Age-specific modification of local cutaneous vasodilation by capsaicin-sensitive primary afferents.
Age-related changes in neurogenic vasodilation mediated by sensory nerves may alter local skin blood flow (SkBF) responses in older individuals. The purpose of this study was to determine the age-specific modification of cutaneous vasodilation by capsaicin-sensitive primary afferent (CSPA) nerves during local heating. Nine young (18-30 yr), eight middle-aged (40-55 yr), and eight older (65-80 yr) healthy men participated in the experiments. Two local-heating protocols (rapid and slow) were performed before and after 1 wk of capsaicin pretreatment (CP), used to desensitize CSPAs. All temperatures were below those that elicit pain. SkBF was measured with a laser-Doppler imager and indexed to percentage of maximal cutaneous vascular conductance (%CVCmax). CP caused a significant reduction in %CVCmax in the middle-aged and older groups during slow heating (P < 0.05), without affecting %CVCmax in the young group. During rapid heating, CP significantly reduced (53.9 +/- 4.4 vs. 74.4 +/- 7.4% CVCmax, P < 0.05), but did not abolish, the initial sensory nerve-mediated rise in SkBF in the young group. No significant effects of CP on SkBF were observed during rapid heating in the middle-aged or older groups. These results indicate that, with advanced age, CSPA activity is more important to the maximal SkBF response during prolonged local heating, whereas it has a reduced role in the initial SkBF peak elicited by rapid local heating. In summary, CSPA activity contributes modestly to the overall SkBF response to local heating in an age-specific manner.
Noll Physiological Research Center, The Pennsylvania State University, PA 16802-6900, USA. tam275@psu.edu
Thayne A
TA
Munce
W Larry
WL
Kenney
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001369:Axons / Q000187:drug effects / Q000502:physiology; D002211:Capsaicin / Q000494:pharmacology*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D017078:Laser-Doppler Flowmetry; D008297:Male; D008875:Middle Aged; D009475:Neurons, Afferent / Q000187:drug effects*; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D012867:Skin / Q000098:blood supply* / Q000187:drug effects / Q000294:innervation*; D015595:Skin Aging / Q000502:physiology*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D002211:Capsaicin