Novel ω-conotoxins from C. catus reverse signs of mouse inflammatory pain after systemic administration.

BACKGROUND: Antagonists of N-type voltage-gated calcium channels (VGCC), Ca(v)2.2, can manage severe chronic pain with intrathecal use and may be effective systemically. A series of novel ω-conotoxins that selectively inhibit N-type VGCCs was isolated from Conus catus. In the present study, the potency and reversibility of ω-conotoxins CVID, CVIE and CVIF to inhibit N-type calcium currents were investigated in mouse isolated dorsal root ganglion (DRG) neurons. The systemic potency of each ω-conotoxin to reverse signs of mouse chronic inflammatory pain was also compared. RESULTS: In DRG neurons, the rank order of potency to inhibit N-type calcium currents was CVIE > CVIF > CVID. After subcutaneous administration, CVID and CVIE, but not CVIF, partially reversed impaired weight bearing in mice injected with Freund's complete adjuvant (CFA) three days prior to testing. No side-effects associated with systemic administration of ω-conotoxins were observed. CONCLUSIONS: The present study indicates a potential for CVID and CVIE to be developed as systemically active analgesics with no accompanying neurological side-effects.