Although there is no direct cause and effect relationship between a drug and a behavior, we do know that the chemical substances called psychoactive drugs, which are discussing in this chapter, alter our moods, consciousness, and behaviors. The brain, it is believed, controls most of these functions. The human brain consists of several structures that are thought to be in control of different behaviors, feelings and thoughts. Psychoactive drugs affect these different structures. However, some drugs are more specific to some structures those others. For example, biochemical studies have shown that certain brain structures contain higher levels of certain types of drug receptors that others.
Narcotic Analgesics: Descendants of the Poppy
An analgesic is a substance that eliminates or reduces the sense of pain. The word narcotic comes to us from the Greek markoun, “to make numb.” The narcotic analgesics do, indeed, make the user numb in both mind and body. They aet on the user’s central nervous system, and are very effective in relieving pain without causing loss of consciousness.
The narcotic analgesics include what are often called the opiates, opium, morphine, and heroin, and the opioids, a group of synthetic drugs that are chemically similar to the opiates. Opium, the parent substance, comes from the juice of the opium poppy, which is native to Asia Minor; the word comes to us nearly uncharged from the ancient Greek opium, “poppy juice.” Morphine is the active ingredient in opium. Heroin, which is in turn derived from morphine, is more than twice as potent as morphine. The opioids, which were first synthezed in the laboratory in this century, include methadone and meperidine, plus other drugs with similar dependence creating potential.