THE PRESENCE IN SCIATIC NERVE OF MATERIAL THAT RELEASES ACETYLCHOLINE

¹ Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut

Extracts of sciatic nerve caused a slow contraction of a fresh strip of guinea-pig ileum. This action was blocked by atropine. Activity was concentrated in the particulate fraction of the nerve, and the nerve bundle contained a higher concentration of activity than the nerve sheath.

The extract had no effect on a strip of ileum that had been kept at room temperature for 24 hours or at 4°C for 3 days. The extract also failed to act upon the ileum bathed in Tyrode solution in which air was replaced with nitrogen. Morphine and HC-3 prevented the action of the extract; hexamethonium, tetraethylammonium, and cocaine did not. The extract was shown to increase the release of acetylcholine from the ileum.

It is concluded that the active substance in the extract causes a slow contraction of the ileum by releasing acetylcholine from the nerve endings of the cholinergic network in the wall of the ileum. It is suggested that atropine prevents the action of the extract not only by blocking the receptors for acetylcholine in the muscle cells but by depleting the stores of acetylcholine in the nerve endings.