Article

Phenotypic changes of morphologically identified guinea-pig myenteric neurons following intestinal inflammation.

Department of Anatomy and Cell Bioology, University of Melbourne, Parkville, Victoria 3010, Australia.
The Journal of Physiology (Impact Factor: 4.38). 10/2007; 583(Pt 2):593-609. DOI: 10.1113/jphysiol.2007.135947
Source: PubMed

ABSTRACT We investigated the responses of morphologically identified myenteric neurons of the guinea-pig ileum to inflammation that was induced by the intraluminal injection of trinitrobenzene sulphonate, 6 or 7 days previously. Electrophysiological properties were examined with intracellular microelectrodes using in vitro preparations from the inflamed or control ileum. The neurons were injected with marker dyes during recording and later they were recovered for morphological examination. A proportion of neurons with Dogiel type I morphology, 45% (32/71), from the inflamed ileum had a changed phenotype. These neurons exhibited an action potential with a tetrodotoxin-resistant component, and a prolonged after-hyperpolarizing potential followed the action potential. Of the other 39 Dogiel type I neurons, no changes were observed in 36 and 3 had increased excitability. The afterhyperpolarizing potential (AHP) in Dogiel type I neurons was blocked by the intermediate conductance, Ca(2+)-dependent K(+) channel blocker TRAM-34. Neurons which showed these phenotypic changes had anally directed axonal projections. Neither a tetrodotoxin-resistant action potential nor an AHP was seen in Dogiel type I neurons from control preparations. Dogiel type II neurons retained their distinguishing AH phenotype, including an inflection on the falling phase of the action potential, an AHP and, in over 90% of neurons, an absence of fast excitatory transmission. However, they became hyperexcitable and exhibited anodal break action potentials, which, unlike control Dogiel type II neurons, were not all blocked by the h current (I(h)) antagonist Cs(+). It is concluded that inflammation selectively affects different classes of myenteric neurons and causes specific changes in their electrophysiological properties.

0 Bookmarks
 · 
68 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background  Commensal bacteria such as probiotics that are neuroactive acutely affect the amplitudes of intestinal migrating motor complexes (MMCs). What is lacking for an improved understanding of these motility effects are region specific measurements of velocity and frequency. We have combined intraluminal pressure recordings with spatiotemporal diameter maps to analyze more completely effects of different strains of beneficial bacteria on motility. Methods  Intraluminal peak pressure (PPr) was measured and video recordings made of mouse ex vivo jejunum and colon segments before and after intraluminal applications of Lactobacillus rhamnosus (JB-1) or Lactobacillus reuteri (DSM 17938). Migrating motor complex frequency and velocity were calculated. Key Results  JB-1 decreased jejunal frequencies by 56% and 34% in colon. Jejunal velocities increased 171%, but decreased 31% in colon. Jejunal PPr decreased by 55% and in colon by 21%. DSM 17938 increased jejunal frequencies 63% and in colon 75%; jejunal velocity decreased 57%, but increased in colon 146%; jejunal PPr was reduced 26% and 12% in colon. TRAM-34 decreased frequency by 71% and increased velocity 200% for jejunum, but increased frequency 46% and velocity 50% for colon; PPr was decreased 59% for jejunum and 39% for colon. Conclusions & Inferences  The results show that probiotics and other beneficial bacteria have strain and region-specific actions on gut motility that can be successfully discriminated using spatiotemporal mapping of diameter changes. Effects are not necessarily the same in colon and jejunum. Further research is needed on the detailed effects of the strains on enteric neuron currents for each gut region.
    Neurogastroenterology and Motility 01/2013; · 2.94 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Inflammation of the colon changes motor function of more proximal regions of the gastrointestinal tract. Colitis alters the neurophysiology of enteric neurons within the region of inflammation, which may contribute to altered colonic motor and secretory function. This study seeks to test the hypothesis that colitis alters the neurophysiology of myenteric neurons in the non-inflamed ileum, and that altered neurophysiology coincides with altered small bowel motor function. Trinitrobenzene sulfonic acid (TNBS)-induced colitis was associated with hyperexcitability of AH neurons in the ileum myenteric plexus, demonstrated by depolarized neurons and increased numbers of action potentials, but without changes in the action potential duration or afterhyperpolarization typical of plasticity in these cells. There were no changes in synaptic transmission of either AH neurons or S neurons observed in the current study. The onset of AH neuron hyperexcitability occurred 24h following administration of TNBS, and persisted to eight weeks, a time point following the resolution of colitis. Small bowel transit was reduced as early as 12h after TNBS and resolved by 48h after TNBS. While AH neurons play a central role in coordinating motor function of the ileum, changes in excitability of these neurons did not coincide with changes in small bowel transit.
    Neuroscience Letters 04/2013; · 2.03 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Oxaliplatin, an anti-cancer chemotherapeutic agent used for the treatment of colorectal cancer, commonly causes gastrointestinal side-effects such as constipation, diarrhoea, nausea, and vomiting. Damage to enteric neurons may underlie some of these gastrointestinal side-effects, as the enteric nervous system (ENS) controls functions of the bowel. In this study, neuronal loss and changes to the structure and immunoreactivity of myenteric neuronal nitric oxide synthase (nNOS) neurons were examined in colonic segments from mice following exposure to oxaliplatin ex vivo and following repeated intraperitoneal injections of oxaliplatin over 3 weeks in vivo, using immunohistochemistry and confocal microscopy. Significant morphological alterations and increases in the proportion of NOS-immunoreactive (IR) neurons were associated with both short-term oxaliplatin exposure and long-term oxaliplatin administration, confirming that oxaliplatin causes changes to the myenteric neurons. Long-term oxaliplatin administration induced substantial neuronal loss that was correlated with a reduction in both the frequency and propagation speed of colonic migrating motor complexes (CMMCs) in vitro. Similar changes probably produce some symptoms experienced by patients undergoing oxaliplatin treatment.
    Frontiers in Neuroscience 01/2013; 7:30.

Full-text

View
0 Downloads
Available from