title: Tonic suppression of gastric acid secretion by endogenous peptides in neonatal rats.
abstract: Stimulation of gastric acid secretion by secretagogues was measured in developing rats by in vivo and in vitro techniques. Basal acid outputs in vivo were very low in 8- and 14-day-old rats compared with those in 20- and 30-day-old rats. In 20-day-old rats, all secretagogues increased acid output in vivo, whereas only carbachol, pentagastrin, and sulfated cholecystokinin octapeptide (CCK-8S) were active in 14-day-old rats. In contrast, basal acid output in vitro and stimulation by secretagogues did not differ significantly with age. CCK-8S-stimulated acid output in vitro in 14-day-old rats was blocked by L-365,260, L-364,718, tetrodotoxin, and atropine, but not by hexamethonium, whereas gastrin-stimulated acid output was blocked only by L-365,260. Furthermore, acid output in vivo was elevated three- to fourfold by subcutaneous naloxone-methiodide or L-364,718, but not by L-365,260, in 14-day-old rats; none of these antagonists produced an effect in 20-day-old rats. These studies show that low basal gastric acid output in neonatal rats is caused by tonic inhibitory regulation by endogenous regulatory peptides.
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D005744:Gastric Acid / Q000378:metabolism*; D005755:Gastrins / Q000494:pharmacology; D009292:Narcotic Antagonists; D010455:Peptides / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012844:Sincalide / Q000031:analogs & derivatives / Q000494:pharmacology; D013268:Stimulation, Chemical
chemical_list: C090019:8-sulfocholecystokinin octapeptide; D005755:Gastrins; D009292:Narcotic Antagonists; D010455:Peptides; C013550:gastrin 17; D012844:Sincalide