cAMP in temperature- and ADH-regulating centers after thermal stress.

cAMP concentrations in temperature-regulating sites of the brain and plasma osmolality were measured after exposure of male rats to 36 degrees C and 37-42% rh. for 10, 20, or 30 min. Plasma osmolality was affected by none of the heat exposures. In both the preoptic area and the posterior medial hypothalamus, cAMP concentrations were increased compared to controls, after 10, 20 and 30 min of heat exposure. In the supraoptic-paraventricular nuclei, neither 10 nor 20 min of exposure resulted in augmented cAMP concentrations; but after 30 min of heat exposure, cAMP levels in these nuclei were significantly greater than in controls. Neurohypophysial cAMP concentrations were increased after both 10 and 30 min of exposure. Cerebral cortical cAMP concentrations were not affected by thermal stress. It is concluded that cAMP is involved in the neural mechanisms which are brought into play to regulate body temperature during acute heat exposure. The significance of this involvement and its relation to the overall temperature-regulating mechanisms of the body are discussed.