Immunocytochemical localization of glutamic acid decarboxylase and substance P in the lateral cervical nucleus: a light and electron microscopic study in the cat.

Using immunocytochemical technique, the light and electron microscopic localization of substance P and glutamic acid decarboxylase (GAD) immunoreactivity in the feline lateral cervical nucleus (LCN) has been investigated. A dense substance P labeling, confined mainly to boutons contacting dendritic profiles, was demonstrated in the ventromedial part of the LCN. GAD-positive boutons, frequently in contact with cell bodies, were found scattered throughout the nucleus. The results suggest that gamma-aminobutyric acid is an inhibitory transmitter in the LCN. The role of the substance P is unclear. Its distribution, however, supports the concept of a separate function of the ventromedial part of the LCN.