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. 2019 May 15;39(20):3812–3831. doi: 10.1523/JNEUROSCI.2130-18.2019

Figure 1.

Figure 1.

A/C synaptic inputs are incapable of inducing LTP-IE of CA3-PCs. A, Induction of LTP-IE by the repetitive somatic firing at 10 Hz (gray) or 20 Hz MF stimulation (red) for 2 s delivered at 0 s. B, Neither local electrical stimulation of A/C fibers (orange) nor high-K+ aCSF (cyan) induced the LTP-IE of CA3-PCs. Electrical stimulation was delivered at 0 min. To enhance A/C fiber inputs, high-K+ aCSF containing 2 μm DCG-IV was applied as indicated by the horizontal bar. A, B, Insets, Representative traces for AP responses (left panels) to conditioning stimulations, and subthreshold voltage responses (right panels) to +30 and −10 pA recorded before (black) and 30 min after conditioning (colored). The conditioning methods are indicated by the same color code in each panel. Ca, Representative traces for membrane potential during and after applying high-K aCSF, which contained 2 μm DCG-IV to suppress MF and PP synaptic inputs (see Materials and Methods). Membrane potential (top) and current injection (bottom) are depicted on the same time axis. The gray and black boxed regions are expanded in time on the inset. To readjust the membrane potential depolarized by high-K+ aCSF to the control level, hyperpolarizing current was injected (gray box, left inset). After a sufficient number of APs were elicited, the generation of APs was stopped by the injection of additional hyperpolarizing current (black box, right inset) The current injection time points are indicated by arrowheads. Cb, Application of synaptic blockers (PTX and CNQX) completely abolished not only the firing of CA3-PCs, but also subthreshold synaptic responses caused by high-K+ aCSF. Da, Relative changes of Gin (ΔGin) as a function of somatic AP frequency elicited by conditioning stimuli (gray, 10 Hz 2 s AP train; red, 20 Hz 2 s MF stimulation; yellow, local stimulation of A/C fibers; cyan, high-K+ aCSF). Db, Summary for ΔGin measured at 30 min after indicated conditioning. The number of APs elicited by each conditioning are also shown. n.s., No statistical significance. *p < 0.05; ***p < 0.005.