Neural regulation of vascular tone and cold induced vasoconstriction in human finger skin

Finger skin blood flow was measured by a laser Doppler during control conditions, after neural blockade at the finger base by prilocaine and after localized anaesthesia of the skin by lidocaine introduced iontophoretically into the finger skin. Vasoconstriction was achieved by local cooling of the finger and by iontophoretic administration of norepinephrine during the described three conditions. Compared to the control condition, blood flow increased after nerve block at the finger base but even more after local skin anaesthesia. This additional increase in blood flow after local application of lidocaine indicates that finger skin vascular tone is partly dependent on local reflexes. Vasoconstriction on local cooling was preserved after nerve blockade at the finger base but inhibited after local skin anaesthesia by iontophoresis of lidocaine. This inhibition was not due to paralysis of the vessel wall since vasoconstriction to norepinephrine was preserved. Thus, vasoconstriction in response to local cooling is mediated by local reflexes.