AQP3 and Constipation: Ikarashi et al. confirmed that an increase in the expression level of Aquaporin 3 (AQP 3) is involved in the onset of morphine‐induced constipation, while an increased intracellular Mg2+ concentration can weaken this effect and promote the water inflow of intestinal mucosal epithelial cells into the intestinal cavity, which is conducive to defecation.29