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Retrograde messenger is a chemical substance that is released from postsynaptic neurons and acts on presynaptic neurons. In the nervous system, information coded by action potentials is transferred from neuron to neuron at a specialized site called “synapse” (Fig. 1). The transmission at Chemical synapses is generally one-directional. Neurotransmitters are released from presynaptic terminals on the arrival of action potentials, and transmit a signal to postsynaptic neurons by activating the corresponding receptors (Fig. 1a). In contrast to this fundamental anterograde information transfer, the signaling from postsynaptic to presynaptic neurons is called retrograde signaling (Fig. 1b) [1,2]. The retrograde signaling can be mediated by either a diffusible factor that is called “retrograde messenger,” or a direct interaction of presynaptic and postsynaptic membrane-bound elements. In typical cases, a retrograde messenger is released from the postsynaptic site lacking...
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