Clinically-styled vagus nerve stimulation augments spontaneous discharge in second and higher order sensory neurons in rat nucleus of the solitary tract.

Clinically-styled vagus nerve stimulation augments spontaneous discharge in second and higher order sensory neurons in rat nucleus of the solitary tract. Am J Physiol Heart Circ Physiol. 2017 May 05;:ajpheart.00070.2017 Authors: Beaumont E, Campbell RBP, Andresen MC, Scofield SL, Singh K, Libbus I, KenKnight BH, Snyder L, Cantrell N Abstract Vagus nerve stimulation (VNS) currently treats patients with drug resistant epilepsy, depression and heart failure. The mild intensities used in chronic VNS suggest that primary visceral afferents and central nervous system activation are involved. Here we measured the activity of neurons in the nucleus of the solitary tract (NTS) in anesthetized rats using clinically-styled VNS. Our chief findings indicate that VNS at threshold bradycardic intensity activated NTS neuron discharge in one third of NTS neurons. This VNS directly activated only myelinated vagal afferents projecting to second order NTS neurons. Most VNS-induced activity in NTS, however, was unsynchronized to vagal stimuli. Thus, VNS activated unsynchronized activity in NTS neurons that were second order to vagal afferent C-fibers as well as higher order NTS neurons only polysynaptically activated by the vagus. Overall, cardiovascular-sensitive and insensitive NTS neurons were similarly activated by VNS: 3/4 neurons with monosynaptic vagal A-fiber afferents, 6/42 neurons with monosynaptic vagal C-fiber afferents and 16/21 polysynaptic...
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Tags: Am J Physiol Heart Circ Physiol Source Type: research