Control of sensory transmission by electrical stimulation within the caudal raphe nuclei of the cat

Abstract

These experiments used evoked potential techniques to define further the role of neurons in the caudal raphe nuclei (CRN) in the control of sensory transmission. In each experiment, single-pulse, low-intensity stimuli were tested for the ability to change the amplitude of potentials in the spinothalamic tract (ST) and medial lemniscus (ML) evoked by superficial radial nerve stimulation. It was shown that the effect of CRN stimulation was directed specifically to neurons of the ST because only a small and variable effect was seen on the sensory-evoked potential in the ML. Also, CRN sites were located in two discontinuous regions where electrical stimulation was most effective in inhibiting sensory-evoked activity in the ST. Finally, it was shown that the effect on inhibition of the ST included activity carried by both large-diameter and small-diameter primary afferent fibers.