PRL and ACTH secretion following acute heat exposure, in intact and in hypothalamic deafferentated male rats.

Adult male rats, intact or bearing complete, anterior or posterior hypothalamic deafferentiations (CHD, AHD AND PHD, respectively) were acutely exposed to environmental temperature of 36 degrees C, and serum PRL and ACTH concentrations were determined by RIA. In intact animals, heat exposure resulted in elevated serum PRL and ACTH levels. None of the deafferentations affected basal serum PRL concentrations, whereas those of ACTH were elevated in both CHD and AHD, but not in PHD groups, as compared to intact controls. The PRL heat response was completely absent in CHD, attenuated in AHD, and delayed in PHD animals, and the ACTH heat response was absent in all three groups. These results demonstrate (1) that acute exposure to elevated environmental temperature stimulates secretion of PRL and of ACTH; (2) that this stimulation is carried out by diverse neural pathways; and, (3) that hypothalamic modulation of the secretion of PRL and ACTH is effected by independent mechanisms.