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

Aims Transdermal iontophoresis in combination with laser Doppler fluxm etry (LDF) are useful techniques for examining dermal microcirculatory responses to different vasodilators. Differences in skin and microcir culation structure could influence the recorded baseline flux, and the observed vasodilatation. To examine this we compared baseline flux an d the response of microvascular blood flow to a single vasodilator, ac etylcholine, at sites in the forearm and hand. Methods Baseline microc irculation flow was recorded by LDF in a temperature controlled labora tory. The change in flux with iontophoresis of identical doses of acet ylcholine, 159 mu A for 40 s, was recorded at 12 different sites in th e forearm and hand in 10 female and 3 male subjects. Results Baseline flux patterns and the vasodilatation to identical periods of iontophor esis of acetylcholine were site dependent. Palmar sites showed a highe r baseline flux, but no vasodilatation to iontophoresis of acetylcholi ne. In contrast the volar forearm, dorsal hand and finger sites showed lower site-dependent baseline flux, but did vasodilate. Conclusions P atterns of baseline flux are specific to sites on the hand and forearm reflecting differences in underlying microvascular structure. The vas odilatation to transdermal delivery of acetylcholine is also site depe ndent, but differences in skin structure may be more important than th e underlying microvasculature in determining the response.