The effect of 1, 3-diamines on basal and spermine-stimulated [3H] MK-801 binding was investigated. Systematic variations in the molecular parameters revealed that, in general, lipophilic 1, 3-diamines inhibited and hydrophilic 1, 3-diamines enhanced [3H] MK-801 binding in the nominal absence of glutamate and glycine. Furthermore, 1, 3-diamines which were highly monoprotonated at physiologic pH were more effective in modulating basal ...