CHARACTERISTICS OF [I-125] OMEGA-CONOTOXIN MVIIA BINDING TO RAT NEOCORTICAL MEMBRANES

[I-125]omega-Conotoxin MVIIA (omega-CTM) binding to N-type voltage-sen sitive calcium channels (VSCCs) was characterized using rat neocortica l membranes. [I-125]omega-CTM bound rapidly and with high affinity; th ese parameters were similar to binding using omega-conotoxin GVIA ([I- 125]omega-CTG). Unlike [I-125]omega-CTG, however, [I-125]omega-CTM rea dily dissociated from its binding site. Monovalent and divalent cation s, polyamines, and aminoglycosides inhibited [I-125]omega-CTM binding. Since [I-125]omega-CTM appears to bind to the same site as [I-125]ome ga-CTG in mammalian neurons, the reversibility of [I-125]omega-CTM bin ding makes this ligand preferable for equilibrium binding analyses.