INTRASTRIATAL CEREBELLAR GRAFTS - DIFFERENTIATION OF CEREBELLAR ANLAGE AND SPROUTING OF PURKINJE-CELL AXONS

Pieces of cerebellar primordia were obtained from G16 (day 16 of gesta tion) rat fetuses and stereotaxically injected into the striatum of ad ult Wistar rats. The transplants were allowed to integrate with the ho st brain for 2 h up to 6 months after implantation. Ninety four out of 105 transplants perfectly integrated with the host brain (90%) and es tablished the typical trilaminar histoarchitecture of cerebellar corte x. The transplants were sufficiently vascularized. Vessels seen within the grafts provided all ultrastructural elements of a blood-brain bar rier. Light microscopic evaluation of graft development showed no cons iderable retardation of cerebellar histogenesis. Electron microscopic examination disclosed normal ultrastructure of cerebellar neurons, as well as elements of regular synaptic organization. The topic of effere nt graft-to-host projections was investigated 2.5 months after transpl antation using the monoclonal Purkinje cell marker anti-Leu-4 (CD3). T his method allowed us to detect immunoreactive, morphologically intact axons of grafted Purkinje cells running over long distances (at least 500 mum) within the host striatum. Whilst afferent but in no case eff erent connections of heterotopic cerebellar transplants had been demon strated elsewhere, we could now prove the reciprocal modus of graft-ho st interaction with heterotopic cerebellar grafts.