Figure 7

Application of exogenous glutamate does not lead to receptor desensitization. A: Currents in PnC giant neurons evoked by local uncaging of CNB-caged glutamate with a 10 μs UV-flash (left) and by presynaptic burst stimulation of auditory fibers in rat brain slices (right). Vertical scale bar corresponds to 300 pA, horizontal scalebar to 50 ms. B: Averaged amplitudes of glutamate-evoked currents (GECs, white triangles) evoked by photolysis of caged glutamate around the giant neuron soma under examination. 100 glutamate applications at 1 Hz produced no change in current amplitude; the means of the first ten and the last ten amplitudes (n = 9 PnC giant neurons) were not significantly different. Error bars indicate S.E.M. between cells. C: Averaged glutamate evoked currents (20 repetitions at 0.1 Hz per cell), before (control: C) and during synaptic depression (test: T). GECs were normalized to the average GEC of each cell under control conditions, since absolute amplitudes differed between cells. Synaptic depression was induced using a sequence of 100 bursts applied to auditory afferent fibers (black circles). cEPSC amplitudes were normalized to the first evoked cEPSC. Glutamate evoked currents did not change during synaptic depression (n = 11). Error bars indicate S.E.M.