Distribution of histamine and substance P in the wall of the dog's digestive tract / by W.W. Douglas [and others].

Date:
[1951?]
Catalogue details

Licence: In copyright

Credit: Distribution of histamine and substance P in the wall of the dog's digestive tract / by W.W. Douglas [and others]. Source: Wellcome Collection.

    12/16 (page 174)
    stimulating substance. In the intestinal wall of the horse most of the sub¬ stance P was found in the muscle layer and not, as in the dog’s intestine, in the mucosa. Here the activity was maximal in extracts from m. mucosae. The active substance of our extracts cannot have been enteramin because of its strong stimulating effects on the atropinized guinea-pig’s and rabbit’s gut. Nevertheless, our extracts probably contained enteramin, which may have augmented the action of substance P and so influenced the quantitative aspect of our results. If, as suggested by Euler, substance P is responsible for the spontaneous rhythmic movements of the intestine which are not abolished by either atropine or mepyramine, its distribution may be related to the degree of this activity in different species and in the different layers of the intestinal wall. In that case the m. mucosa of the dog should exhibit a high degree of spontaneous activity. Apart from the movements of the villi such activity has been described for the large masses of the m. mucosae of the dog’s small intestine by King & Church (1923), and by King & Kobinson (1944). In man the muscle is thought to be responsible for a great deal of the intestinal motility. The fact that this layer contains two very active smooth muscle- stimulating substances in high concentration, shows that from the auto- pharmacological point of view this layer, at least in dogs, is endowed with the requirements for such high activity. Histamine and substance P are not the only smooth muscle-stimulating substances found in the wall of the digestive tract. We have already referred to enteramin, but the wall of the digestive tract contains, in addition, choline and acetylcholine which have been extracted from the m. externa and from the mucosa. According to Abderhalden & Paffrath (1925) the mucosa is the main source for the choline of the intestinal wall. No systematic survey has been made of the distribution of acetylcholine in the different layers of the intestinal wall. But the distribution of the enzyme for synthesis of acetyl¬ choline, the choline acetylase, is known (Feldberg & Lin, 1950); it probably runs parallel to the acetylcholine content. In some respects the distribution ft of the choline acetylase resembles that of histamine and substance P. There : is more in the mucosa than in the m. externa; in the duodenum it accounts v for 70%, in the ileum, 60%. On the other hand, there is this difference, the k concentration of choline acetylase is higher in the gl. mucosae than in the > m. mucosae, and there is none in the submucosa. A great deal is known about the specific secretory, absorptive and motor o activities of the different hormones found in the gastric and intestinal mucosa; i but this is not so with these other more generally distributed and highly active j substances, histamine, substance P, enteramin, choline and acetylcholine, j Yet until their activities are more clearly established, we cannot identify any | of them for certain as the physiological stimuli for any of the diverse functions } of the wall of the digestive tract.