effect of opium on human nervous system

[edit] Chemical and physiological properties



Morphine is the primary biologically active chemical constituent of opium.

See also: Opioid, Opiate, and Morphinan
Opium contains two main groups of alkaloids. Phenanthrenes include morphine, codeine, and thebaine are the main narcotic constituents. Isoquinolines such as papaverine have no significant central nervous system effects and are not regulated under the Controlled Substances Act. Morphine is by far the most prevalent and important alkaloid in opium, consisting of 10%-16% of the total, and is responsible for most of its harmful effects such as lung edema, respiratory difficulties, coma, or cardiac or respiratory collapse, with a normal lethal dose of 120 to 250 milligrams[87]—the amount found in approximately two grams of opium.[88] Morphine binds to and activates μ-opioid receptors in the brain, spinal cord, stomach and intestine. Regular use leads to physical tolerance and dependence. Chronic opium addicts in 1906 China[89] or modern-day Iran[90] consume an average of eight grams daily.
Both analgesia and drug addiction are functions of the mu opioid receptor, the class of opioid receptor first identified as responsive to morphine. Tolerance is associated with the superactivation of the receptor, which may be affected by the degree of endocytosis caused by the opioid administered, and leads to a superactivation of cyclic AMP signalling.[91] Long-term use of morphine in palliative care and management of chronic pain can be managed without the development of drug tolerance or physical dependence. Many techniques of drug treatment exist, including pharmacologically based treatments with naltrexone, methadone, or ibogaine[92].