Expression analysis of P/Q-type Ca²⁺ channel α_1A subunit mRNA in olfactory mitral cell in N-type Ca ²⁺ channel α_1B subunit gene-deficient mice

N-type and P/Q-type Ca²⁺ channels play an important role in the processing of olfactory information. However, N-type Ca²⁺ channel α_1B-deficient mice show normal behavior, presumably owing to compensation by other Ca²⁺ channels. P/Q-type Ca²⁺ channel α_1A mRNA was expressed at a higher level in olfactory bulb of homozygous α_1B-deficient mice than wild-type or heterozygous mice. LacZ expression in olfactory mitral cells of homozygous α_1B-deficient x α_1A1.5-lacZ mice, carrying a 1.5-kb 5′-upstream fragment of the α_1A gene fused to the lacZ reporter gene, was increased compared to that in wild-type or heterozygous mice. Therefore, a possible explanation for the normal behavior of α_1B-deficient mice is compensation by the α_1A gene and that the 1.5-kb 5′-upstream region of this gene contains an enhancer cis-element for compensation in olfactory mitral cells.