Sites of origin and termination of gastric vagus preganglionic neurons: an HRP study in the rat.

Using the horseradish peroxidase (HRP) method, we studied the relation between sites and forms of gastric vagus preganglionic neurons in the rat and gastric regions on which they project. Fifty microliters of a physiological saline solution containing 3 mg of HRP was injected into 6 different gastric regions: cardia, lesser curvature, pyloric antrum, greatger curvature, ventral corpus and dorsal corpus. After a survival period of 24h, the medulla oblongata was serially sectioned and processed for histochemical demonstration of HRP. In the medulla oblongata, HRP-labeled cells were distributed in 2 regions: (1) in the regions within the dorsal vagus nucleus (DVN); (2) in the regions within the ambiguous complex. The labeled cells in the DVN were observed in every experiment, while ones in the ambiguous complex were only seen in the cardia and lesser curvature experiments. In the ventral corpus experiment the labeled cells were observed dominantly on the left side and in the dorsal corpus experiment dominantly on the right side. The majority of the labeled cells in the ambiguous complex were medium-sized and multipolar in shape, while the majority of ones in the DVN were medium-sized and fusiform in shape.