Body-core temperature decreases during hypoxic hypoxia in Long-Evans and Brattleboro rats

In newborn mammals, hypoxic hypoxia produces a regulated decrease in body-core temperature, the mechanism of which is unknown. Since plasma and cerebrospinal fluid levels of arginine vasopressin increase during hypoxemia and intracerebroventricular administration of arginine vasopressin decreases body-core temperature, it has been hypothesized that an increase in central arginine vasopressin may mediate this response. Experiments were therefore carried out to test the hypothesis that the body-core temperature response to hypoxic hypoxia would be different in Brattleboro rats (which lack arginine vasopressin containing cells in the central nervous system) compared with that observed in Long-Evans rats (which have arginine vasopressin containing cells in the central nervous system). Both mild (15% oxygen) and severe (10% oxygen) hypoxic hypoxia decreased body-core temperature in both strains of rats, the decrease actually being accentuated in the Brattleboro rats. Thus, our data do not support the hypothesis that an increase in central arginine vasopressin mediates the regulated decrease in body-core temperature during hypoxic hypoxia in rats.