Abstract
Effects of tetrodotoxin on the spindle potential and the spike of isolated frog muscle spindle recorded using the paraffin gap method were studied.
2×10-8g/ml toxin first abolished the conductive spike and subsequently reduced the amplitude and the rate of rise of the abortive spike or the prepotential. 5×10-8g/ml or more toxin erased the abortive spike and the prepotential without producing any significant effect on the spindle potential.
It is assumed from the results that the prepotential may be the same as the abortive spike, and that the abortive spike may play a primary role in the initiation of the conductive spike as the prepotential when its amplitude is higher than a trigger level.
The spindle potential was modified greatly depending on the sideward displacement of the axon in the paraffin pool during muscle stretch. Consequently, it seems that a part of the spindle potential may consist of an artifact.
