[I.M. Boggled]

[From a Symposium of the "Society for Neuroscience", that was held October 26, 1997 ]

New research shows that substances similar to or derived from marijuana, known as cannabinoids, could benefit the more than 97 million Americans who experience some form of pain each year.
In the past, the majority of evidence suggesting that cannabinoids could crush pain without causing a loss of touch was anecdotal. Some animal studies did show that cannabinoids decreased pain sensitivity in animals, but they also induced a wide variety of additional behavioral effects, such as changes in attention, deficits in movement, and cognitive impairment. It was unclear whether the animals showed a decrease in pain sensitivity because of these other behavioral effects or if the cannabinoids directly targeted the pain system.

Now careful studies are showing that the substances have a direct affect on pain signals in the central nervous system and peripheral tissues. The cannabinoids not only act as an analgesic, but also prevent the condition hyperalgesia, or an enhanced sensitivity to pain, which often accompanies tissue injury and inflammation. In addition, the new research reveals similarities and differences between cannabinoids and a group of pain killers that are used today called opioids or morphine-like drugs. Opioids are very effective but also cause many unwanted side effects. The most severe is physical dependence. The studies show that cannabinoids could be manipulated to form a new type of pain reliever.

In one new study scientists show that the active ingredient in marijuana, delta-9-THC, and another synthetic cannabinoid, WIN 55212, exhibit analgesic characteristics in monkeys. In addition, the pain relief occurs through a system that is different from opioids, according to the researchers from the University of Michigan Medical School.
In the study, the researchers measured the compounds analgesic characteristics in three rhesus monkeys with a technique that involved a warm-water bath. Monkeys will keep their tails in water kept at 50 degrees Celsius for a longer time than normal if they have received drugs with analgesic properties. "As the dose of the cannabinoids or the opioids increased, the monkeys were slower to remove their tails from the warm-water bath, revealing an analgesic action for these compounds," says Jeffrey Vivian. "It is important to note, however, that many cannabinoids produce a very rapid tolerance necessitating the use of higher doses and they aren’t better at reducing pain than traditional analgesics such as opioids. "In general, opioids had a greater analgesic effect than cannabinoids.

In other findings, the scientists dicovered that the administration of a drug that incapacitates the cannabinoids will block the cannabinoid effects but not the opioid effects. And a drug that solely knocks the opioids out of commission will block the opioid effects but not the cannabinoid effects. "This demonstrates the independence of the cannabinoid and opioid systems to cause pain relief," says Vivian.

Another group of researchers also found that cannabinoids and opioids relieve pain through different mechanisms. They found, however, that cannabinoids and opioids both target the same pain-modulating nerve cells or neurons.

"The results suggest that marijuana-like drugs may be useful as an adjuvant in combination with other therapies for treating certain types of pain," says Ian Meng of the University of California at San Francisco.

https://mojo.calyx.net/%7Eolsen/MEDIC...analgesia.html

The Medical Value of Marijuana and Related Substances