Figure 7.

Supplement of Zn²⁺ to aCSF allows 50 Hz somatic stimulation to induce reduction of D-type K current and E-S potentiation of PP inputs. Aa, Ab, Outward K⁺ I_K elicited by a depolarizing step to −20 mV (red), −30 mV (blue), and −40 mV (black) from −70 mV before (Aa, top row) and after bath application of 30 μm 4-AP (Aa, bottom row) in the naive and conditioned CA3-PCs. For each condition, the arithmetical subtraction of I_K under the 4-AP (bottom row) from the total I_K (top row) at the same depolarizing step was regarded as I_KD. Representative traces for I_KD are shown in Ab. Ac, Mean values for peak amplitudes of I_KD induced by a step depolarization to −20, −30, and −40 mV under different conditions. Ctrl, Without conditioning; 50 Hz, after 50 Hz somatic AP trains; 50 Hz + Ab^L and 50 Hz + Ab^M, intracellular perfusion of anti-RPTPα Ab^L and anti-RPTPα Ab^M, respectively; 50 Hz + Zn, 100 nm Zn²⁺ supplemented to aCSF. Ba, Number of APs elicited by five PP-EPSP trains at 20 Hz before and after 50 Hz somatic AP trains (arrowhead at 0 min). The 50 Hz AP train alone did not enhance the number of APs induced by PP synaptic inputs (black symbols). With 100 nm ZnCl₂ supplemented to aCSF, however, the 50 Hz AP train enhanced the number of APs (red symbols. For comparison, AP numbers elicited by PP-EPSP bursts at 20 Hz after a 10 Hz somatic AP train are reproduced from Hyun et al. (2015) (gray symbols). Bb, Exemplar traces for temporal summation of 20 Hz PP-EPSPs before (black) and after (blue) the 50 Hz AP train without (left) and with (right) ZnCl₂ supplement. n.s., No statistical significance. *p < 0.05; ***p < 0.005.