REDUCTION OF OPIATE BINDING TO BRAIN-STEM SLICES ASSOCIATED WITH THE DEVELOPMENT OF TOLERANCE TO MORPHINE IN RATS

  • 1 January 1979
    • journal article
    • research article
    • Vol. 211  (1) , 112-119
Abstract
Previous studies revealed that the characteristics of opiate binding sites are different in brainstem slices and homogenates. The binding of opiate agonists, morphine and etorphine, and that of the antagonist, naloxone, to thin slices of rat brain stem was studied. Na ion inhibits agonist binding and enhances antagonist binding in brainstem slices. Development of the analgesic tolerance to morphine is accompanied by a reduction of opiate binding. The opiate binding recovers partially toward control values during morphine withdrawal. Kinetic analyses indicate that Na induced changes in opiate binding sites are different from those caused by chronic morphine treatment. Apparently, analgesic tolerance is associated with changes in opiate receptors.