Action of atropine on the pancreatic secretory response to secretin before and after cutting the extrinsic nerves of the pancreas in dogs

In two sets of dogs with gastric and pancreatic fistulas, we studied the effect of atropine on the pancreatic secretory response to intravenous secretin before and after cutting the extrinsic nerves of the pancreas, i.e., celiac and superior mesenteric ganglionectomy alone or truncal vagotomy plus celiac and superior mesenteric ganglionectomy. Neither truncal vagotomy alone nor ganglionectomy alone, nor the two together, altered the incremental bicarbonate response to secretin. Irrespective of the degree of integrity of the extrinsic vagal and splanchnic innervation of the pancreas, intravenous atropine (14 nmol/kg X h) significantly (p less than 0.05) depressed the incremental bicarbonate responses to the two lowest (5.2 and 10.3 pmol/kg X h) doses of secretin by 85% and 61%, respectively, but had no significant effect on responses to high doses. We conclude that the pancreatic bicarbonate response to secretin, and the action of atropine on that response, are independent of an intact extrinsic innervation of the gland. The observation of the persistent inhibitory action of atropine after extrinsic denervation of the pancreas is compatible with the hypothesis that endogenous cholinergic activity augments the pancreatic bicarbonate response to secretin.     

Pancreatic secretory response to intravenous caerulein and intraduodenal tryptophan studies: before and after stepwise removal of the extrinsic nerves of the pancreas in dogs

In two sets of 6 dogs with gastric and pancreatic fistulas, we studied the effect of atropine (14 nmol/kg.h i.v.) on the pancreatic secretory response to intravenous caerulein and to intraduodenal perfusion with tryptophan (both given with a secretin background) before and after stepwise removal of the extrinsic nerves of the pancreas, i.e., celiac and superior mesenteric ganglionectomy alone or truncal vagotomy alone and truncal vagotomy plus celiac and superior mesenteric ganglionectomy. Atropine significantly (p less than 0.05) depressed the protein output in the basal state and in response to secretin at each stage of innervation. The incremental protein response to caerulein was not altered by the various denervation operations nor by atropine. Truncal vagotomy alone significantly decreased the incremental protein response to low (0.12, 0.37, and 1.1 mmol/h) but not high loads of tryptophan. Ganglionectomy in combination with vagotomy did not further depress the incremental protein response to low loads of tryptophan. Atropine significantly reduced the incremental protein response to low loads of tryptophan only in intact innervated animals. Ganglionectomy alone did not alter the incremental protein response to any load of tryptophan. Ganglionectomy, truncal vagotomy, and atropine did not alter basal or tryptophan-stimulated levels of plasma cholecystokininlike immunoreactivity. We conclude that (a) neither the extrinsic nor the intrinsic cholinergic pancreatic nerves modulate the protein response to caerulein; (b) the sympathetic pancreatic nerves do not mediate the response to tryptophan; (c) the protein response to intraduodenal tryptophan is at least in part mediated by long, cholinergic, enteropancreatic reflexes with both afferent and efferent fibers running within the vagus nerves; and (d) release of cholecystokinin by intestinal tryptophan is not under cholinergic or splanchnic control.     

Nervous control of gastric and pancreatic secretory response to 2-deoxy-D-glucose in the dog

The relative contribution of the vagus and splanchnic nerves as mediators of the action of 2-deoxy-D-glucose (2-DG) on the stomach and the pancreas is largely unknown. In conscious dogs with gastric and pancreatic fistulas, the effect of 2-DG (100 mg kg-1, given as an intravenous bolus) on gastric acid and pancreatic exocrine secretion was tested before and after bilateral truncal vagotomy and after truncal vagotomy plus celiac and superior mesenteric ganglionectomy (i.e. extrinsic denervation of the stomach and the pancreas). In another set of dogs, only ganglionectomy was performed and the same experiments were done as in the first set of dogs. With the extrinsic nerves intact, 2-DG caused a rapid (within 15 min) and prolonged increase in gastric acid output as well as in pancreatic flow rate, bicarbonate and protein output. Truncal vagotomy abolished the gastric acid and pancreatic secretory response to 2-DG; additional ganglionectomy had no further effect. Ganglionectomy alone did not significantly alter 2-DG-stimulated gastric acid output, pancreatic flow rate and bicarbonate output; protein output, however, was significantly diminished by 57%. These results indicate that (a) intravenous 2-DG is a potent stimulant of gastric acid and pancreatic bicarbonate and protein output; (b) the vagus nerves are the major mediators of the gastric and pancreatic secretory response to 2-DG; (c) the sympathetic nerve fibers running through the celiac and superior mesenteric ganglia are probably not involved in the mediation of the 2-DG-induced gastric acid and pancreatic bicarbonate secretion. The diminished protein response to 2-DG after ganglionectomy is probably due to cut vagal fibers running through these ganglia.     

Neural pathways for the release of gastrin,cholecystokinin, and pancreatic polypeptide after a meal in dogs

We have measured gastrin, cholecystokinin (CCK), and pancreatic polypeptide (PP) release after a meal in normal dogs under basal conditions and during atropine infusion, and after various neural sections. Denervation of the gastric antrum (antral vagotomy) abolished the early part of the gastrin response to food. Truncal vagotomy, celiac ganglionectomy, and atropine reduced the early release of CCK, which occurred before the start of gastric emptying, suggesting that a neural, cholinergic mechanism may release CCK immediately after a meal. PP release was abolished by truncal vagotomy, and also by antral vagotomy. As no direct pathways are known between the antrum and the pancreas, this suggests either that antral afferents are essential for this response or that vagally mediated hormone release from the antrum mediates PP release.     

Intrinsic pancreatic nerves after mechanical denervation of the extrinsic pancreatic nerves in dogs.

Little is known about the influence of cutting the extrinsic pancreatic nerves on the morphology and function of the intrapancreatic nerves in dogs. For this reason, intrapancreatic nerves of mongrel dogs were studied, using electron microscopy and immunohistochemistry, after truncal vagotomy, after celiac and superior mesenteric ganglionectomy, and after a combination of both operations, i.e., removing all extrinsic nerves of the pancreas. Dogs with intact extrinsic and intrinsic pancreatic nerves served as controls. Studies were performed 1-2 weeks and up to 5 months after one or both denervation procedures. For immunohistochemical and electron microscopic studies the animals were perfused with glutaraldehyde-formaldehyde-picric acid solution and the tissue was embedded in Epon or paraffin. Both immunohistochemical and electron microscopic studies revealed that signs of degenerating intrapancreatic nerves occurred only in the early phase (up to 30 days) after operation. After 60 days, hypertrophy of pancreatic nerve fibers was observed. The most striking finding was that the integrity of the intrapancreatic ganglia and nerves was almost preserved after complete extrinsic denervation. In controls there was a strong intrapancreatic innervation with vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI), substance P (SP), and neuropeptide Y (NPY) nerves. SP and NPY-nerves significantly decreased after the different denervation procedures, but the other peptidergic nerves were not altered by truncal vagotomy, ganglionectomy, or the combination of both procedures. We conclude that the dog pancreas contains extensive intrinsic peptidergic nerves, which, with the exception of SP and NPY-nerves, are greatly independent of the integrity of the extrinsic nerves.     

Effects of autonomic denervation on canine exocrine pancreatic secretion and blood flow

Summary The effect of autonomic denervation on the exocrine pancreatic secretion and blood flow was studied in a group of dogs. Pancreatic secretion was collected and analyzed for volume and bicarbonate by direct cannulation of the main papilla through a duodenotomy prior to and following truncal vagotomy and celiac plexus denervation. Pancreatic blood flow was determined by the radioisotope distribution method (¹⁴¹Ce). Truncal vagotomy causes a reduction in pancreatic secretion of volume and bicarbonate by 25–30%, while celiac denervation caused a reduction of 70% in the secretion. The mean baseline pancreatic blood flow was 0.5 ml/g pancreas/min. Truncal vagotomy did not cause any significant flow changes, while celiac denervation caused a significant increase in blood flow of 350% (to 1.75 ml/g/min). These results suggest that both the parasympathetic and the sympathetic system affect pancreatic secretion independently of their effect upon pancreatic blood flow.     

Meal-induced pancreatic polypeptide release in a validated pancreatic denervation model: a role for the distal pancreas?

In previous studies, postprandial pancreatic polypeptide (PP) release was diminished when pancreatic denervation was combined with distal pancreatectomy in animals without chronic fistulae. In contrast, postprandial PP release was reported to be unchanged when the pancreas was denervated without performing a distal pancreatectomy. These findings were unexpected given that the distal pancreas is a PP-poor region. To clarify this issue, we performed extrinsic pancreatic denervation, distal pancreatectomy, and insertion of chronic pancreatic fistulae in nine mongrel dogs. Insulin (0.5 U/kg) and meal-stimulated PP release were measured pre- and postoperatively. In addition, insulin- and meal-induced exocrine secretion was measured postoperatively. Preoperatively, insulin-induced hypoglycemia stimulated significant PP release (80,553 +/- 18,540 pg/min/ml). This response was completely abolished postoperatively (-1,669 +/- 5,054 pg/min/ml). Exocrine secretion did not increase above basal levels after administration of insulin in postoperative animals. These findings suggest adequate pancreatic denervation. Ingestion of a meal evoked significant PP response preoperatively (97,909 +/- 18,394 pg/min/ml). Postoperatively, the response was significantly blunted (17,231 +/- 6,407 pg/min/ml). This finding is in contrast to a previous report using a similar experimental preparation without distal pancreatic resection. We speculate that although the distal pancreas is PP-poor, it may play a role in the regulation of PP release from the PP-rich pancreatic head.     

Role of the distal pancreas in pancreatic polypeptide release.

In two previous studies, postprandial pancreatic polypeptide (PP) release was inhibited when pancreatic denervation was combined with distal pancreatectomy. In contrast, postprandial PP release was unaffected by pancreatic denervation without a distal pancreatectomy. These findings suggested a role for the distal pancreas in regulation of postprandial PP release. To examine this possibility, we performed distal pancreatectomy on four mongrel dogs. Pancreatic polypeptide response to i.v. insulin (0.5 U/kg), a meal, and an infusion of cholecystokinin octapeptide (CCK-8; 50 ng/kg/h) were measured in conscious dogs before and after distal pancreatectomy. Insulin-induced hypoglycemia stimulated PP release both preoperatively (47.0 +/- 8.8 ng.[0-120]min/ml) and postoperatively (61.6 +/- 9.2 ng.[0-120]min/ml). Ingestion of a meal also evoked significant PP release preoperatively (85.8 +/- 22.1 ng.[0-180]min/ml) and postoperatively (105.8 +/- 42.2 ng.[0-180]min/ml). CCK-8 elicited only a small increase in circulating PP, which was not influenced by distal pancreatectomy. These findings demonstrate that distal pancreatectomy does not alter PP response to insulin, a meal, or CCK-8.     

The cephalogastric phase of the pancreatic response to food in the dog

We studied post-meal pancreatic secretion and gastrin release in conscious dogs with duodenal Thomas cannulas. Normal dogs were tested in physiological conditions and with an i.v. infusion of atropine 20 micrograms/kg/h or secretin 0.5 CU/kg/h. The responses were also studied after antral and truncal vagotomy. In the early phase (0-20 min) of the response, before gastric emptying started, antral vagotomy reduced fluid and protein outputs, and truncal vagotomy reduced them still more. Atropine reduced only the protein response. Gastrin release reached a peak after 20-25 min. After antral and truncal vagotomy, gastrin release was reduced within 10 min after the meal. Late-phase (greater than 20 min) pancreatic secretion depended on the presence of chyme in the duodenum. The effects of atropine and antral vagotomy in the cephalogastric phase could be explained by antropancreatic reflexes stimulating fluid secretion (atropine-resistant pathway) and protein output (atropine-sensitive pathway).     

Effects of truncal vagotomy and antrectomy on bombesin-stimulated pancreatic secretion,release of gastrin,and pancreatic polypeptide in the anesthetized dog

The short-term effects of truncal vagotomy and antrectomy on bombesin-stimulated pancreatic secretion and release of gastrin and pancreatic polypeptide (PP) were studied in 18 anesthetized dogs. Together with an intravenous infusion of secretin (250 ng/kg/hr) bombesin (500 ng/kg/hr) was given before and after truncal vagotomy, antrectomy, and sham operation (N=6 dogs per group). Peak incremental pancreatic protein output in procedures (tachyphylaxis). Neither truncal vagotomy nor antrectomy significantly altered the pancreatic protein response to bombesin when compared with sham operation. Bombesin produced a mean 1-hr increase over basal of 196 pM for gastrin, which was abolished by antrectomy but not appreciably affected by truncal vagotomy and sham operation. The mean 1-hr increment (207 pM) for PP in response to bombesin was not changed by truncal vagotomy, antrectomy, and sham operation. This study shows in the anesthetized dog that exogenous bombesin stimulates release of PP as well as gastrin; that the release of gastrin by bombesin is not vagally dependent; that neither truncal vagotomy nor antrectomy alter the release of PP by bombesin; and that the action of bombesin on pancreatic protein secretion does not depend on release of gastrin or on intact vagal nerves.Parts of this paper have been presented at the 12th European Pancreatic Club Meeting, Copenhagen, Denmark, October 11–13, 1979, and at the 3rd International Symposium on Gastrointestinal Hormones, Cambridge, England, September 15–18, 1980.     

Gastric and Pancreatic Sympathetic Denervation in the Rat

The extirpation of the coeliac and superior mesenteric ganglia was found to be a simple and effective method of achieving complete adrenergic denervation of the stomach and pancreas in the rat. Thus, using the formaldehyde fluorescence technique, no remaining adrenergic nerves in these organs could be found after ganglionectomy. The vagus nerves did not significantly contribute to the adrenergic innervation of the stomach and pancreas. Chemical methods revealed minute amounts of noradrenaline in the pancreatic tissue even after complete ganglionectomy. The cellular source of this catecholamine is unknown. Sympathetic denervation of the stomach did not change the gastric acid secretory pattern, as studied with chronic gastric fistula rats.     

Experimental study of the pathogenesis of acute acalculous cholecystitis: Role of autonomic denervation

This study was undertaken to elucidate the role of autonomic denervation in the pathogenesis of acute acalculous cholecystitis. In Experiment I, the gallbladder was denervated by performing either celiac neurotomy (sympathetic denervation) or truncal vagotomy (parasympathetic denervation), or both, in dogs. In Experiment II, 45-min ischemia and 90-min reperfusion of the gallbladder with or without autonomic denervation were performed by simultaneously occluding the middle hepatic artery and superior mesenteric vein. Celiac neurotomy, and truncal vagotomy, or both, did not cause cholecystitis. Sympathetic denervation, however, decreased the amount of mucin in the gallbladder mucosa and parasympathetic denervation caused reduction of the tissue blood flow, as well as the accumulation of lipid peroxide and xanthine oxidase in the gallbladder mucosa. These changes were most remarkable 1–2 weeks after denervation and were alleviated 4 weeks after denervation. Ischemia-reperfusion 2 weeks after denervation caused more severe cholecystitis than ischemia-reperfusion alone. The most severe inflammation developed in animals that received both celiac neurotomy and truncal vagotomy. These results suggest that autonomic denervation alone does not induce acute cholecystitis, but that it plays an important role in the progression of the inflammatory process in ischemia-reperfusion injury.     

Effects of ethanol on meal-stimulated secretion of pancreatic polypeptide and cholecystokinin: Comparison of healthy volunteers,heavy drinkers,and patients with chronic pancreatitis

Tiscornia and Dreiling (Physiopathogenic Hypothesis of Alcoholic Pancreatitis: Supranormal Ecbolic Stimulation of the Pancreon Units Secondary to the Loss of the Negative Component of Pancreas Innervation. Pancreas 1987;2:604–612.) proposed that hypertonicity of intrapancreatic cholinergic neurons provoked by chronic alcoholism may contribute to the pathogenesis of chronic pancreatitis (CP). In the present study, the validity of this hypothesis was investigated in humans by studying the effects of atropine, cisapride, and ethanol on the meal-stimulated secretion of pancreatic polypeptide (PP) and cholecystokinin (CCK) in healthy volunteers, heavy drinkers, and CP patients. In healthy volunteers, the early phase PP response (0–40 min) to a test meal was completely blocked by atropine, whereas it was augmented by cisapride, an enhancer of acetylcholine release from cholinergic nerves. The early phase PP response to a test meal was inhibited by ethanol in healthy volunteers, whereas, in heavy drinkers, the response was augmented and the inhibition by ethanol was abrogated. In CP patients, ethanol tended to enhance the early phase PP response. Ethanol did not affect the early phase CCK response to a test meal in any group, but it significantly enhanced the late phase CCK response (40–120 min) in CP patients. These results suggest that: (i) oral ethanol may inhibit the post-prandial activation of the cholinergic neural pathway to the pancreas in healthy subjects, (ii) in heavy drinkers, postprandial cholinergic tone may be augmented and become resistant to the inhibition by ethanol, and (iii) the ethanol-induced increase in the postprandial CCK response in CP patients may play some role in the pathophysiology of this disease.     

Pyloric Relaxation Regulated Via Intramural Neural Pathway of the Antrum

Current information about pyloric relaxation is not sufficient. For this reason, our study aimed at measuring pyloric relaxation correctly and determining the role of the intrinsic and extrinsic neural pathway in pyloric relaxation. Five groups of dogs were used: five dogs had an intact gastrointestinal tract (control group); five dogs had transection and reanastomosis of the antrum 3 cm proximal to the pylorus (antral transection group); five dogs had extrinsic pyloric denervation (denervation group); five dogs had transection and reanastomosis of the antrum with extrinsic pyloric ring denervation (transection with denervation group); and five dogs had truncal vagotomy (vagotomy group). Gastropyloroduodenal motility was recorded by a strain-gauge force transducer in conscious dogs. In the control and denervation groups, pyloric relaxation was observed only during phase III of the interdigestive migrating motor complex. In the antral transection, transection with denervation, and vagotomy groups, pyloric relaxation was not observed in either the interdigestive or the postprandial state. The frequency of pyloric contractions increased in these groups in comparison with the control group. In conclusion, the results suggest that pyloric relaxation occurred during phase III to expel undigested particles from the stomach and that descending antral intramural pathways play an important role in the control of pyloric relaxation.     

Lipopolysaccharide-induced gastroprotection is independent of the vagus nerve

This study was done to examine the role of the vagus nerve in a model of gastric injury during endotoxemia. In conscious rats, lipopolysaccharide (LPS; 20 mg/kg ip) treatment for 5 hr prevented macroscopic gastric injury caused by acidified ethanol (150 mM HCl/50% ethanol). In addition, LPS enhanced gastric luminal fluid accumulation, decreased gastric mucosal blood flow (laser Doppler), and increased plasma gastrin levels (radioimmunoassay). Subdiaphragmatic truncal vagotomy, performed 7 days prior to LPS inhibited LPS-induced fluid accumulation, further reduced gastric mucosal blood flow following LPS, and augmented LPS-induced gastrin release compared to those in pyloroplasty controls. Atropine (1 mg/kg ip) prevented LPS-induced fluid accumulation but did not influence the effects of LPS on blood flow or gastrin release. Neither vagotomy nor atropine negated LPS-induced gastroprotection. This is the first report to examine the role of cholinergic nerves in the stomach during endotoxemia. The data indicate that LPS causes accumulation of gastric luminal fluid in part through its effects on cholinergic nerves. In contrast, the effects of vagotomy on blood flow and gastrin release following LPS involve a noncholinergic pathway. However, LPS-induced gastroprotection is independent of the vagus nerve.     

Effects of autonomic denervation on canine exocrine pancreatic secretion and blood flow

The effect of autonomic denervation on the exocrine pancreatic secretion and blood flow was studied in a group of dogs. Pancreatic secretion was collected and analyzed for volume and bicarbonate by direct cannulation of the main papilla through a duodenotomy prior to and following truncal vagotomy and celiac plexus denervation. Pancreatic blood flow was determined by the radioisotope distribution method (141Ce). Truncal vagotomy causes a reduction in pancreatic secretion of volume and bicarbonate by 25-30%, while celiac denervation caused a reduction of 70% in the secretion. The mean baseline pancreatic blood flow was 0.5 ml/g pancreas/min. Truncal vagotomy did not cause any significant flow changes, while celiac denervation caused a significant increase in blood flow of 350% (to 1.75 ml/g/min). These results suggest that both the parasympathetic and the sympathetic system affect pancreatic secretion independently of their effect upon pancreatic blood flow.     

Effect of total extrinsic denervation and atropine on HCl-stimulated pancreatic exocrine secretion and CCK release in conscious dogs.

In 10 dogs with pancreatic fistulas, we studied the effect of extrinsic pancreatic innervation and atropine on protein and bicarbonate secretion and cholecystokinin (CCK) release after intraduodenal perfusion with HCl. Before and after extrinsic denervation of the pancreas, the dogs were given 0.05 M HCl in increasing doses (1.5-48 mmol/h). Tests were repeated with atropine. Increasing doses of HCl resulted in a dose-dependent release of protein and bicarbonate output in both the intact and the denervated pancreas. However, pancreatic denervation significantly decreased pancreatic secretion in response to low loads but not to high loads of HCl. HCl-stimulated CCK release was not altered by pancreatic denervation. In the intact pancreas, atropine significantly reduced bicarbonate and protein response to low loads but not to high doses of HCl. In the denervated gland, atropine had no further inhibitory effect on exocrine pancreatic secretion. Furthermore, atropine showed no influence on HCl-stimulated CCK release under either condition.     

After vagotomy atropine suppresses gastrin release by food.

Changes in serum gastrin in response to feeding a meal of beef liver (15 g kg(-1)) were studied in 5 gastric fistula dogs with and without administration of atropine sulfate (0.2 mg kg(-1) intravenously). The studies were repeated after a truncal vagotomy that abolished acid secretion in response to 2-deoxyglucose. Before vagotomy atropine had little effect on the gastrin response to a meal. After vagotomy the gastrin response to feeding was greatly enhanced, but now atropine depressed the gastrin response at all times after the meal. It is concluded that vagotomy enhances the serum gastrin response to feeding and that atropine counteracts this enhancement.     

Effects of amino acids on pancreatic polypeptide before and after vagotomy in the dog

Summary We have previously indicated a marked influence of the vagus nerve on postprandial pancreatic polypeptide secretion. The present study was designed to determine whether the vagus nerve also plays a role in the regulation of pancreatic polypeptide secretion by absorbed nutrients. The pancreatic polypeptide responses to 17 intravenously administered amino acids, as well as arginine and glucose, were measured and compared with those 1 year after truncal vagotomy in conscious dogs. In response to the infusion of a mixture of amino acids (20 g during 60 min), plasma pancreatic polypeptide concentrations decreased in normal dogs. The effect was, however, completely reversed by vagotomy, with a significant pancreatic polypeptide release being observed (p < 0.05). Arginine (5 g during 60 min) also showed a similar, although not statistically significant, effect. After intravenous bolus-injection of glucose (0.5 g/kg body weight), a transient decrease of pancreatic polypeptide secretion was found; vagotomy abolished this response. These results suggest that the vagus nerve may have a suppressive role in the process of pancreatic polypeptide secretion induced by intravenous amino acid(s) and glucose.     

Influence of extrinsic denervation of the pancreas on food-stimulated pancreas secretion and cholecystokinin and neurotensin release in the dog]

In the present study we examined the effect of extrinsic pancreatic denervation on meal-stimulated pancreatic exocrine secretion and the release of neurotensin and CCK in dogs. Denervation of the pancreas significantly decreased protein output from preoperatively 16,661 +/- 1824 mg x 150 min to 2033 +/- 316 mg x 150 min postoperatively (p less than 0.001), and bicarbonate secretion from 297.5 +/- 36 mmol x 150 min to 104.85 +/- 16 mmol x 150 min (p less than 0.01). Release of neurotensin and CCK was not altered by interruption of the extrinsic pancreatic nerves. Our findings are consistent with the hypothesis that pancreatic secretory response to a meal is predominantly mediated by neutral extrinsic reflexes.