Neurophysiological effects of tetrodotoxin in lateral geniculate body and dorsal hippocampus

Abstract

Introduction of tetrodotoxin into the lateral geniculate body of the cat causes the amplitudes of flash evoked potentials in the lateral geniculate body and visual cortex to decrease in a predictable manner. Subsequently the evoked potential amplitude recovers to the initial level. Nystagmic eye movements and a strong tendency for the cats to turn their heads toward the side of tetrodotoxin introduction were observed with higher doses of the drug. During recovery from large doses of tetrodotoxin, seizure-like discharges are observed in the lateral geniculate EEG. Introduction of tetrodotoxin into the hippocampus also results in seizure-like EEG activity. Quantitative analysis of the evoked potential data shows that the diffusion coefficient for tetrodotoxin in the lateral geniculate body is about 4 · 10 −6 cm 2/sec. the bloodstream is 2 h. An estimate for the density of sodium spike current carrying sites on the surfaces of lateral geniculate neurons is 120 sites /gm 2.