An ipsilateral olivocerebellar connection: an autoradiographic study in the unilaterally pedunculotomised neonatal rat

Using autoradiographic techniques the olivocerebellar pathway was investigated in neonatal rats which had undergone a left cerebellar pedunculotomy on postnatal day 7 (p7). Tritiated (3H) leucine was injected into the right inferior olive at the same time as the pedunculotomy and the animals were allowed to survive for two or four days. Autoradiographs were then made of the brainstem and the cerebellum. Only those animals which had had a total left cerebellar pedunculotomy and in which the 3H-leucine did not spill into the left inferior olive were included in the experiment. The results showed the presence of climbing fibres in the cerebellar hemisphere ipsilateral to the injection site, arranged in sagittal bands and topographically organised. The only route for those fibres to enter the cerebellum is through the inferior cerebellar peduncle ipsilateral to the injected olive which is a pathway not present in the adult animal. The possible explanations for these results are discussed.