ABSTRACT
This chapter discusses the effects of the narcotic analgesics upon the synthesis, storage, release, and metabolism of norepinephrine, dopamine, serotonin, and acetylcholine. A good correlation was found between the ability of a narcotic analgesic to increase the locomotor activity of the mouse and its ability to deplete brain catecholamines. Acute administration of morphine increases the release and turnover of catecholamines from the adrenal medulla and the brain. In contrast to the decrease in brain catecholamine content caused by the narcotic analgesics, the acetylcholine content of whole brain is increased in several species by the acute administration of morphine and related drugs. Among the explanations of the morphine-induced increases in brain acetylcholine content are the possibilities that the narcotic analgesics either increase acetylcholine synthesis or inhibit cholinesterases to prevent the enzymatic destruction of acetylcholine. Morphine and related narcotic analgesics inhibit the release of acetylcholine from the coaxially stimulated guinea pig ileum.
