Fig. 1.

Protocol for part 1. Four forearm skin sites were prepared with microdialysis fibers local cooling/heating probe holders and laser-Doppler probes. Sites 2 and 4 were previously treated with bretylium tosylate (BT). All sites were perfused with saline for 10 min for baseline measurements. At 10 min, a 3-min bout of whole body cooling (WBC) was performed to test the adequacy of the BT blockade. Sites 3 and 4 changed to perfusion with N^G-nitro-l-arginine methyl ester (l-NAME). This combination yielded an untreated control (site 1), a site with vasoconstrictor nerve block (site 2), a site with nitric oxide (NO) synthase (NOS) inhibition (site 3), and a site with a combination of vasoconstrictor nerve blockade and NOS inhibition (site 4). l-NAME was infused for 50 min, and then local skin temperature (T_loc) at all four sites was raised from 33 to 40°C at 0.1°C/min and held at 40°C for 10 min. The perfusate was then changed to sodium nitroprusside (SNP), and T_loc was increased to 42°C to attain maximal vascular conductance levels. SLH, slow local heating; T_skin, skin temperature; N/A, not applicable.