Crossed divergent axon collaterals from cerebellar nuclei to thalamus and lateral medulla oblongata in the rat.

The divergent collateralization of the ipsilateral descending limb of the brachium conjunctivum was here studied in the rat by means of fluorescent retrograde double-labeling. Tracer injections in the lateral part of the medulla oblongata were combined with injections of another tracer in the contralateral thalamus. Retrogradely single-labeled cells, as well as a relatively high number of double-labeled ones, were found in the lateral part of the interpositus and in the dorsolateral hump in the cerebellar nuclei ipsilateral to the medullary injections. The present results demonstrate that the same cerebellar cells interconnect by means of axon collaterals the ipsilateral medulla oblongata and the contralateral thalamus.