The cardiac sodium channel mRNA is expressed in the developing and adult rat and human brain

Expression of the rat (RH-I/SkM2) and human hH1/SCN5A) tetrodotoxin-resista nt (TTX-R); voltage-sensitive sodium channels is thought to be specific to cardiac tissue. We detected RH-I/SkM2 mRNA in newborn rat brain using both RNase protection assay analysis and in situ hybridization and in adult rat brain using RNase protection assay analysis. This expression was observed p rimarily in developing limbic structures of the cerebrum and diencephalon, and in the medulla of the brain stern. Using RT-PCR analysis, we detected h H1/SCN5A mRNA in both fetal and adult human brain. interestingly, mutations in the human cardiac sodium channel are known to lead to cardiac abnormali ties, which result in arrhythmias and frequently in sudden cardiac death. I f these mutant channels were also expressed in limbic regions of the brain, alterations in channel function could have drastic effects on the brain's signaling ability, possibly promoting seizure activity. (C) 2000 Elsevier S cience B.V. All rights reserved.