AJP - Regulatory, Integrative and Comparative Physiology, Vol 273, Issue 3 967-R971, Copyright © 1997 by American Physiological Society

ARTICLES

Role of the nitric oxide pathway in hypoxia-induced hypothermia of rats

L. G. Branco, E. C. Carnio and R. C. Barros
Departamento de Fisiologia, Faculdade de Odontologia de Ribeirao Preto, Universidade de Sao Paulo, Brazil.

Hypothermia is a response to hypoxia that occurs in organisms ranging from protozoans to mammals, but very little is known about the mechanisms involved. Recently, the NO pathway has been suggested to be involved in thermoregulation. In the present study, we assessed the participation of nitric oxide in hypoxia-induced hypothermia by means of NO synthase inhibition using NG-nitro-L-arginine methyl ester (L-NAME). The rectal temperature of awake, unrestrained rats was measured before and after hypoxia or L-NAME injection or both treatments together. Control animals received saline injections of the same volume. We observed a significant (P < 0.05) reduction in body temperature of 1.32 +/- 0.36 degrees C after hypoxia (7% inspired O2) and of 0.96 +/- 0.42 degree C after L-NAME (30 mg/kg body wt) injected intravenously. When the two treatments were combined, no significant difference in body temperature was observed. To assess the role of central thermo-regulatory mechanisms, a smaller dose of L-NAME (1 mg/kg) was injected into the third cerebral ventricle or intravenously. Intracerebroventricular injection of L-NAME caused an increase in body temperature, but when L-NAME was combined with hypoxia (7% inspired O2) no change in body temperature was observed. Intravenous injection of 1 mg/kg L-NAME had no effect. The data indicate that NO plays a major role in hypoxia-induced hypothermia at central rather than peripheral sites.

This article has been cited by other articles:

				C. L. Wright, P. W. Burgoon, G. A. Bishop, and J. A. Boulant Cyclic GMP alters the firing rate and thermosensitivity of hypothalamic neurons Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2008; 294(5): R1704 - R1715. [Abstract] [Full Text] [PDF]

				A. A. Steiner, M. J. A. Rocha, and L. G. S. Branco A neurochemical mechanism for hypoxia-induced anapyrexia Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2002; 283(6): R1412 - R1422. [Abstract] [Full Text] [PDF]

				K. Benamar, E. B. Geller, and M. W. Adler Role of the Nitric Oxide Pathway in kappa -Opioid-Induced Hypothermia in Rats J. Pharmacol. Exp. Ther., October 1, 2002; 303(1): 375 - 378. [Abstract] [Full Text] [PDF]

				R. C. H. Barros and L. G. S. Branco Central dopamine modulates anapyrexia but not hyperventilation induced by hypoxia J Appl Physiol, March 1, 2002; 92(3): 975 - 981. [Abstract] [Full Text] [PDF]

				G. J. Tattersall, J. L. Blank, and S. C. Wood Ventilatory and metabolic responses to hypoxia in the smallest simian primate, the pygmy marmoset J Appl Physiol, January 1, 2002; 92(1): 202 - 210. [Abstract] [Full Text] [PDF]

				B. Platzack and J. W. Hicks Reductions in systemic oxygen delivery induce a hypometabolic state in the turtle Trachemys scripta Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2001; 281(4): R1295 - R1301. [Abstract] [Full Text] [PDF]

				R. C. H. Barros, M. E. Zimmer, L. G. S. Branco, and W. K. Milsom Hypoxic metabolic response of the golden-mantled ground squirrel J Appl Physiol, August 1, 2001; 91(2): 603 - 612. [Abstract] [Full Text] [PDF]

				H. NAKANO, S.-D. LEE, A. D. RAY, J. A. KRASNEY, and G. A. FARKAS Role of Nitric Oxide in Thermoregulation and Hypoxic Ventilatory Response in Obese Zucker Rats Am. J. Respir. Crit. Care Med., August 1, 2001; 164(3): 437 - 442. [Abstract] [Full Text] [PDF]

				A. A. Steiner, E. C. Carnio, and L. G. S. Branco Role of neuronal nitric oxide synthase in hypoxia-induced anapyrexia in rats J Appl Physiol, September 1, 2000; 89(3): 1131 - 1136. [Abstract] [Full Text] [PDF]

				L. G. S. Branco, A. A. Steiner, G. J. Tattersall, and S. C. Wood Role of adenosine in the hypoxia-induced hypothermia of toads Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2000; 279(1): R196 - R201. [Abstract] [Full Text] [PDF]

				M. C. Almeida, E. C. Carnio, and L. G. S. Branco Role of nitric oxide in hypoxia inhibition of fever J Appl Physiol, December 1, 1999; 87(6): 2186 - 2190. [Abstract] [Full Text] [PDF]

				A. A. Steiner, E. Colombari, and L. G. S. Branco Carbon monoxide as a novel mediator of the febrile response in the central nervous system Am J Physiol Regulatory Integrative Comp Physiol, August 1, 1999; 277(2): R499 - R507. [Abstract] [Full Text] [PDF]

				H. Gautier and C. Murariu Role of nitric oxide in hypoxic hypometabolism in rats J Appl Physiol, July 1, 1999; 87(1): 104 - 110. [Abstract] [Full Text] [PDF]

				A. A. Steiner, E. C. Carnio, J. Antunes-Rodrigues, and L. G. S. Branco Endogenous vasopressin does not mediate hypoxia-induced anapyrexia in rats J Appl Physiol, February 1, 1999; 86(2): 469 - 473. [Abstract] [Full Text] [PDF]

				A. A. Steiner, E. C. Carnio, J. Antunes-Rodrigues, and L. G. S. Branco Role of nitric oxide in systemic vasopressin-induced hypothermia Am J Physiol Regulatory Integrative Comp Physiol, October 1, 1998; 275(4): R937 - R941. [Abstract] [Full Text] [PDF]

				R. C. H. Barros and L. G. S. Branco Effect of nitric oxide synthase inhibition on hypercapnia-induced hypothermia and hyperventilation J Appl Physiol, September 1, 1998; 85(3): 967 - 972. [Abstract] [Full Text] [PDF]