title: Transient receptor potential vanilloid type 1 channels contribute to reflex cutaneous vasodilation in humans.
abstract: Mechanisms underlying the cutaneous vasodilation in response to an increase in core temperature remain unresolved. The purpose of this study was to determine a potential contribution of transient receptor potential vanilloid type 1 (TRPV-1) channels to reflex cutaneous vasodilation. Twelve subjects were equipped with four microdialysis fibers on the ventral forearm, and each site randomly received 1) 90% propylene glycol + 10% lactated Ringer (vehicle control); 2) 10 mM l-NAME; 3) 20 mM capsazepine to inhibit TRPV-1 channels; 4) combined 10 mM l-NAME + 20 mM capsazepine. Whole body heating was achieved via water-perfused suits sufficient to raise oral temperature at least 0.8°C above baseline. Maximal skin blood flow was achieved by local heating to 43°C and infusion of 28 mM nitroprusside. Systemic arterial pressure (SAP) was measured, and skin blood flow was monitored via laser-Doppler flowmetry (LDF). Cutaneous vascular conductance (CVC) was calculated as LDF/SAP and normalized to maximal vasodilation (%CVC(max)). Capsazepine sites were significantly reduced compared with control (50 ± 4%CVC(max) vs. 67 ± 5%CVC(max), respectively; P < 0.05). l-NAME (33 ± 3%CVC(max)) and l-NAME + capsazepine (30 ± 4%CVC(max)) sites were attenuated compared with control (P < 0.01) and capsazepine (P < 0.05); however, there was no difference between l-NAME and combined l-NAME + capsazepine. These data suggest TRPV-1 channels participate in reflex cutaneous vasodilation and TRPV-1 channels may account for a portion of the NO component. TRPV-1 channels may have a direct neural contribution or have an indirect effect via increased arterial blood temperature. Whether the TRPV-1 channels directly or indirectly contribute to reflex cutaneous vasodilation remains uncertain.
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, Kansas 66506, USA. bwong@k-state.edu
authors.forename: Brett J
authors.initials: BJ
authors.lastname: Wong
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Fieger
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology; D002211:Capsaicin / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D005542:Forearm / Q000098:blood supply / Q000502:physiology; D006361:Heating / Q000379:methods; D006801:Humans; D008297:Male; D017551:Microdialysis / Q000379:methods; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D012018:Reflex / Q000187:drug effects / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects; D012867:Skin / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism; D050916:TRPV Cation Channels / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D055815:Young Adult
chemical_list: D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; D009599:Nitroprusside; D009569:Nitric Oxide; C071423:capsazepine; D002211:Capsaicin; D019331:NG-Nitroarginine Methyl Ester