Developmental modifications of olivocerebellar topography: The granuloprival cerebellum reveals multiple routes from the inferior olive

• Published in: Journal of comparative neurology (1911) 2005-09, Vol.490 (1), p.85-97
• Main Authors: Fournier, Betty, Lohof, Ann M., Bower, Adrian J., Mariani, Jean, Sherrard, Rachel M.
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Brain Mapping; Calbindins; Cerebellum - cytology; Cerebellum - growth & development; Cerebellum - physiology; climbing fibers; Cognitive Sciences; Fluorescent Dyes - pharmacokinetics; Functional Laterality - physiology; Immunohistochemistry - methods; In Vitro Techniques; inferior olivary complex; Life Sciences; Membrane Potentials - drug effects; Membrane Potentials - physiology; Membrane Potentials - radiation effects; Membrane Transport Proteins - metabolism; Neural Pathways - cytology; Neural Pathways - growth & development; Neural Pathways - metabolism; Neurons and Cognition; Olivary Nucleus - cytology; Olivary Nucleus - growth & development; Olivary Nucleus - radiation effects; plasticity; Purkinje Cells - metabolism; Purkinje Cells - radiation effects; Rats; Rats, Wistar; S100 Calcium Binding Protein G - metabolism; synapse elimination; Vesicular Glutamate Transport Protein 2; Whole-Body Irradiation - methods; X-irradiation
• ISSN: 0021-9967; 0092-7317; 1096-9861; 1550-7130
• DOI: 10.1002/cne.20648

Correct function of neural circuits depends on highly organized neuronal connections, refined from less precise projections through synaptic elimination, collateral regression, or neuronal death. We examined regressive phenomena that define olivocerebellar topography during maturation from Purkinje cell polyinnervation to monoinnervation. We used bilateral retrograde tracing to determine the source of olivocerebellar afferents to posterior vermis lobules VII–VIII in a model of retained immature Purkinje cell polyinnervation, the granuloprival cerebellum. In controls, labelled neurons were found only in the contralateral inferior olive (ION) clustered in a small ventromedial locus that is congruent with known olivocerebellar topography. In granuloprival animals, olivary labelling appeared more dispersed and was present in homologous ipsilateral regions. Double‐labelled neurons were never seen. Retrograde tracing following unilateral olivocerebellar transection in adult granuloprival rats revealed: 1) the origin of the normal (remaining) path projecting through the contralateral inferior peduncle was more localized than in irradiated nonpedunculotomized rats, 2) a small double‐crossed path, and 3) a projection that ascends the peduncle ipsilateral to the ION of origin, part of which crosses the midline within the cerebellum. Electrophysiological and immunohistochemical assessment in the neonatal cerebellum revealed that transcommissural paths are not present during development but sprout within the irradiated cerebellum. Therefore, the olivocerebellar projection in the granuloprival rat, as a model of the immature path, shows parasagittal organization similar to that of controls in its normally crossed path but possesses additional abnormal projections. Thus, maturation of olivocerebellar topography involves removal of whole developmental paths to define laterality plus synapse elimination within largely predefined parasagittal zones. J. Comp. Neurol. 490:85–97, 2005. © 2005 Wiley‐Liss, Inc.