Figure 4.
IL-1β increases the TTX-S and the slow and persistent components of the TTX-r sodium current. A, Representative traces of TTX-S before and after IL-1β following a depolarizing step to 0 mV. TTX-S current was assessed by subtraction of the current evoked by a 10 mV depolarization step after a 500 ms step to either −120 mV (for total sodium current) or −40 mV (for TTX-r current). B, C, In cells preincubated with 300 nm TTX, steps to −30 mV evoked TTX-r-per, whereas steps to +10 mV evoked TTX-r slow. D, IL-1β increased the density of TTX-S as well as TTX-r-per and TTX-r slow currents (n = 6 for TTX-S; n = 10 for TTX-R). E, Current–voltage curve during a slow depolarizing ramp (35 mV/s, −70 to +20 mV). Note “W” shaped inward current with clear early and late components. IL-1β increased the amplitude of early and late components of the inward current and shifted their activation and peak to more negative potentials. Fast inward currents after the slow ramp after prolonged (25 min) exposure IL-1β appeared in all recorded cells (n = 15) and reflect lost of voltage-clamp control possibly due to increase in membrane excitability. F, Arrow indicates time of application of IL-1β or vehicle. Time point of “-5” refers to data collected before the application. Recordings for A–D were made using extracellular solution 1, and those for E and F using extracellular solution 3 (Table 1).