Comparison of alpha7 nicotinic acetylcholine receptor development in the hippocampal formation of C3H and DBA/2 mice.

A strain-specific restriction fragment length polymorphism in the alpha7 receptor gene locus has been reported to significantly affect the expression of the alpha7 subtype of nicotinic receptor in adult mouse hippocampus. The goal of the present study was to characterize the development of the alpha7 receptor in hippocampus from two mouse strains (C3H and DBA/2) with different alleles of the alpha7 receptor gene locus by using alpha-bungarotoxin (alpha-BTX) autoradiography. Binding of alpha-BTX was initially detected in fetal C3H mice on embryonic day 13 (E13) in the dorsal portion of the hippocampal anlage. In contrast, alpha-BTX binding was initially detected primarily in hippocampal area CA3 in the DBA/2 strain on E16. Binding of alpha-BTX was absent from the neuroepithelium in both strains. A marked increase in alpha-BTX binding was observed in hippocampal area CA1 and to a lesser extent in area CA3 between E18 and postnatal day 5 (P5) in neonatal C3H mice, an increase that was not observed in the DBA/2 mice. By the end of the first postnatal month, hippocampal alpha-BTX binding appeared adult-like in each strain. These data suggest that variations in the alpha7 receptor gene locus differentially influence the developmental expression of the alpha7 receptor in murine hippocampus. Therefore, the potential influence of the alpha7 receptor on developmental processes such as cell migration, dendritic elaboration and/or axonal connectivity may exhibit strain-selective differences because of the dissimilar time courses of alpha7 receptor expression in C3H and DBA/2 mice.