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Reestablishment of the olivocerebellar projection map by compensatory transcommissural reinnervation following unilateral transection of the inferior cerebellar peduncle in the newborn rat
Author(s) -
Zagrebelsky Marta,
Strata Piergiorgio,
Hawkes Richard,
Rossi Ferdinando
Publication year - 1997
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/(sici)1096-9861(19970310)379:2<283::aid-cne9>3.0.co;2-#
Subject(s) - reinnervation , biology , neuroscience , anatomy , climbing fiber , cerebellum , inferior olivary nucleus , climbing , anterograde tracing , cerebellar cortex , central nervous system , ecology
It is unclear whether reparative processes in the injured mammalian brain are able to restore the topographic organisation of neuronal connections. To address this question, we have investigated the plasticity of the olivocerebellar system. This pathway has a precise topographic arrangement, in which subsets of inferior olivary neurons project to parasagitally oriented Purkinje cell compartments. Following unilateral transection of the inferior cerebellar peduncle in newborn rats, axons from the contralateral projection cross the cerebellar midline and reinnervate the deafferented hemicerebellum. By this experimental approach, we first analysed the behaviour of calcitonin gene‐related peptide (CGRP)‐immunoreactive climbing fibres. This marker is transiently expressed by a subset of developing inferior olivary axons, which terminate in the cerebellar cortex into several parasagittal strips. We show that transcommissural axons reestablish the original pattern of climbing fibre bands within a few days after lesion. Then, in adult animals injured at birth, we assessed whether the newly formed climbing fibre bands align with zebrin II± Purkinje cell compartments, as in normal conditions. The newly formed projection is organised in parasagitally oriented strips which mirror the distribution of their counterparts on the intact side and are precisely aligned to the heterogeneous Purkinje cell compartments. In addition, the patchy distribution of olivo‐nuclear fibres suggests that specific reinnervation is also achieved in the deep nuclei. Thus, transcommissural olivocerebellar reinnervation is not random, but it is regulated by selective interactions between distinct subsets of olivocerebellar axons and target neurons aimed at reestablishing the correct projection map. J. Comp. Neurol. 379:283–299, 1997. © 1997 Wiley‐Liss, Inc.