Rolling Nagoya mice carrying Cav2.1α1 gene mutation show ataxia, whereas heterozygous mice show no apparently abnormal behavior. It has been reported that Cav2.1 regulates neurotransmitter release and that Ca2+ influx through Cav2.1 decreases with aging. Age-related decline in cognitive function could be at least partly attributable to decreases in Cav2.1-related neurotransmission. In this study to examine age-related cognitive alterations in heterozygous mice, we used Y-maze and delayed spatial win-shift eight-arm radial-maze tests, and 2- and 22-month-old mice. Although there was no difference between 2-month-old heterozygous and wild-type mice, 22-month-old heterozygous mice showed decreased memory formation versus 2-month-old heterozygous mice in both tests. Expression analysis in forebrain showed that total Cav2.1α1 mRNA, including wild-type and mutant-type Cav2.1α1 mRNA, in 2-month-old heterozygous mice was expressed at a level similar to that in 22-month-old heterozygous mice. However, wild-type Cav2.1α1 mRNA was expressed at a lower level in 22-month-old mice than in 2-month-old mice, and mutant-type Cav2.1α1 mRNA was expressed at a higher level in 22-month-old versus 2-month-old mice. Our results suggest that aged heterozygous mice show deficits in spatial learning due to Cav2.1 channel dysfunction and that heterozygous mice may be a useful model for examining mechanisms underlying age-related cognitive dysfunction.
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