Figure 5.

Inhibition of VGCC currents by DOR agonist DADLE. A, DADLE (200 nm) inhibited VGCC currents in small-diameter TG sensory neurons. Left, Time course of the exemplary experiment. Middle, Representative current traces. Currents were elicited by stepping to 0 mV for 25 ms every 15 s from a holding potential of −80 mV. Cd²⁺ (100 μm) was applied at the end of the experiment to confirm that the current was carried by VGCC. Gray bars represent timing of drug application. Bar chart on the right represents summary data for 10 of 43 responsive TG neurons. B, In fura-2 Ca²⁺ imaging experiments, Ca²⁺ transients induced by depolarization with 50 mm KCl (K⁺) were decreased by application of DADLE in 14 of 53 of neurons. A total of 50 mm KCl solution was applied for 10 s every 3 min to induce Ca²⁺ transients. Three control applications were followed by a fourth application in the presence of DADLE. Gray bars represent timing of drug application. Bar chart on the right represents summary data for 14 of 53 responsive TG neurons. Areas under the curve for each Ca²⁺ transient were averaged and are shown as mean ± SEM. *, p < 0.05 versus mean of three control transients. ns, Not significant. C, Pie charts represent proportions of DADLE-responsive TG neurons as identified with patch-clamp (left) and Ca²⁺ imaging (right).