Different localization of receptors for omega-conotoxin and nitrendipine in rat brain.

The bindings of radioiodinated omega-conotoxin GVIA and [3H]-nitrendipine to subcellular fractions of rat brain were examined. The results indicated that omega-conotoxin binding site was mainly present in the mitochondrial fraction, whereas nitrendipine binding site was rich in the mitochondrial but also present in the post-mitochondrial fraction. Fractionation of the mitochondrial fraction on a sucrose density gradient centrifugation showed that the both binding sites were localized in the heavy synaptosomal fraction. These results strongly suggest that the N- and L-type voltage-sensitive calcium channels have different localizations.