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. 2006 Dec 21;580(Pt 2):373–383. doi: 10.1113/jphysiol.2006.123570

Figure 6. Extrasynaptic NMDARs mediate the tonic current.

Figure 6

Effect of MK801 (20 μm) on the tonic current (A) and on the peak amplitude of the NMDAR-mediated EPSCs evoked by Schaffer collateral stimulations (B) in a pyramidal cell. Note that the synaptic stimulation was ceased (Stim OFF) during the first 4.5 min application of the use-dependent blocker and then resumed (Stim ON), as indicated in A. MK801 failed to affect the amplitude of the first evoked EPSC while progressively inhibited the subsequent ones (B). Time 0 corresponds to stim OFF and MK801 application. The inset shows the superposition of the last EPSC evoked before MK801 application (a) and of the first EPSC elicited after 4.5 min MK801 (b). Note the faster decay time of the EPSC in b. C, comparison of percentage inhibition produced by 4–5 min application of MK801 on the tonic and synaptic NMDAR-mediated currents. Currents are normalized to the amplitude of the currents fully blocked by MK801 or by addition of 50 μm d-AP5.