THE EFFECT OF SYNTHETIC HYPOTHALAMIC RELEASING FACTORS ON PLASMA LEVELS OF LUTEINIZING HORMONE IN THE COCKEREL

Abstract

SUMMARY The capacity of synthetic luteinizing hormone releasing factor (LH-RF) to stimulate the release of luteinizing hormone (LH) from the pituitary gland of the cockerel has been examined. Administration of LH-RF to 21 intact and 12 castrated cockerels aged between 14 and 20 months resulted in a rapid increase in the levels of LH in the plasma within 5–10 min of injection in both groups of birds. Plasma LH then declined rapidly and returned to basal values within 1 h. The amount of LH released in the intact birds was dependent on the dose of LH-RF. Concentrations of LH in the plasma did not increase after injection of thyroid-stimulating hormone releasing factor but the response of the pituitary gland to a subsequent injection of LH-RF 2 h later was not altered. The pattern of release of LH in the cockerel is compared with that of some mammalian species.