Antagonism by Calcium of the Inhibitory Action of Prostaglandin E2on Sympathetic Neuro‐transmission in the Cat Spleen

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Abstract
Experiments were carried out with the isolated, perfused cat spleen and bovine splenic nerve trunk to study the target for prostaglandin E2induced inhibition of noradrenaline release from sympathetic nervss. Increasing the calcium concentration in the medium perfusing the spleeen was found to increase the outflow of noradrenaline to nerve stimulation and to antagonize the inhibitory action of prostaglandin E2on this parameter. Prostaglandin E2did not affect the noradrenaline releasing effect of tyramine. Atropine did not alter the inhibitory effect of prostaglandin E2on noradrenaline release. Prostaglandin E2did not change the amplitude of action potentials in bovine splenic nerves. There is thus no support for a blocking action on nerve conduction. It is concluded that prostaglandin E2may prevent calcium from gaining access to those sites in sympathetic nerve terminals where it promotes secretion of noradrenaline.