Effects of grayanotoxin-I on threshold intensity and compound action potential of frog sciatic nerve.

Effects of (Grayanotoxin-I) GTX-I, one of the second group of sodium channel toxins, have been investigated on threshold stimulus voltage and upstroke velocity of isolated frog sciatic nerve. GTX-I was isolated from toxic honey obtained from the Black Sea Region of Turkey, and used in the experiments at the concentrations of 3.50(-5), 3.10(-4), 3.10(-3) M. The threshold stimulus voltage and upstroke velocity of CAP were decreased and conduction velocity of frog sciatic nerve preparations was increased by GTX-I. The effects were dose-dependent. As a results, it is suggested that the decrease of threshold stimulus voltage and upstroke velocity of CAP and the increase of conduction velocity of frog sciatic nerve is mainly due to an increase in resting membrane permeability to sodium ions.