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. 2016 Jan 18;594(4):1005–1015. doi: 10.1113/JP271485

Figure 3. Asynchronous release overcomes the post‐spike relative refractory period .

Figure 3

Aa, paired stimulation protocol where two square current pulses are injected into the neuron at different ISIs (20, 50, 100 or 200 ms). The amplitude of the second pulse is set such that it evokes spikes > 70% of the time only at the longest ISI. The mean reduction in spike probability at short ISIs is shown in panel Ab. Ba, paired stimulation protocol where the first spike is now evoked with extracellular synaptic stimulation to induce synchronous and asynchronous glutamate release. The amplitude of the second pulse (square current injection) is the same as in panel Aa. Asynchronous release is able to overcome the post‐spike refractory period to enhance excitability at short ISIs (Bb).