Sympathetic stimulation and small artery constriction

Abstract

The outflow of blood from a digital artery of the dog hind paw to the atmosphere was recorded to determine if this outflow could be stopped completely in response to high-frequency sympathetic stimulation. In 5 of the 12 dogs studied, the outflow was stopped completely by stimulation of the peripheral stump of the sciatic nerve at 15 v, 20–25 stimuli/sec, a pulse duration of 5 msec, and a total stimulation period of approximately 60 sec. In those experiments in which complete cessation of flow was achieved, pressure pulsations were obliterated from the digital artery pressure tracing and the mean pressure decreased to atmospheric pressure levels. In the remaining dogs, in which flow was not stopped, pressure pulsations were evident in the digital artery pressure tracings throughout the stimulation period and mean pressures decreased to values ranging from 15 to 2 mm Hg.