Local thermal sensation and finger vasoconstriction in the locally heated hand.

The effects of local heating on finger blood flow (BF) and local thermal sensation (Sensw) were studied. Finger BFs in both hands were measured simultaneously; one hand was immersed in water the temperature (Tw) of which was raised from 35 degrees C to 43 degrees C by steps of 2 degrees C every 10 min, while the other hand was kept at Tw 35 degrees C. Finger BF in the locally heated hand decreased at Tw 37 to 41 degrees C, while finger BF in the control hand did not alter. Sensw in the heated hand showed a dynamic response, initially increasing concomitantly with an increase in Tw, then gradually returning and adapting to a new level of Sensw. The dynamic response of Sensw was not perceived during mental calculation even when Tw was raised to 40 degrees C, and the reduction in finger blood flow was not observed. These results suggest that finger vasoconstriction caused by local heating closely relates to the dynamic response characteristic of local thermal sensation at Tw above core temperature, and that the perception of local thermal sensation in the central nervous system is involved in the mechanism of this vasoconstrictor response.