Figure 2.

Electroporation on E14.5 resulted in selective transfection of pyramidal neurons. Different interneuronal markers were used to characterize RFP⁺ cells in the pyramidal layers. A, B, RFP⁺ neurons did not colocalize with neither calretinin (A) or parvalbumin (B). C, Single examples of action potential discharge of RFP⁺ (top) and RFP⁻ (middle and bottom) hippocampal CA1 neurons in electroporated brain. The traces illustrate the last 20 s epoch of a 60 s suprathreshold depolarizing current injection (+600 pA) from which the firing frequency was calculated (see values adjacent to traces). All RFP⁺ neurons (14 of 14 cells tested) displayed low-frequency discharge, whereas RFP⁻ neurons displayed either low (<4 Hz; 13 of 15 cells tested) or high-frequency discharge (>40 Hz; 2 of 15 cells tested). D, Morphology of an RFP-positive neuron located in the hippocampal CA1 region from which whole-cell current-clamp recording was performed. Scale bar, 100 μm. Note that because of dialysis and exchange of cell cytoplasm with the pipette solution during recording, varying amounts of RFP fluorescence are lost during whole-cell recording, and in many cases, it is not detected after post hoc analysis. SO, Stratum oriens; SR, stratum radiatum; SP, stratum pyramidale; SL-M, stratum lacunosam-moleculare.