Hypoxia induces a regulated decrease in body temperature (Tb; anapyrexia) i
n organisms ranging from protozoans to mammals, but very little is known ab
out the mechanisms involved. Several candidates have been suggested to medi
ate hypoxia-induced anapyrexia, among them lactate, which is a classical co
mpanion 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 gradien
t (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 simi
lar decrease in Tb, whereas systemic injection caused no change. The data i
ndicate that lactate may play a role in hypoxia-induced anapyrexia in centr
al rather than peripheral sites. (C) 1999 Elsevier Science Inc. All rights
reserved.