[Transplantation of embryonic cerebella into adult rat cerebella].

Cerebellar primordia of rat embryos (embryonic days of 14-20) were transplanted into mature cerebella of normal adult rats (Fischer 344). After 1-12 months, animals were sacrificed, and the development of grafts and the interaction between host and graft were examined by light and electron microscopy. Grafts from E14 rat cerebella showed the highest survival rate (85%), which decreased with increasing donor age. In some experiments, the donor tissue developed and differentiated to form folia with the trilaminar organization of the cerebellar cortex. Synaptic connections between neuronal elements in the graft showed basically the normal pattern. Thus, mossy terminals formed synaptic contacts with dendrites of granule cells, and axons of basket cells made synaptic contacts with somata of Purkinje cells. Many spines of Purkinje dendrites were contacted with parallel fibers, while others were surrounded by processes of astroglia. Migration of donor Purkinje and granule cells in the host molecular layer was frequently observed. Some donor granule cells, implanted in the superficial aspect of the host molecular layer, migrated down along processes of Bergmann glia, which resembled the migration pattern of the normal development. Other granule cells attached to neuroglial processes which ensheathed capillary walls. While the migration of granule cells was found to be glial-dependent, the glial role in the migration of Purkinje cells was not clear. Purkinje cells probably migrated into the host molecular layer under favorable conditions where the loss of host Purkinje cells had been occurred to some extent and consequently followed by the increase of free axon endings of parallel fibers and interneurons of the host.(ABSTRACT TRUNCATED AT 250 WORDS)