Effect of local heating and vasodilation on the cutaneous venoarteriolar response.

The cutaneous venoarteriolar response (CVAR) is a local non-adrenergic vasoconstrictor reflex that is engaged via increases in local transmural pressure. The purpose of this study was to determine if local temperature alters the vasoconstrictor ability of the CVAR. Twelve (5 male, 7 female) subjects performed a CVAR maneuver at local temperatures of 30+/-1, 34, 38, and 42 degrees C. CVAR was also engaged after vasodilation via intradermal perfusion of sodium nitroprusside or the attenuation of local heating-induced vasodilation via intradermal perfusion of N(G)-nitro-L: -arginine methyl ester (L: -NAME) in five subjects (2 male, 3 female). CVAR was elicited by rapid cuff inflation to 45mmHg proximal to two dorsal forearm sites for 2 min in both protocols. Local heating caused a progressive increase in skin blood flow (8+/-1, 18+/-4, 43+/-11, and 78+/-2% maximal skin blood flow for 30+/-1, 34, 38, and 42 degrees C, respectively). Engagement of the CVAR decreased skin blood flow by 53+/-2, 57+/-3, and 51+/-4%, for 30+/-1, 34, and 38 degrees C, respectively. In contrast, local heating to 42 degrees C significantly attenuated the CVAR (16+/-11 %). Local administration of sodium nitroprusside during neutral temperature and L: -NAME during local heating also significantly attenuated the vasoconstrictor response of the CVAR by 27+/-8 and 38+/-4%, respectively. These data indicate that CVAR is attenuated at high (42 degrees C) local skin temperatures and that this attenuation is likely due to an effect of both local heating-induced vasodilation and a direct temperature effect.