VIP and Constipation: Levels of NO and VIP were higher (43.42 ± 47.70 μM/mL, 10.8 ± 0.4 pg/mL), and levels of MTL (58.10 ± 46.00 pg/mL) and SP (25.56 ± 3.52 pg/mL) were much lower in constipation group than those in NC group (25.70 ± 19.56 μM/mL; 9.70 ± 1.77 pg/mL; 123.20 ± 37.00 pg/mL; 48.13 ± 21.9 pg/mL).