Unit activity of raphe nuclei in the cat brainstem.

Abstract

Responses to flashes, clicks, and electrodermal stimulation of the limbs were recorded in the raphe system of nuclei in unanesthetized, immobilized cats. Somatic stimuli were most effective. Acoustic and photic stimuli evoked ill-defined responses or (to acoustic stimulation) irregular responses of very low amplitude. In a second series of experiments on cats anesthetized with Nembutal (30–35 mg/kg) spontaneous and evoked (by somatic stimulation) single unit activity was studied in the caudal group of raphe nuclei. Most neurons 1) exhibited spontaneous activity which was modified (inhibited or facilitated) by somatic (especially repetitive) stimulation, and 2) responded to stimulation of the skin of any limb. During paired stimulation of the skin of limbs on different sides at long intervals (40–60 msec) the testing discharge was inhibited, while if the intervals were short, summation (simple addition) of the spikes took place. In their general characteristics, neurons of the raphe nuclei evidently differ very little from neurons of the brainstem reticular formation.