 30 min, JL 13 like clozapine, increased prolactin concentration only at the higher dose (30 mg/kg) while haloperidol at both tested doses induced a dramatic increase of prolactin concentration. At 150 min after injection, only haloperidol (0.3 mg/kg) significantly increased serum prolactin level. This minimal effect on prolactinemia reinforces the similarity of clozapine and JL 13 regarding the atypical antipsychotic profile. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.