The Role of Nitric Oxide, Acetylcholine, and Vasoactive Intestinal Peptide on Skin Blood Flow During In-Vivo Electrical Field Stimulation

• Main Author: Thiebaud, Robert S.
• Format: Others
• Published: BYU ScholarsArchive 2010
• Subjects: Cutaneous circulation; microdialysis; sympathetic; adrenergic; vasodilation; intradermal; nitric oxide synthase; Exercise Science
• Online Access: https://scholarsarchive.byu.edu/etd/2451; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=3450&context=etd

The purpose of this study was to characterize a novel technique to study neurogenic control of cutaneous vasodilation. We monitored skin blood flow (SkBF) during in-vivo electrical stimulation (e-stim) intended to activate cutaneous nerves and used intradermal microdialysis to deliver receptor antagonists to characterize their contribution to cutaneous vasodilation. We examined the role of acetylcholine receptors (RACh), nitric oxide (NO), and vasoactive intestinal peptide receptors (RVIP) on the cutaneous vasodilation induced by e-stim in the absence of the sympathetic adrenergic nervous system. Six men and three women participated in the study. Three intradermal microdialysis probes were placed in the skin of the dorsal side of their forearm. The adrenergic nervous system was eliminated by delivery of a cocktail of phentolamine (0.01 mg/ml), propranolol (1 mM), and BIBP-3226 (10 µM). At one skin site atropine (0.1 mg/ml) was delivered to block RACh. At a second site we blocked nitric oxide synthase (NOS, 10 mM L-NAME) and RACh. Finally at the third site, we blocked RACh, NOS, and RVIP (0.47 mg/ml VIP10-28). The SkBF response to 1 minute stages of graded increases in frequency (0.2, 1, 2, 4, 8, and 32 Hz) at a current of 1.0 ± 0.1 mA was used to generate a stimulus-response curve before and after drug delivery. At skin site 1 RACh blockade decreased the area under curve (AUC) by 4% from 614 ± 279 to 591 ± 331 (p>0.05). Nitric oxide synthase and RACh blockade reduced the vasodilator response to e-stim by 23% from 1036 ± 457 to 801 ± 448 AUC (p>0.05). Combined NOS, RACh, and RVIP blockade reduced the vasodilator response by 48% from 802 ± 412 to 418 ± 268 AUC (p=0.07). RACh blockade had no effect on the vasodilator response to e-stim. However, in these preliminary studies both NOS and RVIP blockade provided some attenuation of the cutaneous vasodilator response associated with e-stim. Additional studies will focus on these two neurotransmitters as this novel method is refined. Advantages of e-stim include activating the sympathetic nervous system without activating local and humoral factors and studying neurotransmitters in an in-vivo setting during rest, thermal stress, or exercise.