Effect of skin sympathetic response to local or systemic cold exposure on thermoregulatory functions in humans

We studied how sympathetic response to cold exposure determines thermoregul atory function. Three female and seven male volunteers tags, 23.2+/-1.9 yea rs) were exposed to abrupt local cooling and gradual systemic cooling with recording of microneurographic skin sympathetic nerve activity (SSNA), skin temperatures (T-s), tympanic temperature (T-ty), skin blood flow measured by laser Doppler flowmetry, and sweating rate measured with a ventilated ca psule. Local cooling induced an abrupt vasoconstrictor SSNA increase and T- ty rise. There was a significant positive correlation between the increase in the vasoconstrictor SSNA and the change rate of T-ty. Systemic cooling a t 0.2 degreesC/min enhanced SSNA but gradually decreased T-ty, and a signif icant negative correlation was observed between them. A 10-min delay separa ted the SSNA rise from the subsequent T-ty rise following local cooling. A delay of less than 1 min preceded the SSNA increase after the T-ty fall ind uced by systemic cooling. These findings suggested that subjects with a goo d SSNA response to cold stress can maintain core temperature, but 10 min is necessary to raise the core temperature by reducing heat loss from the ski n surface. In contrast, vasoconstrictor SSNA responds linearly to a fall in core temperature with a delay of less than 1 min. (C) 2001 Elsevier Scienc e B.V. All rights reserved.