In neuroscience, retrograde signaling is a phenomenon in which a signal travels from a postsynaptic neuron to a presynaptic one. Endocannabinoids are known to play a role in retrograde signaling, with the molecules being synthesized postsynaptically and acting presynaptically. Retrograde signaling may also play a role in long-term potentiation, a proposed mechanism of learning and memory, although this is controversial (see Retrograde signaling in LTP).