Editing Cannabinoid (section)

==== Retrograde signal ====
Conventional neurotransmitters are released from a 'presynaptic' cell and activate appropriate receptors on a 'postsynaptic' cell, where presynaptic and postsynaptic designate the sending and receiving sides of a synapse, respectively. Endocannabinoids, on the other hand, are described as [[Retrograde signaling|retrograde transmitters]] because they most commonly travel 'backward' against the usual synaptic transmitter flow. They are, in effect, released from the postsynaptic cell and act on the presynaptic cell, where the target receptors are densely concentrated on axonal terminals in the zones from which conventional neurotransmitters are released. Activation of cannabinoid receptors temporarily reduces the amount of conventional neurotransmitter released. This endocannabinoid-mediated system permits the postsynaptic cell to control its own incoming synaptic traffic. The ultimate effect on the endocannabinoid-releasing cell depends on the nature of the conventional transmitter being controlled. For instance, when the release of the inhibitory transmitter [[GABA]] is reduced, the net effect is an increase in the excitability of the endocannabinoid-releasing cell. On the converse, when release of the excitatory neurotransmitter [[Glutamate (neurotransmitter)|glutamate]] is reduced, the net effect is a decrease in the excitability of the endocannabinoid-releasing cell.<ref>{{cite book | vauthors = Vaughan CW, Christie MJ | title = Cannabinoids | chapter = Retrograde signalling by endocannabinoids | series = Handbook of Experimental Pharmacology | volume = 168 | issue = 168 | pages = 367–383 | date = 2005 | pmid = 16596781 | doi = 10.1007/3-540-26573-2_12 | isbn = 3-540-22565-X }}</ref> {{citation needed|date=December 2013}}