ABSENCE OF TRANSSYNAPTIC TRANSPORT IN CEREBELLO-THALAMO-CORTICAL PATHOF THE RAT

Attempts to visualize the cerebello-thalamo-cortical path in the rat w ere made with different approaches. We tried (1) double labelling with somatopetal tracing from the motor cortex and somatofugal from the ce rebellar nuclei, (2) transmembrane labelling by depositing biocytin or wheat germ agglutinin (WGA)into the motor cortex or cerebellum. WCA w as either iodinated with I-125 or conjugated with horseradish peroxida se (HRP). The double labelling technique showed an overlap of the trac ers in the same thalamic region but no evidence of transsynaptic trans port in either direction was obtained. Our results indicate a differen ce in the organization of this system in primates and rodents, since t ranssynaptic labelling in the cerebellar nuclei after injections of WG A-HRP conjugate in the monkey motor cortex has been found.