Figure 3. Menthol causes a capsazepine sensitive [Ca²⁺]i increase in human sperm.

Human sperm were loaded with the fluorescent Ca²⁺ indicator Fluo3-AM (2 µM) and the fluorescence intensity visualized before and after menthol addition as described in methods. Representative single cell (A and C) and group of cells (B and D) spatio-temporal [Ca²⁺]i changes after adding menthol (500 µM, indicated with the light gray bar) in the absence (A and B) and presence of 20 µM Cz (C and D, indicated with the dark gray bar). The panels to the right illustrate representative traces showing the fluorescence change after addition of menthol (light gray bar), in the absence or presence of capsazepine (dark gray bar). The time frame is indicated in each panel. Scales indicate (F/F0) -1 vs time (sec). Note: ∼50% of cells responded to menthol. Color coding: black (−) to red (+) indicates low to high [Ca²⁺]i. n≥3.