Fig. 8.

Role of Ca²⁺-permeable AMPA receptor-mediated currents in methylmercury (MeHg)-induced hyperexcitability. A: representative current recordings of excitatory postsynaptic currents (EPSCs) in lumbar spinal motor neurons in a control slice compared with exposure to 1-napthyl acetyl spermine (NAS; 100 μM) and to NAS combined with MeHg (20 μM). B: the amplitude of EPSCs recorded in the presence of NAS were significantly different from those in control (P = 1.51e-11, Kolmogorov–Smirnov test). C: there was also a significant rightward shift in the cumulative distribution of EPSC intersynaptic intervals (ISIs; P = 1.42e-30, Kolmogorov–Smirnov test). D: the EPSC amplitude cumulative distribution was significantly different between NAS alone and NAS with MeHg (MeHg + NAS; P = 2.2e-10, Kolmogorov–Smirnov test). E: there was not a significant difference between the ISI cumulative distributions of EPSCs recorded in NAS alone vs. MeHg + NAS. F and G: across the population (n = 5), there was a significant increase (**P = 0.008, Wilcoxon rank sum test) in EPSC ISI under control (115.9 ± 10 ms) compared with NAS-exposed conditions (138.42 ± 13 ms), corresponding to a decrease in frequency (8.6 ± 0.7 and 7.2 ± 0.6 Hz, respectively). However, there was no significant difference in event occurrence between NAS alone and MeHg + NAS (126.3 ± 11 ms, 7.9 ± 0.6 Hz). H: across the population, there was no significant difference between pre-NAS EPSC amplitude (23.64 ± 4 pA) compared with NAS exposure (26.5 ± 8 pA) or between NAS alone or MeHg + NAS (29.22 ± 8 pA). con, Control; n.s., no significant difference.