Prolactin-releasing effect of zetidoline, a new neuroleptic agent, in the rat

The effect of a new neuroleptic agent, zetidoline, 1-(3-chlorophenyl)-3-[2-(3,3-dimethyl-l-azetidinyl)ethyl]imidaz olidin-2-one (ZET), on prolactin release was studied in both male and female rats and compared to that of the classic antipsychotic drugs chlorpromazine and haloperidol. Time-course and dose-effect studies showed that ZET induces a rapid and short lasting increase in plasma prolactin levels, with a significant increase after a dose as low as 0.33 mg/kg, i.p.. The overall patterns of prolactin release appeared to be similar in both sexes but the response was markedly greater in females than in males. The prolactin-releasing effect of ZET was counteracted by apomorphine and L-dopa, which indicates that blockade of dopamine receptors is the basis of its neuroendocrine action. As a prolactin-releaser, ZET was found to be about 5 times as potent as chlorpromazine and about one-ninth as potent as haloperidol.