The rat parvocellular reticular formation: I. Afferents from the cerebellar nuclei.

The present report elucidates the location of the cells of origin of the cerebellar nuclear-parvocellular reticular projection in the rat. Injection of horseradish peroxidase (HRP) into the parvocellular reticular formation resulted in labeled neurons in the dorsolateral protuberance of the contralateral medial nucleus and bilaterally in the dorsolateral hump region and the large celled subgroup of the lateral nucleus. A small number of labelled cells were found in the middle part of the contralateral medial nucleus. The few HRP-positive cells in the interpositus nuclei were adjacent to the dorsolateral hump. No labeled neurons were observed in the caudomedial portion of the medial nucleus or the small-celled region of the lateral nucleus.