A crucial problem in neurobiology is how neurons are able to maintain neurotransmitter receptors at specific membrane domains. The large structural heterogeneity of gamma aminobutyric acid receptors (GABAARs) led to the hypothesis that there could be a link between GABAAR gene diversity and the targeting properties of the receptor complex. Previous studies using Fluorescence Recovery After Photobleaching (FRAP) have shown a restricted mobility in GABAARs containing the al subunit. The M3/M4 cytoplasmic loop is the region of the α1 subunit with the lowest sequence homology to other subunits. Therefore, we asked whether the M3/M4 loop is involved in cytoskeletal anchoring and GABAAR clustering. A series of α1 chimeric subunits was constructed: α1CH (control subunit), α1CD (Cytoplasmic loop deleted), α1CD2, and α1CD3 (α1 with the M3/M4 loop from the α2 and α3 subunits, respectively). Our results using FRAP indicate an involvement of the M3/M4 cytoplasmic loop of the α1 subunit in controlling receptor lateral mobility. On the other hand, inmunocytochemical approaches showed that this domain is not involved in subunit targeting to the cell surface, subunit-subunit assembly, or receptor aggregation.