Light microscope study of the coexistence of GABA-like and glycine-like immunoreactivities in the spinal cord of the rat.

The distributions of GABA-like and glycine-like immunoreactivities in the rat spinal cord were compared by using postembedding immunohistochemistry on semithin sections. In laminae I, II, and III, the proportions of GABA immunoreactive cells were 28%, 31%, and 46%, respectively, whereas for glycine immunoreactive cells the proportions were 9%, 14%, and 30%. Nearly all of the glycine immunoreactive cells in this area were also immunoreactive with the anti-GABA antiserum. In lamina II, some Golgi-stained islet cells were glycine immunoreactive, whereas others were not. Immunoreactive cell bodies were also present in the remainder of the grey matter. Some of these reacted with anti-GABA or antiglycine antiserum; others showed immunoreactivity with both antisera. Immunoreactive axons were found in the ventral and lateral funiculi of the white matter. Many large axons reacted with antiglycine antiserum, whereas GABA-immunoreactive axons were mostly of small diameter. Some large and small axons showed both types of immunoreactivity. These results suggest that the inhibitory neurotransmitters GABA and glycine coexist within cell bodies and axons in the rat spinal cord.