Segmental vascular reactivity subsequent to sympathectomy

¹ Department of Physiology, College of Medicine, State University of Iowa, Iowa City, Iowa

The effect of sympathectomy on the vascular bed of the dog was studied by analyzing segmental resistance changes occurring in response to intra-arterial injections of epinephrine and norepinephrine. The results indicate that the increase in total vascular bed reactivity is caused by sensitization of only the small vessel and venous segments. In an attempt to test the possibility that vascular smooth muscle develops supersensitivity in a manner similar to that which causes skeletal muscle supersensitivity, experiments were done on dogs which received intravenous injections of norepinephrine (0.5 µg/kg) every 8 hr for 2 weeks following sympathectomy. This procedure resulted in an increase in sensitivity of the arterial and venous segments in both the control and sympathectomized legs. Since this behavior was seen in both the denervated and innervated vascular beds no definite conclusions could be reached.