Central thermoregulatory effects of lactate in the toad Bufo paracnemis.
Hypoxia induces a regulated decrease in body temperature (Tb; anapyrexia) in organisms ranging from protozoans to mammals, but very little is known about the mechanisms involved. Several candidates have been suggested to mediate hypoxia-induced anapyrexia, among them lactate, which is a classical compansion of hypoxic stress in vertebrates. The present study was designed to assess the central thermoregulatory effects of lactate in Bujo paracnemis. Toads equipped with a temperature probe were tested over a thermal gradient (10-40 degrees C). Lactate injected systemically (4.0 mmol kg-1) caused a significant reduction of Tb from 24.6 +/- 2.1 to 17.4 +/- 3.9 degrees C. To assess the role of central thermoregulatory mechanisms, a lower dose (0.4 mmol kg-1) of lactate was injected into the fourth cerebral ventricle or systemically. Intracerebroventricular injection of lactate caused a similar decrease in Tb, whereas systemic injection caused no change. The data indicate that lactate may play a role in hypoxia-induced anapyrexia in central rather than peripheral sites.
Branco
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LG
Departamento de Fisiologia, Faculdade de Odontologia de Ribeirao, Universidade de São Paulo, Ribeirao Preto, Brazil. lgsbranc@usp.br
Steiner
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AA
D000818:Animals; D001784:Blood Gas Analysis; D001833:Body Temperature Regulation / Q000187:drug effects* / Q000502:physiology; D002025:Bufonidae / Q000502:physiology*; D005260:Female; D006859:Hydrogen / Q000097:blood; D007276:Injections, Intraventricular; D008297:Male; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D019354:Sodium Lactate / Q000378:metabolism / Q000494:pharmacology*
D006859:Hydrogen; D010100:Oxygen; D019354:Sodium Lactate