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Cannabinoids
are natural to the human body
Cannabinoid receptors and ligands exist naturally
throughout the body. In fact, there are 10 times as
many cannabinoid receptors in the body as morphine
receptors. To date, two important cannabinoid receptors
have been identified: CB1 and CB2.
CB1 receptors are found liberally throughout the
brain, including in the cerebellum, hippocampus, basal
ganglia, cerebral cortex, spinal cord, and primary
afferent nociceptors, making them ideally placed to
play a role in pain modulation and visceral sensations
such as nausea and vomiting. Importantly, few CB1
receptors are present in the cardiorespiratory area
of the brain stem, which makes cannabinoid drugs safe
in overdose.
CB2 receptors are found peripherally, mainly in immune
and lymphoid tissue such as the spleen, tonsils, mast
cells, macrophages, and lymphocytes.
The first identified CB receptor ligands that exist
naturally in the body is called anandamide. This endogenous
cannabinoid, or endocannabinoid, binds to both CB1
and CB2 receptors but has the greatest affinity for
CB1, which is an important receptor in terms of pain
modulation and visceral sensations such as nausea
and vomiting. Anandamide has a similar effect to THC,
but less potent. In general, the affinity of anandamide
for cannabinoid receptors is only one-fourth to one-half
that of THC. Several other endogenous compounds that
are chemically related to anandamide and that bind
to cannabinoid receptors have been discovered namely
2AG and PEA.
References :
1. Mack A. Joy J. Marihuana as medicine?
The science beyond the controversy. National Academy
Press 2001.
2. Grotenhermen F. Russo E. Cannabis
and Cannabinoids : Pharmacology, Toxicology, and Therapeutic
Potential. The Haworth Integrative Healing Press.
2002
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