Résumé
Ca sub(v)2.3 calcium channels play an important role in pain transmission in peripheral sensory neurons. Six Ca sub(v)2.3 isoforms resulting from different combinations of three inserts (inserts I and II in the II-III loop and insert III in the carboxyl-terminal region) have been identified in different mammalian tissues. To date, however, Ca sub(v)2.3 isoforms unique to primary sensory neurons have not been identified. In this study, we determined Ca sub(v)2.3 isoforms expressed in the rat trigeminal ganglion neurons. Whole tissue reverse transcription (RT)-PCR analyses revealed that only two isoforms, Ca sub(v)2.3a and Ca sub(v)2.3e, are present in TG neurons. Using single cell RT-PCR, we found that Ca sub(v)2.3e is the major isoform, whereas Ca sub(v)2.3e expression is highly restricted to small (<16 mu m) isolectin B4-negative and tyrosine kinase A-positive neurons. Ca sub(v)2.3e was also preferentially detected in neurons expressing the nociceptive marker, transient receptor potential vanilloid 1. Single cell RT-PCR following calcium imaging and whole-cell patch clamp recordings provided evidence of an association between an R-type calcium channel component and Ca sub(v)2.3e expression. Our results suggest that Ca sub(v)2.3e in sensory neurons may be a potential target for the treatment of pain.