Macromolecular changes in brain stem of morphinized rats.

Incorporation of [3H]valine into trichloroacetic acid-(TCA)-precipitable, water-soluble or membrane-bound material of whole brain and brain-stem did not differ significantly in morphine-intoxicated, morphine abstinent and control rats. The animals were intoxicated with morphine (final dose 340 mg/kg b.w.) for 15 days, using an ingestion method with no impairment of the caloric intake compared to controls. Abstinent rats were withdrawn from morphine for 2 days after 13 days of intoxication. Measurements of [3H]valine or [14C]valine incorporated into soluble or membrane-bound brain stem proteins failed to demonstrate any significant changes in specific protein bands from morphinized rats. Separation was achieved by polyacrylamide gel electrophoresis with or without sodium-dodecyl sulphate (SDS) or by isoelectric focusing. After immunoabsorption chromatography to remove those proteins antigenically similar to serum proteins, an increase in the staining intensity and in incorporation of [3H]valine into two protein bands (with isoelectric points (Ip:s) 5.75 and 7.7) was seen in brain stem from long-term morphine-intoxicated rats. The results show that macromolecular interactions are involved in long-term morphine actions.