Effect of LH-FSH releasing hormone on the sensitivity of cholinergic and adrenergic receptors in toad spinal ganglion neurons

Intracellular recordings were performed on 81 neurons from 53 isolated toad spinal ganglia (SG). The effects of LH-FSH releasing hormone on the sensitivities of muscarinic receptors and alpha-adrenoceptors located on the soma of SG neurons were observed. Perfusing SG with atropine 10 mumol.L-1 in Ringer's solution depressed the amplitude of depolarization response induced by acetylcholine (ACh, 10-100 mumol.L-1). The depolarization and hyperpolarization induced by norepinephrine (NE, 10-100 mumol.L-1) were blocked by alpha 1-adrenoceptor antagonist prazosin and alpha 2-adrenoceptor antagonist yohimbine respectively. These results indicated that ACh-induced depolarization was mediated by muscarinic receptors while NE-induced depolarization and hyperpolarization were mediated by alpha 1- and alpha 2-adrenoceptors respectively. On the other hand, perfusing SG with LH-FSH releasing hormone 10 mumol.L-1 in Ringer's solution increased the depolarization response caused by ACh or NE, but attenuated NE-caused hyperpolarization response. The above results suggest that LH-FSH releasing hormone may modulate the sensitivities of muscarinic receptors and alpha-adrenoceptors on the soma membrane of toad SG neurons.