Barosensory Neurons in the Rostral Ventrolateral Medulla Mediate the Renal-Sympathetic Reflex in Rabbits

In urethane-anesthetized and vagotomized rabbits, activation of C-fibers of renal afferents resulted in a reflex change in multifiber renal nerve activity (RNA) which consisted of inhibitory (I) and excitatory (E) components, either alone or in combination. The I and E components were individually and reversibly blocked by bilateral application of bicuculline and kynurenic acid, respectively, to the ventral surface of medulla. Bicuculline further eliminated the sympathoinhibiton produced by stimulation of the aortic nerve. Within the subjacent rostral ventrolateral medulla (RVLM), we recorded 23 spontaneously active single units that responded to electrical stimulation of renal afferents and were antidromically activated by stimulation of the dorsolateral funiculus at the C2 level. Usually, the neuronal response preceded that of the RNA by about 100 ms. These bulbospinal RVLM neurons were barosensory, since they responded to stimulation of the aortic nerve. We conclude that barosensory neurons in the RVLM mediate the renal-sympathetic reflex in rabbits.