DATA ON SITES OF STIMULATORY FEEDBACK ACTION OF GONADAL STEROIDS INDISPENSABLE FOR LUTEINIZING-HORMONE RELEASE IN RAT

The sites of the stimulatory feedback action of gonadal steroids on LH release were investigated in estrogen-primed ovariectomized rats. Either estradiol benzoate (E2) or estrone (E1) injections 72 h after E2 priming induced a significant increase in serum LH 30 h later, whereas injections of progesterone (P) did so 6 h later. Horizontal sections placed above the medial preoptic area prevented the increase after E2 injections but not after E1 and P injections. Retrochiasmatic sections or bilateral lesions placed in the medialbasal part of the suprachiasmatic area prevented any increases in serum LH induced by steroid injections. Intracerebral implantations of E2 and P in E2-primed ovariectomized rats induced a similar significant increase in serum LH when E2 was implanted into the bed nucleus of stria terminalis (BST), the lateral septum (1- SEPT) and the preoptic suprachiasmatic area (POSC), and when P was implanted in to the medial amygdala, the diagonal band of Broca (DBB), the POSC, the 1- SEPT and the anterior hypothalamic area (AHA). These results suggest that the stimulatory feedback effect of E2 is exerted on the limbic structures, especially the BST and the 1-SEPT, while the main sites of the stimulatory feedback action of P are located in the DBB, the POSC, and the AHA. © 1978 by The Endocrine Society.