REGULATION OF SKIN BLOOD FLOW IN MAN

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The cutaneous circulation has one of the highest potential capacities for blood flow of the regional circulations, approaching 8 liters/minute. The level of skin blood flow falls under sensory control by internal temperature, skin temperature, baroreceptors, the reflexes accompanying exercise, as well as interactions among these sources. Efferent control is brought about through an adrenergic vasoconstrictor system, a non- adrenergic active vasodilator system, the local temperature of the skin itself and, again, interactions among these elements of control. The high potential blood flow dictates that the cutaneous circulation and its control has importance, not only to temperature regulation, but also to blood pressure regulation, the distribution of the cardiac output during exercise, and to general cardiovascular homeostasis. The long term objectives of this application are to better understand these controllers and their circulation and how that control is brought into play by thermoregulatory reflexes, nonthermoregulatory reflexes and their competition. The obvious importance to health is that related disorders, it is required that the control of the cutaneous circulation and its integration with general cardiovascular control be fully understood and appreciated. Aims for the next funding period are generally grouped into three related categories, all involved in the efferent side of reflex control of the cutaneous circulation. These are (a) a thorough and specific examination of the reflex control of the active vasodilator system by baroreceptors, skin temperature and exercise. (b) The postulated series linkage between the reflex control of sweating and of the active cutaneous vasodilator system will be critically tested by monitoring the activity of each while thermoregulatory and non-thermoregulatory reflexes are engaged. It is our hypothesis that parallel patterns of response will be seen with thermoregulatory reflexes, but clear differences in pattern between active vasodilator activity and sweating will accompany exercise or baroreceptor reflexes. (c) To find the roles of physical factors in the skin, first we will examine critically the proposition that the cutaneous vascular responses to local heat or cold are an adrenergically mediated event and find out the role of background vasoconstrictor vasodilator activity in the vascular responses to local heating and cooling of the tissue. Second, we will seek to find whether the distensibility of the resistance vessels can play a role in changes in cutaneous vascular resistance which occur with increased arterial blood pressure.