Abstract

An isolated preparation of the rabbit pulmonary artery with its pre- and postganglionic vasoconstrictor motor innervation has been developed. Pre- and postganglionic neurones may be separately stimulated electrically. A two-chamber tissue bath permitted the actions of drugs on the sympathetic ganglia and post-ganglionic sites to be separately and quantitatively observed. Tetraethylammonium chloride has actions both on the ganglia and postganglionic effector endings. The median effective ganglion blocking dose is 27.4 ± S.E. 6.4 µg/ml. At approximately twice this concentration the vascular muscle response to postganglionic, but not to direct muscle stimulation, is increased. Studies with helical strips of rabbit pulmonary artery reveal that this increase may be accounted for by an increased muscle sensitivity to l-norepinephrine, although there is some evidence of increased transmitter release. Larger doses of TEA increase the muscle response to direct submaximal stimulation.