title: The action of the A1 noradrenergic region on the activity of subfornical organ neurons in the rat.
abstract: Electrical stimulation of the A1 noradrenergic region of the ventrolateral medulla produced synatic excitation (n = 19, 9%), inhibition (n = 5, 2%) or no effect (n = 184, 89%) in the activity of a total of 208 neurons in the subfornical organ (SFO) in male rats under urethane anesthesia. Almost all (n = 18) of the excitatory responses (n = 19) were blocked by microiontophoretically-applied phentolamine, an alpha-adrenergic antagonist, but not by timolol, a beta-adrenergic antagonist. The inhibitory response of all the neurons (n = 5) tested was prevented by iontophoretically applied timolol, but not by phentolamine. Approximately a half (n = 9) of SFO neurons that demonstrated the excitatory response to A1 region stimulation exhibited an increase in neuronal activity in response to hemorrhage (10 ml/kg b.w.t.), while remaining neurons (n = 10) were unresponsive. Hemorrhage did not cause any change in the activity of all the neurons (n = 5) that demonstrated the inhibitory response to A1 region stimulation. These results suggest that the medullary inputs to approximately 10% of SFO neurons tested are mediated by alpha-adrenergic excitatory and beta-adrenergic inhibitory pathways, and imply that a part of the excitatory pathways may transmit the peripheral baroreceptor information.
authors.affiliation: Department of Curriculum, Teaching and Memory, Naruto University of Education, Naruto, Tokushima 772-8502, Japan. tanakaj@naruto-u.ac.jp
authors.forename: Junichi
authors.initials: J
authors.lastname: Tanaka
authors.forename: Norifumi
authors.initials: N
authors.lastname: Mashiko
authors.forename: Ayako
authors.initials: A
authors.lastname: Kawakami
authors.forename: Satoko
authors.initials: S
authors.lastname: Hatakenaka
authors.forename: Shigeko
authors.initials: S
authors.lastname: Fujisawa
authors.forename: Masahiko
authors.initials: M
authors.lastname: Nomura
mesh_terms: D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009638:Norepinephrine / Q000502:physiology; D011311:Pressoreceptors / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D013356:Subfornical Organ / Q000166:cytology* / Q000502:physiology*
chemical_list: D018340:Receptors, Adrenergic, alpha-1; D009638:Norepinephrine