A Neurochemical Perspective on Brain-Gut Communication and its Gastrointestinal Regulation: A ENS as the ''second Brain''

The enteric nervous system (ENS) has been commonly referred to as a "second brain," as it coordinates the gastrointestinal (GI) motility, secretion, and blood flow through a set of neurons and neurotransmitters that act on their own or with the central nervous system. This review discusses the neurochemistry of the somewhat complex system of enteric nerves, emphasizing the presence of dual plexuses the myenteric and submucosal plexuses and the influence exerted by excitatory, inhibitory, and modulatory neurotransmitters in digestive homeostasis. The work dwells on some important neurotransmitters, such as acetylcholine, serotonin, norepinephrine, nitric oxide, and others, describing their roles in motility, secretion, inflammation, and gut-brain signaling. It also explains the cellular organization of the stomach and reveals pharmacological treatments of disorders related to gastric acid. Understanding how the ENS interacts neurochemically illustrates its importance in GI physiology and therapeutic implications for digestive diseases.