title: Immobilization induces acute nitric oxide production in the rat hypothalamus: a role of ionotropic glutamate receptors in the paraventricular nucleus.
abstract: Production of nitric oxide (NO) in the hypothalamic paraventricular nucleus (PVN) was examined by microdialysis in rats subjected to immobilization (IMO) stress. A dialysis probe was implanted in the posterior magnocellular subdivision of the PVN and nitrite (NO(2)(-)), an oxidized product of NO, was measured continuously. NO(2)(-) concentration in dialysate was enhanced to 156% after 30 min of IMO compared with the NO(2)(-) level before IMO. Intraperitoneal administration of N(G)-monomethyl-l-arginine (10 mg/kg), a NO synthase inhibitor, before IMO completely inhibited the increase of NO production that IMO was to induce. Depletion of catecholamines innervating the PVN by an injection of 6-hydroxydopamine into the lateral ventricle before the microdialysis had no suppressive effect on the increase of NO production by IMO. In contrast, NO(2)(-) levels in the PVN were lowered by continuous perfusion of the solution containing the ionotropic glutamate receptor antagonists 2-amino-5-phosphonovaleric acid (500 microm) and 6-cyano-7-nitroquinoxaline-2, 3 dione (50 microm) through the dialysis probe, and the IMO-induced increase of NO production was attenuated by the treatment. These results suggest that catecholaminergic drive to the hypothalamus is not necessary for the IMO-induced increase of NO production and that ionotropic glutamate receptors play a role in the basal and IMO-induced NO production.
authors.affiliation: Center for Advanced Oral Medicine, Hokkaido University Hospital, Sapporo, 060-8586, Japan. tshira@den.hokudai.ac.jp.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Shirakawa
authors.forename: Masato
authors.initials: M
authors.lastname: Mitome
authors.forename: Takashi
authors.initials: T
authors.lastname: Kikuiri
authors.forename: Wataru
authors.initials: W
authors.lastname: Nakamura
authors.forename: Shohei
authors.initials: S
authors.lastname: Oshima
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Masanobu
authors.initials: M
authors.lastname: Shindoh
authors.forename: Haruhisa
authors.initials: H
authors.lastname: Oguchi
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D007103:Immobilization; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis*; D016627:Oxidopamine; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017470:Receptors, Glutamate / Q000502:physiology*; D013312:Stress, Physiological / Q000378:metabolism*
chemical_list: D017470:Receptors, Glutamate; D009569:Nitric Oxide; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate; D016627:Oxidopamine