Distribution of glycine and GABA immunoreactivities in the cochlear nucleus: quantitative patterns of putative inhibitory inputs on three cell types.

Postembedding immunocytochemistry was used to compare the distribution of GABA and glycine immunoreactive labelling in the cochlear nucleus, in particular the number of immunolabeled synaptic boutons apposing the cell body profiles of three major neuronal types. The proportions and absolute numbers of glycine immunoreactive puncta were greatest on fusiform cell body profiles. Glycine immunoreactive puncta also predominated on spherical cell body profiles, although GABA immunoreactive boutons were more abundant than on fusiform cells. Octopus cell body profiles were apposed by the fewest immunoreactive puncta. Puncta colabeled for glycine and GABA were frequently observed on all three cell types. These findings suggest that each major cell type possesses a distinct pattern of glycinergic and GABAergic input, with glycinergic input predominating. Since both tuberculoventral and cartwheel neurons were immunolabeled and are known to project intrinsically, it is clear that a large percentage of glycinergic and GABAergic input to cochlear nucleus neurons originates from intrinsic sources.