NEUROPEPTIDE-Y AND LUTEINIZING-HORMONE-RELEASING HORMONE SYNERGIZE TOSTIMULATE THE DEVELOPMENT OF CELLULAR FOLLICLE-STIMULATING-HORMONE INTHE HAMSTER ADENOHYPOPHYSIS

Luteinizing hormone releasing hormone (LHRH) stimulates the developmen t of cellular FSH immunoreactivity in the perinatal hamster adenohypop hysis. Because neuropeptide Y (NPY) can act directly on rat adenohypop hysial cells to stimulate FSH and LH release and potentiate the stimul atory effect of LHRH on FSH and LH release, we investigated the effect s of NPY alone and in combination with a low, ineffective dose of LHRH on inducing cellular FSH immunoreactivity in the neonatal hamster ade nohypophysis. Neonatal female pituitary glands were grafted beneath th e right renal capsules of hypophysectomized-ovariectomized adult hamst er hosts with a catheter implanted in the external jugular vein, After treatment, hosts were decapitated and graft tissue was stained for FS H and LH immunoreactivity, The mean percentage of adenohypophysial cel ls that stained for FSH was low (2.8%) in grafts in hosts infused cont inuously with heparinized saline vehicle for 7 days, In other hosts, p eptides were pulsed through the catheter every 12 h for 7 days, The me an percentage of FSH cells also was low after pulsing 6 ng LHRH or 2 m u g NPY but increased substantially when the two peptides were pulsed simultaneously, No differences in the mean percentage of LH cells exis ted between any of the groups, The results demonstrate that NPY and LH RH can synergize to induce cellular FSH immunoreactivity in the neonat al female hamster.