Functional α7 Nicotinic ACh Receptors on Astrocytes in Rat Hippocampal CA1 Slices

Although much is known about the functional expression of the neuronal nicotinic acetylcholine receptors (nAChRs) in various neuronal populations in the brain and elsewhere, much less is known about their expression and functional relevance in glial cells. The expression of functional nAChRs has been reported for cultured astrocytes; however, previous work has failed to detect nAChR-mediated responses in astrocytes in acute slices. In the current study, functional alpha 7 nAChRs on astrocytes in the CA1 region of the rat hippocampus were studied in situ using whole-cell patch-clamp recording and two-photon calcium imaging techniques in acute slices. We found that astrocytes and the chondroitin sulfate proteoglycan NG2-expressing (i.e., NG2) cells did express functional alpha 7 nAChRs. Although the amplitudes of the responses were small, they could be enhanced by the alpha 7-selective positive allosteric modulator PNU-120596. Under these conditions, we found that in comparing the properties of these responses between astrocytes, NG2, and interneurons, there were differences in the kinetics and increases in intracellular calcium levels. This is the first demonstration of functional alpha 7 nAChR-mediated current responses in astrocytes in acute hippocampal slices, data which may shed light on the role of alpha 7 nAChRs in neuroprotection.