Characteristics of colonic migrating motor complexes in neuronal NOS (nNOS) knockout mice

This Document is Protected by copyright and was first published by Frontiers. All rights reserved. it is reproduced with permission. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journalis cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.It is well established that the intrinsic pacemaker mechanism that generates cyclical colonic migrating motor complexes (CMMCs) does not require endogenous nitric oxide (NO). However, pharmacological blockade of endogenous NO production potently increases the frequency of CMMCs, suggesting that endogenous NO acts normally to inhibit the CMMC pacemaker mechanism. In this study, we investigated whether mice with a life long genetic deletion of the neuronal nitric oxide synthase (nNOS) gene would show similar CMMC characteristics as wild type mice that have endogenous NO production acutely inhibited. Intracellular electrophysiological and mechanical recordings were made from circular muscle cells of isolated whole mouse colon in wild type and nNOS knockout (KO) mice at 35°C. In wild type mice, the NOS inhibitor, L-NA (100 μM) caused a significant increase in CMMC frequency and a significant depolarization of the CM layer. However, unexpectedly, the frequency of CMMCs in nNOS KO mice was not significantly different from control mice. Also, the resting membrane potential of CM cells in nNOS KO mice was not depolarized compared to controls; and the amplitude of the slow depolarization phase underlying MCs was of similar amplitude between KO and wild type offspring. These findings show that in nNOS KO mice, the major characteristics of CMMCs and their electrical correlates are, at least in adult mice, indistinguishable from wild type control offspring. One possibility why the major characteristics of CMMCs were no different between both types of mice is that nNOS KO mice may compensate for their life long deletion of the nNOS gene, and their permanent loss of neuronal NO production. In this regard, we suggest caution should be exercised when assuming that data obtained from adult nNOS KO mice can be directly extrapolated to wild type mice, that have been acutely exposed to an inhibitor of NOS

Human Perambulation as a Self Calibrating Biometric

This paper introduces a novel method of single camera gait reconstruction which is independent of the walking direction and of the camera parameters. Recognizing people by gait has unique advantages with respect to other biometric techniques: the identification of the walking subject is completely unobtrusive and the identification can be achieved at distance. Recently much research has been conducted into the recognition of frontoparallel gait. The proposed method relies on the very nature of walking to achieve the independence from walking direction. Three major assumptions have been done: human gait is cyclic; the distances between the bone joints are invariant during the execution of the movement; and the articulated leg motion is approximately planar, since almost all of the perceived motion is contained within a single limb swing plane. The method has been tested on several subjects walking freely along six different directions in a small enclosed area. The results show that recognition can be achieved without calibration and without dependence on view direction. The obtained results are particularly encouraging for future system development and for its application in real surveillance scenarios

A novel anterograde neuronal tracing technique to selectively label spinal afferent nerve endings that encode noxious and innocuous stimuli in visceral organs.

This article is under embargo for 12 months from the date of publication in accordance with publisher copyright policy. This is the accepted version of the following article: Kyloh, M. and Spencer, N. J. (2014), A novel anterograde neuronal tracing technique to selectively label spinal afferent nerve endings that encode noxious and innocuous stimuli in visceral organs. Neurogastroenterology & Motility, 26: 440–444.], which has been published in final form at [http://dx.doi.org/10.1111/nmo.12266]. In addition, authors may also transmit, print and share copies with colleagues, provided that there is no systematic distribution of the submitted version, e.g. posting on a listserve, network or automated delivery

What is the role of endogenous gut serotonin in the control of gastrointestinal motility?

© 2018 Elsevier Ltd. . This manuscript version is made available under the CC-BY-NC-ND 4.0 license:http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 12 month embargo from date of publication (June 2018) in accordance with the publisher’s archiving policyIn recent years, there have been dramatic changes in our understanding of the role of endogenous 5-Hydroxytryptamine (5-HT or serotonin) in the control of gastrointestinal (GI) motility. Whilst it is well accepted that there are numerous types of 5-HT receptors expressed on enteric neurons and that exogenous 5-HT potently stimulates GI-motility, understanding the role of endogenous 5-HT in GI-motility has been substantially more difficult to resolve. Recent studies found 5-HT3 and 5-HT4 antagonists have the same effects on peristalsis in colon preparations depleted of endogenous 5-HT. Then, recent work revealed that in mice with genetic mutations to prevent the synthesis of endogenous 5-HT from enterochromaffin EC) cells did not block major neurogenic motor patterns in the gut wall and did not reduce GI-transit in conscious animals, raising doubts about early hypotheses that endogenous 5-HT was critical for neurogenic GI-motility patterns. Indeed, functional evidence now suggests that 5-HT3 and 5-HT4 receptors on enteric nerves display constitutive activity. In summary, recent findings demonstrate that endogenous 5-HT released from the mucosa or enteric neurons is not required for the generation of major neurogenic motor patterns, at least in the large intestine, but that it likely acts as a modulator of contractile frequency. This review will discuss how and why our understanding of endogenous 5-HT has dramatically changed in the past few years

The presence of 5-HT in myenteric varicosities is not due to uptake of 5-HT released from the mucosa during dissection: use of a novel method for quantifying 5-HT immunoreactivity in myenteric ganglia

Author version made available according to Publisher copyright policy. This is the accepted version of the following article: 
Keating, D. J., Peiris, H., Kyloh, M., Brookes, S. J. H. and Spencer, N. J. (2013), The presence of 5-HT in myenteric varicosities is not due to uptake of 5-HT released from the mucosa during dissection: use of a novel method for quantifying 5-HT immunoreactivity in myenteric ganglia. Neurogastroenterology & Motility, 25: 849–853, 

which has been published in final form at 
http://dx.doi.org/10.1111/nmo.12189. 

In addition, authors may also transmit, print and share copies with colleagues, provided that there is no systematic distribution of the submitted version, e.g. posting on a listserve, network or automated delivery

Viscerofugal neurons recorded from guinea-pig colonic nerves after organ culture

This is the accepted version of the following article: [Hibberd, T. J., Zagorodnyuk, V. P., Spencer, N. J. and Brookes, S. J. H. (2012), Viscerofugal neurons recorded from guinea-pig colonic nerves after organ culture. Neurogastroenterology & Motility, 24: 1041–e548], which has been published in final form at [http://dx.doi.org/10.1111/j.1365-2982.2012.01979.x]. In addition, authors may also transmit, print and share copies with colleagues, provided that there is no systematic distribution of the submitted version, e.g. posting on a listserve, network or automated delivery.Background Enteric viscerofugal neurons provide cholinergic synaptic inputs to prevertebral sympathetic neurons, forming reflex circuits that control motility and secretion. Extracellular recordings of identified viscerofugal neurons have not been reported. Methods Preparations of guinea pig distal colon were maintained in organotypic culture for 4-6 days (n = 12), before biotinamide tracing, immunohistochemistry, or extracellular electrophysiological recordings from colonic nerves. Key Results After 4-6 days in organ culture, calcitonin gene-related peptide and tyrosine hydroxylase immunoreactivity in enteric ganglia was depleted, and capsaicin-induced firing (0.4 micromol L-1) was not detected, indicating that extrinsic sympathetic and sensory axons degenerate in organ culture. Neuroanatomical tracing of colonic nerves revealed that viscerofugal neurons persist and increase as a proportion of surviving axons. Extracellular recordings of colonic nerves revealed ongoing action potentials. Interestingly, synchronous bursts of action potentials were seen in 10 of 12 preparations; bursts were abolished by hexamethonium, which also reduced firing rate (400 micromol L-1, P < 0.01, n = 7). DMPP (1,1-dimethyl-4-phenylpiperazinium; 10-4 mol L-1) evoked prolonged action potential discharge. Increased firing preceded both spontaneous and stretch-evoked contractions (X2 = 11.8, df = 1, P < 0.001). Firing was also modestly increased during distensions that did not evoke reflex contractions. All single units (11/11) responded to von Frey hairs (100-300 mg) in hexamethonium or Ca2+-free solution. Conclusions & Inferences Action potentials recorded from colonic nerves in organ cultured preparations originated from viscerofugal neurons. They receive nicotinic input, which coordinates ongoing burst firing. Large bursts preceded spontaneous and reflex-evoked contractions, suggesting their synaptic inputs may arise from enteric circuitry that also drives motility. Viscerofugal neurons were directly mechanosensitive to focal compression by von Frey hairs.Australian National Health & Medical Research Counci

Characterization of primary afferent spinal innervation of mouse uterus

This Document is Protected by copyright and was first published by Frontiers. All rights reserved. it is reproduced with permission. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.The primary afferent innervation of the uterus is incompletely understood. The aim of this study was to identify the location and characteristics of primary afferent neurons that innervate the uterine horn of mice and correlate the different morphological types of putative primary afferent nerve endings, immunoreactive to the sensory marker, calcitonin gene related peptide (CGRP). Using retrograde tracing, injection of 5–10 μL of 1,1′-didodecyl-3,3,3,3′-tetramethylindocarbocyanine perchlorate (DiI) into discrete single sites in each uterine horn revealed a biomodal distribution of sensory neurons in dorsal root ganglia (DRG) with peak labeling occurring between T13-L3 and a second smaller peak between L6-S1. The mean cross sectional area of labeled cells was 463 μm2 ± s.e.m. A significantly greater proportion of labeled neurons consisted of small cell bodies (<300 μm2) in the sacral spinal cord (S2) compared with peak labeling at the lumbar (L2) region. In both sections and whole mount preparations, immunohistochemical staining for CGRP revealed substantial innervation of the uterus by CGRP-positive nerve fibers located primarily at the border between the circular and longitudinal muscle layers (N = 4). The nerve endings were classified into three distinct types: “single,” “branching,” or “complex,” that often aligned preferentially in either the circular or longitudinal axis of the smooth muscles. Complex endings were often associated with mesenteric vessels. We have identified that the cell bodies of primary afferent neurons innervating the mouse uterus lie primarily in DRG at L2 and S1 spinal levels. Also, the greatest density of CGRP immunoreactivity lies within the myometrium, with at least three different morphological types of nerve endings identified. These findings will facilitate further investigations into the mechanisms underlying sensory transduction in mouse uterus

Regional differences in nutrient-induced secretion of gut serotonin

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.Enterochromaffin (EC) cells located in the gastrointestinal (GI) tract provide the vast majority of serotonin (5‐HT) in the body and constitute half of all enteroendocrine cells. EC cells respond to an array of stimuli, including various ingested nutrients. Ensuing 5‐HT release from these cells plays a diverse role in regulating gut motility as well as other important responses to nutrient ingestion such as glucose absorption and fluid balance. Recent data also highlight the role of peripheral 5‐HT in various pathways related to metabolic control. Details related to the manner by which EC cells respond to ingested nutrients are scarce and as that the nutrient environment changes along the length of the gut, it is unknown whether the response of EC cells to nutrients is dependent on their GI location. The aim of the present study was to identify whether regional differences in nutrient sensing capability exist in mouse EC cells. We isolated mouse EC cells from duodenum and colon to demonstrate differential responses to sugars depending on location. Measurements of intracellular calcium concentration and 5‐HT secretion demonstrated that colonic EC cells are more sensitive to glucose, while duodenal EC cells are more sensitive to fructose and sucrose. Short‐chain fatty acids (SCFAs), which are predominantly synthesized by intestinal bacteria, have been previously associated with an increase in circulating 5‐HT; however, we find that SCFAs do not acutely stimulate EC cell 5‐HT release. Thus, we highlight that EC cell physiology is dictated by regional location within the GI tract, and identify differences in the regional responsiveness of EC cells to dietary sugars

Ascending excitatory neural pathways modulate slow phasic myogenic contractions in the isolated human colon

This is the accepted version of the following article: [Carbone, S. E., Dinning, P. G., Costa, M., Spencer, N. J., Brookes, S. J. H. and Wattchow, D. A. (2013), Ascending excitatory neural pathways modulate slow phasic myogenic contractions in the isolated human colon. Neurogastroenterology & Motility, 25: 670–e510.], which has been published in final form at [http://dx.doi.org/10.1111/nmo.12129]. In addition, authors may also transmit, print and share copies with colleagues, provided that there is no systematic distribution of the submitted version, e.g. posting on a listserve, network or automated delivery.Background In animal models, enteric reflex pathways have potent effects on motor activity; their roles have been much less extensively studied in human gut. The aim of this study was to determine if ascending excitatory interneuronal pathways can modulate spontaneous phasic contractions in isolated preparations of human colonic circular muscle. Methods Human colonic preparations were cut into T shapes, with vertical bar of the ‘T’ pharmacologically isolated. Electrical stimulation and the nicotinic agonist, 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP), were applied to the isolated region and circular muscle contractile activity was measured from the cross-bar of the T, more than 10 mm orally from the region of stimulation. Key Results The predominant form of spontaneous muscle activity consisted of tetrodotoxin-resistant, large amplitude, slow phasic contractions (SPCs), occurring at average intervals of 124 ± 68 s. Addition of a high concentration of hexamethonium (1 mmol L-1) to the superfusing solution significantly increased the interval between SPCs to 278.1 ± 138.3 s (P < 0.005). Focal electrical stimulation more than 10 mm aboral to the muscle recording site advanced the onset of the next SPC, and this effect persisted in hexamethonium. However, the effect of electrical stimulation was blocked by tetrodotoxin (TTX, 1 µmol L-1). Application of the nicotinic agonist DMPP (1 mmol L-1) to the aboral chamber often stimulated a premature SPC (n = 4). Conclusions & Inferences The major form of spontaneous contractility in preparations of human colonic circular muscle is SPCs, which are myogenic in origin. Activation of ascending excitatory neural pathways, which involve nicotinic receptors, can modulate the timing of SPCs and thus influence human colonic motility.Australian National Health & Medical Research Counci

Hydrogen peroxide preferentially activates capsaicin-sensitive high threshold afferents via TRPA1 channels in the guinea pig bladder

Embargoed until 6 December 2017 as per publisher's policy