Characteristics of [125I]omega-conotoxin MVIIA binding to rat neocortical membranes

[125I]omega-Conotoxin MVIIA (omega-CTM) binding to N-type voltage-sensitive calcium channels (VSCCs) was characterized using rat neocortical membranes. [125I]omega-CTM bound rapidly and with high affinity; these parameters were similar to binding using omega-conotoxin GVIA ([125I]omega-CTG). Unlike [125I]omega-CTG, however, [125I]omega-CTM readily dissociated from its binding site. Monovalent and divalent cations, polyamines, and aminoglycosides inhibited [125I]omega-CTM binding. Since [125I]omega-CTM appears to bind to the same site as [125I]omega-CTG in mammalian neurons, the reversibility of [125I]omega-CTM binding makes this ligand preferable for equilibrium binding analyses.