The endocannabinoid system was first characterized as the neuronal system to which the psychoactive constituent of cannabis, delta-9-tetrahydrocannabinol (THC), interacted to exert its effects on physiology and behavior. The endocannabinoid system is a unique system, exerting modulatory actions in both central tissue and in the periphery. In the brain, endocannabinoids are generated “on demand” and act retrogradely to regulate release of neurotransmitters. At the signaling level, two cannabinoid receptors have been characterized to date (Howlett, 2002). The cannabinoid CB1 receptor is the receptor that is expressed ubiquitously throughout most regions of the brain (Herkenham et al., 1991; Moldrich and Wenger, 2000; Tsou et al., 1998); however, the CB1 receptor is also known to exhibit some expression patterns in peripheral tissue, such as immune cells, vascular tissue and adipocytes (Cota et al., 2003; Hillard, 2000; Parolaro, 1999). While the CB2 receptor is located predominately in peripheral immune cells and organs (Munro et al., 1993), CB2 receptors are also expressed by microglial cells in injured, infected or inflamed CNS tissue (Benito et al., 2008). There is also recent evidence that cannabinoid CB2
