The dentatorubral projection in the rabbit with emphasis on distinction from the interpositorubral connectivity: an HRP retrograde tracer study.

The projection from the lateral (dentate) cerebellar nucleus (NL) to the red nucleus in the rabbit was investigated using free horseradish peroxidase (HRP). Following injections of this tracer into the red nucleus (RN), the distribution patterns of retrogradely labeled cells were checked in the NL. The projection from the NL was found to extend rostrocaudally throughout the contralateral RN except for the predominant part of the rostral one-quarter and the caudalmost part of the RN, i.e. the regions described to receive projections exclusively from the interpositus nuclear complex (NI). On the other hand, the only region of the RN receiving projection exclusively from the NL appeared to be rostralmost parvocellular region of the RN (RN-PA). This study suggested that, in contrast to other species, the projection from the NL is not confined to the most rostrally localized RN-PA but is distributed throughout predominant part of the nucleus and to a great extent overlapped with projection from the NI. This overlapping projection pattern parallels the absence of clear differentiation between parvo- and magnocellular parts of the rabbit RN.