FIGURE 3.

Characterization of our rapid solution exchange and heterologous expression systems. A, open tip recordings were used to assess the solution exchange time of our θ-glass application pipette system. The solution is applied using SF-77B perfusion step controlled by PatchMaster software through digital to analog converter output in EPC10 amplifier. The 10–90% rise time of the liquid junction currents (resulting from the application of a 1:10 diluted extracellular solution) is ∼250 μs (B). A and B are the same current trace shown in different time scales. C and D, representative traces of outside-out (C) and whole-cell (D) currents recorded from HEK293 cells expressing homomeric GluK2a receptors, evoked by rapid application of glutamate using the rapid solution exchange system. The time courses of current onset and desensitization are comparable with data reported by other laboratories. E–H, no endogenous GluK2a expression in HEK293 cells. E, GluK2a mRNA was not detected by RT-PCR assay in nontransfected HEK293 cells (left lane). F, Western blot analyses confirm the lack of endogenous GluK2a protein in nontransfected HEK293 cells (left lane). G and H, in the absence of heterologously expressed GluK2a, no whole-cell current was evoked by 1 mm glutamate in either vector (G) or 14-3-3τ (H)-transfected HEK293 cells. IB, immunoblot.