Role of nitric oxide in systemic vasopressin-induced hypothermia.
It has been reported that arginine vasopressin (AVP) plays a thermoregulatory action, but very little is known about the mechanisms involved. In the present study, we tested the hypothesis that nitric oxide (NO) plays a role in systemic AVP-induced hypothermia. Rectal temperature was measured before and after AVP, AVP blocker, or NG-nitro-L-arginine methyl ester (L-NAME; NO synthase inhibitor) injection. Control animals received saline injections of the same volume. The basal body temperature (Tb) measured in control animals was 36.53 +/- 0.08 degreesC. We observed a significant (P < 0.05) reduction in Tb to 35.44 +/- 0.19 degreesC after intravenous injection of AVP (2 micrograms/kg) and to 35.74 +/- 0. 10 degreesC after intravenous injection of L-NAME (30 mg/kg). The systemic injection of the AVP blocker [beta-mercapto-beta, beta-cyclopentamethylenepropionyl1,O-Et-Tyr2,Val4,Arg8]vasopressin (10 micrograms/kg) caused a significant increase in Tb to 37.33 +/- 0.23 degreesC, indicating that AVP plays a tonic role by reducing Tb. When the treatments with AVP and L-NAME were combined, systemically injected L-NAME blunted AVP-induced hypothermia. To assess the role of central thermoregulatory mechanisms, a smaller dose of L-NAME (1 mg/kg) was injected into the third cerebral ventricle. Intracerebroventricular injection of L-NAME caused an increase in Tb, but when intracerebroventricular L-NAME was combined with systemic AVP injection (2 micrograms/kg), no change in Tb was observed. The data indicate that central NO plays a major role mediating systemic AVP-induced hypothermia.
Steiner
A A
AA
Faculdade de Odontologia de Ribeirão Preto, Universidade de São Paulo, 14040-904 Ribeirão Preto, São Paulo, Brazil.
Carnio
E C
EC
Antunes-Rodrigues
J
J
Branco
L G
LG
D000818:Animals; D001127:Arginine Vasopressin / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology*; D001833:Body Temperature Regulation / Q000187:drug effects / Q000502:physiology*; D002552:Cerebral Ventricles / Q000187:drug effects / Q000502:physiology*; D006727:Hormone Antagonists / Q000494:pharmacology; D007036:Hypothermia, Induced; D007276:Injections, Intraventricular; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage / Q000494:pharmacology*; D009569:Nitric Oxide / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D006727:Hormone Antagonists; D001127:Arginine Vasopressin; D009569:Nitric Oxide; C050890:1-((beta-mercapto-beta)beta cyclopentamethylenepropionic acid)-2-(O-ethyl-Tyr)-4-Val-9-des-Gly-arginine vasopressin; D019331:NG-Nitroarginine Methyl Ester