Postnatal development of the α1 containing GABA A receptor subunit in rat hippocampus

Abstract

Here we have studied the developmental expression of α1 subunit of the GABA A receptor in comparison with the expression of α2 subunit and several GABAergic markers (parvalbumin (PV), calretinin (CR), somatostatin (SOM), neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP)). The α1 expression (mRNA and protein) was low at birth and increased progressively until the adulthood. This expression pattern was similar to that observed for PV, opposite to that of CR (high at birth and decreased continuously until the adulthood) and differed from that observed for the α2 and neuropeptides (SOM, NPY and VIP) (in all cases, a clear peak in expression was observed at P10). We further investigated the expression of α1, PV and CR by immunohistochemistry. As expected, the α1 and the PV expression were low at birth and increased progressively until the adulthood. Both α1 and PV were co-expressed by the same interneuronal population, however, the maturation of the α1 subunit preceded to that of PV. Finally, we observed a gradient of maturation between the different fields of the hippocampus proper (CA2–3 preceded to CA1 and DG). This gradient could be related to the high expression of CR positive cells and fibers during the first 10 postnatal days, located principally in the stratum lacunosum moleculare of the CA2–3 layers.