The Effects of Iontophoresed Vasoactive Drugs on Cutaneus Blood Flow

A non-randomised study to investigate how 6 different vasoactive substances administrated in 5 different concentrations, and with repeated administration affect the cutaneous superficial vessels. The primary aim is to investigate dose-response mechanisms by use of two non-invasive optical measurement technologies. The substances are administrated by iontophoresis using a protocol with a current of 0.02 mA for 600 seconds, at a total electrical charge of 12 mC. Each drug is diluted using sterile water into five concentration (1%, 0.1%, 0.01%, 0.001% and 0.0001%). In the sixth chamber only sterile water will be administrated. An electrode chamber per concentration is attached to the skin of each subject's forearm and each concentration is administrated three times. Only one substance at a time will be administrated. The substances used are: * Acetylcholine - vasodilator (Miochol-E, 10mg/ml, Bausch and Lomb) * Noradrenaline - vasoconstrictor (Noradrenaline, 10mg/ml, Pfizer) * Phenylephrine - vasoconstrictor (Phenylephrine, 10mg/ml, Unimedic) * Atropine - anticholinergic (Atropine, 10mg/ml, Bausch and Lomb) * Neostigmine - acetylcholineesterase inhibitor (Neostigmine, 10mg/ml, Unimedic Pharma) * Dilutor: sterile water (Sterile water, 100 ml, Braun) Iontophoresis protocol: 0.02 mA x 600 seconds x 3 repetitions per drug concentration and localization. Each iontophoretic pulse is preceded by a baseline registration and followed by a 30 minutes wash-out/recovery period. Vascular effects are continuously, non-invasively and indirectly measured using tissue viability imaging (TiVi, cross-polarized diffuse reflectance spectroscopy) and multi-exposure laser speckle contrast imaging (MELSCI). The optical measurement modalities are placed at a distance of approximately 30 cm above the skin surface so that the vascular responses can be measured in three electrode chambers simultaneously for the duration of the test (120 minutes). TiVi settings - 1 image/minute at 6000 x 4000 pixels MELSCI settings - 15.6 frames/second at 1024 x 1000 pixels