SPI1 and Constipation: Rhizoma Parisdis total saponins (RPS) are known to remarkably inhibit the gastric antral smooth muscle contractility through regulation of muscarinic receptors, while SpiA-containing EtRLP improves the symptoms of Lop-induced constipation in SD rats via the regulation of the mAChR downstream signaling pathway and the ER stress response [22].