Selective blockage of the sensory terminal activities by micro-application of tetrodotoxin in the frog muscle spindle

Abstract Micro-application of tetrodotoxin to the sensory nerve terminal of the frog muscle spindle made a semi-blocked condition, in which propagated spikes were blocked selectively but reversibly, while abortive spikes survived. In the semi-blocked condition an antidromic spike was often followed by an abortive spike without a significant pause, in contrast with the normal condition in which the antidromic spike was always followed by an abortive spike or a propagated spike with a pause more than 50–100 msec. An analysis of the spike train as a stochastic point process suggests that the abortive spikes originate at the places which the antidromic spike can scarcely invade in the semi-blocked condition.