[Transplantation of embryonal cerebral cortex to the adult rat cerebellum: the fiber connections made by cortical transplants and the cerebellum].

Fifteen-day-old embryonic neocortical tissue was transplanted into the mature cerebella of normal adult rats (Fischer 344) heterotopically. After 5-8 months, WGA-HRP was injected into the host inferior olivary nucleus, pontine raphe, pontine nuclei, and neocortical transplants, 0.3 microliter, 0.2 microliter and 0.05 microliter respectively. The animals were sacrificed 48 hours later, and the HRP positive neuron and nerve fibers were examined in the transplants and host brain stem. Other animals were sacrificed for anti-dopamine-beta-hydroxylase immunohistochemical study and electron microscopic observation. Anterograde and retrograde tracing methods with the HRP method revealed on the light microscopic level that the transplants had received afferents from the host's locus coeruleus, and the inferior olivary nucleus. In one case, HRP injected into the host inferior olive was almost limited within the inferior olivary nucleus. Therefore, HRP-labelled fibers in the cerebellum were thought to be climbing fibers. The climbing fibers from the host inferior olivary nucleus entered the transplant from the host cerebellar medullary layers and branched in the transplant. The fiber ingrowth was limited within 300-500 microns for the distance. In another case, HRP injected into the inferior olive extended to the lateral reticular and the pontine nuclei. HRP labelled fibers entered the graft from the host medullary layers and many granular patterns like axon terminals were observed in the graft. In cases, in which HRP was injected into the pontine raphe and pontine nuclei, HRP labelled fibers did not grow into the graft. Retrograde tracing method with HRP injected into the graft showed labelled neurons in the host locus coeruleus.(ABSTRACT TRUNCATED AT 250 WORDS)