Figure 4.

Representative FLIPR traces showing blockade of K⁺ depolarization-induced increase in intracellular calcium by compound 4a in human sperm. a = addition of test compound to sperm pre-loaded with Fluo-4-AM dye; b = addition of activation buffer in the absence (control) or presence of test compound (zeroed here); c = endpoint reading taken. The 1^st phase (a to b interval) is used to assess nonspecific compound effects, whereas CatSper channel blockade is determined during the 2^nd phase (b to c interval).