Functional neuroanatomy of the endocannabinoid system

Several components of the endocannabinoid system have been fully characterized. Among them are two types of cannabinoid receptors (termed CB1 and CB2), endogenous ligands for those receptors (referred to as "endocannabinoids"), and specific enzymes responsible for their degradation and inactivation. The study of the distribution and abundance of these elements in the central nervous system has provided the basis for the well-known effects of exogenous (both natural and synthetic) and endogenous cannabinoids. In addition, recent developments also support the idea that the endocannabinoid system plays a critical neuromodulatory role in the central nervous system. For instance, cannabinoid CB1 receptor activation is known to modify the release of several neurotransmitters, such as glutamate and gamma-aminobutyric acid. However, we still lack knowledge on fundamental aspects of the physiological roles of this system. Interestingly, changes in the distribution and activity of some of these components of the endocannabinoid system have been reported under different pathological conditions, suggesting their possible involvement in the pathogenesis of these diseases. As comprehensive excellent reviews have been recently published, the present review will focus only on the most recent advances in the field, considering a new perspective of the endocannabinoid system as composed of both neuronal and glial divisions.