Melatonin is released from intestinal enterochromaffin cells and from the pineal gland, but its role in gastrointestinal function is largely unknown. Our aim was to study the involvement of intestinal and central nervous melatonin in the neurohumoral control of the duodenal mucosa-protective bicarbonate secretion. Working in anesthetized rats, we cannulated a 12-mm segment of duodenum with an intact blood supply and titrated the local bicarbonate secretion with pH-stat. Melatonin and receptor ligands were supplied to the duodenum by close intra-arterial infusion. Even at low doses, melatonin and the full agonist 2-iodo-N-butanoyl-5-methoxytryptamine increased duodenal bicarbonate secretion. Responses were inhibited by the predominantly MT2-selective antagonist luzindole but not by prazosin, acting at MT3 receptors. Also, luzindole almost abolished the marked rise in secretion induced by intracerebroventricular infusion of the adrenoceptor agonist phenylephrine. This response was also abolished by sublaryngeal ligation of all nerves around the carotid arteries. However, it was insensitive to truncal vagotomy alone or sympathectomy alone and was unaffected by removal of either the pineal gland or pituitary gland. Thus, melatonin stimulates duodenal bicarbonate secretion via action at enterocyte MT2-receptors and mediates neural stimulation of the secretion.
Markus Sjöblom, Gunilla Jedstedt, Gunnar Flemström
Usage data is cumulative from June 2022 through June 2023.
Usage | JCI | PMC |
---|---|---|
Text version | 243 | 43 |
32 | 8 | |
Figure | 123 | 0 |
Citation downloads | 23 | 0 |
Totals | 421 | 51 |
Total Views | 472 |
Usage information is collected from two different sources: this site (JCI) and Pubmed Central (PMC). JCI information (compiled daily) shows human readership based on methods we employ to screen out robotic usage. PMC information (aggregated monthly) is also similarly screened of robotic usage.
Various methods are used to distinguish robotic usage. For example, Google automatically scans articles to add to its search index and identifies itself as robotic; other services might not clearly identify themselves as robotic, or they are new or unknown as robotic. Because this activity can be misinterpreted as human readership, data may be re-processed periodically to reflect an improved understanding of robotic activity. Because of these factors, readers should consider usage information illustrative but subject to change.