γ-Aminobutyric acid-ρ expression in ependymal glial cells of the mouse cerebellum

The ependymal glial cells (EGCs) from the periventricular zone of the cerebellum were studied to determine their distribution and the functional properties of their γ-aminobutyric acid type A (GABA_A) receptors. EGCs were identified by the presence of ciliated structures on their ventricular surface and their expression of glial fibrillary acidic protein (GFAP). Interestingly, diverse cell types, including neurons, astrocytes, and other types of glia, were identified in the subventricular zone by their current profiles. Electron microscopy showed ciliated cells and myelinated axons in this zone, but we found no collateral connections to suggest the presence of functional synapses. GABA-mediated currents were recorded from EGCs in cerebellar slices from postnatal days 13 to 35 (PN13-PN35). These currents were blocked by TPMPA (a highly specific GABA_Aρ subunit antagonist) and bicuculline (a selective antagonist for classic GABA_A receptors). Pentobarbital failed to modulate GABA_A-mediated currents despite the expression of GABAα1 and GABAγ2 subunits. In situ hybridization, RT-PCR, and immunofluorescence studies confirmed GABAρ1 expression in EGCs of the cerebellum. We conclude that cerebellar EGCs express GABAρ1, which is functionally involved in GABA_A receptor-mediated responses that are unique among glial cells of the brain.