PRESYNAPTIC COMPONENT OF INTERMEDIARY CORD POTENTIAL

Abstract

In spinal cats and monkeys (Macacus irus and M. mulatta), a small presynaptic component (N1a) of the negative intermediary cord potential was shown by the following methods: (1) Reduction of the size of the afferent volley. (2) Its greater resistance than that of later components to asphyxia and to conditioning. (3) Its constant negativity in contrast to later components when led from any point on the surface or beneath the surface. Its duration appears to be about 0.8-1.0 msec. The longer waves in records of asphyxia are probably abnormally prolonged, as are those of the presynaptic spikes, due to slowing to conduction. This potential is attributed to afferent terminals in contrast to the major portion of N1 which is ascribed to interneurons.