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Published on: November 14, 2011
Unipolar brush cells form a glutamatergic projection system within the mouse cerebellar cortex
M G Nunzi1, S Birnstiel, B J Bhattacharyya
1Institute for Neuroscience, Northwestern University Medical School, Chicago, Illinois 60611, USA. MG-Nunzi@nortwestern.edu
The Journal of Comparative Neurology
|May 2, 2001
Summary
Unipolar brush cells (UBCs) in the cerebellum use glutamate as their neurotransmitter. This finding reveals how UBCs create excitatory networks that may amplify vestibular signals and synchronize cerebellar granule cell activity.
Area of Science:
- Neuroscience
- Cell Biology
- Neuroanatomy
Background:
- Unipolar brush cells (UBCs) are found in the mammalian vestibulocerebellum.
- UBC axons form intrinsic mossy fibers synapsing with granule cells and other UBCs.
- The neurotransmitter released by UBC axons remains unidentified.
Purpose of the Study:
- To identify the neurotransmitter used by UBC axon terminals.
- To characterize the receptors involved in UBC neurotransmission.
- To understand the functional implications of UBC-mediated neurotransmission in the cerebellum.
Main Methods:
- Organotypic slice cultures of mouse nodulus (lobule X).
- Glutamate immunogold labeling to quantify neurotransmitter density.
- Patch-clamp recordings to measure excitatory postsynaptic currents (EPSCs) and burst discharges.
- Application of ionotropic glutamate receptor antagonists (CNQX and D-AP5).
Main Results:
- UBC axon terminals exhibited high glutamate labeling density, similar to glutamatergic parallel fibers.
- UBCs expressed key glutamate receptor subunits (GluR2/3, NMDAR1, mGluR2/3).
- Evoked and spontaneous EPSCs in UBCs and granule cells were blocked by glutamate receptor antagonists, confirming glutamatergic transmission.
Conclusions:
- Neurotransmission at UBC axon terminals is glutamatergic.
- UBCs establish a feedforward excitatory network within the cerebellar granular layer.
- This network may enhance vestibular signal processing and synchronize cerebellar granule cell activity.
