The role of sensory nerves in the cutaneous vasoconstrictor response to local cooling in humans

Current data suggest an involvement of both sympathetic vasoconstrictor nerves and sensory nerves in the response to local cooling (LC), but it is not clear whether there is a direct relationship between them; thus, we tested whether sensory nerves link LC to vasoconstrictor nerve function. A total of 6 subjects participated. Skin blood flow was monitored by laser‐Doppler flowmetry, and LC was achieved with Peltier heater/cooler probe holders. Four sites were slowly cooled from 34 to 29 °C at −0.33 °C · min −1 : untreated control; topical local anesthesia (LA); bretylium tosylate (BT); and with both LA and BT. Sites treated with LA produced pronounced a vasodilation early in LC (64±55% LA only; 42±14% LA and BT; P≤0.05) that was absent in the control and BT only treated sites (5±6 and 6±8%; P≥ 0.05). There were significant reductions in CVC at all sites after 15 min of LC. Nevertheless, CVC at the control and LA only treated sites decreased (P≤ 0.05 pre cooling) by −39±4 and −46±8 %, which was significantly (P≤ 0.05 sites 1 and 2 vs. sites 3 and 4) more than at the sites treated with BT and BT and LA, (–26±8 and −22±6%, respectively; P ≤ 0.05 pre cooling). We take this as good evidence that sensory nerves are involved early in the vasoconstrictor response to LC, but are not necessary for the longer‐term vasoconstriction due to vasoconstrictor nerves. Supported by an NIH grant ‐ HL059166