Table 3.

The most important gut peptides and their characteristics (HPA—hypothalamic-pituitary-adrenal).

Gut Peptide	Producing Cells	Releasing Factor	Peripheral Function	Central Function
PYY [104,105]	L-cells a	food intake	inhibition of gastric emptying and intestinal motor activity	modulation of anxiety and stress-related disorders
GLP-1 [106,107]	L-cells a	food intake	stimulation of insulin release and inhibition of glucagon secretion	modulation of the HPA axis and response to stress
CCK [108,109]	I-cells a	food intake	suppression of appetite, gastric emptying, gallbladder contraction, pancreatic enzymes release	increased anxiety-like behavior
CRF [110,111,112,113]	effector neurons of hypothalamus and enterochromaffin cells of the colon	stress	inhibition of gastric emptying, stimulation of colonic motility and impairment of the intestinal epithelial barrier	increased anxiety and depressive disorder
ghrelin [114,115]	A-cells a	starvation	increase of appetite and adipogenesis	modulation of stress response, anxiety and depressive disorder
oxytocin [116]	magnocellular neurons in hypothalamus	stress	facilitation of parturition and stimulation of lactation	reduced anxiety-like behavior and antidepressant effect

^a—enteroendocrine cells present in the small intestine.