Rats desensitized by capsaicin alter their food intake regulation especially at cold ambient temperature

Adult rats were treated subcutaneously for 10 days with capsaicin, and their food intake and body weight were recorded for almost 6 weeks after stopping the treatment. The animals were exposed to different ambient temperatures: Ta (22, 32, 35, 10 and 22°C). In the capsaicin-treated group a persistent increase in food intake and a reduction of body weight were observed when the animals were exposed to the lowest T a of 10°C. Starting from this temperature, food intake remained significantly higher than in controls until the end of the experiment at a Ta of 22°C. The discrepancy between body weight increase and food intake especially at low temperature (10°C) suggests that capsaicin could prevent suppression of food intake through the mediation of capsaicin-sensitive vagal afferent fibers by activation of cold-temperature-sensitive receptors.