THE DISTRIBUTION OF OMEGA-CONOTOXIN MVIIC(NLE)-BINDING SITES IN RAT-BRAIN MEASURED BY AUTORADIOGRAPHY

An analogue of omega-conotoxin MVIIC, [I-125]omega-MVIIC(n/e) has been employed in an autoradiographic assay to define the distribution of binding sites in rat brain of this neuronal calcium channel antagonist. In comparison with N-type channels (labeled by [I-125]omega-conotoxin GVIA), omega-MVIIC(n/e) sites are much denser in cerebellum (molecular layer) than in forebrain. Binding in thalamus is also comparatively high for omega-MVIIC(n/e). Under these conditions, [(125I)]omega-MVIIC(n/e) binding to rat brain sections is not displaceable by the N-channel antagonist, omega-conotoxin GVIA. The calcium channel blocker I-125]omega-conotoxin MVIIC(n/e) labels a unique set of binding sites in mammalian brain.