Evidence of a myogenic response in vasomotor control of forearm and palm cutaneous microcirculations. J Appl Physiol 97: 535-539, 2004. First published April 16, 2004 10.1152/japplphysiol.01299.2003.-Previous investigations of autoregulatory mechanisms in the control of skin blood flow suffer from the possibility of interfering effects of the autonomic nervous system. To address this question, in 11 subjects cutaneous vascular responses were measured during acute changes in perfusion pressure (using Valsalva maneuver; VM) before and after ganglionic blockade via systemic trimethaphan infusion. Cutaneous vascular conductance at baseline (CVC base) and during the last 5 s of the VM (CVC VM) were measured from forearm (nonglabrous) and palm (glabrous) skin. During the VM without ganglionic blockade, compared with CVCbase, CVCVM decreased significantly at the palm [0.79 Ϯ 0.17 to 0.55 Ϯ 0.17 arbitrary units (AU)/mmHg; P ϭ 0.002] but was unchanged at the forearm (0.13 Ϯ 0.02 to 0.16 Ϯ 0.02 AU/mmHg; P ϭ 0.50). After ganglionic blockade, VM induced pronounced decreases in perfusion pressure, which resulted in significant increases in CVC VM at both forearm (0.19 Ϯ 0.03 to 0.31 Ϯ 0.07 AU/mmHg; P ϭ 0.008) and palm (1.84 Ϯ 0.29 to 2.76 Ϯ 0.63 AU/mmHg; P ϭ 0.003) sites. These results suggest that, devoid of autonomic control, both glabrous and nonglabrous skin are capable of exhibiting vasomotor autoregulation during pronounced reductions in perfusion pressure. autoregulation; skin blood flow; Valsalva maneuver CUTANEOUS TISSUE HAS RELATIVELY low metabolic requirements, and control of skin blood flow is primary influenced by thermal factors (e.g., local and internal temperatures). Skin blood flow can also be modulated by nonneurally mediated events, one of which may be vascular cutaneous autoregulation. Vascular autoregulation serves to maintain blood flow and nutrient supply when perfusion pressure is altered. In addition, autoregulatory responses attenuate large changes in capillary pressure that otherwise would occur during changes in perfusion pressure (15).Cutaneous blood flow during normothermic conditions is in excess of that required to provide for its metabolic demand. Given this, the requirement to autoregulate blood flow through this vascular bed during relatively small changes in perfusion pressure would be less critical relative to other vascular beds. Such a response is likely advantageous given that precise autoregulation of cutaneous vasculature would oppose thermally induced cutaneous vasoconstriction and vasodilation, which are necessary to maintain temperature homeostasis (21).The venoarteriolar response is an example of a vascular autoregulatory mechanism that has been identified and widely investigated in human skin (3,7,9,13,23). However, the stimulus for this response is a change in venous pressure regardless of whether perfusion pressure changes or remains constant. This response also requires an intact local neural network (3,7,10,13,23), which is in contrast to traditional myogenic vascular autor...