Heat Acclimation in Mice Requires Preoptic BDNF Neurons and Postsynaptic Potentiation.

Abstract Heat acclimation (HA) is a key adaptive response in mammals to repeated heat exposure, essential for fitness and survival 1-3 . HA improves cardiovascular function, thermal comfort, and exercise capacity 4, 5 . However, the lack of a genetically tractable model has hindered understanding of the molecular and neural mechanisms underlying HA. Here, we show that 10 days of daily 38°C exposure lowers core body temperature (T core ) and reduces anxiety during subsequent heat exposures in mice. HA increases brain-derived neurotrophic factor (BDNF) expression in the medial preoptic area (MPO). BDNF-expressing MPO neurons (MPO BDNF ) show increased intrinsic heat sensitivity after HA. These neurons orchestrate downstream targets in the dorsomedial hypothalamus (DMH) and rostral raphe pallidus (rRPa) to mediate HA effects. BDNF, acting through its receptor tropomyosin-related kinase B (TrkB) in the DMH, facilitates the anxiolytic effect of HA by enhancing excitatory synaptic connections between MPO BDNF and DMH neurons. This study provides new insights into HA mechanisms, setting the stage for future research on heat stress reduction and exercise optimization.