Social defeat stress activates thermoregulatory sympathetic premotor neurons in the rostral medullary raphe

Although psychological stress in general elevates body temperature by evoking sympathetic thermogenesis and skin vasoconstriction, the central circuitry mechanism for such stress responses is unknown. Here we sought to identify sympathetic premotor neurons that mediate hyperthermic responses to social defeat stress, a psychological stress model. Rats that received social defeat stress exhibited a rapid increase in abdominal temperature by about 2°C and this hyperthermic response was largely reduced by a prior injection of diazepam, an antianxiety agent. In the rats that received social defeat stress, expression of Fos, a marker of activated neurons, was observed in rostral medullary raphe neurons expressing vesicular glutamate transporter 3 (VGLUT3), which are known as sympathetic premotor neurons controlling the thermoregulatory effectors, brown adipose tissue and skin blood vessels. In control rats or rats that received social defeat stress following diazepam injection, less VGLUT3‐expressing raphe neurons expressed Fos. These results suggest that sympathetic hyperthermic responses to psychological stress are mediated by VGLUT3‐expressing sympathetic premotor neurons in the rostral medullary raphe.