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. 2000 Apr 15;524(Pt 2):485–502. doi: 10.1111/j.1469-7793.2000.00485.x

Figure 6. Spontaneous synaptic events and CA3 cell firing.

Figure 6

A, spontaneous discharge of a CA3 pyramidal cell (spikes are cut) with no injected current. Hyperpolarisations due to IPSPs impinging during the repolarisation trajectory between spikes appear to increase the interval between action potentials. B, in this cell 28 % of action potentials (n = 529) were preceded by an EPSP. C, 72 % of action potentials appeared to be initiated in the absence of an EPSP (larger than 0.3 mV). D, an IPSP occurred in the 20 ms preceding the generation of 22 % of action potentials. E, the spontaneous discharge of a CA3 inhibitory cell (spikes are cut) with no injected current. F and G, in this cell 95 % of action potentials (n = 450) were preceded by an EPSP (F), while 5 % of the action potentials appeared to be initiated in the absence of an EPSP (G). Spontaneous, hyperpolarising IPSPs were difficult to detect at resting potential in this cell. H, histogram of intervals between EPSP onset and action potential initiation (n = 450).