A Combined golgi and postembedding GABA and glutamate electron microscopic study of the nucleus dorsomedialis thalami of the rat.

The synaptic organisation of neurons in the nucleus medialis dorsalis (MD) was investigate by combined Golgi, and post-embedding gamma-aminobutyric acid (GABA) and/or glutamate (GLU) immunogold methods. The morphological features of the impregnated neurons in the MD (detailed by Kuroda et al. 1992a) were similar to thalamocortical relay cells present in other thalamic nuclei. GABAergic cell bodies could not be found. Distal dendritic branches of gold toned neurons established synaptic contacts with small and medium size glutamate as well as GABA-immunoreactive axonal endings. Large glutamate and GABA-positive axon terminals formed synaptic contacts with proximal dendrites. GABAergic axon terminals exhibited symmetric synaptic contacts and contained pleomorphic vesicles. Glutamate immunoreactive terminals formed asymmetric synapses and contained spheroid vesicles, although, some large glutamate immunoreactive endings contained pleomorphic vesicles. Synaptic glomerulus-like complexes could also be observed with the participation of glutamate-, and GABA-positive large axon terminals synapsing with Golgi impregnated proximal dendrites.