Acetylcholine released from cholinergic nerves is involved in heat loss responses of cutaneous vasodilation and sweating. K+ channels are thought to play a role in regulating cholinergic cutaneous vasodilation and sweating, though which K+ channels are involved in their regulation remains unclear. We evaluated the hypotheses that 1) Ca2+-activated K+ (KCa), ATP-sensitive K+ (KATP), and voltage-gated K+ (KV) channels all contribute to cholinergic cutaneous vasodilation; and 2) KV channels, but not KCa and KATP channels, contribute to cholinergic sweating. In 13 young adults (24±5 years), cutaneous vascular conductance (CVC) and sweat rate were evaluated at intradermal microdialysis sites that were continuously perfused with: 1) lactated Ringer (Control), 2) 50mM tetraethylammonium (KCa channel blocker), 3) 5mM glybenclamide (KATP channel blocker), and 4) 10mM 4-aminopyridine (KV channel blocker). At all sites, cholinergic cutaneous vasodilation and sweating were induced by co-administration of methacholine (0.0125, 0.25, 5, 100, and 2000mM, each for 25 min). The methacholine-induced increase in CVC was lower with the KCa channel blocker relative to Control at 0.0125 (1±1 vs. 9±6%max) and 5 (2±5 vs. 17±14%max) mM methacholine, whereas it was lower in the presence of KATP (69±7%max) and KV (57±14%max) channel blocker in comparison to Control (79±6%max) at 100mM methacholine. Further, methacholine-induced sweating was lower at the KV channel blocker site (0.42±0.17mg∙min-1∙cm-2) compared to Control (0.58±0.15mg∙min-1∙cm-2) at 2000mM methacholine. In conclusion, we show that KCa, KATP, and KV channels play a role in cholinergic cutaneous vasodilation, whereas only KV channels contribute to cholinergic sweating in normothermic resting humans.
- potassium channel
- sweat secretion
- Copyright © 2016, American Journal of Physiology - Regulatory, Integrative and Comparative Physiology