EFFECT OF ANGIOTENSIN ON THE RELEASE OF ACETYLCHOLINE FROM PREGANGLIONIC AND POSTGANGLIONIC NERVE ENDINGS

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Abstract
Angiotensin is known to stimulate the synaptic transmission of the cat superior ganglion and the contraction of the isolated guinea pig ileum; to determine whether these effects could be mediated by a cholinergic mechanism, both preparations were tested for the possible release of acetylcholine by angiotensin. The right cervical ganglion of 12 anesthetized cats was perfused with heparinized cat plasma, and the preganglionic sympathetic trunk was electrically stimulated supramaximally at 10-min intervals. After each stimulation, the acetylcholine content of the effluent was determined by bioassay. Angiotensin, injected intraarterially toward the ganglion in amounts ranging from 0.1 to 100 ng immediately before a stimulation period induced a 30 to 50% increase in acetylcholine output. Most effective doses ranged from 0.5 to 20 ng. Comparable experiments were carried out on coaxially stimulated strips of guinea pig ileum in Krebs solution. The addition of angiotensin, 1 ng/ml, was followed by a 4.3-fold increase in acetylcholine release during the period of contractile stimulation. From these two sets of data, it is concluded that angiotensin exerts a cholinergic action at the preganglionic level in the ganglion and at a postganglionic site in the ileum.

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