Ultrastructure of the Vesicular Component in the Intramural Nervous System of the Guinea-pig's Intestines.

In the present paper, a systematic study of the vesicular component found in the unmyelinated nerve fibers of the intestinal nervous plexus from the serosa to the mucosa of the guinea pig was carried out. This vesicular component containing dense granules with diameters from 300 to 1100 Ä was distinguished from the synaptic vesicles of 100 to 500 Ä. The distribution of granules and vesicles of the myenteric plexus of the duodenum and colon and extraganglion nervous fibers of the mucosa, submocusa and muscularis was studied. These results suggest that the vesicles can be the site of synthesis and storage of the substance P and 5-hydroxytryptamine.