The primary action of Nitric oxide (NO) in the gastrointestinal tract is:

C i.e. Gastrointestinal smooth muscle relaxation - Nitric oxide (NO) is synthesized from arginine (02, NADPH) by NO synthase (requiring FMN, FAD, herne & BH4) in nerves and vascular endothelial cells (hence called EDRF). It relaxes smooth muscles by increasing cyclic GMPQ. - Nitric oxide (NO) and atrial natriuretic factor (ANF) are hormones that act through c-GMPQ. - NO (along with VIP and PACAP) are inhibitory neurotransmitter in enteric (gastrointestinal) neurons that primarily mediate gastrointestinal smooth muscle relaxation c-GMP pathwayQ.