PAX4 and Fabry disease: In 2020, Zhao et al. reported that rikkunshito significantly attenuated visceral hypersensitivity in FD model rats, and the overexpression of EC cells, 5HT, TPH1, PAX4, and 5HT3R in the duodenum of FD model rats was also reduced by rikkunshito decoction (Zhao et al., 2020).