PROJECTIONS FROM THE CERVICAL ENLARGEMENT TO THE CEREBELLAR NUCLEI INTHE RAT, STUDIED BY ANTEROGRADE AXONAL TRACING

Spinocerebellar projections from the cervical enlargement originate fr om neurons in the medial part of lamina VI and the central part of lam ina VII. In the present study, the topographic projections of the cerv ical enlargement to the cerebellar nuclei were examined by anterograde tracing with biotinylated dextran in the rat. Following injections of the tracer into the spinal cord at levels between the C5 and T1 segme nts, anterogradely labeled axons and terminals were immunohistochemica lly demonstrated in the cerebellar nuclei. Unilateral injections revea led that projections are bilateral, but predominantly ipsilateral, to the cells of origin. Labeled axons entered the medial nucleus from its rostrodorsal and rostromedial aspects. Labeled terminals were distrib uted to dorsal and medial parts of the middle subdivision at its rostr al levels and to medial parts of the caudomedial subdivision of the me dial nucleus. Most axons terminated in the middle subdivision. Single axons were seen to course rostrocaudally in the medial nucleus and giv e off terminal axons to both subdivisions. A few labeled terminals wer e seen in the dorsolateral protuberance of the medial nucleus, and in the anterior interpositus and the posterior interpositus nuclei. No la beled terminals were seen in the lateral cerebellar nucleus. The prese nt study demonstrates that spinocerebellar neurons in laminae VI and V II of the cervical enlargement project to dorsomedial areas of the med ial nucleus at rostral levels, bilaterally but predominantly ipsilater ally. It is suggested that these areas specifically receive cutaneous and muscular input related to the forelimb movement. (C) 1997 Wiley-Li ss, Inc.