RNA blot hybridization analyses using probes specific for sodium channels I, II and III revealed high levels of sodium channel I mRNA and low levels of sodium channel II and III mRNAs in peripheral nervous system (PNS) tissues. The developmental expression patterns of these mRNAs were generally similar to those described for the central nervous system. The small amounts of sodium channel I and III mRNAs present in tongue muscle were greatly reduced after partial denervation. Expression of the three sodium channels thus appears to be restricted to the nervous system. Putative novel additional mRNAs, specifically expressed in the PNS, were detected with a probe that recognizes nucleotide sequences common to sodium channels I, II and III.
