Effects of hydroxylamine on the consequences of long-lasting administration of morphine in mice. II. Time course of the hydroxylamine effect on morphine tolerance.

Mice injected for 35 days with morphine sulfate in increasing doses did not show tolerance to the analgesic effects of morphine if injected intracranially with 0.3 M hydroxylamine. The excitatory action of morphine was unaffected. The interference with tolerance lasted for at least six weeks following the hydroxylamine injection. There were no apparent histological changes in the brains of treated mice as well as no differences in the composition of water-soluble brain proteins.