15] - ω-Conotoxin GVIA and Its Receptors

Abstract

Publisher Summary This chapter discusses ω-conotoxin and its receptors. ω-Conotoxin GVIA first described as a toxin of Conus geographus produces persistent shaking when administered intracranially to mice, but does not interact with acetylcholine receptors or voltage-sensitive sodium channels. ω-conotoxin is reported to block both N- and L-type voltage-sensitive calcium channels in nerve preparations. Recent electrophysiological reports, however, have shown that the toxin blocks only N-type channels and does not affect L-type channels in neurons. The reason for these discrepant reports can be because L-type channel action cannot be separated sufficiently in previous studies, or because the sensitivities of L-type channels to ω-conotoxin differ in different cells. There are differences in the primary structures of dihydropyridine receptors in skeletal and cardiac muscles. Therefore, the toxin blocks the L-type channels of non-neuronal tissue but does not block those in neuronal cells. The low-affinity binding site of ω-conotoxin in rat brain cannot be of L-type voltage-sensitive calcium channels or dihydropyridine binding sites, because the distributions of the two clearly differ in brain regions.