Article Figures & Data
Figures
- Figure 1.
Properties of GluR6- and GluR6/KA2-mediated currents evoked by long glutamate pulses. A, Dependence of the current peak amplitude on GluR6:KA2 cDNA ratio. Currents were elicited by glutamate pulses (1 mm, 100 ms). B, Typical GluR6 and GluR6/KA2 current responses to glutamate (1 mm, 100 ms). GluR6 and KA2 subunits were transfected at the ratio 1:3. C, Dependence of the rectification index (ratio between the current obtained at membrane potential +120 mV and −120 mV) on GluR6:KA2 cDNA ratio. D, Current–voltage (I–V) curves for current mediated by GluR6 (black triangles) and GluR6/KA2 (gray triangles). GluR6 and KA2 cDNAs were transfected at the ratio 1:3. E, F, Typical GluR6-mediated (E) and GluR6/KA2-mediated (F) currents elicited by glutamate (1 mm and 10 μm). G, Dose–response curve for GluR6 (black triangles) and GluR6/KA2 receptors (gray triangles). H, Same traces as in E and F normalized and superimposed. I, Summary of the desensitization kinetics at different [Glu]. *p < 0.05. J, Typical example of GluR6 and GluR6/KA2 current responses to paired-pulse protocol (1 mm, 100 ms pulse length, 1 s gap). K, Time course of the recovery from desensitization (GluR6 and GluR6/KA2 receptors, black and gray triangles, respectively). In paired-pulse experiments, we only compared traces showing the same peak amplitude when evoked by either 1.5 or 100 ms glutamate pulses. τdes, desensitization time constant; fract., fractional.
- Figure 2.
GluR6/KA2 decay kinetics depends on stimulation pulse length. A, B, GluR6 currents and GluR6/KA2 currents evoked by either long (100 ms) or brief (1.5 ms) glutamate pulses. C, Paired pulses for GluR6- and GluR6/KA2-mediated currents (1 mm, 1.5 ms pulse length, 300 ms gap). D, Summary of the decay kinetics for GluR6 and GluR6/KA2 currents (black and gray bars, respectively) evoked by increasing glutamate pulse duration. E, Time course of recovery from desensitization for GluR6 and GluR6/KA2 receptors (black and gray squares, respectively) obtained with 1.5 ms pulses superimposed on that obtained with 100 ms pulses (same as that shown in Fig. 1M; black and gray triangles for GluR6 and GluR6/KA2 receptors, respectively). fract., Fractional.
- Figure 3.
Model simulation. A, Kinetic scheme previously proposed by Robert and Howe (2003). The rate constants used to simulate the behavior of GluR6 and GluR6/KA2 receptors are listed in supplemental Table 1 (available at www.jneurosci.org as supplemental material). Simulated current traces were obtained by activating 1000 channels at the holding potential of −90 mV. When brief (1.5 ms) pulses were applied, the input waveform was trapezoidal, matching the whole-cell depolarization time course induced by 1.5 ms application of 25 mm potassium concentration saline, as detailed in supplemental Figure 1 (available at www.jneurosci.org as supplemental material). B, E, Simulated GluR6- and GluR6/KA2-mediated current evoked by 1 mm, 100 ms glutamate pulse (left) and by 1 mm, 1.5 ms, glutamate pulse (right). C, F, Simulated paired-pulse protocol for GluR6 and GluR6/KA2 receptors [100 ms, 1 mm, 300 ms gap (left) and 1.5 ms, 1 mm, 300 ms gap (right)]. D, G, Simulated GluR6- and GluR6/KA2-mediated current evoked by a synaptic-like glutamate exposure. The synaptic-like glutamate pulse was assumed to be exponential (see supplemental Model Simulations, available at www.jneurosci.org as supplemental material). H, Summary of the decay time constants for simulated GluR6 and GluR6/KA2 currents elicited by brief (1.5 ms), long (100 ms), and synaptic-like glutamate pulses. I, Time course of the recovery from desensitization for GluR6 and GluR6/KA2 receptors obtained with 1.5 ms pulses and 100 ms pulses (same color and symbol code as in Fig. 2E). fract., Fractional.
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