The Effects Of Marijuana

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derable extent; but more to the point: Do we want to hear the answers?
CANNABIS AND "BLISS" IN THE BRAIN
"Marijuana" is the term for the dried leaves and flowering heads of the cannabis plant. Pioneering chemical detective work by Raphael Mechoulam and his colleagues at the Hebrew University some 30 years ago showed that the principal psychoactive ingredient in cannabis is the complex chemical delta-9-tetrahydocannabinol (THC). This chemical usually accounts for 3-4% of the dry weight of the herb, although modern strains grown indoors under intensive cultivation may contain as much as 15-20% THC. Marijuana is most commonly smoked in cigarettes (joints) or pipes. Just as cigarette smoking delivers nicotine very efficiently, smoking marijuana rapidly delivers THC to the smoker's brain. With this rapid feedback, and by adjusting how they smoke, users can learn to regulate the desired dose of THC accurately. THC is also absorbed when taken by mouth, but absorption is slow (as long as 3-4 hours to reach peak blood levels) and users cannot control whether they overdose or receive a less than an effective dose.
In a major advance, scientists have discovered a specific receptor protein in the brain that recognizes THC (and some closely related, biologically active derivatives). This protein, known as the cannabinoid receptor, belongs to a large family of similar receptor proteins that are part of the complex system of chemical communication in the brain - a system in which the receptors recognize and react to chemical messengers released by activated nerve cells. When a chemical messenger (either a naturally occurring molecule or a drug) binds to its particular receptor, it triggers activity in the nerve cell that has the receptor on its surface.
But why should nerve cells in our brain have developed a receptor that recognizes THC - a chemical found only in the cannabis plant? That question is similar to one posed by the discovery in the 19...