The CB2 receptor is not associated with the mental effects that the CB1 receptor is, in fact its distribution is almost completely opposite. It is barely found in the brain, but is found in moderate amounts around the body, and in high levels in some organs and the intestines.
Initial investigation of CB2 receptor expression patterns focused on the presence of CB2 receptors in the peripheral tissues of the immune system and found CB2 receptors throughout tissues of the spleen, tonsils, and thymus gland. They are also found on immune cells such as monocytes, macrophages, B-cells, and T-cells.
Investigation into the expression patterns of the CB2 receptors revealed that CB2 receptors are also in the brain, though not as densely as the CB1 receptor and located on different cells.
CB2 receptors are also found throughout the gastrointestinal system, where they modulate intestinal inflammatory response. This makes the CB2 receptor is a potential therapeutic target for inflammatory bowel diseases, such as Crohn’s disease and ulcerative colitis, this is already borne out by anecdotal reports from patients and is an area of intense research going forward. The role of endocannabinoids, as such, play an important role in inhibiting unnecessary immune action upon the natural gut flora. Dysfunction of this system, could result in diseases such as those mentioned above, and Irritable Bowel Syndrome. Cannabinoids that work on the CB2 receptor have been shown to reduce symptoms in IBS patients.
Peripheral Nervous System
Application of CB2 targeting cannabinoids has found that these receptors are also involved in mediating the pain relieving effects in the peripheral nervous system. However, these receptors are not expressed by the nerves, and at this point it is unknown where exactly they are. Possible candidates include mast cells, known to facilitate the inflammatory response. It is likely that CB2 targeting cannabinoids reduce pain by reducing the inflammatory response.