Abstract
Corticotropin releasing-hormone (CRH) is recognized as modulating luteinizing hormone releasing hormone (LH-RH) secretion at the medial preoptic area (MPOA), but the physiological significance of the effects of endogenous CRH on LH-RH secretion at the median eminence (ME) is not clear. To clarify the effects of CRH at ME, we used two animal models (adrenalectomized and restraint stressed rats) for hypersecretion of CRH and examined the effects of iv administration of CRH antiserum on LH secretion. Adrenalectomy for 2 weeks clearly increased plasma concentrations of ACTH and decreased plasma concentrations of LH in adult male rats. The iv injection of CRH antiserum attenuated the increased levels of plasma ACTH and restored the suppressed levels of plasma LH in adrenalectomized rats. In response to restraint stress, plasma concentrations of ACTH and PRL were increased and plasma concentrations of LH were decreased in adult male rats. The iv injection of CRH antiserum blocked the suppression of LH secretion induced by stress, but it did not have any effects on PRL secretion. These results suggest that immunoneutralization of endogenous CRH at the ME increases LH secretion probably mediated by LH-RH release and ME is probably one of the action sites of CRH on LH-RH secretion in addition to MPOA.
