EVIDENCE FOR THE INVOLVEMENT OF A CATECHOLAMINERGIC PATHWAY IN GONADO- TROPHIN SECRETION FOR IMPLANTATION IN RATS

Summary. A neuroleptic agent, haloperidol, administered orally to rats induced delayed implantation which could be prevented by a single injection of oestrone, HCG or PMSG on Day 4 of pregnancy implying a central action of haloperidol. In view of the known ability of this agent to interfere selectively with dopaminergic transmission, it is inferred that gonadotrophin release for the oestrogen surge preceding implantation in rats is regulated by a catecholaminergic pathway in the hypothalamus. An increased secretion of oestrogens on Day 4 precedes implantation in rats and mice (see Shelesnyak, 1960; Shaikh, 1971; Finn, 1971). In both species, there appears to be an antecedent secretion ofgonadotrophin from the pituitary as hypothalamic lesions (Gale & McCann, 1961), hypophysectomy followed by autotransplantation of the pituitary (see Everett, 1969), and injection of LH antiserum (Raj, Sairam & Moudgal, 1968) or of tranquillizers such as reser¬ pine and chlorpromazine (Psychoyos, 1968, Bindon, 1969) cause delaye