Journal of physiology and pharmacology : an official journal of the Polish Physiological Society
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J. Physiol. Pharmacol. · Oct 2012
Asymmetric dimethylarginine, an endogenous inhibitor of nitric oxide synthase, interacts with gastric oxidative metabolism and enhances stress-induced gastric lesions.
Asymmetric dimethylarginine (ADMA) is an endogenous competitive inhibitor of nitric oxide (NO) synthase known to exert vasoconstriction of vascular bed. The elevation of ADMA has been considered as the cardiovascular risk factor associated with hyperlipidemia, hypercholesterolemia and metabolic syndrome. ADMA is produced by the action of dimethylarginine dimethylaminohydrolase (DDAH), which hydrolyzes ADMA to L-citrulline and dimethylamine. ⋯ The ADMA induced exacerbation of WRS lesions and the accompanying rise in the plasma ADMA levels and the fall in GBF were significantly attenuated by concurrent treatment with glyceryl trinitrate (GTN) (10 mg/kg i.g.) in the presence of ADMA. Administration of ADMA resulted in a significant decrease in the expression of SOD and GPx mRNAs and the up-regulation of mRNA for IL-1β and TNF-α followed by an increase in these plasma cytokine levels as compared to respective values observed in vehicle-pretreated animals. We conclude that 1) ADMA could be implicated in the mechanism of WRS-induced ulcerogenesis, 2) ADMA exacerbates WRS-induced gastric lesions due to enhancement in neutrophil dependent lipid peroxidation and overexpression and release of proinflammatory cytokines IL-1β and TNF-α and a potent depletion of antioxidative enzymes SOD and GPx expression and activity.
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J. Physiol. Pharmacol. · Feb 2012
Hydrogen sulfide-induced colonic mucosal cytoprotection involves T-type calcium channel-dependent neuronal excitation in rats.
Hydrogen sulfide (H(2)S) is generated from L-cysteine by certain enzymes including cystathionine-γ-lyase (CSE) and cystathionine-β-synthase (CBS), and causes excitation of nociceptors mainly via activation of Ca(v)3.2 T-type Ca(2+) channels in the peripheral tissue, facilitating somatic and colonic pain. Here, we investigated whether sensory nerves and Ca(v)3.2 are involved in the H(2)S-induced mucosal cytoprotection against 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis in rats. Colitis was evaluated 3 days after intracolonic (i.c.) TNBS in the rat. ⋯ Ca(v)3.2 protein was upregulated in DRG 1 day after i.c. TNBS in rats, while CSE, but not CBS, protein was downregulated in the colon. Our findings suggest that luminal H(2)S causes excitation of sensory nerves most probably by activating Ca(v)3.2 T-type Ca(2+) channels that are upregulated in the early stage of colitis, leading to colonic mucosal cytoprotection in rats.
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J. Physiol. Pharmacol. · Dec 2011
ReviewStress and the gut: pathophysiology, clinical consequences, diagnostic approach and treatment options.
Stress, which is defined as an acute threat to homeostasis, shows both short- and long-term effects on the functions of the gastrointestinal tract. Exposure to stress results in alterations of the brain-gut interactions ("brain-gut axis") ultimately leading to the development of a broad array of gastrointestinal disorders including inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) and other functional gastrointestinal diseases, food antigen-related adverse responses, peptic ulcer and gastroesophageal reflux disease (GERD). The major effects of stress on gut physiology include: 1) alterations in gastrointestinal motility; 2) increase in visceral perception; 3) changes in gastrointestinal secretion; 4) increase in intestinal permeability; 5) negative effects on regenerative capacity of gastrointestinal mucosa and mucosal blood flow; and 6) negative effects on intestinal microbiota. ⋯ Additionally, melatonin an important mediator of brain gut axis has been shown to exhibit important protective effects against stress-induced lesions in the gastrointestinal tract. Finally, probiotics may profoundly affect the brain-gut interactions ("microbiome-gut-brain axis") and attenuate the development of stress-induced disorders in both the upper and lower gastrointestinal tract. Further studies on the brain-gut axis are needed to open new therapeutic avenues in the future.
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J. Physiol. Pharmacol. · Oct 2011
5-HT7 receptors modulate GABAergic transmission in rat hippocampal CA1 area.
The effects of the activation of serotonin-7 (5-HT(7)) receptors were investigated in the CA1 area pyramidal cells and stratum radiatum fast spiking GABAergic interneurons of rat hippocampal slices. To activate 5-HT(7) receptors, 5-carboxamidotryptamine (5-CT), a nonselective 5-HT(1A)/5-HT(7) agonist, was applied in the presence of N-[2-[4-(2-methoxyphenyl)-1piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY 100635), a selective 5-HT(1A) receptor antagonist. The activation of 5-HT(7) receptors resulted in a dose-dependent increase in the mean frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) recorded from pyramidal neurons while the mean amplitude of sIPSCs remained unaltered. ⋯ These data suggest that the activation of 5-HT(7) receptors results in an enhancement of the GABAergic transmission in the hippocampal CA1 area via two mechanisms. The first one involves an enhancement of excitatory glutamatergic input to GABAergic interneurons and is likely to be mediated by presynaptic 5-HT(7) receptors. The second effect, most likely related to the activation of 5-HT(7) receptors located on interneurons, results in an enhancement of the release of GABA.
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J. Physiol. Pharmacol. · Aug 2011
Effects of peripherally and centrally applied ghrelin in the pathogenesis of ischemia-reperfusion induced injury of the small intestine.
Ghrelin is an important hormone involved in the control of the human appetite center. Recently, protective properties of this hormone have been recognized in various models of impairment of the gastric mucosa, including stress, ischemia and reperfusion (I/R). Ghrelin is predominantly secreted by the gastric mucosa of stomach, but there are other sources of ghrelin, for example in the hypothalamus and various parts of the central nervous system (CNS) that should be taken into consideration. ⋯ The lack of a protective effect observed after central administration of this peptide against a long lasting I/R period is probably due to damage of neural pathways caused by I/R. Finally, the peripheral activity of ghrelin in the intestine is mediated by the sensory neurons with a prominent role of CGRP released from their endings. However, this peripheral action of ghrelin depends upon the proper functioning of both the sympathetic and parasympathetic system.