Role of sympathetic nerves in the vascular effects of local temperature in human forearm skin.

The role of adrenergic nerve function in the cutaneous vascular response to changes in local skin temperature in the human forearm was examined using three protocols: 1) blocking release of norepinephrine presynaptically by local iontophoresis of bretylium (BT), 2) altering background adrenergic tone by changing whole body skin temperature, and 3) blocking cutaneous nerves by proximal infiltration of local anesthetic. Forearm skin blood flow was measured by laser-Doppler flowmetry (LDF) and cutaneous vascular conductance (CVC) was calculated as LDF/blood pressure. In protocol 1, local cooling (29 degrees C) elicited a rapid and sustained fall in CVC at control sites (-43 +/- 8%) in contrast to a biphasic response at BT-treated sites, consisting of an initial vasodilation followed by a vasoconstriction (percent change CVC = 28 +/- 13 and -34 +/- 18, respectively). Local warming (39 degrees C) increased CVC at control and at BT-treated sites by 331 +/- 46 and 139 +/- 31%, respectively. In protocol 2, at a neutral, cool, or warm whole body skin temperature, local cooling (29 degrees C) elicited similar reductions in CVC (-34 +/- 8, -29 +/- 5, and -30 +/- 4%, respectively), and local warming (38 degrees C) produced similar increases in CVC (89 +/- 15, 85 +/- 21, and 74 +/- 22%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)