Developmental regulation of the quantal contribution of AMPA and kainate receptor-mediated transmission at the thalamocortical input. A, Examples of mean eEPSCs from three different cells showing the exponential fit to the decay (gray lines) and the decay time constants. The quantal amplitude (Q) of the AMPA (Q_AMPA) and kainate (Q_kainate) components estimated from the evoked mEPSCs from the same cells is shown, and the calculated mean quantal content (the number of quanta released per trial; m) for each component is given. B, Summary data plotting m_kainate versus m_AMPA for the eEPSC in all cells (dashed line is the line of unity). Black circles represent cells in which Q_kainate could not be determined, so m_kainate was determined using the mean Q_kainate value (n = 29); gray circles represent cells in which values for both Q_AMPA and Q_kainate could be determined (n = 13), and mean value for all data pooled is also plotted (open circle). C, Developmental profile for the amount of charge carried by the kainate receptor-mediated component of the eEPSC (expressed as percentage of total EPSC charge; P2-P3, n = 5; P4, n = 12; P5, n = 10; P6-P7, n = 6; P8, n = 7; P9, n = 2). D, Developmental profiles for Q_AMPA (filled circles; P2-P3, n = 5; P4, n = 12; P5, n = 10; P6-P7, n = 6; P8-P9, n = 9) and Q_kainate (open circles; note that no estimate for Q_kainate was obtained for P2-P3; P4, n = 3; P5, n = 7; P6-P7, n = 2; P8-P9, n = 1). For this and subsequent panels, data for P2-P3, P6-P7, and P8-P9 are binned together. E, Developmental profiles for synaptic AMPA receptor γ (filled circles; P2-P3, n = 2; P4, n = 12; P5, n = 8; P6-P7, n = 4; P8-P9, n = 9) and number of channels (open circles; P2-P3, n = 2; P4, n = 12; P5, n = 8; P6-P7, n = 4; P8-P9, n = 9).F, Developmental profiles for m_AMPA expressed as a ratio of total m (filled circles, solid lines; P2-P3, n = 5; P4, n = 12; P5, n = 10; P6-P7, n = 6; P8-P9, n = 9) and m_kainate as a ratio of total m (open circles, dashed lines; P2-P3, n = 5; P4, n = 12; P5, n = 10; P6-P7, n = 6; P8-P9, n = 9). G, Developmental profile for m_kainate/m_AMPA (P2-P3, n = 5; P4, n = 12; P5, n = 10; P6-P7, n = 6; P8-P9, n = 9).