The aim of this study was to evaluate the participation of central cholinergic transmission in the regulation of metabolic rate, core temperature (T_C), and heat storage in untrained rats submitted to exercise on a treadmill (20 m.min^-1, 5% inclination) until fatigue. The animals were separated into eight experimental groups and core temperature or metabolic rate were measured in rats exercising or at rest after injecting 2 µl of 5 x 10^-3 M physostigmine (PHY) or 0.15 M NaCl solution (SAL) into the lateral cerebral ventricle. Metabolic rate was determined by the indirect calorimetry system and colonic temperature was recorded as an index of T_C. In resting animals, PHY induced only a small increase in metabolic rate compared with SAL injection, without having any effect on T_C. During exercise, the PHY-treated animals showed a lower core heating rate (0.022 ± 0.003 °C. min^-1, PHY vs 0.033 ± 0.003 °C. min^-1, SAL; p<0.02), heat storage (285 ± 37 cal, PHY vs 436 ± 34 cal, SAL; p<0.02) and lower T_C at fatigue point than the SAL-treated group (38.5 ± 0.1°C, PHY vs 39.0 ±0.1°C, SAL; p<0.05). However, despite the lower core heating rate, heat storage and T_C at fatigue, the PHY-treated rats showed a similar running time to the SAL-treated group. We conclude that the activation of the central cholinergic system during exercise increases heat dissipation and attenuates the exercise-induced increase in core temperature without affecting running performance.