Fig. 6.

Properties of isolated AMPA receptor (AMPAR)-mediated EPSCs evoked in the nRt. A: pharmacologically isolated type 1 (black) and type 2 (gray) AMPAR-mediated EPSCs recorded in representative nRt cells in the presence of the NMDAR antagonist d-(−)-2-amino-5-phosphopentanoic acid (d-AP5) at a holding potential of −70 mV. As shown in the example (A1; each trace is the average of ∼10 EPSCs), type 1 responses tended to be larger and faster. The bottom overlay of the two traces, normalized to the peak and aligned to the onset of the response, highlights the slower rise and decay time course of EPSCs in type 2. These strong differences in the kinetics and amplitude of the total population of AMPAR-mediated responses were apparent in the population statistics (A2) and confirmed the slower rise and decay time, longer half-width, and smaller amplitude of the EPSCs in type 2 (n = 7) compared with type 1 (n = 8). B: example of evoked EPSCs obtained at a range of potentials between −75 and +50 mV using 10-mV voltage increments (1) for a type 1 response (top traces) and a type 2 response (bottom traces) in two nRt cells under control conditions (left traces) and during the application of d-AP5 (traces expanded along the x-axis), which blocks the late and slow component of the response (middle traces), leaving only the fast early component of the EPSC. Each trace is the average of two (type 2) or three (type 1) trials. Mean AMPA conductance tended to be larger in type 1 (n = 6) compared with type 2 (n = 4), although the differences were not significantly different (B2). *P < 0.05; **P < 0.01.