Cannabinoid receptors: which cells, where, how, and why?

Localization of the mRNA for this receptor has identified many regions of the rat brain in which the gene for this receptor is active. Several of these regions are consistent with the cannabinoid- or marijuana-induced effects that occur in both laboratory animals and humans. However, other labeled regions are not easily associated with well-known effects of marijuana (Matsuda et al., submitted for publication). Although great progress has been achieved in elucidating the mechanism of action of cannabis in recent years (Howlett et al. 1990), much remains to be discovered about the expression of cannabinoid receptors in the brain and exactly how this receptor influences numerous brain functions.