| Abstract: | The mechanism of blocking effect of phenylcyclohexyl derivative, IEM-1925, on ionotropic glutamate receptors of the NMDA and AMPA types has been studied on the rat isolated brain neurons. The whole-cell configuration of patck clanp recording technique was used equilibrium conditions and -80 mV holding potential, the IEM-1925 manifests nonselective action on open channels of both receptors. However, the prominent differences in the mechanism of the blocking effect were revealed. Although IEM-1925 can not enter the closed channels of both types, its molecule are able to leave closed channels of the AMPA but not the NMDA receptors. Hyperpolarization reduces removal of blocker from the open channels of the NMDA receptors. Contrary to that, hyperpolarization facilitates going out of the IEM-1925 to cytozol from both open and closed channels. Evidently, the bloker can pass through the AMPA receptor channels into the cell, and the gating mechanism of these channels is located above the binding site for the blocker. The blocking action of the IEM-1925 on the NMDA and AMPA receptors was compared with its potency to weaken the tremor evoked by subcutaneous injection of arecoline to mice. The observed differences in the mechanisms of action help to explain the ambiguous effects of channel blocking drugs on experimental models of pathological processes. |
