Differences in the pore sizes of the N-methyl-D-aspartate and kainate cation channels.

The cation channels in central nervous system neurons gated by the glutamate agonists N-methyl-D-aspartate (NMDA) and kainate have been shown to be similar, but not identical. To analyze the differences in more detail, the permeabilities of the channels to cations of different sizes have been measured. The kainate channel appears to be larger, and the cation permeabilities are similar to those of the acetylcholine gated channel at the neuromuscular junction. The NMDA channel appears to be about 10% smaller in size.