Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6263148 | Brain Research | 2015 | 16 Pages |
â¢Î±7ânAChRs immunofluorescently detected on immature but not mature granule cells.â¢Functional nicotinic receptors found on immature granule cells.â¢Nicotinic receptors of immature granule cells are somato-dendritic α7ânAChRs.â¢Mature granule cells no longer possess functional nicotinic receptors.
Neurogenesis occurs throughout life in the subgranular zone of the dentate gyrus, and postnatal-born granule cells migrate into the granule cell layer and extend axons to their target areas. The α7ânicotinic receptor has been implicated in neuronal maturation during development of the brain and is abundant in interneurons of the hippocampal formation of the adult brain. Signalling through these same receptors is believed also to promote maturation and integration of adult-born granule cells in the hippocampal formation. We therefore aimed to determine whether functional α7ânicotinic receptors are expressed in developing granule cells of the postnatal dentate gyrus. For these experiments we used 2-3 week-old Wistar rats, and 2-9 week old transgenic mice in which GABAergic interneurons were marked by expression of green fluorescent protein. Immunohistochemistry indicated the presence of α7ânicotinic receptor subunits around granule cells close around the subgranular zone which correlated with the distribution of developmental markers for immature granule cells. Whole-cell patch clamp recording showed that a proportion of granule cells responded to puffed ACh in the presence of atropine, and that these cells possessed electrophysiological properties found in immature granule cells. The nicotinic responses were potentiated by an allosteric α7ânicotinic receptor modulator, which were blocked by a specific α7ânicotinic receptor antagonist and were not affected by ionotropic glutamate or GABA receptor antagonists. These results suggest the presence of functional somato-dendritic α7ânicotinic receptors on immature granule cells of the postnatal dentate gyrus, consistent with studies implicating α7ânicotinic receptors in dendritic maturation of dentate gyrus neurons in adult brain.