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The enteric nervous system (ENS) regulates numerous functional and immunological attributes of the gastrointestinal tract. Alterations in ENS cell function have been linked to intestinal outcomes in various metabolic, intestinal, and neurological disorders. Chronic kidney disease (CKD) is associated with a challenging intestinal environment due to gut dysbiosis, which further affects patient quality of life. Although the gut-related repercussions of CKD have been thoroughly investigated, the involvement of the ENS in this puzzle remains unclear. ENS cell dysfunction, such as glial reactivity and alterations in cholinergic signaling in the small intestine and colon, in CKD are associated with a wide range of intestinal pathways and responses in affected patients. This review discusses how the ENS is affected in CKD and how it is involved in gut-related outcomes, including intestinal permeability, inflammation, oxidative stress, and dysmotility. [Display omitted] [ABSTRACT FROM AUTHOR]

• α-Syn is expressed predominantly in cholinergic nerve varicosities and terminals in the mouse colon. • α-Syn KO mice had a higher enteric neuron density and a larger proportion of cholinergic neurons. • α-Syn deletion enhanced the amplitude of nicotinic receptor-mediated [Ca2+] i transients in the ENS. Alpha-Synuclein (α-Syn) is expressed in the central nervous system and the nervous system of the gut (enteric nervous system, ENS), and is well known to be the major constituent of Lewy bodies which are the hallmark of Parkinson's disease. Gastrointestinal disorders frequently manifest several years before motor deficits develop in Parkinson's patients. Despite extensive research on pathological rodent models, the physiological role of α-Syn in the normal ENS is unclear hampering analysis of its neuropathology. We compared the ENS in colons of α-Syn-knockout (α-Syn KO) and wild-type mice using immunohistochemistry and calcium-imaging of responses to synaptic input. We found that α-Syn is predominantly expressed in cholinergic varicosities, which contain vesicular acetylcholine transporter. α-Syn KO mice had higher enteric neuron density and a larger proportion of cholinergic neurons, notably those containing calretinin, demonstrating a role for α-Syn in regulating development of these neurons. Moreover, α-Syn deletion enhanced the amplitude of synaptically activated [Ca2+] i transients that are primarily mediated by acetylcholine activating nicotinic receptors suggesting that α-Syn modulates the availability of acetylcholine in enteric nerve terminals. [ABSTRACT FROM AUTHOR]

Optogenetics has emerged as an important tool in neuroscience, especially in central nervous system research. It allows for the study of the brain's highly complex network with high temporal and spatial resolution. The enteric nervous system (ENS), the brain in the gut, plays critical roles for life. Although advanced progress has been made, the neural circuits of the ENS remain only partly understood because the appropriate research tools are lacking. In this review, I highlight the potential application of optogenetics in ENS research. Firstly, I describe the development of optogenetics with focusing on its three main components. I discuss the applications in vitro and in vivo , and summarize current findings in the ENS research field obtained by optogenetics. Finally, the challenges for the application of optogenetics to the ENS research will be discussed. [ABSTRACT FROM AUTHOR]

This study was designed to appraise the relationship between enteric neuropathy and oxidative stress in cancer cachexia under l -glutamine-supplemented diet. Total and nitrergic neuronal populations were investigated in jejunum and ileum in four experimental groups: control (C); control l -glutamine-supplemented diet (CG); Walker-256 tumor (TW); and Walker-256 tumor supplemented with l -glutamine (TWG). In addition, local oxidative stress, neuronal nitric oxide synthase (nNOS) enzyme and nitric oxide (NO) levels were evaluated. Neuronal density and somatic area of the total and nitrergic populations were reduced in TW rats, which was accompanied by high oxidative stress, NO and nNOS levels. l -glutamine supplementation prevented neuronal atrophy, changes in pan neuronal density and nNOS overexpression (ileum), and restored total antioxidant capacity. Nevertheless, the oxidative stress was partially mitigated and no effect was observed on the reduction of nitrergic population and NO levels. l -glutamine-supplemented diet extenuates NO-mediated damage on the myenteric plexus although has a small benefit on oxidative stress. [ABSTRACT FROM AUTHOR]

Oxaliplatin is a first-line chemotherapeutic agent used for the treatment of colorectal cancer. Its use is associated with severe gastrointestinal (GI) side-effects, associated with oxidative damage and neurotoxicity to the enteric neurons. Resveratrol is a potent anti-oxidant that has been shown to protect against oxidative damage and neurotoxicity in other neurons and could therefore prevent oxaliplatin-induced damage to enteric neurons. We determined whether co-administration of resveratrol with oxaliplatin alleviates enteric neuron toxicity and GI dysfunction in mice. Colons were collected for immunohistochemical analysis of myenteric neurons and assessment of motor activity in organ-bath experiments. Morphological damage to the colonic mucosa and muscles was analysed. Oxaliplatin treatment induced translocation of nitrated proteins into the nuclei of myenteric neurons and significant damage to the mucosal lining, vacuolisation and a decrease in muscle thickness. This damage is linked to motor dysfunction due to inhibition of the amplitude of colonic contractions, leading to chronic constipation. Co-treatment with resveratrol prevented oxaliplatin-induced neurotoxicity, alleviated damage to GI mucosa, crypts and muscle layer, resulting in improved contractility and a decrease in constipation. Resveratrol could be integrated as part of a therapeutic regimen to help alleviate oxaliplatin-induced GI dysfunction. [ABSTRACT FROM AUTHOR]

The intestinal tract is the main organ involved in host nutritional homeostasis. Intestinal function in both vertebrates and invertebrates is partly controlled by enteric neurons that innervate the gut. Though anatomical and functional aspects of enteric neurons are relatively less characterized in Drosophila than in large insects, analyses of the role of the enteric neurons in flies have remarkably progressed in the last few years. In this review, we first provide a summary of the structure and function of the Drosophila intestine. We then discuss recent studies of the structure and function of enteric neurons in Drosophila melanogaster . [ABSTRACT FROM AUTHOR]

Glucagon-like peptide 2 (GLP-2) is a potent intestinotrophic growth factor with therapeutic potential in the treatment of intestinal deficiencies. It has recently been approved for the treatment of short bowel syndrome. The effects of GLP-2 are mediated by specific binding of the hormone to the GLP-2 receptor (GLP-2R) which was cloned in 1999. However, consensus about the exact receptor localization in the intestine has never been established. By physical, chemical and enzymatic tissue fragmentation, we were able to divide rat jejunum into different compartments consisting of: (1) epithelium alone, (2) mucosa with lamina propria and epithelium, (3) the external muscle coat including myenteric plexus, (4) a compartment enriched for the myenteric plexus and (5) intestine without epithelium. Expression of Glp2r ; chromogranin A ; tubulin , beta 3 ; actin , gamma 2 , smooth muscle , enteric and glial fibrillary acidic protein in these isolated tissue fractions was quantified with qRT-PCR. Expression of the Glp2r was confined to compartments containing enteric neurons and receptor expression was absent in the epithelium. Our findings provide evidence for the expression of the GLP-2R in intestinal compartments rich in enteric neurons and, importantly they exclude significant expression in the epithelium of rat jejunal mucosa. [ABSTRACT FROM AUTHOR]

Abstract: Background: Intestinal inflammation is well known to cause gut dysmotility through the effects on the enteric nervous system. Glial-derived neurotrophic factor (GDNF) has been demonstrated to have anti-inflammatory effects and neuronal protective actions. The aim of this study was to investigate whether the GDNF could improve inflammation-induced gut dysmotility. Methods: Recombinant adenoviral vectors encoding GDNF (Ad-GDNF) were administered intracolonically in experimental colitis induced by dextran sulfate sodium (DSS). The disease activity index (DAI) and histological score were measured. Colonic transit was measured by using phenol red and assessed with the geometric center. PGP 9.5 immunostaining was used to examine the number and distribution of enteric neurons. The expression of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and myeloperoxidase (MPO) activity were measured by ELISA assay. The expression of Akt, caspase-3, bcl-2 and PGP 9.5 was analyzed by western blot assay. Results: A significant neuronal cell loss and a significant delay in colonic transit accompanied with the neuronal loss following inflammation were observed. GDNF prevented partially the loss of enteric neurons and ameliorated significantly experimental colitis and delayed colonic transit by, at least in part, down-regulation of TNF-α and IL-1β expression, decrease of infiltration of leukocytes, and inhibition of neuronal cell apoptosis. Conclusions: GDNF reduces inflammation and improves delayed colonic transit in DSS-induced colitis. GDNF may be a useful therapeutic agent for the treatment of gut dysmotility in patients with UC. [Copyright &y& Elsevier]

Highlights: [•] In the intestine, the Glucagon-like peptide-1 receptor (GLP-1r) is expressed by enterocytes, Paneth cells and by a subset of enteric neurons. [•] Exendin 4, a GLP-1r agonist, induced expression of the early gene c-fos in cells expressing the GLP-1r. [•] Expression of c-fos was inhibited by the voltage-gated sodium channel blocker tetrodotoxin and by the GLP-1r antagonist exendin 9–39. [ABSTRACT FROM AUTHOR]

Abstract: The whole-cell configuration, several pharmacological tools, and single-cell RT-PCR were used to investigate the contribution of P2X7 subunits to the ATP-induced currents (IATP) in guinea pig myenteric neurons. IATP was recorded in the great majority of tested neurons. ATP concentration-response curve (0.01–10mM) showed two phases, the first mediated by high-sensitive P2X receptors (hsP2X receptors), observed between 0.01–0.3mM and the second mediated by low-sensitive P2X receptors (lsP2X receptors). The calculated EC50 values of these phases were 38 and 1759μM, respectively. 2′-3′-O-(4-benzoylbenzoyl)-ATP (BzATP) concentration-response curve was monophasic (0.01–1mM), and less potent (EC50 142μM) than ATP to activate hsP2X receptors. A strong inward rectification was noticed when hsP2X receptors were activated with ATP (0.1mM) and for BzATP-induced currents (0.1mM; IBzATP) but a significant lower rectification was noticed when lsP2X receptors were activated (5mM). Brilliant blue G (BBG) at a concentration of 0.3μM (known to inhibit only P2X7 receptors) reduced IATP when lsP2X receptors contributed to it but neither affect hsP2X receptors nor IBzATP. However, hsP2X receptors and IBzATP were both inhibited by concentrations ≥1μM of this antagonist. BzATP inhibited hsP2X receptors and therefore, it behaves as partial agonist on these receptors. Using the single-cell RT-PCR technique P2X7 mRNA was detectable in 7 out of 13 myenteric neurons exhibiting P2X2 mRNA. Altogether, our results show that low-sensitive P2X receptors are likely P2X7, whereas, the high-sensitive P2X channels are probably constituted, at least in part, by P2X2 subunits. [Copyright &y& Elsevier]

Abstract: Patients with Parkinson''s disease develop motor disturbances often accompanied by peripheral autonomic dysfunctions, including gastrointestinal disorders, such as dysphagia, gastric stasis and constipation. While the mechanisms subserving enteric autonomic dysfunctions are not clearly understood, they may involve the enteric dopaminergic and/or nitrergic systems. In the present study, we demonstrate that rats with unilateral 6-hydroxydopamine lesion of nigrostriatal dopaminergic neurons develop a marked inhibition of propulsive activity compared to sham-operated controls, as indicated by a 60% reduction of daily fecal output at the 4th week of observation. Immunohistochemical data revealed that 6-hydroxydopamine treatment did not affect the total number of HuC/D-positive myenteric neurons in both the proximal and distal segments of ileum and colon. Conversely, in the distal ileum and proximal colon the number of nitrergic neurons was significantly reduced. These results suggest that a disturbed distal gut transit, reminiscent of constipation in the clinical setting, may occur as a consequence of a reduced propulsive motility, likely due to an impairment of a nitric oxide-mediated descending inhibition during peristalsis. [Copyright &y& Elsevier]

Abstract: SCG10 (Superior Cervical Ganglia 10, STMN2) is a member of the stathmin family of proteins. Stathmins regulate microtubule dynamics by inhibiting polymerization and promoting their depolymerization. SCG10 is believed to be a neuronal-specific stathmin that is enriched in the growth cones of developing neurons and plays a role in regulating neurite outgrowth. In all species examined so far, SCG10 is expressed in both the CNS and PNS. We have cloned two zebrafish SCG10 homologues and have determined the temporal and spatial expression pattern of both of these genes by RT-PCR and in situ hybridization. RT-PCR shows that both transcripts are expressed maternally and zygotically through at least 5 days. In situ hybridization analysis reveals that both SCG10 orthologues have dynamic, spatial expression patterns that are nearly identical to each other. Initially, these orthologues are expressed in discrete areas of the forebrain, midbrain, and hindbrain, as well as in the anterior and posterior lateral line ganglia and transiently in the spinal cord Rohon-Beard neurons. From 48hpf onwards, the level of expression of both genes increases and becomes mainly restricted to the anterior CNS (the forebrain region, retina, optic tectum, and hindbrain), and to the cranial ganglia. From 72 to 96hpf, SCG10 genes are also expressed in the developing neurons in the gut and in the surrounding intestinal mesenchyme. Our results provide a starting point for future studies that will investigate the in vivo function of SCG10 orthologues in zebrafish neural development. [Copyright &y& Elsevier]

Abstract: Mast cell–nerve interactions play a key role in intestinal inflammation and irritable bowel disease. Loss of enteric neurons has been reported in inflammatory conditions but the contribution of mast cells in this event is unknown. To study neuronal survival and plasticity of myenteric neurons in contact with mast cells a co-culture system using myenteric neurons from rat small intestine and peritoneal mast cells was set up. Dissociated myenteric neurons were cultured for 4 days before addition of mast cells isolated by peritoneal lavage. Neuronal survival and expression of vasoactive intestinal peptide (VIP) and nitric oxide synthase (NOS) were studied by immunocytochemistry and neuronal cell counting. Myenteric neurons cultured without mast cells were used to study the rate of neuronal survival after the addition of various mast cell mediators, proteinase-activated receptor2 (PAR2) agonist, VIP or corticosteroid. A striking mast cell-induced neuronal cell death was found after co-culturing. It was counteracted by the addition of mast cell stabiliser doxantrazole, protease inhibitors, PAR2 antagonist FSLLRY-amide, corticosteroid or VIP. In myenteric neurons cultured without mast cells the PAR2 agonist SLIGRL-amide, prostaglandin D2 and interleukin (IL) 6 reduced neuronal survival while histamine, serotonin, heparin, IL1β and tumour necrosis factor α had no effect; corticosteroid and VIP enhanced neuronal survival. The relative numbers of VIP-, but not NOS-expressing myenteric neurons increased after co-culturing. Mast cell-induced neuronal cell death is suggested to be mediated via PAR2 activation, IL6 and prostaglandin D2. Corticosteroid and VIP are neuroprotective and able to prevent cell death of myenteric neurons in co-culture. [Copyright &y& Elsevier]

Abstract: Cannabinoid-1 (CB1) and CB2 receptors are present on neurons of the enteric nervous system. Our aim was to study whether cannabinoid receptor activation is involved in the regulation of VIP release and NO synthesis in isolated fractions of nerve terminals from rat ileum. VIP was measured by RIA and NO synthesis was analyzed using a l-[3H]arginine assay. Anandamide stimulated VIP release (basal: 245.9±12.4pg/mg, 10−6 M: 307.6±11.7pg/mg, [n =6, P <0.05], 10−7 M: 367.0±26.1pg/mg, [n =6, P <0.01]). The cannabinoid receptor agonist WIN 55,212-2 had similar effects (basal: 250.5±37.4pg/mg, 10−6 M: 320.9±34.7pg/mg; [n =4, P <0.05]). The stimulatory effect of anandamide was blocked by the selective CB2 receptor antagonist, SR144528 (10−7 M) (anandamide 10−6 M: 307.6±11.7pg/mg; +SR144528: 249.0±26.3pg/mg, [n =6, P <0.05]), whereas the selective CB1 receptor antagonist SR141716 A had no effect. NO synthesis was stimulated by anandamide ([fmol/mg/min] basal: 0.08±0.01, 10−6 M: 0.16±0.03; 10−7 M: 0.13±0.02, n =4, P <0.05) and WIN 55,212-2 ([fmol/mg/min] basal: 0.05±0.01, 10−6 M: 0.1±0.02, n =4, P <0.05). The anandamide reuptake inhibitor, AM 404 increased basal NOS activity ([fmol/mg/min] control: 0.1±0.04, 10−6 M: 0.28±0.08, n =7, P <0.05). The stimulatory effect of anandamide on NO synthase was not antagonized by antagonists at the CB1, CB2 or TRPV1 receptor, respectively. In conclusion, in enteric nerves anandamide stimulates VIP release by activation of a CB2 receptor specific pathway, while the stimulation of NO production suggests the existence of an additional type of cannabinoid receptor in the enteric nervous system. [Copyright &y& Elsevier]

Abstract: The classification, morphology and function of enteric neurons have been extensively studied in the small and large intestine. However, little is known about enteric neurons that directly project to the CNS. Previous studies have identified these unique neurons in the rectum, rectospinal neurons, but little was done to characterize them. Therefore, the aim of this study was to identify and characterize enteric neurons in the rat colon that directly project to the CNS by using retrograde neuronal tracing and immunohistochemistry. By applying the retrograde tracers 1,1′-dioctadecyl-3,3,3′,3′-tetramethyl-indocarbocyanine perchlorate (DiI) and Fluorogold (FG) to the L6/S1 segments of the spinal cord, we identified these neurons in both the myenteric and submucosal plexuses of the colon. These neurons were immunoreactive for neurofilament (NF) a marker for Aδ-fibers and isolectin-B4 (IB4) a marker for C-fibers. These neurons expressed the enzyme neuronal nitric oxide synthase (nNOS) as well as peptides associated with sensory neurons such as substance P (SP) and vasoactive intestinal polypeptide (VIP) but did not express calcitonin gene-related peptide (CGRP). The N-methyl-d-aspartate (NMDA) receptor subunits NR1 and NR2D and proteinase-activated receptor-2 (PAR2) were also found in these neurons. However they did not express the transient receptor potential receptor V1 (TRPV1) or neurokinin 1 receptor (NK1). The expression of the peptides and receptors suggests that there are at least two separate populations of neurons projecting from the colon to the CNS. The data suggest that these colospinal afferent neurons (CANs) might be involved in nociception. Whether sensory information from CANs is perceived by the animal or is part of the parasympathetic reflex is currently not known. [Copyright &y& Elsevier]

Abstract: To investigate whether myelomeningocele (MMC) is associated with a global neuromuscular maldevelopment of the lower gastrointestinal (GI) tract and anorectum, the distribution and staining intensity of non-neuronal (α-smooth-muscle-actin), neural crest cell (NCC, [Hoxb5]), and neuronal markers (PGP-9.5, synaptophysin, neurotubulin-β-III) within the distal colon, rectum, and anal sphincters were analyzed by immunohistochemistry and Western blot in rat fetuses with retinoic acid (RA) induced MMC. At term (E22), no gross-morphological differences of the anorectal unit of OIL (n =21) MMC (n =31), and RA-exposed-non MMC (RA, n =19) fetuses were found. Smooth muscle cells were evenly distributed within the muscle layers of the rectum and the internal anal sphincter in OIL, MMC, and RA fetuses. Density and staining intensity of NCC and mature enteric neurons within the myenteric plexus of the distal colon and rectum and innervation pattern within anal sphincters in MMC fetuses were analogous to RA and OIL controls. Normal smooth muscle and myenteric plexus development of the rectum and normal innervation of the anal sphincters and pelvic floor suggests that MMC is not associated with a global neuromuscular maldevelopment of lower GI structures in this short-gestational model. [Copyright &y& Elsevier]

Summary: Slow-transit constipation is usually considered a colonic motor disorder. However, there is some evidence that abnormalities may be present in locations other than the colon. In particular, several studies have reported abnormal motor activity of the small bowel in these patients. We evaluated the neuropathological aspects of the terminal ileum in patients with slow-transit constipation to see whether abnormalities are present that may explain an abnormal motility of the small intestine. Specimens of the terminal ileum were obtained from 16 female patients (age range, 42-76 years) with slow-transit constipation undergoing surgery for intractable symptoms. Fifteen age- and sex-matched controls were used for comparison. Histologic and immunohistochemical evaluation of the myenteric plexus and the smooth muscle of the proximal ileal resection margin was carried out by means of hematoxylin and eosin, trichrome and periodic acid–Schiff stain, neuron-specific enolase, S-100, CD117, CD34, anti–α-actin, desmin, and vimentin antibodies. The patient group displayed a significantly reduced number of glial cells, compared with controls, in both the submucosal and the myenteric plexus. Only 1 of the 3 populations of interstitial cells of Cajal (that associated with the deep muscular plexus) was decreased in patients. No differences were found between patients and controls concerning ganglia neurons, fibroblast-like cells, enteric neurons, apoptotic phenomena, and smooth muscle. Patients with slow-transit constipation display neuropathological abnormalities of the terminal ileum to a lesser extent than those we previously found in the colon, which might explain the abnormal motor aspects sometimes found in these patients. [Copyright &y& Elsevier]

Abstract: The distribution of the neurokinin type 1 receptor (NK1r) in human intestine, mapped in a few immunohistochemical investigations in the antrum and the duodenum, is comparable to that widely studied in rodents. Importantly, despite pharmacological evidence of their presence in mammalian intestinal muscle, their immunohistochemical visualization in smooth muscle cells remains to be determined in human digestive tract. In the present work, we studied the distribution of NK1r in the human colon, with a particular view to visualize their expression in muscle cells. With this aim, part of colonic segments were incubated with nicardipine and TTX in order to induce accumulation of the NK1r on cell membrane. NK1r were visualized by using immunohistochemistry combined with fluorescence and confocal microscopy. Without incubation, NK1r-IR was clearly observed on the membrane and the cytoplasm of myenteric and submucous neurons and interstitial cells of Cajal, but could not be clearly determined in the longitudinal and circular muscle. NK1r-IR-expressing neurons and interstitial cells were closely surrounded by substance P (SP) immunoreactive nerves. Incubation of colonic segments with nicardipine and TTX at 4 °C for 1 h with SP allowed to reveal a strong NK1r-IR at the surface of muscle cells. Incubation with SP (10−6 M) at 37 °C for 1 min induced a relocation of NK1r-IR into the cytoplasm of muscle. This is interpreted as an internalization of NK1r induced by the binding of SP on muscular NK1r. The present data contribute to emphasize the role of NK1r in tachykinin-mediated neuronal processes regulating intestinal motility. [Copyright &y& Elsevier]

Transient receptor potential channel vanilloid subfamily 2 (TRPV2) was shown to receive noxious thermal stimuli (>52 °C), and to be expressed in fine myelinated afferent neurons. The mRNA and the immunoreactivity have also been detected in several peripheral tissues. We examined the expression of TRPV2 in the rat intestine. An analysis by transcriptase–polymerase chain reaction (RT–PCR) demonstrated TRPV2 gene expression in the intestine. Many TRPV2-positive neurons were observed in the myenteric plexus by immunohistochemistry. Some of these neurons were positive for calbindin D-28K (CaBP), which is present in intrinsic afferent neurons. TRPV2 immunoreactivity was also observed in nodose ganglion neurons (vagal afferents). These findings suggest that TRPV2 is expressed not only in sensory ganglion neurons, but also in enteric neurons, including primary afferent neurons. [Copyright &y& Elsevier]

Neuronal plasticity in the enteric nervous system (ENS) is probably a key step in intestinal adaptation during growth, maturation and ageing as well as in several pathophysiological situations. Studies on cultured myenteric neurons have revealed an increased vasoactive intestinal peptide (VIP) expression in neuronal nitric oxide synthase (NOS)-expressing neurons. In addition, both VIP and nitric oxide (NO) promote survival of cultured myenteric neurons.The aim of the present study was to investigate possible changes in the expression of VIP and NOS in cultured submucous neurons from adult rat large intestine. Submucous neurons were cultured as explants or as dissociated neurons for 3 and 8 days. Immunocytochemistry was used to determine the proportions of neurons containing VIP or NOS in preparations of uncultured controls (reflects the conditions in vivo) and in cultured explants of submucosa and dissociated submucous neurons. In situ hybridization was used to determine changes in the expressions of NOS and VIP mRNA.The relative number of NOS-expressing neurons increased significantly during culturing. The percentage of all neurons expressing NOS was 22% in controls, while approximately 50% of the cultured submucous neurons expressed NOS. VIP-expressing neurons constituted approximately 80% of all submucous neurons in controls as well as in cultured explants or dissociated neurons. Studies on coexistence revealed that the VIP-containing neurons were the ones that started to express NOS during culture.The induced expression of NOS in cultured adult submucous neurons indicates that nitric oxide, possibly in cooperation with VIP, is important for neuronal adaptation, maintenance and survival. [Copyright &y& Elsevier]

Nitric oxide synthase catalyzes the production of nitric oxide, a multifunctional signaling molecule that affects diverse aspects of animal physiology such as cell proliferation, differentiation, neurotransmission and apoptosis. Here, we report the cloning and expression pattern of the zebrafish nnos. This gene was mapped to zebrafish linkage group 5. The spatial and temporal expression pattern of nnos in embryonic zebrafish was analyzed by whole mount in situ hybridization. nnos is widely expressed in the embryonic nervous system. Expression of zebrafish nnos appeared at 16 hours post-fertilization in the hypothalamus and by 3 days post-fertilization was present in discrete locations in the central nervous system as well as the enteric nervous system. Some nnos-positive cells were mapped to specific locations in the central nervous system using tyrosine hydroxylase as a specific marker indicating that nnos transcripts were present in the olfactory bulb, anterior diencephalon, posterior hypothalamus and anterior hindbrain. [Copyright &y& Elsevier]

Summary Glucagon-like peptide-1 (GLP-1)-based therapies control glycemia in type 2 diabetic (T2D) patients. However, in some patients the treatment must be discontinued, defining a state of GLP-1 resistance. In animal models we identified a specific set of ileum bacteria impairing the GLP-1-activated gut-brain axis for the control of insulin secretion and gastric emptying. Using prediction algorithms, we identified bacterial pathways related to amino acid metabolism and transport system modules associated to GLP-1 resistance. The conventionalization of germ-free mice demonstrated their role in enteric neuron biology and the gut-brain-periphery axis. Altogether, insulin secretion and gastric emptying require functional GLP-1 receptor and neuronal nitric oxide synthase in the enteric nervous system within a eubiotic gut microbiota environment. Our data open a novel route to improve GLP-1-based therapies. [ABSTRACT FROM AUTHOR]