Branco L G, Steiner A A
Departamento de Fisiologia, Faculdade de Odontologia de Ribeirao, Universidade de São Paulo, Ribeirao Preto, Brazil.
Comp Biochem Physiol A Mol Integr Physiol. 1999 Apr;122(4):457-61. doi: 10.1016/s1095-6433(99)00032-x.
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.
