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.     

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).     

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 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.     

Serum gastrin in duodenal ulcer: Part IV Effect of selective gastric vagotomy

Serum gastrin has been measured in 30 patients following selective gastric vagotomy. Basal serum gastrin was 52+/-5.7 pg/ml which was significantly lower than the corresponding level in 50 patients following truncal vagotomy (84+/-7.9 pg/ml). After a standard protein meal serum gastrin rose to 136+/-8.3 pg/ml at 60 minutes after the meal. The peak rise above basal levels was significantly lower than that achieved in patients who had undergone truncal vagotomy.These results complement our previous hypothesis that section of extragastric vagal fibres permits the release of additional gastrin above that expected with the diminution of acid secretion, and hence the decrease in inhibition of gastrin release from the antrum.     

Pancreatic polypeptide response to a meal before and after cutting the extrinsic nerves of the upper gastrointestinal tract and the pancreas in the dog

The role of the sympathetic and parasympathetic innervation in the release of pancreatic polypeptide (PP) basally and in response to a meal was studied after stepwise extrinsic denervation of the pancreas and the upper gastrointestinal tract in conscious dogs with gastric fistulae. One set of seven dogs was fed a meat meal (35 g/kg body weight) before and after truncal vagotomy and after truncal vagotomy plus celiac and superior mesenteric ganglionectomy, ie, extrinsic denervation of the pancreas and the upper gastrointestinal tract. In another set of six dogs, only ganglionectomy was performed. Experiments were repeated in the presence of atropine (50 g/kg body weight, given as an intravenous bolus 60 min prior to the meal). Truncal vagotomy significantly (P<0.05) reduced the postprandial 120-min integrated plasma PP response (IPPPR) by 84% as compared to the prevagotomy response. Before truncal vagotomy, atropine significantly reduced the IPPPR by 57%. After truncal vagotomy, atropine completely abolished the residual PP response. Additional celiac and superior mesenteric ganglionectomy did not alter the IPPPR already reduced by truncal vagotomy. With the vagus nerves intact, ganglionectomy alone had no effect on the IPPPR whether or not atropine was given. These findings indicate that (1) the splanchnic nerves do not play a significant role in postprandial PP release and (2) that the vagus nerves are important mediators of the response to a meal. The effect of atropine on postprandial PP release after truncal vagotomy may be due to interruption of short enteropancreatic reflexes, suppression of the intrinsic cholinergic activity of the pancreas, or inhibition of hormonally induced PP release.     

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.     

Regulatory mechanism of bombesin on gastrin release

Bombesin has been demonstrated to stimulate gastrin release by an atropine-resistant mechanism. In the present study, the effects of truncal vagotomy and chemical sympathectomy on the gastrin release by exogenous and endogenous bombesin using rat antral mucosa in tissue culture were studied. Exogenous bombesin 10^-8 mol/l significantly stimulated gastrin release. The stimulation of gastrin release by bombesin was abolished by truncal vagotomy, but not altered by chemical sympathectomy. Bombesin antiserum inhibited gastrin release by blocking the effect of endogenous bombesin. The inhibition of gastrin release by bombesin antiserum was abolished by truncal vagotomy, but not altered by chemical sympathectomy. In addition, the concentrations of bombesin-like immunoreactivity in antral mucosa were not altered by truncal vagotomy. These results suggest that the mechanism of gastrin release by bombesin is influenced by non-cholinergic local nerves under vagal control.     

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.     

Laparotomy-induced gastric protection against ethanol injury is mediated by capsaicin-sensitive sensory neurons

Laparotomy significantly attenuates ethanol-induced gastric mucosal lesions in the rat. The effects of sensory denervation by capsaicin, indomethacin, atropine, guanethidine, and hexamethonium on laparotomy-induced protection were studied in the rat. Gastric mucosal injury was induced by the intragastric instillation of 1 mL of 75% ethanol. The laparotomy-induced protection against ethanol injury was abolished by sensory denervation by capsaicin (total dose, 125 mg/kg, SC) and also by pretreatment with indomethacin (5 mg/kg, SC). In contrast, pretreatment with atropine (0.5 mg/kg, IP), guanethidine (total dose, 20 mg/kg, SC), or hexamethonium (20 mg/kg, IP) had no significant effect on laparotomy-induced protection. These data indicate that capsaicin-sensitive sensory afferent neurons, but not cholinergic or adrenergic autonomic neurons, mediate laparotomy-induced protection against ethanol injury. The hypothesis is put forward that the protective response to laparotomy arises from a somatovisceral and/or viscerovisceral axon reflex of capsaicin-sensitive afferent neurons. Prostaglandins might play a mediator role in the activation by laparotomy of somatic and/or visceral branches of the afferent neurons.     

Serum gastrin in duodenal ulcer: Part III Influence of vagotomy and pylorectomy

Following truncal vagotomy and anterior pylorectomy for duodenal ulcer, fasting serum gastrin levels were higher at 84 +/- 7.9 pg per ml than in unoperated patients with duodenal ulcer (16 +/- 1.5 pg per ml). In response to a standard protein meal, the peak serum gastrin achieved in the vagotomized group was 259 +/- 37.8 pg per ml at 75 minutes after ingestion, a much higher response than that obtained with a standard meal plus prior atropinization in the unoperated duodenal ulcer patients.These results suggest that truncal vagotomy allows release of gastrin which was previously inhibited with the vagi intact and the temporal characteristics of the response indicate that some of this gastrin is derived from an extragastric source. The results also exemplify the dependence of gastrin estimations as measured by this immunoassay on the acidity of the contents bathing the gastric antrum.     

Acid-Sensitive and Alkaline-Sensitive Sensory Neurons Regulate pH Dependent Gastrin Secretion in Rat

We examined the role of capsaicin-sensitive afferent neurons in pH-dependent gastrin secretion in the rat stomach. The change in serum gastrin levels relative to changes in luminal pH (using omeprazole for luminal alkalization or 0.1 N HCl for luminal acidification) was studied after oral administration of 4% lidocaine or capsaicin-induced ablation of afferent neurons. The increase of serum gastrin levels by luminal alkalization was significantly inhibited (50%) after administration of 4% lidocaine. Capsaicin pretreatment (125 mg/kg subcutaneously over two days) inhibited the change in serum gastrin levels both the luminal alkalization (38%) and acidification (66%). Antral gastrin contents, somatostatin contents, gastrin mRNA expression, and somatostatin mRNA expression were not significantly affected by capsaicin pretreatment. Our results indicate that capsaicin-sensitive afferent neurons participate in the secretion of gastrin by luminal alkalization and inhibition of gastrin by luminal acidification.     

Stimulation of gastrin release and gastric secretion: effect of bombesin and a nonapeptide in fistula dogs with and without fundic vagotomy.

Bombesin and a synthetic bombesin nonapeptide were studied by intravenous infusion at a dose of 0.5 microgram.kg-1.h-1 for 4 h in 7 dogs with esophagostomy and gastric fistula. In 3 of the dogs who had highly selective (fundic) vagotomy, mean integrated gastrin output over 4 h was double that in the 4 dogs with vagi intact during both nonapeptide (1,554 vs. 700 pg.ml-1.4 h-1) and bombesin infusion (2,442 vs. 1,440 pg.ml-1.4 h-1). Peak concentrations of serum gastrin reached during bombesin (490 +/- 100 vs. 320 +/- 90) were higher than those during nonapeptide infusion (270 +/- 40 vs. 160 +/- 28 pg/ml) in the vagotomized and intact dogs, respectively. The difference between vagotomized and vagally intact dogs suggests that the fundic vagotomy removed an inhibitor of gastrin release from the innervated antrum. Despite these differences in gastrin release, gastric acid output with the two peptides was the same (49--52 mEq/4 h) whether the fundus was denervated or innervated. This suggests that bombesin may stimulate gastric acid secretion by the release of an additional secretagogue which is not measured by the gastrin assay. Neither of the two inhibitors of gastrin release--antral acidification to pH 1.4 or less or atropine (100 microgram/kg)-- inhibited gastrin release by bombesin, even though the atropine reduced acid output by 80%. Bombesin is a potent gastric stimulus whose action is only partly explained by the measured gastrin release.     

An experimental study of the effect of perfusion of duodenal juices in the vagally innervated antral pouch upon gastric endocrine and exocrine function

Vagally innervated antral pouches were created in adult mongrel dogs, the interiors of these antral pouches were perfused with glycocholate, taurocholate, canine bile and human pancreatic juice, and antral function was investigated from the viewpoint of gastric endocrine and exocrine response. Perfusion with glycocholate and taurocholate of 20 mM induced a significant increase in gastric acid secretion as well as serum gastrin secretory response. Perfusion with canine bile and human pancreatic juice induced a pronounced increase in serum gastrin levels as well as gastric acid secretion starting immediately after the beginning of perfusion, and serum gastrin secretory response also displayed a marked increase. These results demonstrated that the regurgitation into the stomach of duodenal fluid containing bile and pancreatic juice, constitutes one factor causing increased serum gastrin levels and gastric acid secretion.     

The effects of the antimuscarinic drugs pirenzepine and atropine on plasma portal levels of somatostatin and gastrin in the dog

The effects of the antimuscarinic drugs pirenzepine and atropine on somatostatin and gastrin portal levels under basal conditions and during bethanechol infusion have been investigated in anesthetized dogs. Iv bolus administration of pirenzepine (1 mg/kg) or atropine (0.1 mg/kg), decreased gastrin concentrations, but did not affect basal somatostatin levels. During 120 min of bethanechol infusion (160 micrograms/kg/h) gastrin levels increased but somatostatin levels were unchanged. Pirenzepine (1 mg/kg iv bolus), administered at the 60th min of bethanechol infusion, decreased the gastrin concentrations, and markedly enhanced somatostatin levels. Under the same conditions atropine (0.1 mg/kg iv bolus) decreased gastrin levels, but had little or no effect on somatostatin levels. These results indicate that muscarinic receptors with similar affinity for pirenzepine and atropine mediate excitatory cholinergic influences on gastrin release. By contrast, muscarinic receptors with higher affinity for pirenzepine seem to be involved in the cholinergic inhibition of somatostatin release: by selectively blocking these receptors, pirenzepine may increase portal somatostatin levels.     

Intracerebroventricular administration of cholecystokinin-8 elevates plasma pancreatic polypeptide levels in awake dogs

The effect of intracerebroventricular (ICV) administration of cholecystokinin-8 (CCK-8) (0.5, 1.0, 2.0, 4.0 micrograms) on plasma levels of pancreatic polypeptide (PP) was studied in conscious dogs. ICV administration of CCK-8 (1.0, 2.0, 4.0 micrograms) produced a rapid and transient elevation in plasma concentrations of PP. Peripheral muscarinic receptor blockade with atropine or truncal vagotomy abolished PP secretion induced by ICV CCK-8. Pretreatment with ICV atropine also prevented the elevation in plasma PP induced by CCK-8. Plasma levels of CCK-33/39, CCK-8, and gastrin were not affected by ICV CCK-8. Our results indicate that central administration of CCK-8 selectively elevated plasma PP concentration. Since the effect of CCK-8 on plasma PP was abolished by central and peripheral atropine pretreatment, as well as by vagotomy, central and peripheral vagal cholinergic mechanisms appear to participate in release of PP that is induced by CCK-8 given by ICV injection.     

Action of ethanol on gastrin release in the dog

In conscious dogs with gastric and duodenal Thomas fistulas, we studied the effect of ethanol on plasma concentrations of gastrin. Ethanol was given either as an infusion into a peripheral vein (1.95 M, 200 ml/hr) or into the duodenum (0.95 M, 400 ml/hr) or as an intragastric bolus injection. The effect of the intragastric bolus injection of 200 ml of different concentrations (0.3 M, 1.7 M, 6.85 M) of ethanol was compared with that of equimolar solutions of urea and sucrose (0.3 M, 1.56 M), and with that of sodium taurocholate (0.06 M) and distilled water. The gastrin responses to an oral mixed-meat meal (35 g/kg) were also investigated. Intragastric bolus injection of isoosmolar *0.3 M) ethanol, but not of equimolar solutions of urea and sucrose or H₂O, significantly (P<0.05) increased plasma gastrin levels above basal. Hyperosmolar solutions of ethanol, urea, and sucrose as well as hypoosmolar sodium taurocholate produced a pronounced increase of plasma gastrin concentrations above basal. The comparison of the mean 2-hr integrated plasma gastrin responses (IRG) showed that ethanol (6.85 M), urea (6.85 M), and sodium taurocholate (0.06 M) are at least as potent stimuli of release of gastrin as the test meal used. Intraduodenal and intravenous infusion of ethanol did not significantly alter mean plasma gastrin concentrations. We conclude that in the dog ethanol, but not urea and sucrose, given in a concentration (0.3 M) which is known not to disrupt the gastric mucosal barrier, increases plasma gastrin levels. This release of gastrin by isoosmolar ethanol is not due to gastric distension and may be a specific effect of ethanol on the gastrin cells. Furthermore, the release of gastrin by hyperosmolar solutions of ethanol, sucrose, and urea is probably a nonspecific effect and due to damage of gastric mucosa. The effect of a hypoosmolar solution of sodium taurocholate, a well-known gastric mucosal barrier breaker, on gastrin release supports this hypothesis.     

Serum disappearance rate of gastrin-17 after vagotomy

Six duodenal ulcer patients were investigated before and after truncal vagotomy and pyloroplasty. Four doses of gastrin-17 were injected intravenously (15.625, 31.25, 62.5, and 125 micrograms/kg body weight); the gastric secretory response and the disappearance rate of gastrin were measured. After vagotomy the basal level of gastrin increased from 64 pg/ml to 106 pg/ml. When corrected for the basal levels of gastrin, the peak levels and disappearance rate of gastrin-17 were observed to be the same after vagotomy as before (half-life before vagotomy, 5.6 min; after, 5.8 min). This indicates that vagus does not influence the metabolism of exogenous gastrin-17. The gastric secretion of acid was reduced to 30% after vagotomy, which shows that there is a synergism between vagus and gastrin-17.     

Gastric acid and pancreatic polypeptide responses to modified sham feeding. Effects of truncal and parietal cell vagotomy.

The effects of truncal vagotomy and parietal cell vagotomy on gastric acid secretion and plasma gastrin and pancreatic polypeptide release were studied in 28 duodenal ulcer patients under basal conditions and after modified sham feeding and infusion of pentagastrin (2 micrograms/kg/h). Before vagotomy gastric acid output in response to modified sham feeding was significantly higher than basal acid secretion in all subjects tested and reached about 45% of the pentagastrin maximum. No difference in the increase in acid response, or in the pancreatic polypeptide response to modified sham feeding was found between patients with high and low basal secretion. Plasma gastrin concentration was unaltered by modified sham feeding before and after truncal vagotomy or parietal cell vagotomy, although after vagotomy it tended to reach higher values than before this procedure. After truncal vagotomy, basal pancreatic polypeptide concentration was decreased and modified sham feeding-induced pancreatic polypeptide increment was completely eliminated. Four weeks after parietal cell vagotomy, the modified sham feeding-induced increment in plasma pancreatic polypeptide was significantly decreased and observed only in seven of 12 patients. Four to five years after parietal cell vagotomy all subjects responded to modified sham feeding with pancreatic polypeptide increment similar to that before vagotomy and in three of 12 patients acid response to modified sham feeding was seen. This study indicates that truncal vagotomy eliminates gastric acid and plasma pancreatic polypeptide responses to vagal excitation while parietal cell vagotomy abolishes gastric acid response and reduces temporarily the pancreatic polypeptide response to modified sham feeding (possibly because of transient impairment of the vagal innervation of the pancreas). (2) A high ratio of basal to maximal acid output in non-operated duodenal ulcer patients is not associated with a low acid response to modified sham feeding, nor with a high pancreatic polypeptide concentration, and (3) Restitution of the pancreatic polypeptide response to modified sham feeding five years after parietal cell vagotomy does not indication ineffective denervation of the parietal cells.     

Histamine H1- and H2-receptor blockade does not maintain electrochemical gradients across canine gastric mucosa exposed to bile salt

We tested the hypothesis that histamine mediates the changes in cation permeability and potential difference characteristic of gastric mucosal barrier disruption. Canine Heidenhain pouches were exposed to 20 mM sodium taurocholate both with and without combined histamine H₁- and H₂-receptor blockade with diphenhydramine 2 mg/kg and metiamide 10 mol (2.5 mg)/kg/hr. Histamine-receptor blockade did not attenuate the flux, clearance rate, or permeability of hydrogen ion due to bile salt exposure and had no effect on the fluxes of sodium, chloride, and volume. Although the potential difference was higher with combined histamine-receptor blockade, the fall in potential difference due to bile salt was not attenuated. Using a pH-stat system to measure acid loss with the incremental addition of sodium taurocholate to final concentrations of 0, 5, 10, and 20 mM, we failed to observe any difference between control and histamine-receptor blockade in hydrogen flux or permeability. Increases in gastric blood flow due to intraarterial injection of histamine were attenuated with diphenhydramine, 2 mg/kg. Further attenuation of this vasodilation was observed with the addition of a histamine H₂ antagonist but not with increasing the dose of the H₁ antagonist to 10 mg/kg. Thus we were unable to document that doses sufficient to antagonize histamine H₁ and H₂ receptors prevent the increase in sodium-hydrogen flux and decrease in potential difference observed with exposure of the canine stomach to bile salt.In conducting the research described in this report, the investigators adhered to the Guide for the Care and Use of Laboratory Animals, DHEW Publication No. (NIH) 73-23, as prepared by the Institute of Laboratory Animal Resources, National Research Council.