Heat loss during exercise is related to serotonin activity in the preoptic area

To investigate the influence of the central cholinergic system on thermoregulation and brain serotonin concentration during exercise; 2 μl of physostigmine (5×10 M) or saline solution was injected into the lateral cerebral ventricle of running rats. At fatigue, brains were quickly removed and serotonin and 5-hydroxyindoleacetic acid were measured in the preoptic area, hypothalamus, frontal cortex, and hippocampus. Physostigmine injection attenuated hyperthermia and exercise-induced heat storage that was closely related to the serotonin content in the preoptic area. Physostigmine treatment also increased the heat dissipation by decreasing core temperature threshold for vasodilation. In conclusion, our data indicated that stimulation of the central cholinergic system promotes heat dissipation in running rats that is related to decreased serotonin content in the preoptic area.