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Role of sensory nerves in gastroprotective effect of anandamide in rats

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Previous studies have shown that stimulation of cannabinoid 1 (CB1) receptor protects the gastric mucosa against stress-induced lesion. Aim of the present study was to examine the influence of anandamide on lipid peroxidation and antioxidant defense system in gastric mucosa and the role of sensory nerves in gastroprotective effects of cannabinoids. Studies were performed on rats with intact or ablated sensory nerves (by neurotoxic doses of capsaicin). Gastric lesions were induced by water immersion and restrain stress (WRS). Anandamide was administered at the dose of 0.3, 1.5 or 3.0 µmol/kg, 30 min before exposure to WRS. CB1 receptor antagonist, AM251 (4.0 µmol/kg) was administered 40 min before WRS. WRS induced gastric lesions associated with the decrease in gastric blood flow, mucosal DNA synthesis and mucosal activity of superoxide dismutase (SOD). Serum level of interleukin-1ß (IL-1ß) and mucosal level of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) were increased. Administration of anandamide reduced the ulcers area, generation of MDA+4-HNE and serum level of IL-1ß, and this effect was associated with the reduction in the WRS-induced decrease in gastric mucosal blood flow, mucosal DNA synthesis and SOD activity. Ablation of sensory nerves increased the area of ulcers, serum level of IL-1ß and mucosal content of MDA+4-HNE, whereas mucosal DNA synthesis, SOD activity and blood flow were additionally decreased. In rats with ablation of sensory nerves, administration of anandamide at the high doses (1.5 and 3.0 µmol/kg) partly reduced deleterious effect of WRS on gastric mucosa, but this effect was weaker than in animals with intact sensory nerves. Low dose of anandamide (0.3 µmol/kg) was ineffective in the protection of gastric mucosa against the WRS-induced lesions in rats with ablation of sensory nerves. In rats with intact sensory nerves and exposed to WRS, administration of AM251 exhibited deleterious effect. In rats with ablation of sensory nerves and exposed to WRS, AM251 failed to affect mucosal injury in the stomach. We conclude that anandamide reduces the mucosal oxidative stress and exhibits gastroprotective effect against WRS-induced ulcers. These effects are partly mediated by sensory nerves.
Acute pancreatitis leads to pancreatic damage followed by subsequent regeneration. The aim of our study was to evaluate the presence of growth factors in the course of spontaneous pancreatic regeneration after ischemia/reperfusion (I/R)-induced pancreatitis. Methods: In rats, I/R was evoked by clamping of splenic artery for 30 min followed by reperfusion. Rats were sacrificed 1, 5, 12 h or 1, 2, 3, 5, 7, 9 or 21 days after removal of vascular clips. Pancreatic blood flow (PBF), plasma lipase, interleukin-1ßb (IL-1ß), interleukin-10, pancreatic cells proliferation and morphological signs of pancreatitis were determined. Pancreatic presence of fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor (VEGF), platelet-derived growth factor-alpha (PDGF-A) and transforming growth factor-ß type II receptor (TGF-ß RII) was detected by immunohistochemisty. Results: Exposure to I/R led to the development of acute necrotizing pancreatitis followed by regeneration. Morphological features showed maximal pancreatic damage between the 1st and 2nd day of reperfusion. It was correlated with a maximal increase in plasma lipase, and pro-inflammatory IL-1ß concentration, as well as, a reduction in PBF and pancreatic DNA synthesis. I/R increased FGF-2 content in pancreatic acinar cells between the 12th and 24th h, and between 5th and 9th day of reperfusion. At the 2nd day the presence of FGF-2 in pancreatic acinar cells was reduced. After I/R PDGF-A appeared in pancreatic vessels from the 12th h to 5th day of reperfusion. PDGF-A was not observed in pancreatic acinar cells in the control or in I/R group. In pancreatic ducts, the presence of PDGF-A was reduced between the 1st and 3rd, and between 7th and 9th day of reperfusion. In acinar cells, VEGF content was increased after I/R at the time between the 1st and 24th h, and between 3rd and 7th day of reperfusion. At the 2nd day of reperfusion, VEGF was not detected in the pancreatic acinar cells. Moreover, VEGF was found in the inflammatory infiltration, in the tubular complexes between the 2nd and 5th day, and in granulation tissue at the 9th day of reperfusion. In pancreatic acinar cells, I/R caused an increase in TGFß RII presence between the 5th and 24th h, and between 7th and 9th day of reperfusion. Between the 2nd and 5th day of reperfusion the acinar presence of TGFß RII was reduced. In the pancreatic ducts, the presence of TGFß RII was increased after I/R from the 1st h to 9th day of observation. Four weeks after induction of acute pancreatitis, the pancreatic regeneration was completed and the presence of growth factors tested returned to control value. Conclusions: The presence of FGF, VEGF, PDGF-A and TGFß RII is modified in the course of I/R-induced acute pancreatitis. Maximal content of FGF, VEGF and TGFß RII has been observed in early stage of pancreatic regeneration suggesting the involvement these factors in pancreatic recovery.
Previous studies have shown that pancreatic polypeptide (PP) inhibits exocrine pancreatic secretion. The aim of present study was to determine the influence of PP administration on gastric growth and blood flow. Methods: Study was performed on regularly fed, fasted or fasted and subsequently refed rats. Rats were treated with saline (intraperitoneally - i.p.), caerulein (0.24 nmol/kg/dose, i.p.), pentagastrin (0.38 µmol/kg/dose, i.p.) or PP (5 nmol/kg/dose, i.p. or 10 pmol/dose intracerebroventricularly - i.c.v.). Saline, caerulein, pentagastrin and PP were administered alone or in combination, 3 times daily during last 48 h of experiment. Results: Treatment with pentagastrin increased gastric mucosa weight, mucosal DNA synthesis and gastric blood flow in all group tested. Intraperitoneal and i.c.v administration of PP alone reduced mucosal DNA synthesis in regularly fed and refed animals, and decreased gastric blood flow in refed animals. Combination of PP i.p. or i.c.v plus pentagastrin significantly reduced the pentagastrin-evoked increase in gastric mucosa weight, gastric DNA synthesis and gastric blood flow in fasted animals, as well as regularly fed animals. In refed animals, influence of PP administration on the pentagastrin-evoked increase in gastric mucosa weight was weak and statistically insignificant, but still i.p or i.c.v administration of PP significantly reduced gastric blood flow and mucosal DNA synthesis in this group of animals. Administration of caerulein caused weak, but significant increase in gastric DNA synthesis, gastric mucosa weight and gastric blood flow in fasted rats. In regularly fed animals, caerulein significantly increased only gastric DNA synthesis and gastric blood flow. In fasted animals with subsequent refeeding, caerulein was without effect on parameters tested in the stomach. Neither i.p. nor i.c.v administration of PP affected the caerulein-evoked effects in the stomach. Conclusions: Peripheral and central administration of PP inhibits food- and pentagastrin-stimulated growth of gastric mucosa. Similar effects of low central doses of PP as the high peripheral doses of PP suggests a crucial role of the central nervous system in the inhibitory effect of PP on gastric mucosa growth.
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