Development of hippocampal α7 nicotinic receptors in C3H and DBA/2 congenic mice

The time course and pattern of development of hippocampal α7 nicotinic acetylcholine receptors is discernibly different in C3H and DBA/2 mice. In C3H mice, the α7 receptor is initially expressed on embryonic day 13, exhibits an increase in density in area CA1 perinatally and is characterized by a dense, diffuse band of α-bungarotoxin binding at the CA3/CA1 border in the adult. In contrast, the α7 receptor is initially expressed on embryonic day 16 in DBA/2 mice, does not exhibit a transient perinatal increase in binding density in area CA1 and is characterized by α-bungarotoxin binding to numerous Nissl-stained structures in CA1 lacunosum/moleculare in the adult. Currently, it is not known whether these developmental differences occur solely as a result of the different alleles of the α7 receptor gene (Chrna7) expressed by the two strains or whether strain-specific background factors also play a role. The present study qualitatively examines this question by comparing α7 receptor development in congenic mice in which the DBA/2 allele of Chrna7 has been introgressed onto a C3H genetic background and, conversely, the C3H allele of Chrna7 has been introgressed onto a DBA/2 genetic background. The data suggest that hippocampal α7 receptor development is controlled predominantly by a region of mouse chromosome 7 that contains the strain-specific Chrna7 allele.