Unipolar brush cell: a potential feedforward excitatory interneuron of the cerebellum
Section snippets
Experimental procedures
Young male and female Sprague–Dawley rats purchased from a commercial breeder were used for this investigation. All efforts were made to minimize both the suffering and the number of animals used. All experiments conformed to protocols approved by the Northwestern University Center for Experimental Animal Resources (CEAR), an AAALAC-accredited facility, and followed guidelines issued by the National Institutes of Health and the Society for Neuroscience.
Morphology of intracellularly labeled unipolar brush cells
More than 50 physiologically identified, Lucifer Yellow/Biocytin-filled UBCs were screened by light and electron microscopy and were selected for this study if the tracer appeared strictly intracellular and ultrastructure was well preserved. Eleven UBCs that met these criteria were subjected to further analysis. Three of these were stained with the DAB chromogen and eight with gold-conjugated avidin followed by silver intensification. All the UBCs in the sample were obtained from 15–28-day-old
Discussion
In this paper, we provide the first demonstration that UBC axon terminals target multiple granule cell dendrites and also brush dendrioles of other UBCs. We confirm that the UBC brush participates in a glomerular array where its dendrioles are innervated by a mossy fiber rosette, and demonstrate that branched UBC axons form rosette-shaped endings occupying glomeruli within the granule cell layer of the mammalian cerebellum. The UBC axons form asymmetric small synaptic junctions with granule
Acknowledgements
This study was supported by National Institutes of Health Grants NS-09904 (E.M.), NS-34840 (N.T.S.) and DC-002764 (N.T.S. and E.M.). We are grateful to Dr Linda Overstreet for providing the recording illustrated in Fig. 2, to Dr David Rossi for participation in preliminary experiments, and to Dr Simon Alford for assistance with confocal microscopy.
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Present address: Department of Physiology, West China University of Medical Sciences, Chemgdu, Sichuan 610041, P.R. China