Effects of atropine and L-NAME on cutaneous blood flow during body heatingin humans

We sought to investigate further the roles of sweating, ACh spillover, and nitric oxide (NO) in the neurally mediated cutaneous vasodilation during bo dy heating in humans. Six subjects were heated with a water-perfused suit w hile cutaneous blood flow was measured with a laser-Doppler flowmeter. Afte r a rise in core temperature (1.0 +/- 0.1 degrees C) and the establishment of cutaneous vasodilation, atropine and subsequently the NO synthase inhibi tor N-G-nitro-L-arginine methyl ester (L-NAME) were given to the forearm vi a a brachial artery catheter. After atropine infusion, cutaneous vascular c onductance (CVC) remained constant in five of six subjects, whereas L-NAME administration blunted the rise in CVC in three of six subjects. A subseque nt set of studies using intradermal microdialysis probes to selectively del iver drugs into forearm skin confirmed that atropine did not affect CVC. Ho wever, perfusion of L-NAME resulted in a significant decrease in CVC (37 +/ - 4%, P < 0.05). The results indicate that neither sweating nor NO release via muscarinic receptor activation is essential to sustain cutaneous dilati on during heating in humans.