An N-sulfonyl-polyamine that acts as a potent and more specific antagonist ofnMDA receptors expressed in Xenopus oocytes (IC50 = 310, 340nM in NR1/NR2A and NR1/NR2B, respectively). The inhibition appears to be voltage-dependent and is non-competitive with respect to glutamate and glycine. Exhibits about 50-fold greater selectivity over NR1/NR2C and NR1/NR2D receptors (IC50 = 16 and 13uM, respectively). Also shown to block c-AMP-dependent, calmodulin-activated phosphodiesterase (IC50 = 58uM) and diminishes the induction of ornithine decarboxylase. At higher concentration (˜100uM) it is shown to reduce spontaneous epileptiform activity in mouse cortical slices.