Effect of angiotensin and phenoxybenzamine on release of norepinephrine in vessels during sympathetic nerve stimulation

Zimmerman, B. G.; Whitmore, L.

The release of norepinephrine during sympathetic stimulation was determined in experiments involving perfusion of the paw and gracilis muscle at constant flow. During stimulation at 20 c/s a greater increase in concentration of norepinephrine was obtained in the venous effluent of the muscle than in the paw, especially when sampling early after the start of stimulation. One minute later during stimulation, the change in concentration in the paw was greater, but still less thin that in muscle. During infusion of angiotensin intra-arteriatly (0.5-1 [mu]g/min) stimulation at 20 c/s elicited a small but greater release of norepinephrine in the paw but not in muscle. The vasoconstrictor response in the paw tended to be increased, and that in muscle to be decreased at this time. After the intra-arterial administration of phenoxybenzamine (1.5-14 mg) the change in concentration of norepinephrine elicited during sympathetic stimulation in the paw and muscle effluent was greatly increased and the vasoconstrictor response reduced. After the intra-arterial administration of imipramine (10-15 mg) in the paw only, a similar increased release during sympathetic stimulation resulted.