Influence of catecholaminergic agents on narcotic binding in brain

The effects of various agents on the specific tissue binding of 3H-naloxone and 3H-naltrexone were examined. In addition to the narcotics, alpha-adrenergic blockers and dopamine antagonists also significantly inhibited the specific bindings of these opiates. The binding of naloxone or naltrexone was not significantly altered by beta-adrenergic blockers, agents which block the effects of acetylcholine, serotonin and histamine at the receptor level, and a number of other drugs. Kinetic analyses revealed that the alpha-adrenergic and dopamine antagonists competitively inhibited the binding of naloxone. The results of these studies provide additional evidence for an interaction between the narcotics and catecholaminergic agents.