Separating The Therapeutic Benefits Of Cannabis From Its Mood-altering Side-effects
Scientists from Queen Mary, University of London, have discovered a new way to separate the therapeutic benefits of cannabis from its mood-altering side-effects.
Cannabis contains a chemical called THC, which binds to, and activates, proteins in the brain known as ‘CB1 cannabinoid receptors’. Activating these receptors can relieve pain and prevent epileptic seizures; but it also causes the mood-altering effect experienced by people who use cannabis as a recreational drug. (Credit: iStockphoto/Dmitriy Norov)
Cannabis contains a chemical called THC, which binds to, and activates, proteins in the brain known as ‘CB1 cannabinoid receptors’. Activating these receptors can relieve pain and prevent epileptic seizures; but it also causes the mood-altering effect experienced by people who use cannabis as a recreational drug.
Now, Professor Maurice Elphick and Dr Michaela Egertová from Queen Mary’s School of Biological and Chemical Sciences may have found a way of separating out the effects of cannabis – a discovery which could lead to the development of new medicines to treat conditions such as epilepsy, obesity and chronic pain. The research is described in the December issue of the journal Molecular Pharmacology.
Working in collaboration with scientists based in the USA*, they have identified a protein that binds to the CB1 receptors in the brain. But unlike THC, this ‘Cannabinoid Receptor Interacting Protein’ or CRIP1a, suppresses the activity of CB1 receptors.
Professor Elphick explains: “Because CRIP1a inhibits the activity of the brain’s cannabinoid receptors, it may be possible to develop drugs that block this interaction, and in turn enhance CB1 activity. This may give patients the pain relief associated with CB1 activity, without the ‘high’ that cannabis users experience.”
Leslie Iversen FRS, Professor of Pharmacology at the University of Oxford and author of The Science of Marijuana, commented on the new findings: “This interesting discovery provides a completely new insight into the regulation of the cannabinoid system in the brain – and could offer a new approach to the discovery of cannabis-based medicines in the future.”
Mol Pharmacol. 2007 Dec;72(6):1557-66. Epub 2007 Sep 25.
Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, GA 30912, USA.
The CB1 cannabinoid receptor is a G-protein coupled receptor that has important physiological roles in synaptic plasticity, analgesia, appetite, and neuroprotection. We report the discovery of two structurally related CB1 cannabinoid receptor interacting proteins (CRIP1a and CRIP1b) that bind to the distal C-terminal tail of CB1. CRIP1a and CRIP1b are generated by alternative splicing of a gene located on chromosome 2 in humans, and orthologs of CRIP1a occur throughout the vertebrates, whereas CRIP1b seems to be unique to primates. CRIP1a coimmunoprecipitates with CB1 receptors derived from rat brain homogenates, indicating that CRIP1a and CB1 interact in vivo. Furthermore, in superior cervical ganglion neurons coinjected with CB1 and CRIP1a or CRIP1b cDNA, CRIP1a, but not CRIP1b, suppresses CB1-mediated tonic inhibition of voltage-gated Ca2+ channels. Discovery of CRIP1a provides the basis for a new avenue of research on mechanisms of CB1 regulation in the nervous system and may lead to development of novel drugs to treat disorders where modulation of CB1 activity has therapeutic potential (e.g., chronic pain, obesity, and epilepsy).