Analgesic α-conotoxins Vc1.1 and RgIA inhibit N-type calcium channels in sensory neurons of α9 nicotinic receptor knockout mice

Channels (Austin). Jan-Feb 2010;4(1):51-4. doi: 10.4161/chan.4.1.10281. Epub 2010 Jan 8.

Abstract

Alpha-conotoxins Vc1.1 and RgIA are peptides from the venom of marine Conus snails that are currently in development as a treatment for neuropathic pain. We have reported previously that the alpha9alpha10 nicotinic acetylcholine receptor (nAChR) selective-conotoxins Vc1.1 and RgIA potently and selectively inhibit high voltage-activated (HVA) N-type calcium channel currents in dissociated neurons from rat dorsal root ganglia (DRG). Our data indicated that Vc1.1 does not interact directly with N-type Ca(2+) channels but inhibits them via GABA(B) receptor activation. The present study investigated Vc1.1 and RgIA inhibition of N-type Ca(2+) channels currents in DRG neurons of wild-type and alpha9 knockout (KO) mice to determine if the alpha9 nAChR was necessary for inhibition of the Ca(2+) channel current. Application of Vc1.1 (100 nM) inhibited N-type Ca(2+) channel currents to 69.2 +/- 3.5% of control in DRG neurons isolated from wild-type mice. In >70% of DRG neurons isolated from the alpha9 KO mice, both Vc1.1 and RgIA selectively inhibited N-type Ca(2+) channel currents with an IC(50) of 24.6 nM and 22.4 nM, respectively. The GABA(B) receptor antagonist CGP55845 (1 microM) antagonized the effect of Vc1.1 and RgIA on the N-type calcium channels in alpha9 KO mice. RT-PCR and western blot analysis confirmed the absence of the alpha9 nAChR in mice carrying a null mutation for the nAChR alpha9 gene. These results demonstrate that the inhibition of N-type Ca(2+) channel channels by Vc1.1 and RgIA is not mediated by the expression of alpha9alpha10 nAChRs in DRG neurons.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analgesics / pharmacology*
  • Animals
  • Blotting, Western
  • Calcium Channel Blockers / pharmacology*
  • Calcium Channels, N-Type / drug effects*
  • Conotoxins / pharmacology*
  • Dose-Response Relationship, Drug
  • GABA Antagonists / pharmacology
  • GABA-B Receptor Antagonists
  • Ganglia, Spinal / cytology
  • Ganglia, Spinal / drug effects*
  • Ganglia, Spinal / metabolism
  • Membrane Potentials
  • Mice
  • Mice, Inbred CBA
  • Mice, Knockout
  • Phosphinic Acids / pharmacology
  • Propanolamines / pharmacology
  • Receptors, GABA-B / metabolism
  • Receptors, Nicotinic / deficiency*
  • Receptors, Nicotinic / genetics
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sensory Receptor Cells / drug effects*
  • Sensory Receptor Cells / metabolism
  • Time Factors

Substances

  • Analgesics
  • Calcium Channel Blockers
  • Calcium Channels, N-Type
  • Chrna9 protein, mouse
  • Conotoxins
  • GABA Antagonists
  • GABA-B Receptor Antagonists
  • Phosphinic Acids
  • Propanolamines
  • Receptors, GABA-B
  • Receptors, Nicotinic
  • conotoxin alpha-RgIA, Conus regius
  • CGP 55845A
  • alpha-conotoxin Vc1.1