Cerebellar projections of the central cervical nucleus in the rat: an anterograde tracing study.

The projection of the spinocerebellar tract arising from the central cervical nucleus was examined by the anterograde transport of wheatgerm agglutinin or cholera toxin subunit B (choleragenoid) conjugated to horseradish peroxidase in the rat. Following bilateral injections of the tracers into the C1-C3 segments, labeled terminals were seen in lobules I-VI, sublobule VIIb, lobule VIII, sublobule IXa + b and the copula pyramids. The labeled terminals were densely distributed in the basal half or basal two thirds of lobules I-III in their apicobasal extent, and the transitional areas between the neighboring lobules. The projection field in the horizontal plane of the lobules was reconstructed from a series of transverse sections through each lobule. In the anterior lobe, labeled terminals were distributed in 3 longitudinal areas, named areas 1, 2 and 3, respectively. These areas were confined in the basal half to the basal two-thirds of lobules II and III; area 1 was located in zone A1 of Voogd (within 250 microns of the midline); area 2 was located in zones A1-A2 (about 250 microns lateral to the midline); and area 3 was located in the lateral part of zone A2 to zone B (between 0.5 and 1.0 mm lateral to the midline). In lobule II, another area (area 4) was present lateral to the vermis. In lobule I the 3 longitudinal areas extended over the apicobasal length of the lobule. In sublobule IXa + b and lobule VIII, 4 ill-defined longitudinal areas appeared in the basal two-thirds. The present study confirmed that the projection pattern of the central cervical nucleus is identical in both the rat and the cat.