Figure 6

K⁺-evoked firing activity of hippocampal slices can be inhibited by NIR stimulation.

(a) Experimental set-up and representative trace (overlay of 30 sweeps) under illumination (red bar; 780 nm, 500 ms, 24 mW/mm²). (b,c) Mean (±sem) percent firing changes during (b) and after (c) illumination. During: Glass:PCPDTBT, −46.44 ± 5.11%, n = 80; Glass, 2.27 ± 4.73%, n = 97; ****p < 0.0001. After: Glass:PCPDTBT, −10.60 ± 6.67%, n = 80; Glass, 8.44 ± 5.18%, n = 97; **p < 0.01, Mann-Whitney U test. (d) Mean (±sem) percent firing changes during illumination for three distance ranges of the electrode from the PCPDTBT or glass surface (0–100 μm: Glass:PCPDTBT, −51.82 ± 6.74%, n = 36; Glass, 5.24 ± 6.57%, n = 38; ****p < 0.0001. 100–200 μm: Glass:PCPDTBT, −46.92 ± 7.97%, n = 20 Glass, −7.07 ± 9.84%, n = 27; ***p < 0.001. 200–400 μm; Glass:PCPDTBT, −37.96 ± 12.08%, n = 24 Glass, 4.76 ± 8.73%, n = 32, **p < 0.01. Kolmogorov-Smirnov test). (e) Distribution of neurons, layered onto Glass:PCPDTBT or glass, showing a statistically significant decrease (black), increase (white) or remained stable (grey) during illumination (Glass:PCPDTBT vs Glass: decreasing 55.00% vs 14.43%; stable 43.75% vs 75.26%; increasing 1.25% vs 10.31%). The percentage of cell showing a decrease on Glass: PCPDTBT is statistically significant with respect of those on Glass (p < 0.001, Fisher’s test). For cells showing a decrease during illumination, the distribution after the pulse is reported as part of the whole (Glass: PCPDTBT vs Glass: decreasing 47.73% vs 64.29%; stable 40.91% vs 14.29%; increasing 11.36% vs 21.43%). (f) PSTH (bins 50 ms, mean ± sem) of neurons on glass:PCPDTBT or glass. Neurons on Glass:PCPDTBT showed a significant decrease of the firing activity during the pulse (n = 44, black bars) with respect to those on Glass (n = 97, white bars). The horizontal broken line represents the average baseline value, the horizontal red bar represents the NIR stimulation.