Figure 5. Gating of TRPC5 by hypoosmotic stimulation is independent of phospholipase C activation.

TRPC5-transfected cells were preincubated for 30–60 min with 5 μm of the PLC inhibitor U-73122 or the inactive analogue U-73343. Thereafter cells were probed with 210 mosmol kg⁻¹ extracellular solution and 10 μm carbachol (Cch). A, I–V relationship of TRPC5 current evoked by hypoosmotic solution and 10 μm carbachol (Cch) in the presence of 5 μm U-73122. B, effect of U-73122 and U-73343 on percentage of responsive cells to hypoosmotic stimulus and Cch compared to untreated TRPC5(+) cells obtained from the type of recordings shown in A. **P < 0.01, compared with non-treated cells and #P < 0.05 compared with U-73343 treated cells (Z-test; n = 6 patches for each condition). C, bar graph summarizing the effects of U-73122 and U-73343 on TRPC5 currents induced by hypoosmotic solution and 10 μm Cch. Mean values were measured in > 6 cells for each experimental condition (*,#P < 0.05; the * denotes statistical significance between cells treated with U-73122 and untreated cells and # between cells treated with U-73343 and untreated cells; one-way ANOVA). D, cytosolic Ca²⁺ signals from cells transfected with TRPC5 in response to 210 mosmol kg⁻¹ solution in the presence of ACA. E, whole-cell current obtained from ± 100 mV voltage ramps in a cell expressing the TRPC5 channel during the exposure of 210 mosmol kg⁻¹ solution in the presence of ACA. Note the current activation by ACA. F, I–V relationship measured at maximal current from the same cell as E (colour dots) during the different experimental conditions (n = 4 patches).