A Neurophysiological Study on the Sympathetic Premotor Nuclei in the Pons and Medulla Oblongata

Abstract

The aim of this study was to neurophysiologically demonstrate the activities of the premotor nuclei of sympathetic  vasomotion, by capturing the diachronic changes in the action potentials which are generated in  the pons and medulla oblongata. To do so, ten male Wistar rats weighing 300g were used as subjects.  Microelectrodes were inserted in the muscular branch of the sciatic nerve and the ventral side of the pons  and medulla oblongata, and the muscle sympathetic nerve activity (MSA) was induced. The regular spontaneous  action potentials, which synchronize with muscle sympathetic nerve activity, were observed in the  rostral ventrolateral medulla oblongata (RVLM), and the differences among the action potentials of individual  cells of the RVLM region noted. Autonomic postganglionic nerves are controlled in turn by preganglionic  nerves that originate from specific nuclei in the medulla. These nerves directly influence cardiovascular  function by regulating the rate and force of contraction of the heart and the diameter of blood  vessels. RVLM cells in fact exert a widespread control over the sympathetic outflow. We conclude from the  experiment that premotor nuclei of sympathetic vasomotion exist in the RVLM.