Chronic sympathectomy of the caudal artery delays cutaneous heat loss during passive heating

Abstract

The present study aimed to investigate the chronic effects of caudal artery sympathectomy on thermoregulatory adjustments induced by passive heating. Male Wistar rats were subjected to two surgical procedures: caudal artery denervation (CAD) or sham surgery (Sham-CAD) and intraperitoneal implantation of a temperature sensor. On the day of the experiments, the animals were exposed to an ambient temperature of 36°C for 60min or allowed to rest under thermoneutral conditions (26°C). During the experiments, the tail skin temperature (Tskin) and the core body temperature (Tcore) were measured. Under thermoneutral conditions, although sympathetic denervation did not change the average values of Tcore and Tskin, CAD rats exhibited decreased Tskin variability compared with Sham-CAD rats (0.020±0.005°C vs. 0.031±0.005°C; P=0.024). During heat exposure, no differences were observed in the Tcore between the groups. In contrast, although peak Tskin values were not affected by chronic sympathectomy of the caudal artery, CAD animals showed a delayed increase in Tskin; the time until the stabilization of Tskin was three-fold longer in CAD rats than in Sham-CAD rats (15.3±2.5min vs. 4.9±0.6min; P=0.001). In conclusion, chronic sympathectomy of the caudal artery delays cutaneous heat loss during passive heating and decreases Tskin variability under thermoneutral conditions. Taken together, our results indicate that the sympathetic innervation of cutaneous vessels is essential for the precise regulation of tail heat loss.