The discovery that depolarization-induced suppression of inhibition is mediated by endocannabinoids finally explained why both the CB1 receptor and the endocannabinoids are both so widely distributed in the brain. Depolarization-induced suppression of inhibition is a very common form of short-term plasticity and thus needs to be mediated by a commonly found neurotransmitter. The use of endocannabinoids such as anandamide and 2-arachidonoyl glycerol in this method of signalling is quite logical, since both molecules can be synthesized relatively easily from lipids in the plasma membrane, a fundamental constituent of all cells. Depolarization-induced suppression of inhibition is therefore the primary cortical process mediated by the endocannabinoids, and may contribute to many forms of cortical plasticity and synaptic strengthening, such as in long-term potentiation (Carlson "et al." 2002).