Duodenal ulcers are associated with a depletion of duodenal calcitonin gene-related peptide-like immunoreactivity in rats

Gastric lesions induced by concentrated ethanol are associated with a decrease in gastric calcitonin gene-related peptide-like immunoreactivity in rats

Gastric calcitonin gene-related peptide-like immunoreactivity (CGRP-li) was decreased in the gastric corpus of rats treated with 75% or 96% ethanol but not with 50% ethanol. The extent of gastric lesions was related to the increasing concentrations of ethanol (50-96%). CGRP-li decrease was evident already at 5 min after the 96% ethanol challenge, whereas a peptide recovery resulted 10 days after, concomitant with the healing of gastric lesions. Ethanol (96%) produced a significant decrease of CGRP-li in the whole thickness of the gastric corpus but not in the mucosal layers of the same area, indicating that the muscular layer of the gastric corpus is the zone involved in this phenomenon. Pretreatment with the selective sensory neurotoxin capsaicin induced a gastric CGRP-li decrease in the corpus and forestomach. Ethanol (96%) did not further decrease gastric corpus CGRP-li in capsaicin-pretreated rats. These findings suggest that 96% ethanol induced a decrease of CGRP-li deriving from a capsaicin-sensitive pool and that CGRP may play a role in gastric ulcer pathogenesis of haemorrhagic lesions induced by concentrated ethanol.

Cysteamine induced-duodenal ulcers are associated with a selective depletion in gastric and duodenal calcitonin gene-related peptide-like immunoreactivity in rats

We have measured the endogenous levels of gastric and duodenal calcitonin gene-related peptide (CGRP)-, neurokinin A (NKA)-, galanin-vasoactive intestinal polypeptide (VIP)- and neuropeptide Y (NPY)-like immunoreactivity (li) in relation to cysteamine-induced gastric lesions and duodenal ulcers in rats. CGRP-li but not NKA-, galanin-, VIP- or NPY-li was decreased in gastric and duodenal samples following a single ulcerogenic dose of cysteamine (900 mg/kg p.o.). Temporal relationships of this phenomenon showed that CGRP-li was selectively decreased (stomach 45%, duodenum 68% as compared to controls, respectively after 24 h) concomitantly to the formation of acute gastric lesions and duodenal ulcers. Animals bearing healed ulcers 12 days after cysteamine, had gastroduodenal CGRP-li similar to control values. Pretreatment with the selective sensory neurotoxin capsaicin decreased gastroduodenal CGRP-li but not NKA-, galanin-, VIP- or NPY-li, showing that CGRP might be considered a marker of the afferent innervation of the gastroduodenal tract. The residual gastroduodenal CGRP-li levels in capsaicin-pretreated animals were not decreased by cysteamine administration, indicating that the effect of cysteamine is restricted to a peptide pool of primary afferent origin. Duodenal CGRP-li is selectively decreased by the duodenal ulcerogen cysteamine during the acute phase of ulcers formation and might be among the local mediators which afford protection against the ulcerogenic stimuli.

Selective ablation of spinal afferent neurons containing CGRP attenuates gastric hyperemic response to acid

The gastric mucosa, in particular submucosal blood vessels, are innervated by afferent neurons containing neuropeptides such as calcitonin gene-related peptide. Stimulation of sensory neurons innervating the gastric mucosa increases submucosal blood flow. Since sensory neurons supplying the stomach are of dual origin from nodose and dorsal root ganglia, we examined the effect of selective ablation of either the vagal or spinal sensory innervation to the upper gastrointestinal tract on the increase in gastric mucosal blood flow in response to acid back diffusion into the gastric mucosa. Perineural application of capsaicin to the celiac/superior mesenteric ganglia, but not to the vagus nerves, significantly inhibited by 53% the hyperemic response to acid back diffusion. Tissue levels of immunoreactive calcitonin gene-related peptide in the gastric corpus were significantly reduced (by 73%) by periceliac capsaicin treatment, but unaffected by perivagal capsaicin treatment. These data suggest that spinal capsaicin-sensitive afferents containing calcitonin gene-related peptide immunoreactivity are involved in mediating increases in gastric mucosal blood flow. This increase in gastric mucosal blood flow mediated by sensory neurons may act as a protective mechanism against mucosal injury, similar to responses seen in other tissues such as skin.

Capsaicin-like activity of N-ethylmaleimide in rat stomach

1. N-Ethylmaleimide (NEM) and capsaicin induced a release of calcitonin gene-related peptide-like immunoreactivity (CGRP-li) in superfusates from rat gastric corpus. 2. The prior application of capsaicin completely blocked CGRP-li release by NEM while the exposure to NEM reduced the capsaicin-evoked CGRP-li outflow by about 51%. 3. These findings provide evidence that NEM might exert capsaicin-like activity in rat stomach and the release of CGRP-li from capsaicin-sensitive afferent fibres might influence the properties exerted by NEM in this tissue.

The neurobiology of stress ulcers

We have reviewed the neurobiology of stress ulcers from animal models to potential pharmacotherapeutic mechanisms. The evidence strongly supports the hypothesis that certain stress-related gastric lesions are 'brain-driven' events which may be more effectively managed through central manipulations than by altering local, gastric factors. Recent advances in the use of anxiolytic and antidepressant drugs in the management of stress-related gastric mucosal injury further supports the contention that a brain-gut axis, which may have nervous, peptidergic and classic monoaminergic components, modulates the intricate and complicated pattern of communication between the brain and the stomach. Delineation of the precise pathways which make up this communication as well as their manipulation by various pharmacological agents will be the focus of future research endeavour.

Interactions between sialoadenectomy and capsaicin-sensitive afferent fibers on gastric acid secretion in rats

In this study we have investigated the relative influence of capsaicin-sensitive afferents and sialoadenectomy on gastric acid secretion. Sialoadenectomized (SALX) rats showed a decrease in gastric acid secretion and an increase in gastric calcitonin gene-related peptide-like immunoreactivity (CGRP-li) as compared to sham-operated animals. Capsaicin pretreatment (50 + 100 mg kg-1 in two days) markedly decreased gastric CGRP-li in both sham and SALX-operated rats and increased acid concentration and output only in SALX animals. In this latter case the concomitant absence of two potent endogenous antisecretory agents (CGRP and epidermal growth factor; EGF) may contribute to the observed hypersecretion. Gastric content of vasoactive intestinal polypeptide (VIP)-li was unaffected in SALX and capsaicin-treated rats. Capsaicin-sensitive afferents and EGF contained in the salivary glands may interact in the regulation of the gastric acid secretion.

Decrease of duodenal calcitonin gene-related peptide- and substance P-like immunoreactivity in rat duodenal ulcers

We have investigated the endogenous levels of duodenal calcitonin gene-related peptide- (CGRP) and Substance P- (SP) like immunoreactivity (li) following the induction of duodenal ulcers in rats. Using three duodenal ulcerogens, namely cysteamine, dulcerozine or mepirizole given in a single oral dose, a decrease of duodenal CGRP-li and SP-li was observed. Time-relationship studies of this phenomenon show that CGRP-li and SP-li were decreased concomitantly to the formation of gastroduodenal ulcers after the administration of cysteamine (900 mg/kg p.o.). Pretreatment with the selective sensory neurotoxin capsaicin induced CGRP-li decrease in the duodenum, which was not further decreased by an ulcerogenic dose of cysteamine, indicating that cysteamine induced a release of CGRP-li of capsaicin-sensitive origin. Otherwise duodenal SP-li was not sensitive to capsaicin pretreatment and its duodenal content decreased by cysteamine originates from an intrinsic source. Our observations indicate that CGRP and SP may play an important local role in duodenal ulcerogenesis.

Duodenal SP-like immunoreactivity is decreased in experimentally-induced duodenal ulcers

Substance P-like immunoreactivity (SP-li) is decreased in duodenal samples of animals treated with a single dose of an ulcerogen such as dulcerozine, mepirizole or cysteamine. Unlike dulcerozine- or mepirizole-induced ulcers the degree of cysteamine-induced duodenal lesions is inversely correlated with the levels of duodenal SP-li. A significant decrease in duodenal SP-li was observed at 24 h, but not at 6 h after a single oral dose of cysteamine. These findings show that endogenous SP may play an important local role in duodenal ulcerogenesis.

Analogs of neurokinin A(4-10) afford protection against gastroduodenal ulcers in rats

We have developed a novel series of peptides, related to the NKA(4-10) sequence, in which substitution of selected amino acids determined variations in the affinity for the TK receptor subtypes. Subcutaneous pretreatment of rats with some peptides of this series reduced gastric ulcers induced by ethanol, indomethacin or acetylsalicylic acid (ASA) as well as duodenal ulcers induced by dulcerozine. In particular [Ala5]NKA(4-10) and [Ala5,beta Ala8]NKA(4-10) possess a broad spectrum of antiulcer activity which is long lasting and stronger than the precursor NKA(4-10). The observation that the prevention of ethanol-induced gastric lesions could be reversed by pretreatment with indomethacin favors the possible involvement of prostaglandins in the observed gastroprotection by TK analogs.