Figure 1. Distinctive features of synaptic kainate receptors.

a | Synaptic kainate receptors mediate smaller amplitude currents with much slower kinetics than AMPA receptors. Traces from recordings of synaptic currents at mossy fibre–CA3 synapses in the hippocampus show a mixed AMPA and kainate receptor-mediated excitatory postsynaptic current (EPSC_AMPA–KA; black), which is predominantly mediated by AMPA receptors, the low-amplitude pharmacologically isolated EPSC_KA (grey), and the peak-scaled EPSC_KA (red), which illustrates the relatively slow kinetics of kainate receptors. b | Repetitive activation of pharmacologically isolated mossy fibre kainate receptors (at 20 Hz in the example) results in EPSC_KA summation and increases the total charge transferred during the synaptic currents. c | Excitatory postsynaptic potentials (EPSPs) recorded during a train of mossy fibre stimulation exhibit a tonic depolarization ‘envelope’ that is contributed to by the activation of kainate receptors. This is evident in the example traces as the difference between EPSP_AMPA–KA (black) and EPSP_AMPA (blue) recorded in the presence of the selective postsynaptic kainate receptor antagonist UBP310 (REF. 29). d | Incorporation of the GluK4 and GluK5 subunits shape postsynaptic kainate receptor responses. The left panel shows example traces of EPSCs_KA recorded from CA3 pyramidal cells following stimulation of mossy fibre projections from wild-type (black) and GluK4^−/− (blue) mice (A. Contractor, unpublished results). The right panel shows that under the same recording conditions as in the previous experiment, the EPSC_KA at this synapse exhibits faster kinetics in GluK5^−/− mice (green) than in wild-type mice (black)⁴⁶. Parts a and d (right panel) are modified, with permission, from REF. 46 © (2003) Society for Neuroscience. Part b is modified, with permission, from REF. 126 © (2007) Society for Neuroscience. Part c is modified, with permission, from REF. 29 © (2012) Oxford University Press.