Thermoregulatory heat-escape/cold-seeking behavior in mice and the influence of TRPV1 channels

The present study assessed heat-escape/cold-seeking behavior during thermoregulation in mice and the influence of TRPV1 channels. Mice received subcutaneous injection of capsaicin (50 mg/kg; CAP group) for desensitization of TRPV1 channels or vehicle (control [CON] group). In Experiment 1, heat-escape/cold-seeking behavior was assessed using a newly developed system comprising five temperature-controlled boards placed in a cross-shape. Each mouse completed three 90-min trials. In the trials, the four boards, including the center board, were set at either 36̊C, 38̊C, or 40̊C, while one corner board was set at 32̊C, which was rotated every 5 min. In Experiment 2, mice were exposed to an ambient temperature of 37̊C for 30 min. cFos expression in the preoptic area of the hypothalamus (POA) was assessed. In Experiment 1, the CON group stayed on the 32̊C board for the longest duration relative to that on other boards, and intra-abdominal temperature (T_abd) was maintained. In the CAP group, no preference for the 32̊C board was observed, and T_abd increased. In Experiment 2, cFos expression in the POA decreased in the CAP group. Capsaicin-induced desensitization of TRPV1 channels suppressed heat-escape/cold-seeking behavior in mice during heat exposure, resulting in hyperthermia. In conclusion, our findings suggest that heat sensation from the body surface may be a key inducer of thermoregulatory behaviors in mice.