GI Mediators

Gastrin

stimulates acid and histamine; growth of the gastric mucosa

Cholecystokinin (CCK)

stimulates gallbladder contraction, pancreatic enzyme secretion, inhibits gastric emptying, signals satiety

Secretin

stimulates pancreatic/biliary bicarbonate secretion, promotes pancreatic growth, & inhibits gastric acid secretion

Glucose-dependent Insulinotropic Peptide (GIP)

stimulates insulin secretion in response to intake, inhibits gastric acid secretion, and slows gastric emptying (at high doses)

Motilin

GI motility, migrating motor complex, sweeps remaining food towards the rectum every 90 minutes

Ghrelin

hunger hormone, increased appetite, stimulates gastric acid and motility

Glucagon-like Peptide (GLP-1)

enhances insulin secretion, inhibits glucagon release, slows gastric emptying, and signals satiety

Glucagon-like Peptide (GLP-2)

promotes mucosal cell growth

Peptide YY

inhibits acid secretion & gastric emptying, inhibits intestinal motility, signals satiety

Acetylcholine

stimulates motility & secretions, relaxes sphincters

Norepinephrine

decreases motility & secretions, constricts sphincters, vasoconstriction of the GI vasculature

Dopamine

mixed effects/stimulation and inhibition of motility

Enkephalin

endogenous opioid, inhibits motility

Substance P

increases motility, neurogenic inflammation

Vasoactive Intestinal Peptide

inhibits motility, stimulates fluid & electrolyte secretion from epithelium & bile duct cells

Histamine

stimulates gastric acid secretion & inflammatory response

Serotonin

Stimulates sensory neurons to increase motility & secretions; role in nausea/emesis

Somatostatin

“brakes of the GI system” inhibits gastric acid secretion, insulin & glucagon secretion and the gut motility