STUDIES ON THE USE OF DOPAMINE ANTAGONIST,PIMOZIDE, TO POTENTIATE THE EFFECTS OF LRH-A ON OVULATION IN PARAMISGURNUS DABRYANUS

A single injection of low dose LRH-A alone was relatively ineffective for inducing ovulation in Paramisgurnus dabryanus, however, the injection of low dose LRH-A in association with pimozide (PIM), a dopamine antagonist, significantly potentiated the effects of LRH-A on ovulation, the rate of ovulation being 100%. The histological and ultrastructural studies of pituitary showed that the injection of low dose LRH-A together with PIM greatly potentiated the LRH-A stimulated synthesis and release of GtH, whereas the injection of dopamine (DA) blocked the stimulation of GtH release induced by injection of LRH-A. These results demonstrated that dopamine, having GtH release iuhibitory activity in Paramisgurnus dabryanus, acts directly at the pituitary level, so, the combination of treatment with PIM and LRH-A is a highly effective means of inducing ovulation in this fish.