Omega Conus geographus toxin: a peptide that blocks calcium channels.
We previously reported that omega Conus geographus toxin (omega CgTX), blocks evoked-release of transmitter at synapses in frog and attenuates the Ca2+ component of the action potential of chick dorsal root ganglion neurons. We report here voltage-clamp experiments on cultured chick dorsal root ganglion neurons which demonstrate that omega CgTX produces a persistent block of voltage-gated Ca2+ currents. Thus, we conclude that omega CgTX inhibits synaptic transmission by blocking Ca2+ channels in the presynaptic nerve terminal. The toxin had no effect on K+ currents; however, in some but not all neurons, omega CgTX reduced Na+ currents by 10-25%. These findings suggest that omega CgTX should be useful as a probe to examine synaptic Ca2+ channels.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects* / Q000378:metabolism; D008978:Mollusk Venoms / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013569:Synapses / Q000187:drug effects / Q000378:metabolism; D020866:omega-Conotoxin GVIA
D007473:Ion Channels; D008978:Mollusk Venoms; D010455:Peptides; D020866:omega-Conotoxin GVIA; D012964:Sodium; D011188:Potassium; D002118:Calcium