Regional influence of nitric oxide on cutaneous vasodilatation and sweating during exercise-heat stress in young men.

While it is established that nitric oxide synthase (NOS) is an important modulator of forearm cutaneous vasodilatation and sweating during an exercise-heat stress in young men, it remains unclear if regional differences exist in this response. In 15 habitually active young men (24 ± 4 (SD) years), cutaneous vascular conductance (CVC) and local sweat rate (LSR) were assessed at three body regions. On each of the dorsal forearm, chest and upper-back (trapezius), sites were continuously perfused with either (1) lactated Ringer solution (control) or (2) 10 Mm Nω -nitro-l-arginine (l-NNA, NOS inhibitor), via microdialysis. Participants rested in the heat (35°C) for ∼75 min, followed by 60 min of semi-recumbent cycling performed at a fixed rate of heat production of 200 W m-2 (equivalent to ∼42% V ̇ O 2 peak ). During exercise, the chest and upper-back regions showed higher CVC and LSR responses relative to the forearm (all P < 0.05). Within each region, l-NNA attenuated CVC and LSR relative to control (all P < 0.05). However, the NOS contribution was not different across regions for the rate of change and plateau for CVC or for the LSR plateau (all P > 0.05). Conversely, there was a greater NOS contribution to the rate of change for LSR at the chest relative to the forearm (P < 0.05) with a similar trend for the back. In habitually active young men, NOS-dependent cutaneous vasodilatation was similar across regions while the NOS contribution to LSR was greater on the chest relative to the forearm. These findings advance our understanding of the mechanisms influencing regional variations in cutaneous vasodilatation and sweating during an exercise-heat stress.