Cannabinoid Signaling Suppresses Activity in the Hippocampus

Cannabinoid Signaling Suppresses Activity in the Hippocampus

Cannabinoids—THC and other psychoactive ingredients found in marijuana—bind to cannabinoid receptors in the brain to produce their effects. A study published online on January 19 by Pablo Castillo, M.D., Ph.D., in the Proceedings of the National Academy of Sciences, has provided a novel mechanism for cannabinoids in dampening neuronal activity in the hippocampus, a brain region important for learning and memory.

The hippocampus contains two highly interconnected populations of excitatory neurons: dentate granule cells and mossy cells. The mossy cells project extensively throughout the hippocampus. As a result, high activity of a single mossy cell can profoundly affect many dentate granule cells. Left unchecked, mossy-cell activity can impair the encoding of memories and potentially cause epilepsy. Dr. Castillo’s team has discovered several mechanisms by which cannabinoid receptors on mossy-cell axons can dampen the excitation of granule cells. The new findings suggest that promoting cannabinoid signaling might be a useful strategy for treating epileptic seizures.

Dr. Castillo is a professor in the Dominick P. Purpura Department of Neuroscience and of psychiatry and behavioral sciences, and is the Harold and Muriel Block Chair in Neuroscience at Einstein.

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