Central nervous system action of calcitonin to alter experimental gastric ulcers in rats

Genetics of irritable bowel syndrome: shifting gear via biobank-scale studies

The pathophysiology of irritable bowel syndrome (IBS) is multifactorial and probably involves genetic predisposition and the effect of environmental factors. Unlike other gastrointestinal diseases with a heritable component, genetic research in IBS has been scarce and mostly characterized by small underpowered studies, leading to inconclusive results. The availability of genomic and health-related data from large international cohorts and population-based biobanks offers unprecedented opportunities for long-awaited, well-powered genetic studies in IBS. This Review focuses on the latest advances that provide compelling evidence for the importance of genes involved in the digestion of carbohydrates, ion channel function, neurotransmitters and their receptors, neuronal pathways and the control of gut motility. These discoveries have generated novel information that might be further refined for the identification of predisposed individuals and selection of management strategies for patients. This Review presents a conceptual framework, the advantages and potential limitations of modern genetic research in IBS, and a summary of available evidence.

Stable Gastric Pentadecapeptide BPC 157, Robert's Stomach Cytoprotection/Adaptive Cytoprotection/Organoprotection, and Selye's Stress Coping Response: Progress, Achievements, and the Future

We reviewed again the significance of the stable gastric pentadecapeptide BPC 157 as a likely mediator of Robert's stomach cytoprotection/adaptive cytoprotection and organoprotection and as novel mediator of Selye's stress coping response to reestablish homeostasis. Specific points of BPC 157 therapy and the original concept of Robert's cytoprotection/adaptive cytoprotection/organoprotection are discussed, including the beneficial effects of BPC 157. First, BPC 157 protects stomach cells and maintains gastric integrity against various noxious agents (Robert's killing cell by contact) and is continuously present in the gastric mucosa and gastric juice. Additionally, BPC 157 protects against the adverse effects of alcohol and nonsteroidal anti-inflammatory drugs on the gastric epithelium and other epithelia, that is, skin, liver, pancreas, heart (organoprotection), and brain, thereby suggesting its use in wound healing. Additionally, BPC 157 counteracts gastric endothelial injury that precedes and induces damage to the gastric epithelium and generalizes "gastric endothelial protection" to protection of the endothelium of other vessels (thrombosis, prolonged bleeding, and thrombocytopenia). BPC 157 also has an effect on blood vessels, resulting in vessel recruitment that circumvents vessel occlusion and the development of additional shunting and rapid bypass loops to rapidly reestablish the integrity of blood flow (ischemic/reperfusion colitis, duodenal lesions, cecal perforation, and inferior vena caval occlusion). Lastly, BPC 157 counteracts tumor cachexia, muscle wasting, and increases in pro-inflammatory/procachectic cytokines, such as interleukin-6 and tumor necrosis factor-α, and significantly corrects deranged muscle proliferation and myogenesis through changes in the expression of FoxO3a, p-AKT, p-mTOR, and p-GSK-3β (mitigating cancer cachexia).

Brain-gut Axis and Pentadecapeptide BPC 157: Theoretical and Practical Implications

BACKGROUND

Brain-gut interaction involves, among others, peptidergic growth factors which are native in GI tract and have strong antiulcer potency and thus could from periphery beneficially affect CNS-disorders. We focused on the stable gastric pentadecapeptide BPC 157, an antiulcer peptidergic agent, safe in inflammatory bowel disease trials and now in multiple sclerosis trial, native and stable in human gastric juice.

METHODS

Review of our research on BPC 157 in terms of brain-gut axis.

RESULTS

BPC 157 may serve as a novel mediator of Robert's cytoprotection, involved in maintaining of GI mucosa integrity, with no toxic effect. BPC 157 was successful in the therapy of GI tract, periodontitis, liver and pancreas lesions, and in the healing of various tissues and wounds. Stimulated Egr-1 gene, NAB2, FAK-paxillin and JAK-2 pathways are hitherto implicated. Initially corresponding beneficial central influence was seen when BPC 157 was given peripherally and a serotonin release in particular brain areas, mostly nigrostriatal, was changed. BPC 157 modulates serotonergic and dopaminergic systems, beneficially affects various behavioral disturbances that otherwise appeared due to specifically (over)stimulated/damaged neurotransmitters systems. Besides, BPC 157 has neuroprotective effects: protects somatosensory neurons; peripheral nerve regeneration appearent after transection; after traumatic brain injury counteracts the otherwise progressing course, in rat spinal cord compression with tail paralysis, axonal and neuronal necrosis, demyelination, cyst formation and rescues tail function in both short-terms and long-terms; after NSAIDs or insulin overdose or cuprizone encephalopathies were attenuated along with GI, liver and vascular injuries.

CONCLUSION

BPC 157, a gastric peptide, may serve as remedy in various CNS-disorders.

Brainstem neuropeptides and vagal protection of the gastric mucosal against injury: role of prostaglandins, nitric oxide and calcitonin-gene related peptide in capsaicin afferents

Earlier experimental studies indicated that the integrity of vagal pathway was required to confer gastric protection against damaging agents. Several peptides located in the brainstem initially identified to influence vagal outflow to the stomach, as assessed by electrophysiological approach or by vagal dependent alterations of gastric secretory and motor function, were investigated for their influence in the vagal regulation of the resistance of the gastric mucosa to injury. Thyrotropin releasing hormone (TRH), or its stable TRH analog, RX-77368, injected at low doses into the cisterna magna or the dorsal motor nucleus (DMN) was the first peptide reported to protect the gastric mucosa against ethanol injury through stimulation of vagal cholinergic pathways, inducing the release of gastric prostaglandins/nitric oxide (NO) and the recruitment of efferent function of capsaicin sensitive afferent fibers containing calcitonin-gene related peptide (CGRP). Activation of endogenous TRH-TRH1 receptor signaling located in the brainstem plays a role in adaptive gastric protection against damaging agents. Since then, an expanding number of peptides, namely peptide YY, CGRP, adrenomedullin, amylin, glugacon-like peptide, opioid peptides acting on µ, δ1 or δ2 receptors, nocicpetin, nocistatin, ghrelin, leptin and TLQP-21, a peptide derived from VGF prohormone, have been reported to act in the brainstem to afford gastric protection against ethanol injury largely through similar peripheral effectors mechanisms than TRH. Therefore gastric prostaglandins and CGRP/NO pathways represent a common final mechanism through which brain peptides confer vagally mediated gastroprotection against injury. A better understanding of brain circuitries through which these peptides are released will provide new strategies to recruit integrated and multifaceted gastroprotective mechanisms.

Restraint stress augments postprandial gastric contractions but impairs antropyloric coordination in conscious rats

Central corticotropin-releasing factor (CRF) plays an important role in mediating restraint stress-induced delayed gastric emptying. However, it is unclear how restraint stress modulates gastric motility to delay gastric emptying. Inasmuch as solid gastric emptying is regulated via antropyloric coordination, we hypothesized that restraint stress impairs antropyloric coordination, resulting in delayed solid gastric emptying in conscious rats. Two strain gauge transducers were sutured onto the serosal surface of the antrum and pylorus, and postprandial gastric motility was monitored before, during, and after restraint stress. Antropyloric coordination, defined as a propagated single contraction from the antrum to the pylorus within 10 s, was followed by > or = 20 s of quiescence. Restraint stress enhanced postprandial gastric motility in the antrum and pylorus to 140 +/- 9% and 134 +/- 9% of basal, respectively (n = 6). The number of episodes of antropyloric coordination before restraint stress, 2.4 +/- 0.4/10 min, was significantly reduced to 0.6 +/- 0.3/10 min by restraint stress. Intracisternal injection of the CRF type 2 receptor antagonist astressin 2B (60 microg) or guanethidine partially restored restraint stress-induced impairment of antropyloric coordination (1.6 +/- 0.3/10 min, n = 6). The restraint stress-induced augmentation of antral and pyloric contractions was increased by astressin 2B and guanethidine but abolished by atropine, hexamethonium, and vagotomy. Restraint stress enhanced postprandial gastric motility via a vagal cholinergic pathway. Restraint stress-induced delay of solid gastric emptying is due to impairment of antropyloric coordination. Restraint stress-induced impairment of antropyloric coordination might be mediated via a central CRF pathway.

Intracerebroventricular calcitonin prevents stress-induced gastric dysfunction

BACKGROUND

Restraint stress produces gastric hypercontractility and acidity leading to stress ulceration. Intracerebroventricular (ICV) salmon calcitonin (sCT) decreases restraint injury and acidity, but its effects on restraint-induced hypercontractility are unknown.

METHODS

Using stereotactic guidance, ICV catheters were placed into the lateral ventricle of adult male rats and calibrated gastric strain gauge transducers were implanted 5 days prior to restraint stress. sCT rats (n = 8) were pretreated with 5 microg of calcitonin ICV (10 microl volume), while controls (n = 10) received 10 microl of ICV saline prior to restraint for 2 h at 20 degrees C followed by 2 h at 4 degrees C. Gastric motility data were collected with AT-CODAS and analyzed with ADVANCED CODAS. Gastric volume, pH, and lesions were recorded following the stress.

RESULTS

ICV calcitonin prevented gastric mucosal injury in all animals (0% vs 100%, P <.01) and elevated pH slightly (2.5 +/-.3 vs 1.6 +/-.1, P <.05). Stress caused the force of contractions to increase from 0.35 +/-.1 to 1.38 +/-.4 g in controls (P <.01), while treated animal's force fell from.42 +/-.1 to 0.2 +/-.05 g (P <.01 vs control). Stress did not affect contractions/min (3.4 +.6 vs 3.5 +.3), but sCT increased frequency (2.5 +.4 to 5.0 +.2, P <.01). Stress prolonged contraction duration (11.5 + 1 to 16.5 + 1.7 s, P <.01), but stress's effect was prevented by sCT (11.0 +.5 to 11.2 +.3, P <.01 vs control).

CONCLUSIONS

Pretreatment with 5 microg central sCT prevents the increased amplitude and duration of gastric contractions produced by restraint stress for 2 h, in association with gastroprotection.

Glucagon-like peptide (GLP-1) is involved in the central modulation of fecal output in rats

In addition to its insulinotropic action, exogenously administered glucagon-like peptide (GLP-1) inhibits gastropancreatic motility and secretion via central pathways. The aims of the present study were to evaluate the effects of exogenous GLP-1-(7-36) amide on fecal output and to investigate the role of endogenous GLP-1 on stress-induced colonic activity. With the use of a stereotaxic instrument, adult male Sprague-Dawley rats weighing 200-250 g were fitted with stainless steel cerebroventricular guide cannulas under ketamine anesthesia. A group of rats were placed in Bollman-type cages to induce restraint stress. Fecal output monitored for 2 h was increased significantly by intracerebroventricular GLP-1 to 500, 1, 000, and 3,000 pmol/rat (P < 0.05-0.01), whereas intraperitoneal GLP-1 had no effect. Intracerebroventricular administration of the GLP-1 receptor antagonist exendin-(9-39) (10 nmol/rat) reversed the increases induced by GLP-1 (500 pmol/rat; P<0.01). Similar results were also observed with the injection of corticotropin-releasing factor receptor antagonist astressin (10 microg/rat icv). The significant increase in fecal pellet output induced by restraint stress was also decreased by both intracerebroventricular exendin (10 nmol/rat) and astressin (10 microg/rat; P<0.01-0.001). These results suggest that GLP-1 participates in the central, but not peripheral, regulation of colonic motility via its own receptor and that GLP-1 is likely to be a candidate brain-gut peptide that acts as a physiological modulator of stress-induced colonic motility.

Investigation on the mechanisms involved in the central protective effect of amylin on gastric ulcers in rats

1. The mechanisms involved in the protective effect of amylin (administered into the brain ventricle, i.c.v.) on gastric ulcers induced by the oral administration of ethanol 50% (EtOH, 2 ml/rat) or indomethacin (indomethacin, 20 mg kg(-1), at a dosing volume of 5 ml) were investigated in rats. 2. The possible involvement of endogenous nitric oxide (NO) in the beneficial effect of amylin against EtOH-induced ulcers was examined. The inhibitor of NO-synthesis, NG-nitro-L-arginine methyl ester (L-NAME, 70 mg kg(-1), s.c.) was injected 30 min before amylin (2.2 microg/rat, i.c.v.) followed by EtOH after a further 30 min. Rats were sacrificed 1 h after EtOH. L-NAME completely removed the protective effect of amylin. 3. The interaction between amylin and gastric nonprotein sulfhydryl groups was studied. The rats were treated with N-ethyl-maleimide (NEM, 25 mg kg(-1), s.c.) 30 min before amylin (2.2 microg/rat, i.c.v.) followed by EtOH 30 min after or by indomethacin 5 min after amylin. Rats were sacrificed 1 h or 6 h respectively after EtOH or indomethacin. NEM counteracted the protective effect of amylin against EtOH-induced ulcers but not against those provoked by indomethacin. 4. To determine whether amylin was able to promote ulcer healing, the peptide was injected 5 min after EtOH or 1 h after indomethacin. In the case of EtOH, the beneficial effect of amylin was lost whereas it was still effective on indomethacin-induced ulcers. 5. The results indicate that: the mechanisms involved in the antiulcer effects of amylin are different in these two types of gastric lesions probably because of the different etiopathology of various types of ulcers. Endogenous NO and nonprotein sulfhydryl groups are involved in the mucosal protective effects of amylin on EtOH and not on indomethacin-induced ulcers. Furthermore the effectiveness of amylin against indomethacin-induced lesions when administered after the ulcerogenic process has started suggests that amylin is involved not only in the protection but also in the healing mechanisms in this type of ulcer.

Calcitropic peptides: neural perspectives

In mammals and higher vertebrates, calcitropic peptides are produced by peripheral endocrine glands: the parathyroid gland (PTH), thyroid or ultimobranchial gland (calcitonin) and the anterior pituitary gland (growth hormone and prolactin). These hormones are, however, also found in the neural tissues of lower vertebrates and invertebrates that lack these endocrine organs, suggesting that neural tissue may be an ancestral site of calcitropic peptide synthesis. Indeed, the demonstration of CNS receptors for these calcitropic peptides and their induction of neurological actions suggest that these hormones arose as neuropeptides. Neural and neuroendocrine roles of some of these calcitropic hormones (calcitonin and parathyroid hormone) and related peptides (calcitonin gene related peptide, stanniocalcin and parathyroid hormone related peptide) are thus the focus of this review.

Effect of peripherally and centrally administered calcitonin on gallbladder emptying in dogs

The effect of calcitonin on meal-stimulated gallbladder emptying (GBE) was examined after intravenous (i.v.) and intracerebroventricular (i.c.v.) administration in six mongrel dogs. The gallbladder contraction was surveyed by means of real-time ultrasonography in conscious dogs. Calcitonin given i.v. elicited an immediate and strong inhibition of postprandial GBE-the integrated 0- to 120-min gallbladder response was 118.1 +/- 8.0%.h after placebo, whereas it was 91.8 +/- 2.1%.h, 59.4 +/- 17.9%.h (P < 0.001), and 14.2 +/- 20.5%.h (P < 0.001) after 3.6, 18.0, and 90.0 pmol.kg-1 calcitonin, respectively. After i.c.v. administration (1.8 and 18.0 pmol.kg-1), only the higher calcitonin dose exerted a moderate inhibitory effect on postprandial GBE. The calcitonin doses required to evoke a 50% inhibition of meal-stimulated GBE were 15- to 10-fold lower after i.v. than i.c.v. application. Peripherally given calcitonin brought about a dose-dependent increase in the interdigestive gallbladder volume-the linear regression of the relative gallbladder volume versus calcitonin dose was y = 11.60 [ln(dose + 1)] + 97.02 (r = 0.864, P < 0.001). Intravenous application of calcitonin did not affect caerulein-induced GBE. The results obtained imply that: (i) calcitonin exerts an inhibitory influence on meal-induced GBE and that this effect is more pronounced after i.v. than after i.c.v. administration, and (ii) peripherally given calcitonin does not inhibit caerulein-induced gallbladder contraction in the dog.

The protective effect of 5-HT3 receptor antagonist in thyrotropin releasing hormone-induced gastric lesions

The present study examined 1) oxidative stress and gastric lesions induced by thyrotropin releasing hormone (TRH) 2) The effect of a 5-hydroxytryptamine3 (5-HT3) receptor antagonist, ICS 205930 on protective effect of calcitonin on gastric lesions produced by TRH. Calcitonin (5 micrograms/10 microliter) was injected i.c.v. 10 min before TRH (10 micrograms/10 microliter, i.c.v.) injection or ICS 0.5 mg/kg, (i.p.) was given 60 min prior to calcitonin or TRH to rats. Ulcer index, lipid peroxidation (LP) and glutathione (GSH) levels were quantified 3 h after TRH injection in the stomach, liver and brain. TRH caused mucosal lesions (UI: 10.0 +/- 2.0 mm) without changing gastric GSH and LP. JCS did not alter the protective effect of calcitonin against TRH-induced lesions but attenuated. TRH-induced lesion formation. The oxidative effects of calcitonin or ICS were similar to TRH but both drugs attenuated gastric lesion formation. Hence, oxidative changes in tissues studied are not directly involved in TRH-induced lesions.

Cold-restraint- and TRH-induced ulcer models demonstrate different biochemical and morphological manifestations in gastric and hepatic tissues in rats. Role of calcitonin

In the present study, two ulcer models--central thyrotropin-releasing hormone (TRH) injection and cold-restraint stress (CRS) application--were compared. Animals were treated either with salmon calcitonin (sCT) or saline intracerebroventricularly (ICV) before CRS exposure or ICV TRH injection. In both models, besides ultrastructural properties, ulcer indexes and lipid peroxidation (LP) and glutathione (GSH) levels of liver and stomach were determined. While TRH treatment did not affect GSH and LP levels of the stomach and led to a slight decrease in hepatic GSH levels, CRS induced a marked reduction in gastric and hepatic GSH and an increase in LP levels of both tissues. sCT pretreatment prevented the reduction of gastric and hepatic GSH levels and morphological damage of both tissues in the CRS group. However, the same treatment did not prevent the TRH-induced reduction of hepatic GSH levels and, interestingly, it worsened the ultrastructural disturbances in the liver. Although sCT prevented macroscopic ulcer formation in both models, it did not totally reverse the microscopic effects of TRH.

Wound healing of acetic acid-induced gastric ulcer in rats and the effects of cimetidine and calcitonin, with special reference to prolylhydroxylase and collagenase enzyme activity

The healing of acetic acid-induced gastric ulcer in rats and the effects of cimetidine and calcitonin were investigated with reference to the enzyme activity of both prolylhydroxylase and collagenase as related to histological findings. The rats were observed by endoscopy on the 3rd day after the subserosal injection of acetic acid; rats with ulcers were divided into three groups: non-treated, and cimetidine- and calcitonin-treated. The latter two groups were treated for 7 days. Prolylhydroxylase activity in active ulcers in the non-treated group was slightly higher on the 3rd day and significantly higher on the 10th day than the activity in control rats that had received subserosal injections of physiological saline solution on the respective days. In non-treated rats, the healed ulcer on the 10th day showed lower prolylhydroxylase activity than that in the active ulcer on the same day. Cimetidine did not affect prolylhydroxylase activity, but, with calcitonin, there was higher prolylhydroxylase activity in the healed than in the active ulcer, although the difference was not significant. Interstitial collagenase showed the highest activity on the 3rd day and decreased on the 10th day in non-treated rats. Collagenase activity was higher in the cimetidine-treated group, than that in the non-treated group, and numerous peroxidase-positive granulocytes were seen in the mucosa and submucosa. Calcitonin did not affect collagenase activity. The participation of both enzymes is indispensable in the healing process and the effects of anti-ulcer agents on these enzymes must be considered.

The role of 5-HT3 receptors in the anti-ulcer effect of calcitonin

1. The aim of the present study was to determine the role of 5-HT3 receptors of the gastroprotective effect of salmon calcitonin (sCT) and sCT-induced changes in gastric, hepatic, brain and brainstem glutathione (GSH) and lipid-peroxidation (LP) levels in rats subjected to cold-immobilization stress. 2. Stress exposure resulted in ulcer formation and a decrease in GSH levels of the liver, brain and brainstem and an increase in gastric and hepatic LP (P < 0.05). 3. sCT prevented stress-induced gastric ulcer development (P < 0.01) and reversed the decrease in hepatic and brain GSH levels (P < 0.05). 4. In the present study, a 5-HT3 receptor antagonist, ICS 205,930 was used. Interestingly, the effect of the blocker on GSH and LP levels of the tissues studied was similar to those of sCT. 5. ICS 205,930 dose dependently reversed the anti-ulcer effect of sCT although it did not antagonize the effect of sCT on GSH and LP levels, but it seemed to show an additive interaction for brain and brainstem GSH and gastric LP levels with sCT.

Hypoplasia of G cells in long term steroid-treated rats after ultra-high dose of salmon calcitonin

Male young adult Wistar rats were treated parenterally with cortisol and cortisol combined with salmon calcitonin for 28 and 56 days and the stomach was investigated histologically as well as the G cells using immunohistochemistry. After 28 days of cortisol administration desquamation of the superficial layers of gastric mucosa was found and after 56 days ulcer-like changes developed and increased gastrin immunoreactivity was observed. Administration of high doses of salmon calcitonin together with cortisol resulted in a significant hypoplasia of G cells and prevented the pathological changes in the gastric mucosa.

Mechanism of action of calcitonin gene-related peptide in inhibiting pancreatic enzyme secretion in rats

BACKGROUND

Recently, calcitonin gene-related peptide (CGRP) receptors have been identified in the central nervous system. Therefore whether CGRP inhibits pancreatic enzyme secretion at a central site was investigated.

METHODS

In vivo studies were performed on rats to examine the effect of CGRP on pancreatic enzyme secretion evoked by stimulants that act on different sites: (1) 2-Deoxy-D-glucose (2DG), a central vagal stimulant; (2) cholecystokinin, which acts via vagal afferent pathways under physiologic conditions; (3) electric vagal nerve stimulation, which stimulates vagal release of acetylcholine in the pancreas; and (4) bethanechol, which directly activates pancreatic muscarinic receptors.

RESULTS

CGRP produced a dose related inhibition of pancreatic secretion evoked by 2DG. Complete inhibition was observed at a dose of 25 micrograms.kg-1 x h-1. Similarly, CGRP at a dose of 50 micrograms.kg-1 x h-1 completely inhibited pancreatic protein secretion in response to a physiological concentration of cholecystokinin octapeptide (CCK-8). In contrast, pancreatic protein secretion evoked by bethanechol or electrical stimulation of the vagal trunk were unaffected by CGRP. It was also shown that perivagal capsaicin treatment impaired pancreatic responses to CCK-8 but not to 2DG ruling out an effect of CGRP on vagal afferent pathway.

CONCLUSIONS

Our data indicates that CGRP inhibits pancreatic enzyme secretion evoked by 2DG or CCK-8 via vagal pathways. CGRP exerts its inhibitory action at a central vagal site.

Inhibition of gastric acid secretion and ulcers by calcitonin [correction of calciton] gene-related peptide

A central action of CGRP to inhibit gastric acid secretion, demonstrated in rats and dogs, is mediated at least in rats through modulation of parasympathetic outflow to the stomach. The centrally mediated protective effects of CGRP against ethanol-induced lesions is unique to this peptide and not shared by other centrally acting inhibitors of gastric function. It may be related to the increase in gastric mucosal blood flow induced by central CGRP. The presence of CGRP-like immunoreactivity and receptors in medullary nuclei receiving visceral information and influencing vagal outflow suggests a possible role of the peptide in the central regulation of gastric function. Peripheral injection of CGRP is well established to inhibit acid secretion in rats, dogs, rabbits, and humans. Its antisecretory effect is unlikely to be related to a direct action on the parietal cells. It involves specific and marked release of gastric somatostatin through an interaction with CGRP receptors characterized on D cells and coupled with cAMP. In addition, CGRP induces a decrease in acetylcholine transmission in the enteric nervous system, which may contribute to the inhibition of acid. The rich innervation of the stomach with CGRP-like immunoreactivity, which forms the major component of gastric sensory fibers, along with peptide release by sensory stimulation and potent actions on gastric secretions suggests a role of the peptide in the regulation of gastric function.

Central thyrotropin-releasing factor analog prevents ethanol-induced gastric damage through prostaglandins in rats

The effects of intracisternal injection of the stable thyrotropin-releasing factor (TRH) analog RX 77368 on gastric lesions induced by 60% ethanol and gastric prostaglandin E2 (PGE2) release were studied in rats. RX 77368 (1.0 and 1.5 ng) injected intracisternally inhibited (by 58% and 78%, respectively) macroscopic gastric damage induced by ethanol. Higher doses (3 and 300 ng) inhibited ethanol-induced gastric injury only in rats pretreated with omeprazole (20 mg/kg SC). Gastric acid output measured in conscious rats 2 hours after pylorus ligation was not modified by intracisternal injection of RX 77368 at 1.5 ng but was significantly increased by 54% at the 3-ng dose. The protective effect of TRH analog (1.5 ng) was completely abolished by indomethacin (5 mg/kg IP) and atropine (2 mg/kg SC) pretreatment. In pylorus-ligated rats, intracisternal RX 77368 (1.5 ng) inhibited ethanol-induced gastric lesions by 64%. Intracisternal injection of RX 77368 (1.5 ng) increased PGE2 levels measured in the effluent of dialysis fibers implanted into the corpus submucosa of urethane-anesthetized rats. Peripheral administration of omeprazole, atropine, indomethacin, or RX 77368 (1.5 ng IV) did not influence gastric damage induced by ethanol. These data show that the stable TRH analog, RX 77368, injected intracisternally at low non-secretory doses acts in the brain to protect against ethanol lesions through prostaglandin and cholinergic pathways. These findings suggest that central vagal activation induced by TRH may play a role in the control of mucosal integrity against ethanol through cholinergic prostaglandin release.

Gastric cytoprotection by intracisternal interleukin-1 beta in the rat

The effects of intracisternal (ic) injection of recombinant interleukin-1 beta (IL-1) on absolute ethanol-induced gastric necrotic lesions were studied in conscious rats. IL-1 given ic inhibited ethanol-induced gastric lesions. The cytoprotective effect was dose dependent (ED175 ng/rat), long lasting with a maximal action when given 1-3 h prior to ethanol, blocked by ic injection of a IL-1 receptor antagonist protein (IRAP), and by intraperitoneal injection of indomethacin. IL-1, injected ic, was detected in the peripheral blood. However, IL-1 serum levels were lower after IL-1 injection ic than after ip at a dose giving equal gastric protection. These data show that ic IL-1 induces long lasting gastric protection mediated by interaction with IL-1 receptors and prostaglandin pathways at central and/or peripheral sites that remain to be localized.

Effect of calcitonin on gall-bladder volume in man

The effect of increasing intravenous doses of synthetic salmon calcitonin (0.0044, 0.0088, 0.0175, and 0.0350 iu/kg per min) versus placebo on the fasted gall-bladder volume was assessed in seven normal subjects according to a double-blind study protocol. In addition, the action of calcitonin on meal-induced gall-bladder emptying was examined. Gall-bladder volumes were measured by means of real-time ultrasonography. Calcitonin evoked a dose-dependent relaxation of the fasted gall-bladder. A statistically significant increase of the fasted gall-bladder volume was observed with 0.0175 (23.4 +/- 5.5 cm3 placebo versus 33.9 +/- 7.7 cm3 calcitonin, P less than 0.001) and 0.0350 (21.4 +/- 4.6 cm3 placebo versus 36.1 +/- 8.4 cm3 calcitonin, P less than 0.01) iu/kg per min calcitonin, whereas a mean increase of the gall-bladder volume amounted to 32.1% and 46.5%, respectively. A significant delay of the gall-bladder emptying after calcitonin was reflected by a decrease of the ejection fraction: 23.2 +/- 8.3% calcitonin versus 57.8 +/- 6.9% placebo (P less than 0.02) at 20 min, and 40.5 +/- 8.8% calcitonin versus 67.2 +/- 3.8% placebo (P less than 0.02) at 30 min after the test meal. Calcitonin is concluded to have a potent relaxing effect on the human gall-bladder.

Close arterial infusion of calcitonin gene-related peptide into the rat stomach inhibits aspirin- and ethanol-induced hemorrhagic damage

Afferent neuron-mediated gastric mucosal protection has been suggested to result from the local release of vasodilator peptides such as calcitonin gene-related peptide (CGRP) from afferent nerve endings within the stomach. The present study, therefore, examined whether rat alpha-CGRP, administered via different routes, is able to protect against mucosal injury induced by gastric perfusion with 25% ethanol or acidified aspirin (25 mM, pH 1.5) in urethane-anesthetized rats. Close arterial infusion of CGRP (15 pmol/min) to the stomach, via a catheter placed in the abdominal aorta proximal to the celiac artery, significantly reduced gross mucosal damage caused by ethanol and aspirin whereas mean arterial blood pressure (BP) was not altered. Intravenous infusion of CGRP (50 pmol/min) did not affect aspirin-induced mucosal injury but significantly enhanced ethanol-induced lesion formation. Intravenous CGRP (50 pmol/min) also lowered BP and increased the gastric clearance of [14C]aminopyrine, an indirect measure of gastric mucosal blood flow while basal gastric output of acid and bicarbonate was not altered. Intragastric administration of CGRP (260 nM) significantly inhibited aspirin-induced mucosal damage but did not influence damage in response to ethanol. BP, gastric clearance of [14C]aminopyrine, and gastric output of acid and bicarbonate remained unaltered by intragastric CGRP. These data indicate that only close arterial administration of CGRP to the rat stomach, at doses devoid of a systemic hypotensive effect, is able to protect against both ethanol- and aspirin-induced mucosal damage. As this route of administration closely resembles local release of the peptide in the stomach, CGRP may be considered as a candidate mediator of afferent nerve-induced gastric mucosal protection.

Intrahypothalamic microinjection of calcitonin prevents stress-induced gastric lesions in rats

Injection of salmon calcitonin into the lateral ventricle or the cisterna magna was reported to potently inhibit gastric lesions induced by cold restraint stress. The forebrain sites of action were investigated using unilateral microinjection of salmon calcitonin prior to exposing conscious pylorus-ligated rats to cold restraint stress for 2 hr. Calcitonin (100 ng), microinjected in 100 nl volume by pressure ejection from glass micropipette positioned into the lateral or ventromedial hypothalamus or the paraventricular nucleus, prevented the development of gastric lesions whereas microinjections into the caudate putamen, the cerebral cortex or the hippocampus were ineffective. The antiulcerogenic effect of lateral hypothalamic injection was dose dependent and specific since calcitonin gene-related peptide, tested under the same conditions, had no effect. Microinjection of calcitonin at 100 ng dose into the ventromedial hypothalamus did not modify gastric secretion whereas microinjection into the lateral hypothalamus or the paraventricular nucleus induced 75-82% inhibition of gastric acid output in pylorus-ligated rats exposed to restraint stress. These results demonstrate that the hypothalamus including the lateral, ventromedial and paraventricular nuclei are responsive sites of action for calcitonin-induced inhibition of cold restraint stress ulcers. The antiulcerogenic effect may be related to suppression of gastric acid secretion along with other mechanisms that remain to be elucidated.