VIP and Constipation: The purgative mechanisms of UW were mainly attributed to its regulation of serum biochemical indices related to constipation, i.e., increasing serum levels of excitatory neurotransmitters (i.e., MTL, SP, VIP, and AChE) and decreasing serum levels of inhibitory neurotransmitters (i.e., SS), which promoted gastro-intestinal peristalsis and increased gastric evacuation.