title: Characteristics of caudal ventrolateral medullary neurons antidromically activated from rostral ventrolateral medulla in the rabbit.
abstract: We made extracellular recordings from 107 spontaneously active neurons in the caudal ventrolateral medulla, after identifying the cells by antidromically activating them from the rostral ventrolateral medulla, in urethane-anesthetized rabbits. We tested the response of these neurons to inputs from baroreceptors and chemoreceptors. The median conduction velocity for antidromically activated neurons was 0.84 m/s. Raising blood pressure with intravenous noradrenaline excited 22% of 96 neurons tested, inhibited 61%, and had no effect on the remaining 17%. The spontaneous discharge rate of neurons excited by an increase in blood pressure was 1.6 +/- 0.3 spikes/s, lower than the discharge rate of neurons inhibited by this procedure (4.9 +/- 0.5 spikes/s). Excitation of chemoreceptors by hypoxia increased the discharge rate of 14/16 neurons tested in the group excited by baroreceptor inputs. In the group inhibited by baroreceptor inputs 21/35 neurons tested were excited and 12/35 neurons were inhibited by chemoreceptor inputs. Neurons excited by an increase in blood pressure were located in the previously defined caudal vasodepressor region and in a region just rostral to the obex, intermediate between the vasodepressor region and the rostral sympathoexcitatory region. These neurons may form part of the central inhibitory link in the baroreceptor-vasomotor pathway. Other antidromically activated neurons in the vasodepressor region may be inhibitory vasomotor cells with a function relatively independent of baroreceptor inputs, or they may be A1 catecholamine neurons, with axons passing through the rostral medulla en route to the forebrain.
authors.affiliation: Department of Medicine and Physiology, Centre for Neuroscience, Flinders University of South Australia.
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Gieroba
authors.forename: Y W
authors.initials: YW
authors.lastname: Li
authors.forename: W W
authors.initials: WW
authors.lastname: Blessing
mesh_terms: D000818:Animals; D001011:Aorta / Q000294:innervation; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D014630:Vagus Nerve / Q000502:physiology