Association between thermal response and endogenous dopamine: Step-change environments in winter.

Temperature step change is the typical transient thermal environment. The purpose of this study was to explore the association of subjective and objective parameters in a step-change environment, including thermal sensation vote (TSV), thermal comfort vote (TCV), mean skin temperature (MST) and endogenous dopamine (DA). Three temperature step changes defined as I3 (15 °C-18 °C to 15 °C), I9 (15 °C-24 °C to 15 °C) and I15 (15 °C-30 °C to 15 °C) were designed for this experiment. Eight male and eight female healthy subjects who participated in the experiment reported thermal perception (TSV and TCV). Skin temperatures of six body parts and DA were measured. Results show that the inverted U-shaped in TSV and TCV was deviated by seasonal factors of the experiment. The deviation direction of TSV in winter was to the warm sensation side, which was opposite to the inherent cold and hot impression of people in winter and summer. The association between dimensionless dopamine (DA*), TSV and MST were described as follows: DA* was the U-shaped change with exposure times when MST was not greater than 31 °C, and TSV was at -2 and -1, and DA* increased with exposure times when MST was greater than 31 °C, and TSV was at 0, 1 and 2. The changes in the body heat storage and autonomous thermal regulation under temperature step changes may potentially be related to the concentration of DA. The human state on thermal nonequilibrium and stronger thermal regulation would correspond to a higher concentration of DA. This work is conducive to exploring the human regulation mechanism in a transient environment.