Neurohumoral Control of Blood Vessels

Abstract

Renkin and Rosell (1962) reported specific sites for eNS control of arterioles and precapillary sphincters. Gootman et al. (1973) showed that all segments of precapillary microvessel and sphincter can respond to eNS stimulation. However, precapillary arterioles (metarterioles) and precapillary sphincters failed to respond to supramaximal stimulation of paravascular nerves in rat mesentery (Furness and Marshall, 1974). In the present experiment, responses of the larger consecutive segments of arterioles (Art) were measured during electrical stimulation of vasoactive eNS sites in nine rats with chronically implanted unipolar electrodes. Currents were for maximal constriction or lumen closure of precapillary sphincter (Pc sph) and/or immediately preceding metarteriole (Met): 0.08–0.15 mA (10- strains, 100-μs pulses 5–100 Hz). Under pentobarbital sodium (25 mg/kg, i.m.), responses of microvessels were measured by image-splitting methods in mesoappendix in six rats,cremaster in two rats, and both in one. In all experiments, stimulation resulted in blood pressure elevation (112.6 ± 17.6% to 165.2 ± 18.5% mm Hg, mean and standard deviation) and constriction of three consecutive segments of precapillary vessels and sphincter: 10.5 ± 9.3% for Artl (43.4 ± 8.8 μm, ID), 40.0 ± 26.6% for All (20.4 ± 3.7 μm, ID), 70.3 ± 24.6% for Met (11.4 ± 3.7 μm, ID), and 75.5 ± 20.2% for Pc sph (7.5 ± 1.3 μm, ID). Stimulation characteristically increased (×3) vasomotor activity of Pc sph and Met, but infrequently increased that of larger arterioles at currents used.