Identification of thalamic projection cells in the rat cuneate nucleus: a light and electron microscopic study using horseradish peroxidase.

Cuneo-thalamic projection cells in the rat were identified after injection of horseradish peroxidase into the contralateral thalamic nucleus ventralis posterolateralis. By light microscopy, labelled cells were 16-20 microm in diameter, round or oval in shape, distributed throughout the cuneate nucleus and concentrated in the region of the obex. By electron microscopy, reaction products were found in two different types of neuronal profile. Most were 16-19 microm in diameter, round or slightly oval, with a smooth nucleus, small stacks of rough endoplasmic reticulum and many axo-somatic synapses. The remaining profiles were oval, 14-19 microm in long diameter, with a flattened, indented nucleus and very few axo-somatic synapses.