First, the identification and cloning of two different cannabinoid receptor subtypes, the brain cannabinoid receptor (CB1), which is located in neural cells, and the peripheral cannabinoid receptor (CB2), which is expressed in various cells of the immune system. Second, the identification of two groups of endogenous ligands for the cannabinoid receptors (anandamides and 2-arachidonyl-glycerol). Research in progress is presently exploring the biochemical and pharmacological aspects of this new system.

These recent discoveries represent that cannabinoids are not only the psychoactive constituents of a drug of abuse, marihuana, but they constitute an endogenous system (endogenous ligands + receptor signalling pathways) that might play a role in a variety of physiological processes, mainly in the brain. It has been proposed, based on the distribution of cannabinoid receptor binding and mRNA levels in the brain and on the well-known pharmacological effects of plant and synthetic cannabinoids, that the endogenous cannabinoid system would be involved in the regulation of motor behavior, cognition, learning and memory, neuroendocrine control and antinociception, as well as that it might play a role in brain development.

A future objective will be, then, to elucidate the role of the endogenous cannabinoid system in these processes. Moreover, endogenous cannabinoids might represent a new family of compounds susceptible to be chemically modified and used with therapeutic purposes in the physiopathology of these processes.