An investigation into variability in microvascular skin blood flow and the responses to transdermal delivery of acetylcholine at different sites in the forearm and hand

Abstract

Transdermal iontophoresis in combination with laser Doppler fluxmetry (LDF) are useful techniques for examining dermal microcirculatory responses to different vasodilators. Differences in skin and microcirculation structure could influence the recorded baseline flux, and the observed vasodilatation. To examine this we compared baseline flux and the response of microvascular blood flow to a single vasodilator, acetylcholine, at sites in the forearm and hand. Baseline microcirculation flow was recorded by LDF in a temperature controlled laboratory. The change in flux with iontophoresis of identical doses of acetylcholine, 150 microA for 40 s, was recorded at 12 different sites in the forearm and hand in 10 female and 3 male subjects. Baseline flux patterns and the vasodilatation to identical periods of iontophoresis of acetylcholine were site dependent. Palmar sites showed a higher baseline flux, but no vasodilatation to iontophoresis of acetylcholine. In contrast the volar forearm, dorsal hand and finger sites showed lower site-dependent baseline flux, but did vasodilate. Patterns of baseline flux are specific to sites on the hand and forearm reflecting differences in underlying microvascular structure. The vasodilatation to transdermal delivery of acetylcholine is also site dependent, but differences in skin structure may be more important than the underlying microvasculature in determining the response.