Activation of the central cholinergic pathway increases post-exercise tail heat loss in rats

The aim of this study was to evaluate the effects of stimulation of the central cholinergic pathway on the regulation of post-exercise tail heat loss in rats. Either 2.0 mu L of 25 x 10(-3) M physostigmine (Phy) or 0.15 M NaCl solution (Sal) were injected into the right lateral cerebral ventricle of both resting (n = 8) and post-exercising rats (n = 6; 24 m min(-1) Z; 25 min; 5% inclination). Tail temperature (T-tail) was measured using a thermistor taped to the tail, and intraperitoneal temperature, an index of core temperature (T-c), was recorded using a telemetry sensor implanted into the peritoneal cavity. In resting rats, Phy induced an increase in both T-tail (26.8 +/- 0.3 degrees C Phy versus 25.2 +/- 0.6 degrees C Sal; P < 0.05) and in heat loss index (0.26 +/- 0.03 Phy versus 0.14 +/- 10.05 Sal; P < 0.05; 30 min after injection), and a decrease in T-c compared to the Sal injection group (36.6 +/- 0.2 degrees C Phy versus 37.0 +/- 0.2 degrees C Sal; P < 0.05). In post-exercising rats, Phy injection attenuated the decrease in both Tlail (28.3 +/- 0.8 degrees C Phy versus 26.4 +/- 0.6 degrees C Sal; P < 0.05) and heat loss index (0.37 +/- 0.07 Phy versus 0.19 +/- 0.02 Sal; P < 0.05) without altering T-c. We conclude that activation of the central cholinergic pathway increases post-exercise tail heat loss in rats. (c) 2006 Elsevier Ireland Ltd. All rights reserved.