NOS inhibition and cutaneous vasodilation during local heating

We compared the physiological efficacy of 10 mM L‐NAME and 10 mM L‐NMMA in blunting nitric oxide mediated dilation associated with local skin heating. Fifteen subjects were instrumented with an intradermal microdialysis probe in the dorsal forearm skin and perfused with saline while waiting for the trauma induced dilation to dissipate. Local skin temperature was controlled via a computer regulated peltier unit located directly on top of the microdialysis probe and set at 34°C. Skin blood flow (SkBF, laser Doppler velocemetry) was recorded directly over the microdialysis probe. The probe was perfused with either normal saline (n=3), 10 mM L‐NAME (n=6) or 10 mm L‐NMMA (n=6) for 60 min. Local skin temperature was elevated to 42°C (0.1 °C/s) and held for 50 min. The biphasic SkBF response to local heating was described by an initial peak SkBF, a nadir in SkBF following the peak, and a plateau in SkBF at the end of the 50 min heating period. The SkBF response was expressed as a % of the baseline SkBF measured at a local skin temperature of 34°C. The data are summarized in the following table:10 mM L‐NAME produces a general reduction in the peak, nadir and plateau SkBF response during local heating. 10 mM L‐NMMA also reduces the plateau SkBF response to local heating but does not alter the initial vasodilator peak or the nadir SkBF. We conclude that 10 mM L‐NAME and 10 mM L‐NMMA have similar potencies in blocking nitric oxide mediated dilation in human skin. However, L‐NAME has some additional influence on the SkBF response to local heating possibly via its anti‐muscarinic action. Funded by NIH HL39818.