Spontaneous rhythmic activity of single nerve fibers of the cervical sympathetic nerve trunk of the rabbit

Abstract

In experiments on rabbits anesthetized with urethane, we recorded spontaneous sympathetic activity of single nerve fibers. The activity was recorded from fine filaments dissected from the cervical sympathetic nerve trunk (CSNT). Conduction velocities in CSNT fibers and action-potential amplitude of single B-fibers were measured during recording of whole nerve trunk. Spectral analysis of the activity recorded was carried out. It was shown that unmyelinated CSNT fibers are under stronger baroreceptor control than myelinated fibers. Also, a periodic component of 2–3 Hz, noted by a number of authors after denervation of baroreceptors, was detected in intact animals along with a rhythm at the pulse rate. This component was found equally often in the activity of B- and C-fibers. Cross-correlation analysis of the simultaneously recorded activities of 24 pairs of CSNT single fibers was carried out. A correlation due to synchronization of the activities of pairs of fibers with a physiological rhythm (respiration, pulse) was found in five pairs. The correlation in one pair suggests the presence of a common excitatory synaptic input into two distinct preganglionic neurons.