Localization of low affinity nerve growth factor receptor in the rat inferior olivary complex during development and plasticity of climbing fibres

The rat olivocerebellar pathway has a precise topography from an inferior o live (TOC) to Purkinje cells in the contralateral hemicerebellum. While its development and plasticity have been documented, the molecular mechanisms underlying these events are not fully elucidated. Neurotrophins are a famil y of growth factors with diverse roles in development and neuronal plastici ty, acting through a two-receptor system, including a low affinity receptor (LNGFR) which binds all neurotrophins with similar affinity. Since neurotr ophins are present in the cerebellum during early postnatal development whe n LNGFR is synthesized in the IOC, they may act as target-derived trophic a gents for climbing fibres during development and plasticity. To assess this , standard immunohistochemistry was used to document the distribution of LN GFR in the rat. IOC during climbing fibre development and until cerebellar development was complete at postnatal day 28 (P28). LNGFR immunoreactivity (LNGFR-IR) was detected in the IOC from P0 until P15, however after P7 it d iminished in intensity and distribution, a change which indicates a relatio nship between cerebellar neurotrophins and climbing fibre development. Afte r denervation of the left hemicerebellum, there was an apparent increase in inferior olivary LNGFR-IR that was concurrent with climbing fibre re-inner vation. Thus the results of this study support the hypothesis that neuroutr ophins are involved in climbing fibre development and suggest a possible co ntribution to the plasticity of the olivocerebellar pathway. (C) 2001 Elsev ier Science B.V. All rights reserved.