Participation of angiotensin II in presser response and norepinephrine release to spinal nerve stimulation in pithed rats

Experiments were carried out to examine whether endogenous angiotensin II ( A-II) is involved in the regulation of release of norepinephrine (NE) elici ted by the stimulation of spinal sympathetic nerves in pithed rats. It was assessed in terms of the alterations in concentrations of arterial blood pl asma A-II and NE elicited by nerve stimulation (5 Hz, 50 V, 1 msec for 45 s ) in pithed rats under vehicle or captopril (3 mg/kg, i.v.) treatment. Comp arative study with pentobarbital anesthetized rats showed that pithing rats have the characteristics of lower basal blood pressure and lower NE level, whereas they have higher basal A-II level. In pithed rats treated with veh icle, presser response to nerve stimulation was accompanied by increases in both A-II and NE level. In rats treated with captopril, the nerve stimulat ion caused about 40% lower increases in presser response and NE level than those observed in rats treated with vehicle. These results suggest that the sympathetic nerve-induced NE release is facilitated by endogenous A-II in pithed rats, and that captopril exerts its inhibitory effect on the presser response to nerve stimulation through the suppression of this interaction.