Temperature-dependent interaction between vasoconstrictor and vasodilator mechanisms in human skin.

The putative influence of the thermoregulatory state on skin blood-flow responses to various stimuli was studied in 17 healthy subjects exposed to different ambient temperatures. Skin blood flow was monitored by laser Doppler flowmeters and photoelectrical pulse plethysmographs. Stimuli included painful intraneural electrical stimulation (INS) in the median nerve at the wrist, mental stress, arousal stimuli and deep breaths. Intraneural electrical stimulation and mental stress were accompanied by virtually identical changes in skin blood flow, warm subjects responding with cutaneous vasoconstriction whereas cold subjects responded with vasodilatation. Similar but less pronounced responses were obtained with arousal stimuli and single deep breaths. The data indicate that the thermoregulatory state profoundly influences the extent and direction of various cutaneous vasomotor reflex responses. Furthermore, there were differences between responses in hands and feet, suggesting a spatial organization of vasomotor control.