Endogenous vasopressin does not mediate hypoxia-induced anapyrexia in rats

The present study was designed to test the hypothesis that arginine vasopre ssin (AVP) mediates hypoxia-induced anapyrexia. The rectal temperature of a wake, unrestrained rats was measured before and after hypoxic hypoxia, AVP- blocker injection, or a combination of the two. Control animals received sa line injections of the same volume. Basal body temperature was 36.52 +/- 0. 29 degrees C. We observed a significant (P < 0.05) reduction in body temper ature of 1.45 +/- 0.33 degrees C after hypoxia (7% inspired O-2), whereas s ystemic and central injections of AVP V-1- and AVP V-2-receptor blockers ca used no change in body temperature. When intravenous injection of AVP block ers was combined with hypoxia, we observed a reduction in body temperature of 1.49 +/- 0.41 degrees C (V-1-receptor blocker) and of 1.30 +/- 0.13 degr ees C (V-2-receptor blocker), similar to that obtained by application of hy poxia only. Similar results were observed when the blockers were injected i ntracerebroventricularly. The data indicate that endogenous AVP does not me diate hypoxia-induced anapyrexia in rats.