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Myenteric Neurones (myenteric + neurone)
Selected AbstractsLactobacillus reuteri ingestion and IKCa channel blockade have similar effects on rat colon motility and myenteric neuronesNEUROGASTROENTEROLOGY & MOTILITY, Issue 1 2010B. Wang Abstract, Background, We have previously shown that ingestion of Lactobacillus reuteri may modulate colonic enteric neuron activity but with unknown effects on colon motility. The aim of the present report was to elucidate the neuronal mechanisms of action of the probiotic by comparing the effects on motility of L. reuteri ingestion with blockade of a specific ionic current in enteric neurons. Methods, We have used intraluminal pressure recordings from ex vivo rat colon segments and whole cell patch clamp recordings from neurons of rat longitudinal muscle myenteric plexus preparations to investigate the effects of L. reuteri and TRAM-34 on colon motility and neurophysiology. The effects of daily feeding of 109L. reuteri bacteria or acute application of TRAM-34 on threshold fluid filling pressure or pulse pressure was measured. Key Results,Lactobacillus reuteri increased intraluminal fluid filling pressure thresholds for evoking pressure pulses by 51% from 0.47 ± 0.17 hPa; the probiotic also decreased the pulse pressure amplitudes, but not frequency, by 18% from 3.91 ± 0.52 hPa. The intermediate conductance calcium-dependent potassium (IKCa) channel blocker TRAM-34 (3 ,mol L,1) increased filling threshold pressure by 43% from 0.52 ± 0.22 hPa and reduced pulse pressure amplitude by 40% from 2.63 ± 1.11 hPa; contraction frequency was unaltered. TRAM-34 (3 ,mol L,1) reduced membrane polarization, leak conductance and the slow afterhyperpolarization current in 16/16 myenteric rat colon AH cells but 19/19 S cells were unaffected. Conclusions & Inferences, The present results are consistent with L. reuteri enhancing tonic inhibition of colon contractile activity by acting via the IKCa channel current in AH cells. [source] Cannabinoid receptor 1 signalling dampens activity and mitochondrial transport in networks of enteric neuronesNEUROGASTROENTEROLOGY & MOTILITY, Issue 9 2009W. Boesmans Abstract, Cannabinoid (CB) receptors are expressed in the enteric nervous system (ENS) and CB1 receptor activity slows down motility and delays gastric emptying. This receptor system has become an important target for GI-related drug development such as in obesity treatment. The aim of the study was to investigate how CB1 ligands and antagonists affect ongoing activity in enteric neurone networks, modulate synaptic vesicle cycling and influence mitochondrial transport in nerve processes. Primary cultures of guinea-pig myenteric neurones were loaded with different fluorescent markers: Fluo-4 to measure network activity, FM1-43 to image synaptic vesicles and Mitotracker green to label mitochondria. Synaptic vesicle cluster density was assessed by immunohistochemistry and expression of CB1 receptors was confirmed by RT-PCR. Spontaneous network activity, displayed by both excitatory and inhibitory neurones, was significantly increased by CB1 receptor antagonists (AM-251 and SR141716), abolished by CB1 activation (methanandamide, mAEA) and reduced by two different inhibitors (arachidonylamide serotonin, AA-5HT and URB597) of fatty acid amide hydrolase. Antagonists reduced the number of synaptic vesicles that were recycled during an electrical stimulus. CB1 agonists (mAEA and WIN55,212) reduced and antagonists enhanced the fraction of transported mitochondria in enteric nerve fibres. We found immunohistochemical evidence for an enhancement of synaptophysin-positive release sites with SR141716, while WIN55,212 caused a reduction. The opposite effects of agonists and antagonists suggest that enteric nerve signalling is under the permanent control of CB1 receptor activity. Using inhibitors of the endocannabinoid degrading enzyme, we were able to show there is endogenous production of a CB ligand in the ENS. [source] Actions of sumatriptan on myenteric neurones: relief from an old headache in the enteric nervous system?NEUROGASTROENTEROLOGY & MOTILITY, Issue 1 2007J. J. Galligan No abstract is available for this article. [source] The opioid system in the gastrointestinal tractNEUROGASTROENTEROLOGY & MOTILITY, Issue 2004C. Sternini Abstract ΅-, ,- and ,-opioid receptors (ORs) mediate the effects of endogenous opioids and opiate drugs. Here we report (1) the distribution of ΅OR in the guinea-pig and human gastrointestinal tract in relation to endogenous ligands, to functionally distinct structures in the gut and to ,OR and ,OR; and (2) the ligand-induced ΅OR endocytosis in enteric neurones using in vitro and in vivo models. In the guinea pig, ΅OR immunoreactivity is confined mainly to the myenteric plexus. ΅OR myenteric neurones are most numerous in the small intestine, followed by the stomach and the proximal colon. ΅OR immunoreactive fibres are dense in the muscle layer and the deep muscular plexus, where they are in close association with interstitial cells of Cajal. This distribution closely matches the pattern of enkephalin. ΅OR enteric neurones comprise functionally distinct populations of neurones of the ascending and descending pathways of the peristaltic reflex. In human gut, ΅OR immunoreactivity is localized to myenteric and submucosal neurones and to immune cells of the lamina propria. ,OR immunoreactivity is located in both plexuses where it is predominantly in varicose fibres in the plexuses, muscle and mucosa, whereas ,OR immunoreactivity appears to be confined to the myenteric plexus and to bundles of fibres in the muscle. ΅OR undergoes endocytosis in a concentration-dependent manner, in vitro and in vivo. Pronounced ΅OR endocytosis is observed in neurones from animals that underwent abdominal surgery that has been shown to induce delay in gastrointestinal transit. We can conclude that all three ORs are localized to the enteric nervous system with differences among species, and that ΅OR endocytosis can be utilized as a means to visualize enteric neurones activated by opioids and sites of opioid release. [source] Electrical behaviour of interleukin-1 beta (IL-1,) and prostaglandin-E2 (PGE2) on colonic myenteric neuronesNEUROGASTROENTEROLOGY & MOTILITY, Issue 4 2002A. Kelles Abstract,Intracellular recordings were used to examine the effects on electrical and synaptic behaviour of interleukin (IL)-1, and prostaglandin E2(PGE2) on myenteric neurones of the guinea-pig colon. Application of IL-1, and PGE2resulted in a concentration-dependent slow depolarization with enhanced spike discharge in, respectively, 45% (21/47) and 83% (33/41) of the impaled colonic neurones. Administration of IL-1, in three neurones (6%) elicited a hyperpolarization. Responses remained during tetrodotoxin application, indicative of a direct effect of both substances on the impaled neurones. The effects of IL-1, remained in the presence of indomethacine, a prostaglandin synthase inhibitor. Responses were seen in both nitric oxide synthase- and choline acetyl transferase-immunoreactive neurones. IL-1, evoked a 26% reduction of the fast excitatory postsynaptic potential. These results indicate that the application of IL-1, and PGE2evoke direct excitatory actions on a subset of myenteric neurones. For IL-1,, direct inhibition and presynaptic inhibition of the fast excitatory postsynaptic potential has also been found. In the distal colon, responses to IL-1, are not mediated through PGE2pathways. [source] Functional antagonism between nitric oxide and ATP in the motor responses of guinea-pig ileumAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 3 2000Chr. Ivancheva 1 The interaction of nitric oxide and ATP in the non-adrenergic, non-cholinergic (NANC) motor responses and the presence of NADPH-diaphorase and quinacrine-positive myenteric neurones were studied on guinea-pig ileum using mechanographic, histochemical and quinacrine-fluorescence techniques. In the presence of phentolamine, propranolol and atropine, the non-precontracted longitudinally oriented organ bath preparations responded to sodium nitroprusside (1,100 ,m) or ATP (5,50 ,m) with tetrodotoxin (0.1 ,m)-resistant relaxation or contraction, respectively. The effects of ATP were suramin (50 ,m)- and apamin (5 ,m)-sensitive. 2 The NANC motor responses elicited by electrical stimulation (0.8 ms, 1,20 Hz, 20 s) consisted of tetrodotoxin-sensitive relaxation phase followed by a phase of twitch-like and tonic contractions. 3 NG-nitro-L-arginine (L-NNA, 0.1,0.5 mm) inhibited or abolished the relaxation phase. L-arginine (0.5 mm), but not D-arginine (0.5 mm), restored the relaxation phase in L-NNA-pretreated preparations. The relaxation phase increased after ATP-induced desensitization of purinoceptors and in the presence of suramin (50 ,m) but was abolished by apamin (5 ,m). 4 The phase of contractions was enhanced by L-NNA (0.1,0.5 mm) and restored by L-arginine (0.5 mm). The twitch-like and tonic contractions were decreased during ATP-induced purinoceptor desensitization and in the presence of suramin (50 ,m). Apamin (5 ,m) inhibited the tonic contractions. 5 The desensitization of purinoceptors by ATP did not change the L-NNA-induced inhibition of the relaxation phase but decreased the L-NNA-increased phase of contractions. L-NNA reduced the relaxation phase and increased the phase of contractions during purinoceptor desensitization. 6 We conclude that in the longitudinal muscle layer of the guinea-pig ileum, nitric oxide mediates the relaxation phase while ATP contributes via smooth muscle P2 purinoceptors to the phase of contractions suggesting a postjunctional functional antagonism between nitric oxide and ATP. The presence of NADPH-diaphorase- and quinacrine-positive neuronal cells and processes running to the muscle cells confirms a physiological role of nitric oxide and ATP in the ileal neurotransmission. [source] | ||||||||||