THE EFFECT OF BODY-TEMPERATURE ON THE HUNTING RESPONSE OF THE MIDDLE FINGER SKIN TEMPERATURE

The relationship between body temperature and the hunting response (in termittent supply of warm blood to cold exposed extremities) was quant ified for nine subjects by immersing one hand in 8 degrees C water whi le their body was either warm, cool or comfortable. Core and skin temp eratures were manipulated by exposing the subjects to different ambien t temperatures (30, 22, or 15 degrees C), by adjusting their clothing insulation (moderate, light, or none), and by drinking beverages at di fferent temperatures (43, 37 and 0 degrees C). The middle finger tempe rature (T-fi) response was recorded, together with ear canal (T-ear), rectal (T-re), and mean skin temperature ((T) over bar(sk)) The induce d mean T-ear changes were -0.34 (0.08) and + 0.29 (0.03)degrees C foll owing consumption of the cold and hot beverage? respectively. (T) over bar(sk) ranged from 26.7 to 34.5 degrees C during the tests. In the w arm environment after a hot drink, the initial finger temperature (T-f i,T-base) was 35.3 (0.4)degrees C, the minimum finger temperature duri ng immersion (T-fi.min) was 11.3 (0.5)degrees C, and 2.6 (0.4) hunting waves occurred in the 30-min immersion period. In the neutral conditi on (thermoneutral room and beverage) T-fi.base was 32.1 (1.0)degrees C , T-fi.min was 9.6 (0.3)degrees C, and 1.6 (0.2) waves occurred. In th e cold environment after a cold drink, these values were 19.3 (0.9)deg rees C, 5.7 (0.2)degrees C, and 0.8 (0.2) waves, respectively. A colde r body induced a decrease in the magnitude and frequency of the huntin g response. The total heat transferred from the hand to the water, as estimated by the area under the middle finger temperature curve, was a lso dependent upon the induced increase or decrease in T-ear and (T) o ver bar(sk). We conclude that the characteristics of the hunting tempe rature response curve of the finger are in part determined by core tem perature and (T) over bar(sk). Both T-fi.min and the maximal finger te mperature during immersion were higher when the core temperature was e levated; (T) over bar(sk) seemed to be an important determinant of the onset time of the cold-induced vasodilation response.