Fig. 5
Persistent Na+ current (INa,P) amplifies LPP-evoked EPSP summation and is essential for burst firing. A Left & Middle, AP trains in BS elicited by somatic rheobase current injection in control (red, Con) and after applying riluzole (blue, Ril, 10 μM). Right, Mean Finit before and after application of riluzole (Con, 176.5 ± 12.9 Hz; Ril, 5.7 ± 1.4 Hz; n = 10; **p < 0.01). B Left, EPSP summation evoked by HFSL-2 before and after applying riluzole. Right, Cumulative EPSP amplitudes in control and riluzole conditions (n = 24). C Representative voltage response to HFSH-2 (left) and time course of normalized EPSP before and after HFSH-2 (right, n = 5) in the presence of riluzole. D Similar as in C, but evoked by a pairing protocol. E Early (LTP5, open circle) and late phase (LTP30, closed circle) LTP evoked by a pairing protocol in control and riluzole conditions, showing that late LTPAP was rescued (Con, n = 14; Ril, n = 10). F Cartoon for focal application of riluzole (50 μM) at soma or dendrite during somatic current injection or HFSL of LPP. Scale bar is 100 μm. G Representative traces (upper) and mean Finit (lower) of intrinsic AP bursts with somatic (left) and dendritic (right) puff of riluzole [Soma, 128.8 ± 12.8 Hz (Con) vs. 9.0 ± 3.0 Hz (Ril), n = 12, **p < 0.01; Dend, 137.5 ± 13.3 Hz (Con) vs. 137.6 ± 14.1 Hz, n = 6]. H Similar as in G, but area of subthreshold EPSP summation evoked by HFSL-2. The EPSP summation was not reduced by somatic puff (left) but by dendritic puff (right) [Soma, 2.6 ± 0.3 mV s (Con) vs. 2.5 ± 0.4 mV s (Ril), n = 7; Dend, 2.9 ± 0.5 mV s (Con) vs. 1.1 ± 0.1 mV s, n = 8]. I Left, Procedure for measuring INa,P in GCs. Right, Representative current responses of RS- (black) and BS-GC (red) to a voltage ramp. J Peak INa,P amplitude in RS and BS cells (RS, 144.9 ± 15.6 pA, n = 10; BS, 245.4 ± 16.4 pA, n = 8; ***p < 0.001). Shades and error bars, S.E.M. *p < 0.05. **p < 0.01. ***p < 0.001. n.s., not significant (p > 0.05)