Differential responses of hypothalamic LHRH-I and -II to castration and gonadal steroid or tamoxifen treatment in cockerels

Changes in the hypothalamic contents of LHRH-I and LHRH-II were determined in intact and castrated cockerels injected i.m. with gonadal steroids or tamoxifen. There was no evidence of any changes in the hypothalamic content of LHRH-II after castration, with or without gonadal steroid replacement. A change in the hypothalamic content of LHRH-I in response to manipulation of the steroid environment would imply an involvement of this peptide in the mechanism by which gonadal steroids regulate the release of LH