Experimental hyperphenylalaninemia: Dendritic alterations in cerebellum of rat

A quantitative analysis was made of the morphology of the cerebellar vermis in rats rendered hyperphenylalaninemic by daily injections on postnatal days 3 through 82 of the phenylalanine hydroxylase inhibitor, p-chlorophenylalanine (60 mg/kg), in combination with phenylalanine (300 mg/kg). This treatment resulted in a significant hyperphenylalaninemia (HPA) compared with saline-injected controls. In HPA animals there was a reduction in the cerebellar cross-sectional areas and in molecular layer thickness of midsagittal sections. Utilization of a classification strategy showed no specific qualitative changes in Purkinje cell structure between groups, but did indicate a hetereogeneity in Purkinje cell morphology between specific lobular sites of both HPA and control groups. Areas encompassed by Golgi-Cox-stained Purkinje cell dendritic trees were significantly smaller in HPA animals than in controls. The changes produced by HPA were of lesser degree in the nodulus than in the remaining lobes of the vermis. It is proposed that the decreased effect of HPA in the nodulus is related to normal differences in monoaminergic innervation between the nodulus and the other regions of the cerebellum.