Cholinergic mechanisms of cutaneous active vasodilation during heat stress in cystic fibrosis.
To test the hypothesis that cutaneous active vasodilation in heat stress is mediated by a redundant cholinergic cotransmitter system, we examined the effects of atropine on skin blood flow (SkBF) increases during heat stress in persons with (CF) and without cystic fibrosis (non-CF). Vasoactive intestinal peptide (VIP) has been implicated as a mediator of cutaneous vasodilation in heat stress. VIP-containing cutaneous neurons are sparse in CF, yet SkBF increases during heat stress are normal. In CF, augmented ACh release or muscarinic receptor sensitivity could compensate for decreased VIP; if so, active vasodilation would be attenuated by atropine in CF relative to non-CF. Atropine was administered into skin by iontophoresis in seven CF and seven matched non-CF subjects. SkBF was monitored by laser-Doppler flowmetry (LDF) at atropine treated and untreated sites. Blood pressure [mean arterial pressure (MAP)] was monitored (Finapres), and cutaneous vascular conductance was calculated (CVC = LDF/MAP). The protocol began with a normothermic period followed by a 3-min cold stress and 30-45 min of heat stress. Finally, LDF sites were warmed to 42 degrees C to effect maximal vasodilation. CVC was normalized to its site-specific maximum. During heat stress, CVC increased in both CF and non-CF (P < 0.01). CVC increases were attenuated by atropine in both groups (P < 0.01); however, the responses did not differ between groups (P = 0.99). We conclude that in CF there is not greater dependence on redundant cholinergic mechanisms for cutaneous active vasodilation than in non-CF.
Kellogg
D L
DL
Geriatric Research, Education, and Clinical Center, Department of Veterans Affairs, South Texas Veterans Health Care System, Audie L. Murphy Memorial Veterans Hospital Division, San Antonio, TX 78229, USA. kelloggd@uthscsa.edu
Hodges
G J
GJ
Orozco
C R
CR
Phillips
T M
TM
Zhao
J L
JL
Johnson
J M
JM
D000109:Acetylcholine / Q000502:physiology*; D000328:Adult; D001285:Atropine / Q000008:administration & dosage; D003550:Cystic Fibrosis / Q000150:complications / Q000503:physiopathology*; D005260:Female; D018882:Heat Stress Disorders / Q000150:complications / Q000503:physiopathology*; D006801:Humans; D008297:Male; D018727:Muscarinic Antagonists / Q000008:administration & dosage; D012867:Skin / Q000098:blood supply*; D014660:Vasoactive Intestinal Peptide / Q000502:physiology; D014664:Vasodilation / Q000502:physiology*
D018727:Muscarinic Antagonists; D014660:Vasoactive Intestinal Peptide; D001285:Atropine; D000109:Acetylcholine