Peptide hormones were originally described in the gut and in endocrine organs associated with the gut. Thus the gut was thought to be the major site of production of peptide hormones. The discovery of secretin and gastrin marked the beginning of gastrointestinal endocrinology. However some peptides were discovered in the brain recently and they were then ascribed the functions of neurotransmission. Substance P, encephalins and endorphins were discovered as peptidergic neurotransmitter in the brain.
When vasoactive intestinal peptide (VIP) originally described to occur is D1 cell for the gut as peptide hormone was found to occur in ganglioneroblastona, phaeochromocytomas and other neural tumours, it became obvious that peptides thought to be mainly found in the gut could exist in nerve cells. This finding only served to lighten the no longer acceptable Unitarian ontogenetic theory of APUD cells as being derived from neural elements proposed originally by Pearse and his associate served to strengthen the concept of paraneurons of Fujita and his associates.
Substance P thought to be present in the brain as a peptidergic transmitter was found in the gut. It is today known to be produced by EC1 cell of the stomach. Later on hypothalamic hormone – somatostatin was also located in gut endocrine cells and the pancreatic D cell; again it was localized in the intestinal D cell.
Further studies demonstrated the occurrence of gastrin and calcitonin in the anterior pituitary gland. Also calcitonin was discovered in the parvicellular preoptic nucleus and the nucleus infundibularis ventralis (NIV) of the bull frog by immunohistochemistry. This to postulation that calcitonin may act as peptidergic neurotransmitter in the preoptic area of the bull frog bring and as an adenohypophysiotropic enurohormone in the NIV. Very recent studies revealed the co-existence of VIP and H1 demonstrated in intestinal nerves of the rat and pig.
The following peptides are part of the family of brain-gut peptides.
1) Arginine vasotocin
2) Lutropin – releasing hormone
3) Arginine vastocin
4) Arginnie vasopressin
5) Hypothalamic release factors (RFS)
6) Hypothalamic release inhibitory factors (RIFs)
7) Follicle stimulating hormone
8) Leutinizing hormone
9) Thyroid stimulating hormone
10) Growth hormone
11) Pinealocyte stimulating hormone
13) Andrenocorticotrophic hormone
23) Pancreatic pohypeptide
24) Gastrin 17
25) a-melanocyte-stimulating hormone
27) Substance P
31) Cholectstokinin (CCK)
32) Gastrin inhibitory peptide
34) Vasoactive intestinal peptide (VIP)
35) Porcine intestinal heptacosa peptide (PH1)
36) Gastrin – 34
37) C-terminal gastrin
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Creator: Oluwole Ogunranti