Whereas every other neurotransmitters enables nerve impulses to jump across the synaptic cleft, endocannabinoid compounds travel backward and interact with CB receptors strategically situated on “presynaptic nerve axons...retrograde signaling facilitates a process known as “presynaptic inhibition” which interrupts and slows down the release of other neurotransmitters such as norepinephrine and glutamate; and cannabinoid  receptors also transmit chemical signals that “slow down” the release of sedative neurotransmitters such as GABA (which binds to the same receptor as Valium and alcohol). By inhibiting GABA activity, the endocannabinoid system speeds things up (213). - Martin A. Lee, Smoke Signals