EFFECT OF EXTRINSIC DENERVATION ON ENDOGENOUS NORADRENALINE AND [3H]NORADRENALINE UPTAKE IN THE GUINEA-PIG COLON

—The concentration of noradrenaline was studied in the proximal colon of the guinea-pig, where intrinsic adrenergic neurons are present in the myenteric plexus. The noradrenaline content is higher than in the myenteric plexus of other parts of the alimentary tract. After extrinsic denervation of the colon, about 25% of the original content of noradrenaline remains in the myenteric plexus, and this is considered to be the amount due to the intrinsic adrenergic neurons; also a substantial noradrenaline uptake activity is still detectable. On the other hand, in the part of the wall formed by circular muscle-submucous plexus-submucosa-mucosa, which has control values close to those of the ileum, extrinsic denervation causes a nearly complete depletion of noradrenaline. This is considered as evidence that the intrinsic neurons do not project to the circular musculature, or the submucosa or mucosa.