Co-localization of μ and δ opioid receptors on SK-N-SH cells detected by fluorescence microscopy using labeled anti-idiotypic antibodies

Selective fluorescence labeling of opioid receptor subclasses on SK-N-SH cultured cells has been accomplished using labeled polyclonal anti-idiotypic antibodies along with subclass-selective opioid agonists (DPDPE, δ-selective; DAMGO, μ-selective) as blocking reagents. Labeling of the cells was examined using conventional fluorescence microscopy. Co-localization of μ- and δ- opioid receptors on SK-N-SH cells has been studied by double labeling fluorescence experiments. In agreement with our own, and other workers', previous observations on NG108-15 cells, a subpopulation of viable cells in asynchronous cultures are labeled. Amon those SK-N-SH cells that are labeled, both subclasses of receptors are seen. On the basis of sequential blocking experiments we interpret our combined results to be consistent with a model where μ- and δ- binding sites reside on different subunits of a multimeric complex.