Fig. 3.

Effect of ruthenium red on RTX-induced⁴⁵Ca uptake and on RTX-induced desensitization in rat DRG neurons. Cells were incubated in the presence of 250 pm RTX and different concentrations of ruthenium red for 6 hr and then challenged with 200 nm RTX (▪). To evaluate the effect of ruthenium red just on desensitization, after the above incubation cells were washed three times with serum-free DMEM containing 0.25 mg/ml BSA to remove the pretreatment compounds before the cells were challenged to induce ⁴⁵Ca uptake (▿). To measure the effect of ruthenium red just on ⁴⁵Ca uptake, varying concentrations of ruthenium red and 200 nm RTX were applied together, and⁴⁵Ca uptake was determined (○). Points represent mean values from sets of eight determinations in a single experiment; error bars indicate SEM. The theoretical curve for blocking the RTX-induced⁴⁵Ca uptake was calculated by fitting the measured values to the modified Hill equation, whereas data for blocking the RTX-induced desensitization was fitted to the Hill equation. Two additional experiments yielded similar results.