Abstract
Cutaneous vascular responses to mental tasks and physical exercise were studied independently and combined at the different levels of baseline skin blood flow (SkBF). We hypothesized that combined mental and physical stresses produce a synergistic interaction in the cutaneous vascular responses at any levels of SkBF. We studied the responses of cutaneous vascular conductance (CVC) to 2 min of static handgrip (HG), mental arithmetic (MA), and the combined (COM) stimuli in random order in 9 healthy subjects. SkBF was monitored from the calf and foot by laser-Doppler flowmetry. Local temperature around the sites of SkBF measurement was maintained at 29, 34 and 39°C to change the baseline levels of SkBF. CVC was calculated as the ratio of SkBF to blood pressure and expressed as percent change from the baseline control value at 34°C. The baseline values of CVC in calf and foot decreased by 60-70% at 29°C and increased by 140-160% at 39°C compared with those at 34°C. HG, MA and COM significantly decreased CVC in each skin site, and the stress-induced decrease of CVC increased with increasing baseline levels of SkBF. In each level of SkBF, the decrease of CVC in calf and foot during HG or MA did not differ from those during COM. The sum of the CVC responses during HG and MA was greater than those during COM. Hence, MA and HG induce the vasoconstrictor responses in glabrous and nonglabrous skin, resulting in a nonadditive effect of these two stresses regardless of the baseline SkBF. [J Physiol Sci. 2008;58 Suppl:S161]
