IP3 RECEPTOR ANTAGONIST HEPARIN UNCOMPETITIVELY INHIBITS [H-3] (-SKF-10047 BINDING TO SIGMA-RECEPTORS())

Interaction of a receptors with intracellular Ca2+ channel blocker and modulators was examined. Ryanodine and inositol 1,4,5-trisphosphate ( IP3) did not inhibit [H-3](+)-N-allylnormetazocine ([H-3](+)-SKF-10047 ) binding to sigma receptors from either brain microsomal fractions or liver membrane extracts of the rat. However, the IP3 receptor antagon ist heparin inhibited [H-3](+)-SKF-10047 to sigma receptors in an unco mpetitive manner with a K-i of 93 mu M. These results suggest that sig ma receptors may bear some relationship with IP3 receptor associated p roteins or channels.