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. 2003 Jul 23;23(16):6660–6670. doi: 10.1523/JNEUROSCI.23-16-06660.2003

Figure 5.

Figure 5.

Evidence for a mainly extrasynaptic location of KARs. A, Glutamatergic synapses were activated in a defined region of the apical dendrite by local electrical stimulation. In the presence of d-AP-5 (control) (1) single stimuli reliably evoked EPSCs. GYKI 53655 blocked ∼90% of the EPSC amplitude (2). Because the remaining current was blocked completely by CNQX (3), it has to be mediated by KARs. Interestingly, the mixed AMPA/KAR-mediated EPSC and the isolated KAR-mediated EPSC showed nearly identical fast kinetics (4). In the same experiment glutamate was applied photolytically to the region of synaptic stimulation (B). Only ∼40% of the glutamate response amplitude was blocked by GYKI 53655. Because photolytic application of glutamate also activates extrasynaptic receptors, these results strongly suggest that KARs are located mainly at extrasynaptic sites. A, B, Single experiments are shown. C, Statistical evaluation of the experiments shown in A, B. D, Spatial resolution of electrical stimulation (single experiment).