Alexey Semyanov and Pei-Yu Shih describe their discovery of potassium as a fundamental form of retrograde synaptic signaling.

RIKEN RESEARCH: Research Highlight
http://www.riken.jp/en/research/rikenresearch/highlights/7603

Reference
Pei-Yu Shih, Leonid P Savtchenko, Naomi Kamasawa, Yulia Dembitskaya, Thomas J McHugh, Dmitri A Rusakov, Ryuichi Shigemoto, and Alexey Semyanov. "Retrograde Synaptic Signaling Mediated by K+ Efflux through Postsynaptic NMDA Receptors." Cell Reports, 2013. doi:10.1016/j.celrep.2013.10.026