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 μL of 25 × 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; 25 min; 5% inclination). Tail temperature (Ttail) was measured using a thermistor taped to the tail, and intraperitoneal temperature, an index of core temperature (Tc), was recorded using a telemetry sensor implanted into the peritoneal cavity. In resting rats, Phy induced an increase in both Ttail (26.8 ± 0.3 °C Phy versus 25.2 ± 0.6 °C Sal; P < 0.05) and in heat loss index (0.26 ± 0.03 Phy versus 0.14 ± 0.05 Sal; P < 0.05; 30 min after injection), and a decrease in Tc compared to the Sal injection group (36.6 ± 0.2 °C Phy versus 37.0 ± 0.2 °C Sal; P < 0.05). In post-exercising rats, Phy injection attenuated the decrease in both Ttail (28.3 ± 0.8 °C Phy versus 26.4 ± 0.6 °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 Tc. We conclude that activation of the central cholinergic pathway increases post-exercise tail heat loss in rats.