Structure of the myenteric plexus in the sphincters of cat gastro-intestinal tract. III. Character and distribution of the dense-core vesicles in the axonal varicosities.

Attempts at differentiating the axonal varicosities and the vesicular population in them in the myenteric plexus of the gastro-intestinal tract, result from the participation of these structures in the metabolism of various transmitters. The present work studies the spatial distribution of the populations of dense-core vesicles in the different axonal varicosities in the myenteric plexus of the sphincters of cat gastro-intestinal tract. It is found that the axonal varicosities are characterized by a definite number of populations of dense-core vesicles and by their respective densities. Moreover, each group of varicosities has features common for the sphincters studied and at the same time characteristics observed in only one sphincter. The changes in the densities of the different populations of dense-core vesicles in the groups of axonal varicostities after reserpine treatment suggest their connection with different transmitter systems.