Figure 1. A tribute to the discoveries unraveling the endocannabinoid system.

A,B) First identification of the chemical structure with its absolute configuration of the psychoactive compound in marijuana, Δ⁹-THC (Gaoni and Mechoulam 1967). C) First demonstration by competitive inhibition of the existence of a high affinity, stereoselective, pharmacologically distinct cannabinoid receptor in brain tissue (Devane et al., 1988). D) The 3D molecular model of the 7-transmembrane CB₁ receptor (Shim, 2009). E) Localization of CB₁ by high affinity receptor binding and autoradiography in the rat (Herkenham et al 1990), and F) by PET in human brain (Burns et al 2007). G) Mass spectra of anandamide (Devane 1992) and H-J) 2-AG, together with the chemical structures of the two major endocannabinoids (Mechoulam et al., 1995). The individual figures have been modified from the originals with permission from the authors.