Figure 2
Contrasting sodium currents in masseter afferents. MeV masseter afferents express only TTX-sensitive I Na, but trigeminal ganglion masseter afferents display great variation in the proportion of TTX-sensitive to TTX-resistant I Na among cells. I Na were elicited by voltage steps from a holding potential of -90 mV, as diagrammed next to each set of traces. TTX-sensitive I Na were obtained by digitally subtracting the I Na remaining in TTX (300 nM) from the total I Na. A trigeminal ganglion masseter afferent is illustrated in A; (i) illustrates the TTX-sensitive and TTX-resistant I Na at -20 mV, a potential where TTX-sensitive current predominates while (ii) shows the total I Na and TTX-insensitive I Na at the potential where TTX-sensitive I Na is maximal. The peak amplitudes of the total I Na, TTX-sensitive and -resistant I Na are plotted in (iii). A typical MeV masseter afferent is illustrated in B, (i) illustrates the I Na and TTX-insensitive inward current at the test potential where I Na is maximal; (ii) shows the TTX-sensitive I Na over a range of test potentials. The peak amplitudes of the total I Na, TTX-sensitive and residual current (I Ca, see Table 1) are plotted in (iii). C) Illustrates the proportion of the peak inward current in TG and MeV masseter afferents that was sensitive to TTX (300 nM). The proportion of TTX-sensitive I Na for the cell illustrated in A) would be calculated at a test potential of +5 mV.