Spinocerebellar projections from the central cervical nucleus in the cat, as studied by anterograde transport of wheat germ agglutinin-horseradish peroxidase.

Abstract

The projection of the spinocerebellar tract arising from the central cervical nucleus with crossed ascending axons was studied by the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) in the cat. Following injections of WGA-HRP into the C1 to the C4 or C5 segments, labeled terminals were seen in lobules I-VI, sublobule VIIb, lobules VIII and IX, the paramedian lobule, crus I and crus II, and the simple lobule. About 67-80% of the total number of labeled terminals were in the anterior lobe and 20-33% in the posterior lobe; the labeled terminals were abundant in lobules I (11-20%), II (11-28%), III (5.7-9.6%), IV (8.6-15.4%), and VIII (9-12%). The labeled terminals were densely distributed in the basal half or basal two-thirds of sublobules IIa-Va and VIf-VIb in their apicobasal extent and the transitional areas between neighboring sublobules. In sublobules Ia, Ib, and Vg they were distributed over the entire sublobule. The labeled terminals were most abundant within 0.5 mm of the midline (30-55% of the total number in each sublobule). Results in cases with injections into the C2-C4 segments, preceded by hemisection between the C1 and C2 segments, revealed that the projections were bilateral but predominantly contralateral to the cells of origin; the proportion of the quantity of the contralateral projection to that of the ipsilateral was about 60:40% in sublobules Ia-Vb and sublobules Ve-Vg. The projection field in the horizontal plane of the lobule was reconstructed from a series of cross sections through each sublobule. The labeled terminals were distributed in three major longitudinal areas named areas 1, 2, and 3, respectively. These areas were confined in the basal half to two-thirds of lobules III-V: area 1 located in zone A1 of Voogd (within 0.25 mm of the midline); area 2 located in zones A1 to A2 (at around 0.5 mm lateral to the midline); and area 3 located in the lateral part of zone A2 to zone B (between 0.75 mm and 1.5 mm lateral to the midline in lobule III, and between 1.0 mm and 2.0 mm lateral to the midline in lobules IV-VI). An indefinite area 4 appeared in zones B and C of some lobules. In sublobules Ia, Ib, Vf, and Vg the three areas extended throughout the apicobasal length.(ABSTRACT TRUNCATED AT 400 WORDS)