AN INVESTIGATION OF EFFECTS OF ANGIOTENSIN ON RELEASE OF NEUROHUMORAL TRANSMITTERS AT MOTOR ADRENERGIC AND CHOLINERGIC NERVE TERMINALS

On the sciatic nerve‐gastrocnemius‐soleus muscle preparation of the cat, angiotensin (1–5 μg/kg, i.v.) potentiated the twitch response to maximal and submaximal stimulation of the sciatic nerve and produced partial reversal of an incomplete tubocurarine blockade. These actions could not be explained in terms of increased acetylcholine release since they were not seen in isolated motor nerve‐striated muscle preparations and were probably secondary to the cardiovascular actions of angiotensin. Blockade of conduction in the postganglionic cholinergic nerves in the guinea‐pig isolated ileum preparation by cooling or anoxia antagonized the response of this tissue to angiotensin. These procedures left the response to exogenous acetylcholine unchanged though they removed the cholinergic component of the response to angiotensin which is known to be present in this tissue. No evidence of increase in catecholamine output could be found in preparations of guinea‐pig and rabbit vasa deferentia or rabbit duodenum responding to submaximal stimulation of their adrenergic nerves. It is concluded that angiotensin has no direct action on the stores of neurohumoral transmitter at motor, postganglionic cholinergic or postganglionic adrenergic nerves and that its known acetylcholine releasing action in the isolated ileum results from stimulation of the ganglia. 1968 Royal Pharmaceutical Society of Great Britain