Figure 10.

Effects of combined application of TTX (1 μm) and 4-AP (1 mm) on light-evoked action potential in Cajal-Retzius cells, and light-evoked synaptic currents in interneurons and pyramidal cells. A, Top, Light-evoked action potentials in Cajal-Retzius cells are prevented by adding TTX and 4-AP (black bar) to the external solution (four sweeps superimposed in both conditions). Bottom, Summary plot showing the time course of the effect (norm APs, normalized number of action potentials; empty circles and bars, mean and SE). B, Top, Light-evoked synaptic currents in interneurons are not abolished by the combined application of TTX and 4-AP. Notice however, the increased latency of the light-evoked events (dotted blue line indicates the beginning of the light flash for reference). Four responses superimposed in both condition. Bottom, Summary graph form several experiments (norm peak, normalized peak of the synaptic response). C, As in B; however, notice that the application of TTX and 4-AP completely abolishes responses in pyramidal neurons.