Molecular Basis of Cav2.3 Calcium Channels in Rat Nociceptive Neurons

Abstract Cav2.3 calcium channels play an important role in pain transmission in peripheral sensory neurons. Six Cav2.3 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, Cav2.3 isoforms unique to primary sensory neurons have not been identified. In this study, we determined Cav2.3 isoforms expressed in the rat trigeminal ganglion neurons. Whole tissue reverse transcription (RT)-PCR analyses revealed that only two isoforms, Cav2.3a and Cav2.3e, are present in TG neurons. Using single cell RT-PCR, we found that Cav2.3e is the major isoform, whereas Cav2.3e expression is highly restricted to small (<16 μm) isolectin B4-negative and tyrosine kinase A-positive neurons. Cav2.3e 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 Cav2.3e expression. Our results suggest that Cav2.3e in sensory neurons may be a potential target for the treatment of pain.