EVIDENCE FOR THE INVOLVEMENT OF NITRIC-OXIDE IN THE INHIBITORY EFFECTOF GSPYFVAMIDE ON HELIX-ASPERSA CENTRAL NEURONS

Intracellular recordings were made from neurones E-8, E-16 and E-13a i n the visceral ganglion of Helix aspersa. GSPYFVamide inhibits the act ivity of these neurones and the role of a second messenger system in t his inhibition was investigated. 8-Bromo-cGMP, 100 mu M was found to p otentiate this inhibition while ODQ, 100 mu M, an inhibitor of guanyly l cyclase, almost completely blocked GSPYFVamide-induced inhibition. F our NO donors sodium nitroprusside, 100 mu M, sodium nitrite, 1 mM, SN OG, 50 mu M, and SNAP, 10-50 mu M, all potentiated the GSPYFVamide-ind uced inhibition. L-NAME, 100-1000 mu M, a competitive inhibitor of NOS , blocked the GSPYFVamide-induced inhibition. In some cases recovery w as only partial. The possible role of NO in modulating the inhibitory response to GSPYFVamide is discussed. (C) 1998 Elsevier Science BN.