Neurotransmitters regulate β cells insulin secretion: A neglected factor

Figure 1 Regulation of insulin secretion by neurotransmitters. With the increase of glucose concentration, the concentration of adenosine triphosphate (ATP) produced by glucose metabolism also increases correspondingly, and the closure of internal rectifying K⁺-ATP channels leads to membrane depolarization, which opens volt-sensitive Ca²⁺ channels, and Ca²⁺ enters intracellularly to mediate insulin secretion in large quantity. Acetylcholine, gastrin releasing peptide, 5-hydroxytryptophan, vasoactive intestinal peptide, pituitary adenylate cyclase activating polypeptide and nitric oxide promote insulin secretion. Dopamine, neuropeptide Y, galanin and norepinephrine inhibit insulin secretion. 5-HTTP: 5-hydroxytryptophan; AADC: Amino acid decarboxylase; ADP: Adenosine diphosphate; cAMP: Cyclic adenosine monophosphate; CCK: Cholecystokinin; cGMP: Cyclic guanosine monophosphate; DAG: Diacylglycerol; GCRP: Calcitoningenerelatedpeptide; GTP: Guanosine triphosphate; IP3: Inositol triphosphate; L-Arg: Levo-arginine; L-DOPA: Levo-dopa; NOS: Nitric oxide synthase; PIP2: Phosphatidylinositol(4,5)bisphosphate; PKA: Protein kinases A; PKC: Protein kinase C; PKG: Protein kinases G; PLC: Phospholipase C; SP: Substance P; TCA: Tricarboxylic acid cycle; TPH: Tryptophan hydroxylase; Trp: Tryptophan; VIP: Vasoactive intestinal peptide.