Monday, December 2, 2002
By Jacqueline Stenson
Seeking to induce the anxiety-reducing effects of marijuana without causing mental stupor or the munchies, scientists have identified two experimental drugs that appear to do just that in lab rats.
The research might eventually lead to an entirely new class of medications to combat anxiety and depression, said study author Daniele Piomelli, a professor of pharmacology at the University of California at Irvine.
The active component in marijuana, THC, acts similarly to naturally occurring neurotransmitters in the brain called cannabinoids, which can play a role in mood, he told Reuters Health.
The new drugs, URB532 and URB597, work by inhibiting an enzyme that breaks down the cannabinoid known as anandamide, he explained.
And as evidenced by his animal research, reported in the advance online publication of the January issue of Nature Medicine, the result is higher brain levels of anandamide, which in turn ease anxiety in rats. When given the drugs, the animals squeaked less when subjected to isolation and were less tentative when placed in a maze with exposed spaces. In the wild, such spaces put the animals at risk of predator attack.
However, the rats did not experience typical THC side effects such as increased appetite, reduced body temperature or loss of motor function, all of which would signal cannabinoid intoxication in the animals. That's probably because THC acts directly on cannabinoid receptors on brain cells, whereas the new drugs work in a different, more subtle way, Piomelli said.
The effect of the experimental drugs is similar to antidepressants like Prozac, which boost brain levels of another neurotransmitter, serotonin, he said. "Some people have low levels of serotonin, and maybe there are some people who have low levels of anandamide," he said.
The new drugs show promise as novel ways to treat anxiety and depression in people, Piomelli said.
Human studies with the new drugs could begin within a year, he added.
SOURCE: Nature Medicine 2002;10.1038/nm803.
Copyright 2002 Reuters