Figure 2. Zinc Changes Desensitization and Sensitivity to Glutamate of GluK3 Currents Recorded in Outside-Out Patches.
(A) Effect of various concentrations of zinc on currents evoked by glutamate (10 mM) on an outside-out patch pulled from a GluK3-expressing cell is presented.
(B) Normalization of traces in (A) reveals the dose-dependent effect of zinc on desensitization kinetics.
(C) Values of τdes for GluK2 and GluK3 mediated currents with increasing zinc concentration (n = 5). A total of 30 and 100 μM zinc induces a significant increase of τdes relative to control (Ctrl). ***p < 0.001.
(D and E) Effect of zinc on currents evoked by 1 ms pulses of glutamate (10 mM) is illustrated. In (E), the two traces of (D) are normalized to maximum amplitude.
(F–H) Effect of zinc on glutamate sensitivity is demonstrated. (F) The amplitude of currents relative to their maximum amplitude (30 mM glutamate) is increased in the presence of 100 μM zinc (red traces). (G) Glutamate dose-response curves in the absence (black circles) or presence (red squares) of 100 μM zinc are shown. The lines are fits with the Hill equation, with EC50 values of 10.1 ± 1.1 and 4.8 ± 1.1 mM, respectively. (H) Relationship between current amplitude and decay time with (red squares) or without (black circles) 100 μM zinc (n = 4–9) is shown.
(I) Paired applications of glutamate (10 mM; 100 ms) separated by intervals ranging from 0.2 to 5 s on an outside-out patch pulled from a cell-expressing GluK3, in the absence (top) or presence (bottom) of 100 μM zinc, are illustrated.
(J) Plot of the amplitude ratio of two successive responses versus time interval for GluK3, with (red squares) or without (black circles) 100 μM zinc, is presented. The lines are fits with an exponential equation, with time constant values of 432 ± 1 and 933 ± 1 ms, respectively (n = 5). fract. amplitude, fraction amplitude.