INHIBITION OF OVULATION IN THE GONADOTROPHIN-TREATED IMMATURE RAT BY CHLORPROMAZINE

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Abstract
SUMMARY: The effect of age and dose of a single injection of pregnant mare serum gonadotrophin (PMS) on spontaneous ovulation in immature Wistar rats is described. Ovulation could be induced by human chorionic gonadotrophin (HCG) at least 6 days before it occurred when pregnant mare serum gonadotrophin alone was given. Chlorpromazine was shown to block pregnant mare serum gonadotrophin-induced ovulation at a dose level (0·25 mg. in a 60 g. rat) which has no effect on the ovulatory response to human chorionic gonadotrophin. Higher doses interfered with the action of injected human chorionic gonadotrophin. Ovulation could be induced in the chlorpromazine-blocked animals by the systemic injection of an extract of bovine median eminence, but the sensitivity was too low to use this response for an assay method.