Melatonin inhibition of the neonatal pituitary response to luteinizing hormone-releasing factor.

Neonatal rat anterior pituitary glands treated in organ culture with 1 nanomolar luteinzing hormone-releasing factor (LRF) showed a tenfold increase in medium luteinizing hormone (LH) concentrations over control values. Simultaneous treatment of the glands with 1 nanomolar melatonin significantly reduced the stimulatory effect of LRF on release of LH. This finding indicates that melatonin can act directly on the neonatal pituitary to inhibit the LH response to LRF.