Some observations on the postnatal development of the rat cerebellum following unilateral pedunclotomy

The structure of the cerebellum, its cortex and the cells contained therein have been described. Also, the distribution of both afferent and efferent fibres has been summarised from the literature. The cerebellar development and experiments which have been performed upon it have also been briefly outlined. The technique for surgical pedunclotomy is described and its effect on cerebellar and Purkinje cell development were found. The effect of pedunclotomy on cerebellar growth and the Purkinje cell numbers is differential, a lesion on postnatal day 7 causing the most severe effect. Also, the Purkinje cell size was reduced following pedunclotomy after the age of 3 days. However the cortical histology was otherwise qualitatively normal. The response of the noradrenergic afferente to the cerebellum to pedunclotomy was observed. Qualitatively the density of fibres was equivalent to normal after 4 days, which is in keeping with previous experiments, but there was no hyperinnervation 35 days post pedunclotomy a result not in agreement with the studies using 6-hydroxydopamine. The olivocerebellar projection 35 days after pedunclotomy on days 3 and 7 shows a reinnervation of the deafferented hemicerebellum. However, this response was not seen after pedunclotomy on day 10. The topography of this aberrant path is organised roughly into sagittal bands although not as discretely as that seen in the normal animal. In neonatal rats there was some evidence that this path may already exist in those animals pedunclotomised on days 3 and 7. Also, an additional ipsilateral projection was found following acute pedunclotomy, which entered the cerebellum through the ipsilateral inferior cerebellar peduncle. The results have been discussed in relation to other experiments on cerebellar development and with studies in the literature on plasticity within the central nervous system.