Exposure of organism to the heat stress causes a significant increase in skin blood flow. The heat stress-induced cutaneous vasodilation initially results from the withdrawal of cutaneous sympathetic vasoconstrictor activity. In addition, there is a sympathetic active cutaneous vasodilator system which is activated during another increase of the core temperature. The mechanism for this active cutaneous vasodilation is not clear and according to several experimental studies it involves a release of a vasodilator substance bradykinin from sweat glands activated by the sudomotor nerves. According to other studies the active cutaneous vasodilation is caused by the cholinergic vasodilator nerves through release of a yet-to-be-determined neurotransmitter in the presence of the basal pool of nitric oxide. Interaction of local and reflex influences is important in the control of skin blood flow during both rest and exercise.

        Key words: active cutaneous vasodilation, sympathetic active cutaneous vasodilator system, hyperthermia