Immunocytochemical localization of glutamate containing neurons in the ventrolateral medulla oblongata and the nucleus tractus solitarius of the rat.

Using antisera raised against excitatory neurotransmitter glutamate fixed to carrier proteins and purified by affinity chromatography, localization of glutamate in the ventrolateral medulla oblongata and the nucleus tractus solitarius of the rat was studied. Within the rostral portion of the ventrolateral medulla, glutamate-like immunoreactive neurons were found in the lateral wing of the raphe magnus and in the region of the paragigantocellular reticular nucleus. In the caudal portion of the ventrolateral medulla, glutamate-positive neurons were clustered within the nucleus reticularis lateralis and a lesser number of stained neurons were scattered in the region around this nucleus. Glutamate-immunoreactive neurons were found in the nucleus tractus solitarius at the level of the area postrema. They were densely distributed especially in the medial subdivision of the nucleus whereas other subdivisions contained considerable glutamate positive cells. These results provide immunohistochemical evidence for the presence of glutamate-containing neurons in the ventrolateral medulla oblongata and the nucleus tractus solitarius of the rat.