Comparative study of the effects of lisuride and pimozide on the preovulatory surge of FSH, LH and prolactin in rat.
In experiments conducted on adult female Wistar rats, lisuride hydrogen maleate, injected before the critical period of proestrus (between 11 h-13 h) in a single s.c. dose of 0.125 mg/kg body, significantly elevated the preovulatory gonadotropin surge and slightly, non-significantly lowered that of prolactin (assessed between 15-16 h). Pimozide, a selective antidopaminergic neuroleptic, injected according to the same schedule in a dose of 2.5 mg/kg body, strongly augmented the LH surge and also prolactin secretion. Thus, stimulation of gonadotropin secretion by lisuride cannot be ascribed to its dopaminergic agonistic action, but may be attributed to its antiserotoninic activity or to the action on the presynaptic dopamine receptors of the tuberoinfundibular neurons, reducing their inhibitory influence on the gonadotropin surge. The results plead for the inhibitory role of DA in the LH and prolactin secretion; 5-HT may have a similar action in the preovulatory gonadotropin surge and a stimulatory one in the surge of prolactin.