IMMUNOHISTOCHEMICAL DETECTION OF GLUTAMATE IN RAT VAGAL SENSORY NEURONS

Vagal primary afferent neurons have their cell bodies located in the n odose (inferior) and jugular (superior) vagal ganglia and send termina ls into the nucleus tractus solitarii (NTS) which lies in the dorsomed ial medulla. The presence of glutamate (Glu)-containing neurons in the rat nodose ganglion was investigated using immunohistochemistry. Glu- immunoreactivity on nodose sections was found in neuronal perikarya an d nerve fibers, but not in non-neuronal elements such as Schwann cells and satellite cells. Both immunoreactive and non-immunoreactive gangl ion cells were observed. The immunoreactive ganglion cells amounted to about 60%? of the nodose population. No specific intraganglionic, loc alization was observed for the non-immunoreactive cells. Immunoreactiv e perikarya were slightly smaller than the non-immunoreactive ones, bu t no relationship was found between size and staining intensities of i mmunoreactive neurons. The present data indicate that immunodetectable Glu is present in a large population of vagal afferent neurons. They therefore add to a growing body of evidence suggesting that Glu may be the main neurotransmitter released by vagal afferent terminals within the nucleus tractus solitarii. (C) 1997 Elsevier Science B.V.