Formation and Maturation of Parallel Fiber-Purkinje Cell Synapses in the Staggerer Cerebellum Ex Vivo

In vivo, homozygous staggerer (Rora(sg/sg)) Purkinje cells (PCs) remain in an early stage of development with rudimentary spineless dendrites, associated with a lack of parallel fiber (PF) input and the persistence of multiple climbing fibers (CFs). In this immunocytochemical study we used cerebellar organotypic cultures to monitor the development of Rora(sg/sg) PF-PC synapses in the absence of CF innervation. Ex vivo the vesicular glutamate transporters VGluT1 and VGluT2 reactivity was preferentially localized around the Rora(sg/sg) PC soma and proximal dendrites, which are typically CF domains. The shift from VGluT2 to VGluT1 in PF terminals during development was delayed in Rora(sg/sg) slices. The postsynaptic receptors mGluR1 and GluR52 were differently distributed on Rorasglsg PCs. mGluR1 reactivity was evenly distributed in PC soma and dendrites, whereas GluRS2 reactivity, normally restricted at PF synapses, was dense in Rora(sg/sg) PC somata. The presynaptic distribution of VGluT1 and VGluT2 on Rora'glsg PCs matched the postsynaptic distribution of the glutamate receptor GluR82, but not mGluR1. J. Comp. Neurol. 512: 467-477,2009. (c) 2008 Wiley-Liss, Inc.