Tuesday, January 29, 2008
Anandamide: The Brain’s Own Marijuana
Anxiety and the THC receptor.
Several years ago, molecular biologists identified the elusive brain receptor where THC, the active ingredient in marijuana, did its work. Shortly after that discovery, researchers at Hebrew University in Jerusalem identified the body’s own form of THC, which sticks to the same receptors, in pulverized pig brains. They christened the internally manufactured substance “anandamide,” after the Sanskrit ananda, or bliss.
Anandamide has a streamlined three-dimensional structure that THC mimics, and both molecules slipped easily across the blood-brain barrier. Anandamide is a short-lived, fragile molecule, and does not produce a dramatic natural high, unlike a surge of endorphins, or dopamine—or the THC in a joint. In 2001, researchers at the Keck Center for Integrative Neuroscience at the University of California-San Francisco found evidence that THC may perform a signaling function in neurons containing GABA and glutamate. It appears that marijuana increases dopamine and serotonin levels through the intermediary activation of opiate and GABA receptors.
However, anandamide has a number of other effects, particularly on movement and cognition. Because of this, the “bliss molecule” moniker is a bit misleading. THC and its organic cousin make an impressive triple play in the brain: They effect movement through receptors in the basal ganglia, they alter sensory perception through receptors in the cerebral cortex, and they impact memory by means of receptors in the hippocampus.
It was left for animal physiologist Gary Weesner of the U.S. Department of Agriculture (USDA) to answer the burning question: “How do pigs use their anandamide?” While studying the possibility of using anandamide as a sedative for animals, Dr. Weesner discovered that pigs treated with anandamide tended to have lower body temperature, slower respiration, and less movement—all of which are signs of a calmer porcine state of mind.
So much for pigs. What does anandamide do in the human brain? For starters, we can look toward those controversial indications for which marijuana is already being prescribed: anxiety relief, appetite enhancement (compounds similar to anandamide have been discovered in dark chocolate) suppression of nausea, relief from the symptoms of glaucoma, and amelioration of certain kinds of pain. U.S. pharmaceutical houses, Pfizer in particular, worked with THC for years, seeking profitable patents. But Pfizer never succeeded in separating out the various pharmacological effects of marijuana, and in the end, their efforts were limited to the manufacture of synthetic THC.
Ten years ago, scientists at the National Institute of Mental Health (NIMH) uncovered preliminary evidence that cannabis may afford a measure of protection from brain cell damage due to stroke. An Israeli pharmaceutical company announced plans to test a synthetic marijuana derivative for the treatment of strokes and brain injury. There are few effective treatments for stroke, the third leading killer in the United States.
The question of short-term memory loss under the influence of pot appears to have been answered by related research. Findings from the Neurosciences Institute in San Diego show that cannabinoids are capable of blocking new memory formation in animal brain tissue. If anandamide receptors trigger a form of forgetfulness, this may be part of the brain’s system of filtering out unimportant or unpleasant memories—a vital function, without which we would all be overwhelmed by irrelevant and unprovoked memories at every turn.
For example, the brain’s own cannabis may help women “forget” the pain and stress of childbearing, allowing them to concentrate on the immediate needs of the newborn. Other animal research suggests that the uterus grows anandamide receptors in heavy concentrations before embryo implantation. Still other studies show that newborn kittens and monkeys have more marijuana receptors in the cortex than adults do, so it is possible that anandamide may play some role in setting up the development of cortical function in infants.
For more, see earlier posts:
Is Marijuana Addictive?
Photo Credit: National Institute of Drug Abuse