Figure 3.

Properties of active and passive spike propagation in GnRH neuron dendrites. Whole-cell recordings were performed at the soma while simultaneous on-cell recordings were performed on the dendrite of GnRH neurons. Ai, The soma was held in voltage clamp and an action potential waveform was injected into the cell (top trace). This induced a dendritic spike that was recorded in the on-cell recording electrode (bottom trace). The first derivative of the somatic membrane potential is shown in the middle trace. In the cell shown in Ai, the peak of the dendritic spike comes before the peak of the first derivative of the somatic voltage. Aii, After bath application of 1 μm TTX, the amplitude of the dendritic spike is reduced without affecting the amplitude of the voltage-clamp spike. B, The effect of TTX on the dendritic spike recorded from the neuron in A is shown at a higher temporal resolution in B. Black, Control; gray, after TTX. C, Summary graph showing the effect of TTX on dendritic spike amplitude. D, Summary graph showing that the effect of TTX on dendritic spike amplitude is greater for spikes recorded at greater distances from the soma. E, Summary graph showing the effect of the latency of the dendritic spike before and after TTX. Negative latencies indicate that the peak of the dendritic spike occurred before the peak of the first derivative of the somatic voltage.