Stock Photo: SYNAPSE. SYNAPSE LTP (long-term potentiation). Mechanism of LTP (long-term potentiation), which plays a role in learning. Stage 1 (See images no. 11969 05 and 11970 05 for stages 2 and 3). In response to a stimulus (sight, taste, touch, etc.), an electrical signal is produced which triggers the release of massive quantities of glutamate (purple triangles) by the presynaptic element. This in turn triggers a massive release of calcium (red spheres) in the dendrite (postsynaptic element), se