Luteinizing hormone-releasing hormone modulates nicotinic ACh-receptor sensitivity in amphibian cholinergic transmission.

Luteinizing hormone-releasing hormone (LH-RH; 100 nM-50 microM) reduced the sensitivity of the nicotinic ACh-receptor in amphibian sympathetic ganglion cells and skeletal muscle end-plates. Analyses of LH-RH action, based on a Michaelis-Menten type kinetics, revealed that LH-RH depressed the maximum response (Vmax) of the dose-response curve of ACh currents without changing the affinity (Km) of ACh to the receptor. It was suggested that LH-RH reduced the sensitivity of nicotinic receptor by acting on a certain allosteric site of the receptor-ionic channel complex. Probably, LH-RH reduces the ACh current by decreasing the number of channels available.