The role of nicotinic receptors in dog pancreatic exocrine secretion

Abstract

The effects of pentamethonium, an autonomic ganglion blocker, were studied on the exocrine pancreatic secretion of six conscious dogs given intravenous infusions of urecholine, caerulein or pentagastrin on a background of submaximal doses of secretin. 2 Urecholine-induced protein secretion was not affected but both caerulein-and to a smaller extent, pentagastrin-induced protein secretions were depressed by pentamethonium. 3 These results indicate that intravenous caerulein and pentagastrin, but not urecholine, act at least partially via nicotinic receptors. 4 Volume and bicarbonate output were depressed by pentamethonium when stimulated by intravenous caerulein with a background of secretin, but not when stimulated by pentagastrin on a background of secretin. 5 From these data it is suggested that caerulein and pentagastrin may potentiate secretinstimulated hydrelatic secretion by different mechanisms. IntroductionExocrine pancreatic secretion is regulated by both neural and hormonal mechanisms. The interaction on exocrine pancreatic secretion between cholinergic nerves and gastrointestinal hormones (GI hormones) has been investigated chiefly with atropine, which blocks muscarinic receptors. In spite of extensive studies, there still exists a diversity of opinion about the action of atropine and acetylcholine on exocrine pancreatic secretion (Thomas, 1964;Magee, Fragola & White, 1965;Henriksen, 1969;Konturek, Tasler & Obtulowicz, 1972; Vaysse, Bastie, Pascal, Roux, Martinel, Lacroix & Ribet, 1975). In addition, it is not clear whether or not nicotinic receptors play a part in the exocrine pancreatic secretory response to GI hormones.The purpose of this study was to examine the effects of an autonomic ganglionic blocker (pentamethonium) on the pancreatic secretion stimulated by urecholine, caerulein or pentagastrin and to elucidate the possible role of the nicotinic receptors on stimulated pancreatic secretion. MethodsSix male Beagle dogs, weighing 12-17 kg, were prepared with Thomas cannulae (Thomas, 1941) in both duodenum and stomach after preliminary ligation of the accessory pancreatic duct. Experiments were started no sooner than three weeks after surgery. Dogs were deprived of food but not water for at least 18 h before each test. The gastric cannula was kept open during tests. The dogs were restrained in Pavlov stands.The exocrine pancreas was stimulated by: (1) urecholine (carbamylmethylcholine chloride, Sigma) 200 gig/h, (2) caerulein (ceruletide, Farmitalia) 35 ng kglh-1, or (3) pentagastrin (Peptavlon, ICI) 3ygkg-1h-1. Caerulein was used in preference to cholecystokinin (CCK) because it can be much more readily and inexpensively obtained in pure form. Each stimulant dissolved in saline was infused on a background of GIH secretin 0.5 clinical unit kg-I h-l. Without secretin the volume of juice varies between zero and 1-3 ml/10 min. It is, therefore, impossible to monitor change in both directions. In order to give these stimulants continuously, a Venocath (G-21, Abbott) was placed in a leg vein and a ...

Galanin inhibits caerulein-stimulated pancreatic amylase secretion via cholinergic nerves and insulin

“…M3 receptors are also located on insulin-secreting islet cells; however, in the present study, the carbachol-stimulated amylase secretion was not influenced by diazoxide, suggesting that carbachol activation of the acinar cell muscarinic receptors was dominant. In contrast, caerulein, at concentrations comparable to physiological concentrations of CCK, has been postulated to stimulate amylase secretion via mechanisms including CCK-1 receptors (18), atropine-sensitive neural pathways (21,46), and nicotinic receptors (11). Our findings that caerulein-stimulated amylase secretion is completely abrogated by atropine and tetrodotoxin confirms previous reports that the effect of caerulein on pancreatic exocrine secretion is mediated through cholinergic neural pathways (21,46).…”

How does cigarette smoking cause acute pancreatitis?

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Characteristics of secretin‐stimulated pancreatic secretion in dogs.

“…The action of atropine was to shift the peak curve to the nadir one. A further shift by hexamethonium indicates the importance of nicotinic mechanisms (Hong & Magee, 1970;Devaux, Diaz, Kubota, Magee & Sarles, 1983 (Fig. 5 and Table 1)).…”