ω-conotoxin MVIIC (omega conotoxin MVIIC) has been isolated from the venom of the cone Conus magus. ω-conotoxin MVIIC is a blocker of P/Q and N-type calcium channels. It inhibits presynaptic Ca²⁺ channels, including the Ca²⁺ channels responsible for Ca²⁺ uptake by rat brain synaptosomes, the P-type Ca²⁺ channels in cerebellar Purkinje cells, and a significant fraction of ω-conotoxin GVIA-resistant currents in hippocampal CA1 neurons. ω-conotoxin MVIIC also presents an inhibition of ω-conotoxin GVIA-resistant depolarization-induced neurotransmitter release in cerebellar neurons of rats.