title: Baro-excited neurons in the caudal ventrolateral medulla (CVLM) recorded using the whole-cell patch-clamp technique.
abstract: Caudal ventrolateral medulla (CVLM) neurons have important roles in the regulation of sympathetic nerve activity and blood pressure through their tonic inhibition of rostral ventrolateral medulla neurons. As few reports have demonstrated CVLM neuronal activity using the whole-cell patch-clamp technique, we attempted to find neurons in the CVLM that are depolarized by the stimulation of baroreceptors. To record the membrane potentials of the neurons in the CVLM, we developed a modified brainstem-spinal cord preparation that enabled us to change the pressure exerted on the aortic arch and carotid sinuses. We were able to identify neurons in the CVLM in which they were depolarized and the action potential (AP) frequency was increased upon baroreceptor stimulation. We referred to these neurons as baro-excited CVLM neurons. When these preparations were superfused with an angiotensin-II (Ang-II) solution, the frequency of the APs increased in 10 of the 14 baro-excited CVLM neurons. Superfusion with a low-Ca(2+), high-Mg(2+) solution abolished the APs in all seven baro-excited CVLM neurons, suggesting that the baro-excited CVLM neurons did not fire spontaneously. When the preparation was superfused with a low-Ca(2+) solution, 6 of the 7 baro-excited CVLM neurons did not respond to Ang-II superfusion. We for the first time found the baro-excited CVLM neurons, which depolarized pressure dependently but may not fire spontaneously. As Ang-II did not change the activity of the CVLM neurons during superfusion with a low-Ca(2+), high-Mg(2+) solution, the presynaptic neurons may be mandatory for the Ang-II-induced activation of postsynaptic baro-excited CVLM neurons.
authors.affiliation: Department of Nephrology, National Defense Medical College, Saitama, Japan. oshima@ndmc.ac.jp
authors.forename: Naoki
authors.initials: N
authors.lastname: Oshima
authors.forename: Hiroo
authors.initials: H
authors.lastname: Kumagai
authors.forename: Kamon
authors.initials: K
authors.lastname: Iigaya
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Onimaru
authors.forename: Akira
authors.initials: A
authors.lastname: Kawai
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Nishida
authors.forename: Takao
authors.initials: T
authors.lastname: Saruta
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Itoh
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology; D001933:Brain Stem / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000502:physiology; D008274:Magnesium / Q000502:physiology; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology
chemical_list: D000804:Angiotensin II; D008274:Magnesium; D002118:Calcium