Figure 3

Light stimulation of primary hippocampal neurons grown on P3HT induces membrane hyperpolarization.

(a) Analysis of the distribution of neurons grown on either glass:P3HT or glass and responding with a decreased, increased or stable firing rate during the light pulse (Glass:P3HT vs Glass: decreasing 55.56% vs 0.00%; stable 37.04% vs 100.00%, increasing 7.40% vs 0.00%). The percentage of cell showing a decrease during the pulse on glass:P3HT is statistically significant with respect to those on glass (p < 0.0001, Fisher’s test). For neurons on glass:P3HT showing a decrease in the firing rate during the light pulse, the distribution of the response after the pulse is also described as part of the whole (decreasing 13.33%; stable 20.00%, increasing 66.67%). (b) Mean (±sem) hyperpolarization amplitude recorded in neurons grown on glass:P3HT (grey and black bars) or glass (white bar) in the presence of the synaptic blockers AP5/CNQX/PTX (glass:P3HT, −5.74 ± 0.71 mV, n = 27; glass:P3HT with blockers, −5.62 ± 1.55 mV, n = 14; Glass, −1.08 ± 0.10 mV, n = 14; Glass:P3HT vs Glass ****p < 0.0001, Glass:P3HT Blockers vs Glass ****p < 0.0001, Glass:P3HT vs Glass:P3HT Blockers p > 0.9999; Kruskal-Wallis test with Dunn’s multiple comparison test). (c) Linear correlation between the hyperpolarization amplitude during illumination and the firing rate after illumination in individual neurons grown on glass:P3HT (Pearson’s correlation coefficient r = 0.69, n = 27; p < 0.001). (d) Amplitude of the hyperpolarization response to 15 consecutive stimulations (green bars) performed at 0.1 Hz. Potential traces were averaged over the recorded cells on glass:P3HT (n = 27). Left panel: full traces for sweeps 1, 2 and 15. Right panel: average hyperpolarization amplitude of cells grown onto glass:P3HT over the repeated stimulations (sweeps 1–15).