Electroacupuncture may relieve constipation in PD by upregulating 5-HT and 5-HT4R in the colon tissue, thereby activating the downstream cAMP/PKA pathway, regulating the expression of the related neurotransmitters SP and CGRP, and further regulating the enteric nervous system to improve intestinal motility disorders. Here, HTR4 is linked to Parkinson disease.