Polarized distribution of AMPA, but not GABAA, receptors in radial glia-like cells of the adult dentate gyrus

Glial fibrillary acidic protein (GFAP)-positive astrocytes with radial processes [radial glia (RG)-like cells] in the postnatal dentate gyrus share many of the characteristics of embryonic radial glia and appear to act as precursor cells for adult dentate neurogenesis, a process important for pattern separation and hippocampus-dependent learning. Although much work has delineated the mechanisms underlying activity-neurogenesis coupling via gamma-amino butyric acid (GABA)ergic neurotransmission on GFAP-negative transient-amplifying cells and neuroblasts, little is known regarding the effects of neurotransmitters on RG-like cells. Conflicting evidence exists for both GABA and glutamate receptors on these cells. Here, using GFAP reporter mice, we show that the somatic membrane of RG-like cells carries GABAA receptors and glutamate transporters but not ionotropic glutamate receptors, whereas 2-amino-3-(hydroxyl-5-methylisoxazole-4-yl) propionic acid (AMPA) and GABAA receptors are expressed on the processes of these cells. Almost all RG-like cells expressed the GluA2 subunit, which restricts the Ca2+ permeability of AMPA receptors. The glial GABAA receptors mainly comprised 2/4, 1, and 1/3. The selective presence of AMPA receptors on the radial processes may be important for sensing and responding to local activity-driven glutamate release and supports the concept that RG-like astrocytes are composed of functional and structural domains.