The mystery of the munchies, the craving for food experienced by cannabis users, has been unravelled. Neuroscientists hope that by piecing together the brain circuits involved in switching on the urge to eat they will be able to identify ways to block the craving with new anti-obesity drugs.
David Talmage's team at Columbia University, New York, whose work appears in the journal Neuron, took slices from parts of the mouse brain called the lateral hypothalamus, known to regulate appetite. They then used ultra-slim electrodes to measure the electrical activity along single neurons. Cannabis produces a "high" thanks to an active ingredient called tetrahydrocannabinol, but a similar chemical or cannabinoid is also produced naturally in the body. The researchers found that when neurons were exposed to the natural cannabinoid they became more excitable.
The researchers then tested neurons from mice bred to lack an appetite-suppressing hormone, leptin. They found that when these neurons were exposed to the natural cannabinoid they were even more excitable. The researchers believe leptin suppresses appetite by "short-circuiting" the effect of cannabinoids by changing how calcium ions flow along neurons. Calcium is needed to make cannabinoids in the body.
"What this gives us is a neural circuit for the well-known munchies effect that makes you hungry," said Dr Talmage.
