Researchers of the Institute of Neurology in London found out that the activation of CB1 receptors causes inhibition of the nerve cells that control the blood vessels of the trigeminus nerve. Migraine involves activation, or the perception of activation, of the blood vessel system of the trigeminus. They concluded that these data "suggest that CB receptors may have therapeutic potential in migraine, cluster headache or other primary headaches." (Source: Akerman S, et al. J Pharmacol Exp Ther 2006 Oct 3; [electronic publication ahead of print])