Fig. 6.

Axotomy decreases persistent currents in C-type neurons. A, Family of currents recorded from a control small DRG neuron. Current was elicited by test potentials from −75 to −25 in 10 mV steps. The peak current in this cell was 47 nA.B, Current–voltage relationship for the persistent current in small DRG neurons. Cells were held at −100 mV and stepped to step voltages from −80 to 40 mV for 40 msec. The average current measured from 38 to 40 msec was normalized to the maximum peak current for each cell and is plotted against the test voltage. Data are shown for control (▴, n = 12), DPA6 (•,n = 14), and DPA22 (▪, n = 14). Axotomized cells in the DPA6 and DPA22 groups were identified with a fluorescent label. For the control neurons the persistent current also was measured by using 200 msec test depolarizations (▵,n = 11). C, The persistent current in control neurons (n = 4) that express both TTX-S and TTX-R currents is shown before (▴) and after (▵) 100 nm TTX. In control neurons that express only TTX-S currents (n = 5), the persistent currents were small (□). Persistent currents were measured at 38–40 msec, as in A.