Postvagotomy degeneration of the dog stomach smooth muscles was studied using an electron microscope. By one week after complete vagotomy, many preganglionic axons in both Auerbach's and Meissner's plexus had degenerated. Subsequently, the affected smooth muscles associated with disintegrated axons showed various types of degenerative changes, and such occurred markedly 2 to 6 weeks after vagotomy. These changes included:
loss of electron density in the intercellular matrix and the cytoplasm of muscle cells due to edematous swelling ; vacuolar dilatation of both endoplasmic reticulum and mitochondria ; lipid accumlation in the cytoplasm ; and lysis of myofilaments. Four or more weeks after vagotomy, necrotic smooth muscle cells and cellular debris considerably increased in the two muscle layers.Increased permeability of endothelial cells and openings of endothelial junctions that induced an extravascular infiltration of fibrin resulted in fibrinoid necrosis of the capillary wall and smooth muscles. Eight weeks after vagotomy, these changes were less frequently observed in the two muscle layers where thete was an increase in the number of both fibroblasts and macrophages in active forms, and which were associated with an increased proportion of attenuated muscle cells. Possible mechanisms of these degenerative changes were discussed.It was emphasized that on occasion the considerable functional changes of the stomach muscles might be induced by damage to both smooth muscle cells and the microvascular system when the stomach was completely denervated.