Effects of capsaicin on cutaneous vasodilator responses in humans
- 36 Downloads
The neurovascular responses to noxious electrically evoked axon reflex (EAR) stimulation and iontophoretic application of endothelium-dependent [acetylcholine (ACh)] and independent [sodium nitrite (NaNO2)] vasodilator substances were examined in human forearm skin using laser Doppler flowmetry, before and after repeated topical applications of the neurotoxin capsaicin (chronic capsaicin pre-treatment). Following 3 or 4 days of capsaicin pre-treatment the normal vasodilator response to acute application of capsaicin was significantly reduced as was the EAR response. There were, however, no significant changes in the vasodilator responses to either ACh or NaNO2, suggesting that the neurogenic axon reflex is in series with the endothelial and microvascular smooth muscle mechanisms of vasodilatation. Recovery of normal EAR occurred within 2–4 weeks of cessation of capsaicin pre-treatment.
KeywordsCapsaicin Laser Doppler Flowmetry Sodium Nitrite Vasodilator Response Human Forearm
Unable to display preview. Download preview PDF.
- N. Jansco, A. Jansco-Gabor and J. SzolcsanyiDirect evidence for neurogenic inflammation and its prevention by denervation and by pretreatment with capsaicin. Br. J. Pharmacol. Chemother.31, 138–151 (1967).Google Scholar
- R. G. D. Roberts, R. A. Westerman, R. E. Widdop, R. R. Kotzmann and B. Carter,Effects of capsaicin on cutaneous axon reflex dilatation in man. Proc. Aust. Physiol. Pharmacol. Soc.18, 95P (1987).Google Scholar
- R. G. D. Roberts, R. A. Westerman and P. KentAcute neurovascular responses to TENS and capsaicin. Proc. Aust. Physiol. Pharmacol. Soc.19, 184P (1988).Google Scholar
- R. A. Westerman, R. G. D. Roberts, R. R. Kotzmann, D. A. Westerman, C. Delaney, R. E. Widdop and B. Carter,Effects of topical capsaicin on normal skin and affected dermatomes in herpes zoster. Clin. Exp. Neurol.25, 71–84 (1989).Google Scholar
- W. W. Douglas and J. M. Ritchie,The excitatory action of acetylcholine on cutaneous non-myelinated fibres. J. Physiol. (Lond.)150, 501–514 (1960).Google Scholar
- R. A. Westerman, R. E. Widdop, J. Hannaford, C. Hogan, R. Roberts and P. Zimmet,Non-invasive tests of neurovascular function Clin. Exp. Neurol.24, 129–137 (1988).Google Scholar