Comparison of the anticonvulsive activities of organic mono- and dications with their abilities to inhibit NMDA and AMPA glutamate receptors.

The abilities of mono- and dicationic adamantane and phenylcyclohexyl derivatives to (a) block open NMDA and AMPA glutamate receptors in isolated rat brain neurons and (b) prevent convulsions induced in mice by intraventricular NMDA or kainate were studied. Monocations inhibited NMDA receptors in vitro and produced corresponding protection against NMDA-induced convulsions in vivo, but lacked the ability to block AMPA receptors or prevent kainate-induced convulsions. Dications (IEM-1754 and IEM-1925), which inhibited both NMDA and AMPA receptors, were highly effective at protecting against kainate convulsions and were more effective than the corresponding monocations in preventing NMDA convulsions. The origin of convulsions induced by NMDA appears to be based on a component mediated by activation of AMPA receptors. The anticonvulsive activity of IEM-1754 and IEM-1925 were comparable with those of the known NMDA receptor blockers memantine and MK-801. This was combined with an almost complete absence of the side effects characteristic of memantine and MK-801. The complete correspondence between the in vitro data and in vivo results seen with some of the study compounds is evidently associated with their pharmacokinetic properties.