Lack of postulated opiate-receptor antagonistic properties of compound 48/80

The previously suggested opiate-receptor antagonistic properties of compound 48/80 were checked both in vivo and in vitro. In electrically stimulated guinea pig ileum and rat vas deferens preparations compound 48/80 did not reverse the inhibition of the twitches caused either by morphine or Met5-enkephalin. In mice hot-plate test compound 48/80 did not decrease the analgesic activity of morphine. In radioreceptor studies compound 48/80 shows rather low affinity to the 3H-naloxone receptor sites from striatal homogenates of the rat, as compared to non-labelled naloxone and on the other hand it produced moderate, as compared to d-butaclamol, displacement of ³H-spiroperidol from rat striatal homogenates. The variation of composition of various polymers making compound 48/80 is suggested for explanation of obtained results.