SYNAPTIC ACTIVATION OF KAINATE RECEPTORS ON HIPPOCAMPAL INTERNEURONS

Although kainate receptor activation has been known to evoke epileptif orm activity, little is known about the role of kainate receptors in s ynaptic transmission. Here we report that kainate (KA) receptors are p resent on interneurons and, when activated, cause a large increase in the frequency of spontaneous inhibitory postsynaptic currents (IPSCs) driven by action potentials. Stimulation of excitatory afferents gener ates a pharmacologically identifiable synaptic current mediated by KA receptors in interneurons. This synaptic current is similar to that me diated by AM PA receptors in its response to short stimulus trains, cu rrent-voltage relations and coefficient of variation, but it is much s maller in peak amplitude and much slower. KA application also consider ably depresses evoked IPSCs. This depression seems to be in large part an indirect consequence of the repetitive firing evoked by the activa tion of the interneuronal somatic/dendritic KA receptors.