Glial endocannabinoid system in pain modulation.

Pain is affecting the human for centuries and there still is no satisfactory strategy for patients suffering pain particularly chronic pain although intensive studies about its mechanism have been performed in order to improve the treatment of pain. Cannabinoid is a group of chemicals extracted from plants and has a long history in treating pain through the endogenous cannabinoid receptor in the body; however, its application in pain treatment is limited due to its inverse effects. Recent studies have indicated that glial cells play critical role in mediating pain processing through multiple pathway, including excitatory and inhibitory neurotransmission in different levels of the nervous system. Furthermore, the glial cells are found to express cannabinoid receptors. This review summarized the recent studies about the cannabinoid system in glial cells, which may provide some insight for the studying of pain.