Changes in the hypothalamic mechanisms involved in the control of body temperature induced by the early thermal environment

The experiments reported in this study were designed to investigate the influence of the early thermal environment on the functional properties of certain putative thermoregulatory neurotransmitters within the hypothalamus of the Sprague-Dawley rat. The effects on body temperature of serotonin, dopamine, carbachol, PGE₂ and endotoxin when microinjected into the anterior hypothalamic/preoptic region of the brain have been examined in warm-reared, control and warm-acclimated animals. Serotonin and PGE₂ are shown to have different effects on body temperature in warm-reared as compared to warm-acclimated and control animals. The thermoregulatory effects of intrahypothalamic dopamine are shown to be changed by the normal acclimation process, while carbachol and endotoxin have similar effects on the body temperature of all 3 groups of animals. These data suggest that the thermal environment may significantly affect the roles which specific neurotransmitters play in the control of body temperature.