The use of computer analysis in describing multiple opiate receptors

The computer curve fitting program LIGAND has been used to simultaneously analyze 50 competition experiments using five labeled opioid ligands. The results describe four or five distinct sites, although the maximum number of sites cannot be determined. A site with high affinity for all the compounds tested, similar to the mu 1 site described by Pasternak, was apparent in 4 and 5-site models.