EN
The study was initiated to determine the projection pattern of the climbing fibers from the inferior olivary complex (IO) to the two lobules of the caudal vermis, both independent and by way of axonal collaterals. Different fluorescent tracers, Fast Blue and Diamidino Yellow, unilaterally injected into the pyramis and uvula in the seven rabbits, resulted in single (n=32020) and double (n=403) labeling of neurons in defined restricted regions of the contralateral IO. These neurons, parent for independent and collateral projections, respectively, clustered in two aggregations (lateral and medial) through the rostrocaudal extent of IO. IO consists of a complex of three nuclei: the dorsal (DAO) and medial (MAO) accessory olive, and the principal olive (PO). MAO is accompanied by the dorsomedial cell column (dmcc) and the β nucleus (β). PO is composed of the dorsal (dlPO) and ventral (vlPO) laminas and comprises the ventrolateral outgrowth (vlo) and dorsal cap (dc). Distribution pattern of single labeled neurons indicates that the strongest projection to the pyramis and uvula arises from the lateral region of entire extent of MAO and that to the pyramis is more intensive. Neurons in the lateral region of DAO send numerous fibers exclusively to the pyramis. The rostral part of β more frequently supplies the uvula whereas the caudal part - the pyramis. Neurons of dmcc in similar degree project to the two cerebellar targets, however, from the rostral part projection is stronger to the uvula. Weak connections come from vlo and vlPO, and from dc only to the uvula. Neurons participating in collateral projection were found in the lateral region of MAO, the entire extent of β, the rostral and caudal levels of dmcc, and in vlo. To sum up, (1) the IO-pyramis and IO-uvula projecting neurons vary in number and in distribution, and (2) there is a small population of the IO neurons which project by divergent axons.