Simultaneous differentiation of three opiate receptor subpopulations by computer modelling.

[3H]-(-)-bremazocine was displaced from guinea-pig brain membrane homogenates by three compounds having different specificity to opiate receptor subpopulations. A three site receptor model showed the best fit of the calculated to the measured value for the opiate mu (DAla2,MePhe4,Gly(ol)5-enkephalin) and the delta specific compound (DAla2,DLeu5-enkephalin). Computer modelling of data from displacement curves with the opiate kappa specific compound U-50.488H favored a two site receptor model.