Glutamate but not glycine agonist affinity for NMDA receptors is influenced by small cations.
Nahum-Levy R, Tam E, Shavit S, Benveniste M. Glutamate but not glycine agonist affinity for NMDA receptors is influenced by small cations. J Neurosci. 2002 Apr 01; 22(7):2550-60.