Membrane properties of cat sensory neurones with chemoreceptor and baroreceptor endings.

Abstract

The properties of chemoreceptor and baroreceptor neurons in the petrosal ganglion of the cat were examined in vitro with intracellular micro-electrodes. Chemoreceptor neurons with myelinated axons (average conduction velocity, 11 m/s) showed action potentials with a hump on the falling phase, followed by a prolonged after-hyperpolarization (averaged duration, 260 ms). The duration of the hump present in the action potential of chemoreceptor neurons was positively correlated with the duration of the after-hyperpolarization. In response to prolonged depolarization, chemoreceptor neurons showed only 1 or a few action potentials at the beginning of the depolarization. Two types of baroreceptor neurons with myelinated axons were found: fast (F) baroreceptors (average conduction velocity, 33 m/s) and slow (S) baroreceptors (average conduction velocity, 10 m/s). F baroreceptors had action potentials without a hump followed by a short after-hyperpolarization (average duration, 43 ms), while S baroreceptors had spikes similar to those found in chemoreceptors except for a shorter hyperpolarization (average duration, 145 ms). Both types of baroreceptor neurons fired repetitively throughout prolonged depolarization. Apparently in the petrosal ganglion, primary sensory neurons originating a given type of sensory terminal share a particular set of electrophysiological properties.