Current-clamp properties of trigeminal ganglion neurons transfected with I228M. Excitability of trigeminal ganglion neurons expressing I228M: (A) RMP of trigeminal ganglion neurons expressing WT (-60.9 ± 2.2, n = 17) or I228M (-52.4 ± 1.8, n = 14); *p < 0.05. (B) Current threshold of DRG neurons expressing WT (122 ± 37, n = 13) or I228M (78 ± 31, n = 12) to 200 msec stimuli; p < 0.05. (C) Comparison of mean firing frequency in trigeminal ganglion neurons expressing WT and I228M across a range of current injections from 25 to 500 pA; *p < 0.05. (D) Bar graph showing the proportion of spontaneous firing cells for trigeminal neurons expressing I228M (red) and WT channels (black); numbers to the right of the bar graph show mean values for WT (lower value in parentheses) and I228M (upper value). The recording on the right shows spontaneous firing (10 seconds) of representative trigeminal neuron expressing I228M; the numbers above the trace show average ± standard deviation frequency of spontaneous action potentials. APs = action potentials.