1
|
Hibberd TJ, Ramsay S, Spencer-Merris P, Dinning PG, Zagorodnyuk VP, Spencer NJ. Circadian rhythms in colonic function. Front Physiol 2023; 14:1239278. [PMID: 37711458 PMCID: PMC10498548 DOI: 10.3389/fphys.2023.1239278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 08/17/2023] [Indexed: 09/16/2023] Open
Abstract
A rhythmic expression of clock genes occurs within the cells of multiple organs and tissues throughout the body, termed "peripheral clocks." Peripheral clocks are subject to entrainment by a multitude of factors, many of which are directly or indirectly controlled by the light-entrainable clock located in the suprachiasmatic nucleus of the hypothalamus. Peripheral clocks occur in the gastrointestinal tract, notably the epithelia whose functions include regulation of absorption, permeability, and secretion of hormones; and in the myenteric plexus, which is the intrinsic neural network principally responsible for the coordination of muscular activity in the gut. This review focuses on the physiological circadian variation of major colonic functions and their entraining mechanisms, including colonic motility, absorption, hormone secretion, permeability, and pain signalling. Pathophysiological states such as irritable bowel syndrome and ulcerative colitis and their interactions with circadian rhythmicity are also described. Finally, the classic circadian hormone melatonin is discussed, which is expressed in the gut in greater quantities than the pineal gland, and whose exogenous use has been of therapeutic interest in treating colonic pathophysiological states, including those exacerbated by chronic circadian disruption.
Collapse
Affiliation(s)
- Timothy J. Hibberd
- College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Stewart Ramsay
- College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | | | - Phil G. Dinning
- College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
- Colorectal Surgical Unit, Division of Surgery, Flinders Medical Centre, Adelaide, SA, Australia
| | | | - Nick J. Spencer
- College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| |
Collapse
|
2
|
Kyloh MA, Hibberd TJ, Castro J, Harrington AM, Travis L, Dodds KN, Wiklendt L, Brierley SM, Zagorodnyuk VP, Spencer NJ. Disengaging spinal afferent nerve communication with the brain in live mice. Commun Biol 2022; 5:915. [PMID: 36104503 PMCID: PMC9475039 DOI: 10.1038/s42003-022-03876-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 08/23/2022] [Indexed: 11/24/2022] Open
Abstract
Our understanding of how abdominal organs (like the gut) communicate with the brain, via sensory nerves, has been limited by a lack of techniques to selectively activate or inhibit populations of spinal primary afferent neurons within dorsal root ganglia (DRG), of live animals. We report a survival surgery technique in mice, where select DRG are surgically removed (unilaterally or bilaterally), without interfering with other sensory or motor nerves. Using this approach, pain responses evoked by rectal distension were abolished by bilateral lumbosacral L5-S1 DRG removal, but not thoracolumbar T13-L1 DRG removal. However, animals lacking T13-L1 or L5-S1 DRG both showed reduced pain sensitivity to distal colonic distension. Removal of DRG led to selective loss of peripheral CGRP-expressing spinal afferent axons innervating visceral organs, arising from discrete spinal segments. This method thus allows spinal segment-specific determination of sensory pathway functions in conscious, free-to-move animals, without genetic modification. A surgical method in mice can selectively remove dorsal root ganglia (DRG) at specific spinal levels without interfering with other nerves, providing insight on thoracolumbar vs. lumbosacral DRG contributions to pain signalling and behaviour.
Collapse
|
3
|
Humenick A, Chen BN, Wattchow DA, Zagorodnyuk VP, Dinning PG, Spencer NJ, Costa M, Brookes SJH. Characterization of putative interneurons in the myenteric plexus of human colon. Neurogastroenterol Motil 2021; 33:e13964. [PMID: 32839997 PMCID: PMC7772282 DOI: 10.1111/nmo.13964] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 07/07/2020] [Accepted: 07/20/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND The enteric nervous system contains multiple classes of neurons, distinguishable by morphology, immunohistochemical markers, and projections; however, specific combinations differ between species. Here, types of enteric neurons in human colon were characterized immunohistochemically, using retrograde tracing combined with multiple labeling immunohistochemistry, focussing on non-motor neurons. METHODS The fluorescent carbocyanine tracer, DiI, was applied to the myenteric plexus in ex vivo preparations, filling neurons projecting within the plexus. Limits of projection lengths of motor neurons were established, allowing them to be excluded from the analysis. Long ascending and descending interneurons were then distinguished by labeling for discriminating immunohistochemical markers: calbindin, calretinin, enkephalin, 5-hydroxytryptamine, nitric oxide synthase, and substance P. These results were combined with a previous published study in which nitric oxide synthase and choline acetyltransferase immunoreactivities were established. KEY RESULTS Long ascending neurons (with projections longer than 8 mm, which excludes more than 95% motor neurons) formed four types, in descending order of abundance, defined by immunoreactivity for: (a) ChAT+/ENK+, (b) ChAT+/ENK+/SP+, (c) ChAT+/Calb+, and (d) ChAT+/ENK+/Calb+. Long descending neurons, up to 70 mm long also formed at least four types, distinguished by immunoreactivity for (a) NOS + cells (without ChAT), (b) ChAT+/NOS+, (c) ChAT+/Calret+, and (d) ChAT+/5HT + cells (with or without NOS). CONCLUSIONS AND INFERENCES Long interneurons, which do not innervate muscularis externa, are likely to coordinate neural activity over distances of many centimeters along the colon. Characterizing their neurochemical coding provides a basis for understanding their roles, investigating their connectivity, and building a comprehensive account of human colonic enteric neurons.
Collapse
Affiliation(s)
- Adam Humenick
- Human Physiology, Medical Bioscience, College of Medicine and Public Health, Flinders University, South Australia 5042
| | - Bao Nan Chen
- Human Physiology, Medical Bioscience, College of Medicine and Public Health, Flinders University, South Australia 5042
| | - David A Wattchow
- Department of Surgery, Flinders Medical Centre, Human, South Australia 5042
| | | | - Phil G Dinning
- Department of Surgery, Flinders Medical Centre, Human, South Australia 5042
| | - Nick J Spencer
- Human Physiology, Medical Bioscience, College of Medicine and Public Health, Flinders University, South Australia 5042
| | - Marcello Costa
- Human Physiology, Medical Bioscience, College of Medicine and Public Health, Flinders University, South Australia 5042
| | - Simon JH Brookes
- Human Physiology, Medical Bioscience, College of Medicine and Public Health, Flinders University, South Australia 5042
| |
Collapse
|
4
|
Sharma H, Kyloh M, Brookes SJH, Costa M, Spencer NJ, Zagorodnyuk VP. Morphological and neurochemical characterisation of anterogradely labelled spinal sensory and autonomic nerve endings in the mouse bladder. Auton Neurosci 2020; 227:102697. [PMID: 32645688 DOI: 10.1016/j.autneu.2020.102697] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 06/26/2020] [Accepted: 06/27/2020] [Indexed: 11/29/2022]
Abstract
The bladder is innervated by axons of sympathetic and parasympathetic efferent nerves, and by spinal afferent neurons. The objective was to characterise anatomically and immunohistochemically the terminal endings of sensory and autonomic motor nerve endings in wholemount preparations of the mouse bladder. We used both anterograde labelling of pelvic and hypogastric nerves ex vivo and anterograde labelling from lumbosacral dorsal root ganglia (DRG) in vivo in male and female mice. These were combined with immunohistochemistry for major markers of sensory, sympathetic and parasympathetic nerves. Selective labelling of spinal afferent endings following dextran biotin-labelling from DRGs in vivo showed no co-localisation of VAChT or TH in sensory terminals in the detrusor and suburothelial plexus. Biotinamide was applied ex vivo to nerve trunks arising in the pelvic ganglion and running towards the bladder. Among the filled axons, 38% of detrusor fibres and 47% of suburothelial axons were immunoreactive for calcitonin-gene related peptide (CGRP). Vesicular acetylcholine transporter (VAChT) immunoreactivity was present in 26% of both detrusor and suburothelial axons. For tyrosine hydroxylase (TH), the proportions were 15% and 17%, respectively. Three major morphological types of CGRP-immunoreactive nerve endings were distinguished in the bladder wall: simple, branching and complex. VAChT-immunoreactive parasympathetic axons had simple and branching endings; TH immunoreactive axons all had simple morphologies. Our findings revealed that different subtypes of sensory and autonomic nerve endings can be reliably identified by combining anterograde labelling ex vivo with specific immunohistochemical markers, although morphologically some of these types of endings were indistinguishable.
Collapse
Affiliation(s)
- Harman Sharma
- Discipline of Human Physiology, Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, Australia
| | - Melinda Kyloh
- Discipline of Human Physiology, Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, Australia
| | - Simon J H Brookes
- Discipline of Human Physiology, Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, Australia
| | - Marcello Costa
- Discipline of Human Physiology, Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, Australia
| | - Nick J Spencer
- Discipline of Human Physiology, Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, Australia.
| | - Vladimir P Zagorodnyuk
- Discipline of Human Physiology, Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, Australia.
| |
Collapse
|
5
|
Humenick A, Chen BN, Lauder CIW, Wattchow DA, Zagorodnyuk VP, Dinning PG, Spencer NJ, Costa M, Brookes SJH. Characterization of projections of longitudinal muscle motor neurons in human colon. Neurogastroenterol Motil 2019; 31:e13685. [PMID: 31355986 DOI: 10.1111/nmo.13685] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Revised: 07/07/2019] [Accepted: 07/08/2019] [Indexed: 12/08/2022]
Abstract
BACKGROUND The enteric nervous system contains inhibitory and excitatory motor neurons which modulate smooth muscle contractility. Cell bodies of longitudinal muscle motor neurons have not been identified in human intestine. METHODS We used retrograde tracing ex vivo with DiI, with multiple labeling immunohistochemistry, to characterize motor neurons innervating tenial and inter-tenial longitudinal muscle of human colon. KEY RESULTS The most abundant immunohistochemical markers in the tertiary plexus were vesicular acetylcholine transporter, nitric oxide synthase (NOS), and vasoactive intestinal polypeptide (VIP). Of retrogradely traced motor neurons innervating inter-tenial longitudinal muscle, 95% were located within 6mm oral or anal to the DiI application site. Excitatory motor neuron cell bodies, immunoreactive for choline acetyltransferase (ChAT), were clustered aborally, whereas NOS-immunoreactive cell bodies were distributed either side of the DiI application site. Motor neurons had small cell bodies, averaging 438 + 18µm2 in cross-sectional area, similar for ChAT- and NOS-immunoreactive subtypes. Motor neurons innervating the tenia had slightly longer axial projections, with 95% located within 9mm. ChAT-immunoreactive excitatory motor neurons to tenia were clustered aborally, whereas NOS-immunoreactive inhibitory motor neurons had both ascending and descending projections. VIP immunoreactivity was rarely present without NOS immunoreactivity in motor neurons. CONCLUSIONS AND INFERENCES Tenial and inter-tenial motor neurons innervating the longitudinal muscle have short projections. Inhibitory motor neurons have less polarized projections than cholinergic excitatory motor neurons. Longitudinal and circular muscle layers are innervated by distinct local populations of excitatory and inhibitory motor neurons. A population of human enteric neurons that contribute significantly to colonic motility has been characterized.
Collapse
Affiliation(s)
- Adam Humenick
- Human Physiology, Medical Bioscience, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Bao Nan Chen
- Human Physiology, Medical Bioscience, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Chris I W Lauder
- Department of Surgery, Flinders Medical Centre, Adelaide, SA, Australia
| | - David A Wattchow
- Department of Surgery, Flinders Medical Centre, Adelaide, SA, Australia
| | - Vladimir P Zagorodnyuk
- Human Physiology, Medical Bioscience, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Phil G Dinning
- Department of Surgery, Flinders Medical Centre, Adelaide, SA, Australia
| | - Nick J Spencer
- Human Physiology, Medical Bioscience, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Marcello Costa
- Human Physiology, Medical Bioscience, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Simon J H Brookes
- Human Physiology, Medical Bioscience, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| |
Collapse
|
6
|
Zagorodnyuk VP, Keightley LJ, Brookes SJH, Spencer NJ, Costa M, Nicholas SJ. Functional changes in low- and high-threshold afferents in obstruction-induced bladder overactivity. Am J Physiol Renal Physiol 2019; 316:F1103-F1113. [PMID: 30908933 DOI: 10.1152/ajprenal.00058.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Neural mechanisms of lower urinary tract symptoms in obstruction-induced bladder overactivity remain unclear. We made the first single unit recordings from different types of spinal afferents to determine the effects of bladder outlet obstruction in guinea pigs. A model of gradual bladder outlet obstruction in male guinea pigs was used to produce overactive bladder. Conscious voiding was assessed in metabolic cages, and micturition was recorded in anesthetized guinea pigs in vivo. Single unit extracellular recordings were made ex vivo from spinal afferent nerves in flat sheet preparations of the bladder. Guinea pigs with partially obstructed bladders showed a significant increase in conscious voiding frequency compared with sham-operated guinea pigs. Also, nonvoiding contractions increased significantly in both frequency and amplitude. Although spontaneous firing of low-threshold bladder afferents was increased, their stretch-induced firing was reduced. The proportion of capsaicin-sensitive low-threshold afferents increased in obstructed bladders. Interestingly, spontaneous and stretch-induced firing were both significantly increased in high-threshold afferents after obstruction. In summary, sensory signaling increased in the obstructed bladder during the filling phase. This is largely mediated by low-threshold stretch-sensitive afferents that are activated by increased local nonvoiding contractions. Increased spontaneous firing by high-threshold afferents also contributes. Our findings revealed a complex effect of bladder outlet obstruction on different types of bladder afferents that needs consideration for potential therapeutic targeting of lower urinary tract symptoms in obstruction-induced bladder overactivity.
Collapse
Affiliation(s)
- Vladimir P Zagorodnyuk
- Discipline of Human Physiology and Centre for Neuroscience, College of Medicine and Public Health, Flinders University of South Australia , Adelaide, South Australia
| | - Lauren J Keightley
- Discipline of Human Physiology and Centre for Neuroscience, College of Medicine and Public Health, Flinders University of South Australia , Adelaide, South Australia
| | - Simon J H Brookes
- Discipline of Human Physiology and Centre for Neuroscience, College of Medicine and Public Health, Flinders University of South Australia , Adelaide, South Australia
| | - Nick J Spencer
- Discipline of Human Physiology and Centre for Neuroscience, College of Medicine and Public Health, Flinders University of South Australia , Adelaide, South Australia
| | - Marcello Costa
- Discipline of Human Physiology and Centre for Neuroscience, College of Medicine and Public Health, Flinders University of South Australia , Adelaide, South Australia
| | - Sarah J Nicholas
- Discipline of Human Physiology and Centre for Neuroscience, College of Medicine and Public Health, Flinders University of South Australia , Adelaide, South Australia
| |
Collapse
|
7
|
Spencer NJ, Greenheigh S, Kyloh M, Hibberd TJ, Sharma H, Grundy L, Brierley SM, Harrington AM, Beckett EA, Brookes SJ, Zagorodnyuk VP. Identifying unique subtypes of spinal afferent nerve endings within the urinary bladder of mice. J Comp Neurol 2017; 526:707-720. [DOI: 10.1002/cne.24362] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 11/07/2017] [Accepted: 11/16/2017] [Indexed: 01/02/2023]
Affiliation(s)
- Nick J. Spencer
- College of Medicine and Public Health; Centre for Neuroscience, School of Medicine, Flinders University of South Australia; Adelaide South Australia Australia
| | - Sarah Greenheigh
- College of Medicine and Public Health; Centre for Neuroscience, School of Medicine, Flinders University of South Australia; Adelaide South Australia Australia
| | - Melinda Kyloh
- College of Medicine and Public Health; Centre for Neuroscience, School of Medicine, Flinders University of South Australia; Adelaide South Australia Australia
| | - Tim J. Hibberd
- College of Medicine and Public Health; Centre for Neuroscience, School of Medicine, Flinders University of South Australia; Adelaide South Australia Australia
| | - Harman Sharma
- College of Medicine and Public Health; Centre for Neuroscience, School of Medicine, Flinders University of South Australia; Adelaide South Australia Australia
| | - Luke Grundy
- College of Medicine and Public Health; Centre for Neuroscience, School of Medicine, Flinders University of South Australia; Adelaide South Australia Australia
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine; University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace; Adelaide South Australia Australia
| | - Stuart M. Brierley
- College of Medicine and Public Health; Centre for Neuroscience, School of Medicine, Flinders University of South Australia; Adelaide South Australia Australia
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine; University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace; Adelaide South Australia Australia
| | - Andrea M. Harrington
- College of Medicine and Public Health; Centre for Neuroscience, School of Medicine, Flinders University of South Australia; Adelaide South Australia Australia
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine; University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), North Terrace; Adelaide South Australia Australia
| | | | - Simon J. Brookes
- College of Medicine and Public Health; Centre for Neuroscience, School of Medicine, Flinders University of South Australia; Adelaide South Australia Australia
| | - Vladimir P. Zagorodnyuk
- College of Medicine and Public Health; Centre for Neuroscience, School of Medicine, Flinders University of South Australia; Adelaide South Australia Australia
| |
Collapse
|
8
|
Nicholas S, Yuan SY, Brookes SJH, Spencer NJ, Zagorodnyuk VP. Hydrogen peroxide preferentially activates capsaicin-sensitive high threshold afferents via TRPA1 channels in the guinea pig bladder. Br J Pharmacol 2016; 174:126-138. [PMID: 27792844 DOI: 10.1111/bph.13661] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 09/22/2016] [Accepted: 10/19/2016] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE There is increasing evidence suggesting that ROS play a major pathological role in bladder dysfunction induced by bladder inflammation and/or obstruction. The aim of this study was to determine the effect of H2 O2 on different types of bladder afferents and its mechanism of action on sensory neurons in the guinea pig bladder. EXPERIMENTAL APPROACH 'Close-to-target' single unit extracellular recordings were made from fine branches of pelvic nerves entering the guinea pig bladder, in flat sheet preparations, in vitro. KEY RESULTS H2 O2 (300-1000 μM) preferentially and potently activated capsaicin-sensitive high threshold afferents but not low threshold stretch-sensitive afferents, which were only activated by significantly higher concentrations of hydrogen peroxide. The TRPV1 channel agonist, capsaicin, excited 86% of high threshold afferents. The TRPA1 channel agonist, allyl isothiocyanate and the TRPM8 channel agonist, icilin activated 72% and 47% of capsaicin-sensitive high threshold afferents respectively. The TRPA1 channel antagonist, HC-030031, but not the TRPV1 channel antagonist, capsazepine or the TRPM8 channel antagonist, N-(2-aminoethyl)-N-[[3-methoxy-4-(phenylmethoxy)phenyl]methyl]thiophene-2-carboxamide, significantly inhibited the H2 O2 -induced activation of high threshold afferents. Dimethylthiourea and deferoxamine did not significantly change the effect of H2 O2 on high threshold afferents. CONCLUSIONS AND IMPLICATIONS The findings show that H2 O2 , in the concentration range detected in inflammation or reperfusion after ischaemia, evoked long-lasting activation of the majority of capsaicin-sensitive high threshold afferents, but not low threshold stretch-sensitive afferents. The data suggest that the TRPA1 channels located on these capsaicin-sensitive afferent fibres are probable targets of ROS released during oxidative stress.
Collapse
Affiliation(s)
- S Nicholas
- Discipline of Human Physiology & Centre for Neuroscience, Flinders University of South Australia, Adelaide, SA, Australia
| | - S Y Yuan
- Discipline of Anatomy and Histology & Centre for Neuroscience, Flinders University of South Australia, Adelaide, SA, Australia
| | - S J H Brookes
- Discipline of Human Physiology & Centre for Neuroscience, Flinders University of South Australia, Adelaide, SA, Australia
| | - N J Spencer
- Discipline of Human Physiology & Centre for Neuroscience, Flinders University of South Australia, Adelaide, SA, Australia
| | - V P Zagorodnyuk
- Discipline of Human Physiology & Centre for Neuroscience, Flinders University of South Australia, Adelaide, SA, Australia
| |
Collapse
|
9
|
Humenick A, Chen BN, Wiklendt L, Spencer NJ, Zagorodnyuk VP, Dinning PG, Costa M, Brookes SJH. Activation of intestinal spinal afferent endings by changes in intra-mesenteric arterial pressure. J Physiol 2015; 593:3693-709. [PMID: 26010893 DOI: 10.1113/jp270378] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 05/18/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS A major class of mechano-nociceptors to the intestine have mechanotransduction sites on extramural and intramural arteries and arterioles ('vascular afferents'). These sensory neurons can be activated by compression or axial stretch of vessels. Using isolated preparations we showed that increasing intra-arterial pressure, within the physiological range, activated mechano-nociceptors on vessels in intact mesenteric arcades, but not in isolated arteries. This suggests that distortion of the branching vascular tree is the mechanical adequate stimulus for these sensory neurons, rather than simple distension. The same rises in pressure also activated intestinal peristalsis in a partially capsaicin-sensitive manner indicating that pressure-sensitive vascular afferents influence enteric circuits. The results identify the mechanical adequate stimulus for a major class of mechano-nociceptors with endings on blood vessels supplying the gut wall; these afferents have similar endings to ones supplying other viscera, striated muscle and dural vessels. ABSTRACT Spinal sensory neurons innervate many large blood vessels throughout the body. Their activation causes the hallmarks of neurogenic inflammation: vasodilatation through the release of the neuropeptide calcitonin gene-related peptide and plasma extravasation via tachykinins. The same vasodilator afferent neurons show mechanical sensitivity, responding to crushing, compression or axial stretch of blood vessels - responses which activate pain pathways and which can be modified by cell damage and inflammation. In the present study, we tested whether spinal afferent axons ending on branching mesenteric arteries ('vascular afferents') are sensitive to increased intravascular pressure. From a holding pressure of 5 mmHg, distension to 20, 40, 60 or 80 mmHg caused graded, slowly adapting increases in firing of vascular afferents. Many of the same afferent units showed responses to axial stretch, which summed with responses evoked by raised pressure. Many vascular afferents were also sensitive to raised temperature, capsaicin and/or local compression with von Frey hairs. However, responses to raised pressure in single, isolated vessels were negligible, suggesting that the adequate stimulus is distortion of the arterial arcade rather than distension per se. Increasing arterial pressure often triggered peristaltic contractions in the neighbouring segment of intestine, an effect that was mimicked by acute exposure to capsaicin (1 μm) and which was reduced after desensitisation to capsaicin. These results indicate that sensory fibres with perivascular endings are sensitive to pressure-induced distortion of branched arteries, in addition to compression and axial stretch, and that they contribute functional inputs to enteric motor circuits.
Collapse
Affiliation(s)
- A Humenick
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, South Australia
| | - B N Chen
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, South Australia
| | - L Wiklendt
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, South Australia
| | - N J Spencer
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, South Australia
| | - V P Zagorodnyuk
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, South Australia
| | - P G Dinning
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, South Australia
| | - M Costa
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, South Australia
| | - S J H Brookes
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, South Australia
| |
Collapse
|
10
|
Chen BN, Sharrad DF, Hibberd TJ, Zagorodnyuk VP, Costa M, Brookes SJ. Neurochemical characterization of extrinsic nerves in myenteric ganglia of the guinea pig distal colon. J Comp Neurol 2014; 523:742-56. [DOI: 10.1002/cne.23704] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 10/24/2014] [Accepted: 10/29/2014] [Indexed: 12/18/2022]
Affiliation(s)
- Bao Nan Chen
- Department of Human Physiology and Centre for Neuroscience; Flinders Medical Science and Technology, School of Medicine, Flinders University; Bedford Park South Australia Australia
| | - Dale F. Sharrad
- Department of Human Physiology and Centre for Neuroscience; Flinders Medical Science and Technology, School of Medicine, Flinders University; Bedford Park South Australia Australia
| | - Timothy J. Hibberd
- Department of Human Physiology and Centre for Neuroscience; Flinders Medical Science and Technology, School of Medicine, Flinders University; Bedford Park South Australia Australia
| | - Vladimir P. Zagorodnyuk
- Department of Human Physiology and Centre for Neuroscience; Flinders Medical Science and Technology, School of Medicine, Flinders University; Bedford Park South Australia Australia
| | - Marcello Costa
- Department of Human Physiology and Centre for Neuroscience; Flinders Medical Science and Technology, School of Medicine, Flinders University; Bedford Park South Australia Australia
| | - Simon J.H. Brookes
- Department of Human Physiology and Centre for Neuroscience; Flinders Medical Science and Technology, School of Medicine, Flinders University; Bedford Park South Australia Australia
| |
Collapse
|
11
|
Brookes SJH, Spencer NJ, Costa M, Zagorodnyuk VP. Extrinsic primary afferent signalling in the gut. Nat Rev Gastroenterol Hepatol 2013. [PMID: 23438947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
Visceral sensory neurons activate reflex pathways that control gut function and also give rise to important sensations, such as fullness, bloating, nausea, discomfort, urgency and pain. Sensory neurons are organised into three distinct anatomical pathways to the central nervous system (vagal, thoracolumbar and lumbosacral). Although remarkable progress has been made in characterizing the roles of many ion channels, receptors and second messengers in visceral sensory neurons, the basic aim of understanding how many classes there are, and how they differ, has proven difficult to achieve. We suggest that just five structurally distinct types of sensory endings are present in the gut wall that account for essentially all of the primary afferent neurons in the three pathways. Each of these five major structural types of endings seems to show distinctive combinations of physiological responses. These types are: 'intraganglionic laminar' endings in myenteric ganglia; 'mucosal' endings located in the subepithelial layer; 'muscular-mucosal' afferents, with mechanosensitive endings close to the muscularis mucosae; 'intramuscular' endings, with endings within the smooth muscle layers; and 'vascular' afferents, with sensitive endings primarily on blood vessels. 'Silent' afferents might be a subset of inexcitable 'vascular' afferents, which can be switched on by inflammatory mediators. Extrinsic sensory neurons comprise an attractive focus for targeted therapeutic intervention in a range of gastrointestinal disorders.
Collapse
Affiliation(s)
- Simon J H Brookes
- Centre for Neuroscience and Discipline of Human Physiology, Flinders Medical Science and Technology, Flinders University, Sturt Road, Bedford Park, SA 5042, Australia.
| | | | | | | |
Collapse
|
12
|
Abstract
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 μmol 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 μmol 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 (χ(2) = 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 Ca(2+) -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.
Collapse
Affiliation(s)
- T J Hibberd
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | | | | | | |
Collapse
|
13
|
Zagorodnyuk VP, Kyloh M, Brookes SJ, Nicholas SJ, Spencer NJ. Firing patterns and functional roles of different classes of spinal afferents in rectal nerves during colonic migrating motor complexes in mouse colon. Am J Physiol Gastrointest Liver Physiol 2012; 303:G404-11. [PMID: 22628035 DOI: 10.1152/ajpgi.00047.2012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The functional role of the different classes of visceral afferents that innervate the large intestine is poorly understood. Recent evidence suggests that low-threshold, wide-dynamic-range rectal afferents play an important role in the detection and transmission of visceral pain induced by noxious colorectal distension in mice. However, it is not clear which classes of spinal afferents are activated during naturally occurring colonic motor patterns or during intense contractions of the gut smooth muscle. We developed an in vitro colorectum preparation to test how the major classes of rectal afferents are activated during spontaneous colonic migrating motor complex (CMMC) or pharmacologically induced contraction. During CMMCs, circular muscle contractions increased firing in low-threshold, wide-dynamic-range muscular afferents and muscular-mucosal afferents, which generated a mean firing rate of 1.53 ± 0.23 Hz (n = 8) under isotonic conditions and 2.52 ± 0.36 Hz (n = 17) under isometric conditions. These low-threshold rectal afferents were reliably activated by low levels of circumferential stretch induced by increases in length (1-2 mm) or load (1-3 g). In a small proportion of cases (5 of 34 units), some low-threshold muscular and muscular-mucosal afferents decreased their firing rate during the peak of the CMMC contractions. High-threshold afferents were never activated during spontaneous CMMC contractions or tonic contractions induced by bethanechol (100 μM). High-threshold rectal afferents were only activated by intense levels of circumferential stretch (10-20 g). These results show that, in the rectal nerves of mice, low-threshold, wide-dynamic-range muscular and muscular-mucosal afferents are excited during contraction of the circular muscle that occurs during spontaneous CMMCs. No activation of high-threshold rectal afferents was detected during CMMCs or intense contractile activity in naïve mouse colorectum.
Collapse
Affiliation(s)
- Vladimir P Zagorodnyuk
- Discipline of Human Physiology and Centre for Neuroscience, Flinders Medical Science and Technology Cluster, Flinders University, South Australia, Australia
| | | | | | | | | |
Collapse
|
14
|
Zagorodnyuk VP, Spencer NJ. Localization of the sensory neurons and mechanoreceptors required for stretch-evoked colonic migrating motor complexes in mouse colon. Front Physiol 2011; 2:98. [PMID: 22203805 PMCID: PMC3244083 DOI: 10.3389/fphys.2011.00098] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Accepted: 11/24/2011] [Indexed: 12/16/2022] Open
Abstract
The pacemaker and pattern generator that underlies the cyclical generation of spontaneous colonic migrating motor complexes (CMMCs) has recently been identified to lie within the myenteric plexus and/or muscularis externa. Neither the mucosa, nor the release of substances from the mucosa were found to be required for the spontaneous generation of CMMCs. However, it is known that stretch applied to the colonic wall can also evoke CMMCs and since stretch of the gut wall is known to stimulate the mucosa, it is not clear whether release of substances from the mucosa and/or submucosal plexus are required for stretch-evoked CMMCs. Therefore, the aim of this study was to determine whether circumferential stretch-evoked CMMCs require the presence of the mucosa and/or submucosal plexus in isolated mouse colon. Spontaneous CMMCs were recorded from full length sheet preparations of colon in vitro. Graded circumferential stretch (at a rate of 100 μm/s) applied to a 15-mm segment of mid–distal colon reliably evoked a CMMC, which propagated to the oral recording site. Sharp dissection to remove the mucosa and submucosal plexus from the entire colon did not prevent spontaneous CMMCs and circumferential stretch-evoked CMMCs were still reliably evoked by circumferential stretch, even at significantly lower thresholds. In contrast, in intact preparations, direct stimulation of the mucosa (without accompanying stretch) proved highly inconsistent and rarely evoked a CMMC. These observations lead to the inescapable conclusion that the sensory neurons activated by colonic stretch to initiate CMMCs lie in the myenteric plexus, while the mechanoreceptors activated by stretch, lie in the myenteric ganglia and/or muscularis externa. Stretch activation of these mechanoreceptors does not require release of any substance(s) from the mucosa, or neural inputs arising from submucosal ganglia.
Collapse
Affiliation(s)
- Vladimir P Zagorodnyuk
- Department of Human Physiology and Centre for Neuroscience, Flinders University Adelaide, SA, Australia
| | | |
Collapse
|
15
|
Spencer NJ, Nicholas SJ, Robinson L, Kyloh M, Flack N, Brookes SJ, Zagorodnyuk VP, Keating DJ. Mechanisms underlying distension-evoked peristalsis in guinea pig distal colon: is there a role for enterochromaffin cells? Am J Physiol Gastrointest Liver Physiol 2011; 301:G519-27. [PMID: 21700904 DOI: 10.1152/ajpgi.00101.2011] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The mechanisms underlying distension-evoked peristalsis in the colon are incompletely understood. It is well known that, following colonic distension, 5-hydroxytryptamine (5-HT) is released from enterochromaffin (EC) cells in the intestinal mucosa. It is also known that exogenous 5-HT can stimulate peristalsis. These observations have led some investigators to propose that endogenous 5-HT release from EC cells might be involved in the initiation of colonic peristalsis, following distension. However, because no direct evidence exists to support this hypothesis, the aim of this study was to determine directly whether release of 5-HT from EC cells was required for distension-evoked colonic peristalsis. Real-time amperometric recordings of 5-HT release and video imaging of colonic wall movements were performed on isolated segments of guinea pig distal colon, during distension-evoked peristalsis. Amperometric recordings revealed basal and transient release of 5-HT from EC cells before and during the initiation of peristalsis, respectively. However, removal of mucosa (and submucosal plexus) abolished 5-HT release but did not inhibit the initiation of peristalsis nor prevent the propagation of fecal pellets or intraluminal fluid. Maintained colonic distension by fecal pellets induced repetitive peristaltic waves, whose intrinsic frequency was also unaffected by removal of the submucosal plexus and mucosa, although their propagation velocities were slower. In conclusion, the mechanoreceptors and sensory neurons activated by radial distension to initiate peristalsis lie in the myenteric plexus and/or muscularis externa, and their activation does not require the submucosal plexus, release of 5-HT from EC cells, nor the presence of the mucosa. The propagation of peristalsis and propulsion of liquid or solid content along the colon is entrained by activity within the myenteric plexus and/or muscularis externa and does not require sensory feedback from the mucosa, nor neural inputs arising from submucosal ganglia.
Collapse
Affiliation(s)
- Nick J Spencer
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia.
| | | | | | | | | | | | | | | |
Collapse
|
16
|
Yuan SY, Gibbins IL, Zagorodnyuk VP, Morris JL. Sacro-lumbar Intersegmental Spinal Reflex in Autonomic Pathways Mediating Female Sexual Function. J Sex Med 2011; 8:1931-42. [DOI: 10.1111/j.1743-6109.2010.02160.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
17
|
Kyloh M, Nicholas S, Zagorodnyuk VP, Brookes SJ, Spencer NJ. Identification of the visceral pain pathway activated by noxious colorectal distension in mice. Front Neurosci 2011; 5:16. [PMID: 21390285 PMCID: PMC3046361 DOI: 10.3389/fnins.2011.00016] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Accepted: 01/27/2011] [Indexed: 01/10/2023] Open
Abstract
In patients with irritable bowel syndrome, visceral pain is evoked more readily following distension of the colorectum. However, the identity of extrinsic afferent nerve pathway that detects and transmits visceral pain from the colorectum to the spinal cord is unclear. In this study, we identified which extrinsic nerve pathway(s) underlies nociception from the colorectum to the spinal cord of rodents. Electromyogram recordings were made from the transverse oblique abdominal muscles in anesthetized wild type (C57BL/6) mice and acute noxious intraluminal distension stimuli (100-120 mmHg) were applied to the terminal 15 mm of colorectum to activate visceromotor responses (VMRs). Lesioning the lumbar colonic nerves in vivo had no detectable effect on the VMRs evoked by colorectal distension. Also, lesions applied to the right or left hypogastric nerves failed to reduce VMRs. However, lesions applied to both left and right branches of the rectal nerves abolished VMRs, regardless of whether the lumbar colonic or hypogastric nerves were severed. Electrical stimulation applied to either the lumbar colonic or hypogastric nerves in vivo, failed to elicit a VMR. In contrast, electrical stimulation (2-5 Hz, 0.4 ms, 60 V) applied to the rectum reliably elicited VMRs, which were abolished by selective lesioning of the rectal nerves. DiI retrograde labeling from the colorectum (injection sites 9-15 mm from the anus, measured in unstretched preparations) labeled sensory neurons primarily in dorsal root ganglia (DRG) of the lumbosacral region of the spinal cord (L6-S1). In contrast, injection of DiI into the mid to proximal colon (injection sites 30-75 mm from the anus, measured in unstretched preparations) labeled sensory neurons in DRG primarily of the lower thoracic level (T6-L2) of the spinal cord. The visceral pain pathway activated by acute noxious distension of the terminal 15 mm of mouse colorectum is transmitted predominantly, if not solely, through rectal/pelvic afferent nerve fibers to the spinal cord. The sensory neurons of this spinal afferent pathway lie primarily in the lumbosacral region of the spinal cord, between L6 and S1.
Collapse
Affiliation(s)
- Melinda Kyloh
- Department of Human Physiology, Flinders Medical Science and Technology Cluster, Flinders University Adelaide, SA, Australia
| | | | | | | | | |
Collapse
|
18
|
Zagorodnyuk VP, Kyloh M, Nicholas S, Peiris H, Brookes SJ, Chen BN, Spencer NJ. Loss of visceral pain following colorectal distension in an endothelin-3 deficient mouse model of Hirschsprung's disease. J Physiol 2011; 589:1691-706. [PMID: 21320883 DOI: 10.1113/jphysiol.2010.202820] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Endothelin peptides and their endogenous receptors play a major role in nociception in a variety of different organs. They also play an essential role in the development of the enteric nervous system. Mice with deletions of the endothelin-3 gene (lethal spotted mice, ls/ls) develop congenital aganglionosis. However, little is known about how nociception might be affected in the aganglionic rectum of mice deficient in endothelin-3. In this study we investigated changes in spinal afferent innervation and visceral pain transmission from the aganglionic rectum in ls/ls mice. Electromyogram recordings from anaesthetized ls/ls mice revealed a deficit in visceromotor responses arising from the aganglionic colorectum in response to noxious colorectal distension. Loss of visceromotor responses (VMRs) in ls/ls mice was selective, as no reduction in VMRs was detected after stimulation of the bladder or somatic organs. Calcitonin gene related peptide (CGRP) immunoreactivity, retrograde neuronal tracing and extracellular afferent recordings from the aganglionic rectum revealed decreased colorectal spinal innervation, combined with a reduction in mechanosensitivity of rectal afferents. The sensory defect in ls/ls mice is primarily associated with changes in low threshold wide dynamic range rectal afferents. In conclusion, disruption of endothelin 3 gene expression not only affects development and function of the enteric nervous system, but also specific classes of spinal rectal mechanoreceptors, which are required for visceral nociception from the colorectum.
Collapse
Affiliation(s)
- Vladimir P Zagorodnyuk
- Discipline of Human Physiology, Flinders Medical Science and Technology Cluster, Flinders University, 5001, South Australia, Australia
| | | | | | | | | | | | | |
Collapse
|
19
|
Zagorodnyuk VP, Brookes SJH, Spencer NJ. Structure-function relationship of sensory endings in the gut and bladder. Auton Neurosci 2009; 153:3-11. [PMID: 19682956 DOI: 10.1016/j.autneu.2009.07.018] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Revised: 07/14/2009] [Accepted: 07/20/2009] [Indexed: 11/28/2022]
Abstract
Visceral afferents play a key role in neural circuits underlying the physiological function of visceral organs. They are responsible for the detection and transmission of a variety of visceral sensations (e.g. satiety, urge, discomfort and pain) from the viscera to the central nervous system. A comprehensive account of the different functional types of visceral sensory neurons would be invaluable in understanding how sensory dysfunction occurs and how it might be diagnosed and treated. Our aim was to explore the morphology of different nerve endings of visceral afferents within the gastrointestinal tract and urinary bladder and how the morphology of these nerve endings may relate to their functional properties. Morphological studies of mechanosensitive endings of visceral afferents to the gut and bladder correlated with physiological recordings have added a new dimension to our ability to distinguish different functional classes of visceral afferents.
Collapse
Affiliation(s)
- Vladimir P Zagorodnyuk
- Department of Human Physiology & Centre for Neuroscience, Flinders University of South Australia, GPO Box 2100, Adelaide, South Australia, Australia.
| | | | | |
Collapse
|
20
|
Song X, Chen BN, Zagorodnyuk VP, Lynn PA, Blackshaw LA, Grundy D, Brunsden AM, Costa M, Brookes SJH. Identification of medium/high-threshold extrinsic mechanosensitive afferent nerves to the gastrointestinal tract. Gastroenterology 2009; 137:274-84, 284.e1. [PMID: 19268671 PMCID: PMC2704260 DOI: 10.1053/j.gastro.2009.02.061] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Revised: 02/18/2009] [Accepted: 02/25/2009] [Indexed: 01/05/2023]
Abstract
BACKGROUND & AIMS Large distentions reliably evoke sensation from the noninflamed, nonischemic bowel, but the specialized afferent axonal structures responsible have not been morphologically identified. We investigated whether their transduction sites are located on major blood vessels close to and within the gut wall. METHODS In vitro extracellular recordings were made from mesenteric nerve trunks in guinea pig ileum, combined with rapid axonal dye filling and immunohistochemical analysis of nerve trunks. RESULTS Recordings revealed sensory fibers with focal mechanosensitive sites in the mesenteries that could be activated by von Frey hairs and by stretch. Dye filling revealed varicose branching sensory axons on mesenteric blood vessels but no other anatomically specialized structures in mesenteric membranes or the serosa. Large-amplitude stretch and von Frey hairs also activated sensory endings within the gut wall itself but only if the submucosa was present; mechanotransduction sites in the serosa or outer muscle layers were sparse. Mechanosensitive sites in submucosa were exclusively associated with submucosal blood vessels. Submucosal endings had significantly higher thresholds to stretch than specialized low-threshold mechanoreceptors characterized previously in the rectum (P < .05) and were therefore classified as medium/high-threshold mechanoreceptors. Capsaicin (0.3-1 micromol/L) activated most mechanosensitive mesenteric (68%) and submucosal (85%) afferent endings. Similar intramural mechanosensitive afferent endings on blood vessels also exist in the colon and bladder. CONCLUSIONS Varicose branching axons of sensory neurons on intramural blood vessels, previously shown to mediate sensory vasodilation, are transduction sites for medium/high-threshold, stretch-sensitive mechanoreceptors, encoding large distentions in hollow viscera.
Collapse
Affiliation(s)
- Xingyun Song
- Dept of Human Physiology, Flinders University, Bedford Park, South Australia 5042, Tel: +61 8 8204 4201, Fax: +61 8 8204 5768
| | - Bao Nan Chen
- Dept of Human Physiology, Flinders University, Bedford Park, South Australia 5042, Tel: +61 8 8204 4201, Fax: +61 8 8204 5768
| | - Vladimir P Zagorodnyuk
- Dept of Human Physiology, Flinders University, Bedford Park, South Australia 5042, Tel: +61 8 8204 4201, Fax: +61 8 8204 5768
| | - Penny A Lynn
- Dept of Human Physiology, Flinders University, Bedford Park, South Australia 5042, Tel: +61 8 8204 4201, Fax: +61 8 8204 5768
| | - L Ashley Blackshaw
- Nerve–Gut Research Laboratory, Department of Gastroenterology, Hepatology and General Medicine, Royal Adelaide Hospital, Adelaide, South Australia, 5000, Australia
| | - David Grundy
- Dept of Biomedical Science, University of Sheffield, Alfred Denny Building, Western Bank, Sheffield S10-2TN, UK
| | - Alan M Brunsden
- Dept of Biomedical Science, University of Sheffield, Alfred Denny Building, Western Bank, Sheffield S10-2TN, UK
| | - Marcello Costa
- Dept of Human Physiology, Flinders University, Bedford Park, South Australia 5042, Tel: +61 8 8204 4201, Fax: +61 8 8204 5768
| | - Simon JH Brookes
- Dept of Human Physiology, Flinders University, Bedford Park, South Australia 5042, Tel: +61 8 8204 4201, Fax: +61 8 8204 5768
| |
Collapse
|
21
|
Zagorodnyuk VP, Brookes SJH, Spencer NJ, Gregory S. Mechanotransduction and chemosensitivity of two major classes of bladder afferents with endings in the vicinity to the urothelium. J Physiol 2009; 587:3523-38. [PMID: 19470774 DOI: 10.1113/jphysiol.2009.172577] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The guinea pig bladder is innervated by at least five distinct major classes of extrinsic sensory neurons. In this study, we have examined the mechanisms of mechanotransduction and chemosensitivity of two classes of bladder afferents that have their endings in the vicinity of the urothelium: stretch-sensitive muscle-mucosal mechanoreceptors and stretch-insensitive, mucosal high-responding afferents. The non-selective P2 purinoreceptor antagonist pyridoxal phosphate-6-azophenyl-2',4'-disulphonic acid did not affect stretch- or stroking-induced firing of these afferents but significantly reduced the excitatory action of alpha,beta-methylene ATP. Blocking synaptic transmission in Ca(2+)-free solution did not affect stretch-evoked firing but slightly reduced stretch-induced tension responses. Stroking-induced firing of both classes of afferents was also not affected in Ca(2+)-free solution. Of blockers of mechano-gated channels, benzamil (100 microM), but not amiloride (100 microM), Gd(3+) (100 microM) or SKF 96365 (50 microM), inhibited stretch- and stroking-induced firing. Serotonin (100 microM) applied directly onto receptive fields predominantly activated muscle-mucosal afferents. Muscarine (100 microM) and substance P (100 microM) in 24% and 36% cases activated only mucosal high-responding units. Bradykinin (10 microM), but not prostaglandin E2 (10 microM), excites predominantly mucosal units. High (80 mM) K(+) solution activated both afferent classes, but responses of mucosal units were 4 times greater. In contrast to muscle-mucosal units, most mucosal high-responding units were activated by hot Krebs solution (45-46 degrees C), low pH (pH 4) and capsaicin (3 microm). TRPV1 antagonist, capsazepine (10 microM) was without effect on mechanotransduction by mucosal high-responding afferents. The results show that mechanotransduction of these two types of afferents are not dependant upon Ca(2+)-dependent exocytotic release of mediators, or ATP, and it is likely that benzamil-sensitive stretch-activated ion channels on their endings are involved in direct mechanotransduction. The chemosensitivity to agonists and noxious stimuli differs significantly between these two major classes of bladder afferents that reflects their different physiological and pathophysiological roles in the bladder.
Collapse
Affiliation(s)
- Vladimir P Zagorodnyuk
- Department of Human Physiology, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia.
| | | | | | | |
Collapse
|
22
|
Zagorodnyuk VP, Gregory S, Costa M, Brookes SJH, Tramontana M, Giuliani S, Maggi CA. Spontaneous release of acetylcholine from autonomic nerves in the bladder. Br J Pharmacol 2009; 157:607-19. [PMID: 19371347 DOI: 10.1111/j.1476-5381.2009.00166.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Bladder contractility is regulated by intrinsic myogenic mechanisms interacting with autonomic nerves. In this study, we have investigated the physiological role of spontaneous release of acetylcholine in guinea pig and rat bladders. EXPERIMENTAL APPROACH Conventional isotonic or pressure transducers were used to record contractile activity of guinea pig and rat bladders. KEY RESULTS Hyoscine (3 micromol x L(-1)), but not tetrodotoxin (TTX, 1 micromol x L(-1)), reduced basal tension, distension-evoked contractile activity and physostigmine (1 micromol x L(-1))-evoked contractions of the whole guinea pig bladder and muscle strips in vitro. omega-Conotoxin GVIA (0.3 micromol x L(-1)) did not affect physostigmine-induced contractions when given either alone or in combination with omega-agatoxin IVA (0.1 micromol x L(-1)) and SNX 482 (0.3 micromol x L(-1)). After 5 days in organotypic culture, when extrinsic nerves had significantly degenerated, the ability of physostigmine to induce contractions was reduced in the dorso-medial strips, but not in lateral strips (which have around 15 times more intramural neurones). Most muscle strips from adult rats lacked intramural neurones. After 5 days in culture, physostigmine-induced or electrical field stimulation-induced contractions of the rat bladder strips were greatly reduced. In anaesthetized rats, topical application of physostigmine (5-500 nmol) on the bladder produced a TTX-resistant tonic contraction that was abolished by atropine (4.4 micromol x kg(-1) i.v.). CONCLUSIONS AND IMPLICATIONS The data indicate that there is spontaneous TTX-resistant release of acetylcholine from autonomic cholinergic extrinsic and intrinsic nerves, which significantly affects bladder contractility. This release is resistant to blockade of N, P/Q and R type Ca(2+) channels.
Collapse
Affiliation(s)
- V P Zagorodnyuk
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia, Australia.
| | | | | | | | | | | | | |
Collapse
|
23
|
Brookes SJH, Zagorodnyuk VP, Lynn PA, Song X, Chen N, Olsson C, Costa M. Structural basis of sensory nerve pathways from the gut. Eur Rev Med Pharmacol Sci 2008; 12 Suppl 1:132-133. [PMID: 18924453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Affiliation(s)
- S J H Brookes
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Bedford Park, SA, Australia.
| | | | | | | | | | | | | |
Collapse
|
24
|
Spencer NJ, Kerrin A, Zagorodnyuk VP, Hennig GW, Muto M, Brookes SJ, McDonnell O. Identification of functional intramuscular rectal mechanoreceptors in aganglionic rectal smooth muscle from piebald lethal mice. Am J Physiol Gastrointest Liver Physiol 2008; 294:G855-67. [PMID: 18218672 DOI: 10.1152/ajpgi.00502.2007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The mechanosensitive endings of low-threshold, slowly adapting pelvic afferents that innervate the rectum have been previously identified as rectal intraganglionic laminar endings (rIGLEs) that lie within myenteric ganglia. We tested whether the aganglionic rectum of piebald-lethal (s(l)/s(l)) mice lacks rIGLEs and whether this could explain impaired distension-evoked reflexes from this region. Extracellular recordings were made from fine rectal nerves in C57BL/6 wild-type and s(l)/s(l) mice, combined with anterograde labeling. In C57BL/6 mice, graded circumferential stretch applied to the rectum activated graded increases in firing of slowly adapting rectal mechanoreceptors. In s(l)/s(l) mice, graded stretch of the aganglionic rectum activated similar graded increases in rectal afferent firing. Stretch-sensitive afferents responded at low mechanical thresholds and fired more intensely at noxious levels of stretch. They could also be activated by probing their receptive fields with von Frey hairs and by muscle contraction. Anterograde labeling from recorded rectal nerves identified the mechanoreceptors of muscular afferents in the aganglionic rectal smooth muscle. A population of afferents were also recorded in both C57BL/6 and s(l)/s(l) mice that were activated by von Frey hair probing, but not stretch. In summary, the aganglionic rectum is innervated by a population of stretch-sensitive rectal afferent mechanoreceptor which develops and functions in the absence of any enteric ganglia. These results suggest that in patients with Hirschsprung's disease the inability to activate extrinsic distension reflexes from the aganglionic rectum is unlikely to be due to the absence of stretch-sensitive extrinsic mechanoreceptors.
Collapse
Affiliation(s)
- Nick J Spencer
- Dept. of Human Physiology, School of Medicine, Flinders Univ., South Australia, Australia.
| | | | | | | | | | | | | |
Collapse
|
25
|
Zagorodnyuk VP, Gibbins IL, Costa M, Brookes SJH, Gregory SJ. Properties of the major classes of mechanoreceptors in the guinea pig bladder. J Physiol 2007; 585:147-63. [PMID: 17916614 DOI: 10.1113/jphysiol.2007.140244] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Sensory neurons represent an attractive target for pharmacological treatment of various bladder disorders. However the properties of major classes of mechano-sensory neurons projecting to the bladder have not been systematically established. An in vitro bladder preparation was used to examine the effects of a range of mechanical stimuli (stretch, von Frey hair stroking and focal compression of receptive fields) and chemical stimuli (1 mm alpha,beta-methylene ATP, hypertonic solutions (500 mm NaCl) and 3 microm capsaicin) during electrophysiological recordings from guinea pig bladder afferents. Four functionally distinct populations of bladder sensory neurons were distinguished by these stimuli. The first class, muscle mechanoreceptors, were activated by stretch but not by mucosal stroking with light (0.05-0.1 mN) von Frey hairs or by hypertonic saline, alpha,beta-methylene ATP or capsaicin. Removal of the urothelium did not affect their stretch-induced firing. The second class, muscle-mucosal mechanoreceptors, were activated by both stretch and mucosal stroking with light von Frey hairs or by hypertonic saline and by alpha,beta-methylene ATP, but not by capsaicin. Removal of the urothelium reduced their stretch- and stroking-induced firing. The third class, mucosal high-responding mechanoreceptors, were stretch-insensitive but could be activated by mucosal stroking with light von Frey hairs or by hypertonic saline, alpha,beta-methylene ATP and capsaicin. Stroking-induced firing was significantly reduced by removal of the urothelium. The fourth class, mucosal low-responding mechanoreceptors, were stretch insensitive but could be weakly activated by mucosal stroking with light von Frey hairs but not by hypertonic saline, alpha,beta-methylene ATP or capsaicin. Removal of the urothelium reduced mucosal stroking-induced firing. All four populations of afferents conducted in the C-fibre range and showed class-dependent differences in spike amplitude and duration. At least four functional classes of bladder mechanoreceptors can be readily distinguished by different mechanisms of activation and are likely to transmit different types of information to the central nervous system.
Collapse
Affiliation(s)
- Vladimir P Zagorodnyuk
- Department of Human Physiology, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia.
| | | | | | | | | |
Collapse
|
26
|
Zagorodnyuk VP. Properties of major classes of guinea pig bladder mechanoreceptors in vitro. Auton Neurosci 2007. [DOI: 10.1016/j.autneu.2007.06.090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
|
27
|
Zagorodnyuk VP, Costa M, Brookes SJH. Major classes of sensory neurons to the urinary bladder. Auton Neurosci 2006; 126-127:390-7. [PMID: 16581309 DOI: 10.1016/j.autneu.2006.02.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2005] [Revised: 02/15/2006] [Accepted: 02/20/2006] [Indexed: 01/21/2023]
Abstract
A novel in vitro bladder preparation was used to examine effect of various stimuli (stretch, von Frey hair compression, stroking of receptive fields, applications of chemical stimuli to the mucosa) on electrophysiological recordings from guinea pig bladder afferents in vitro. Several functionally distinct classes of bladder sensory neurons were distinguished. These include stretch-sensitive afferents-muscle mechanoreceptors which behaved as "in-series tension receptors" and tension-mucosal mechanoreceptors, which could be activated by stretch, mucosal stroking with light von Frey hair (0.1-2 mN) and by hypertonic solutions (1 M mannitol and 490-850 mM NaCl) applied locally to their receptive fields in the mucosa. In addition, we have recorded stretch-insensitive afferents-mucosal mechanoreceptors and chemoreceptors. The non-selective P2X/P2Y purinoreceptor antagonist, PPADS (30 microM) did not affect stretch-induced firing by low threshold muscle mechanoreceptors but significantly inhibited alpha,beta-methylene ATP (30 microM)-induced contractions and associated afferent firing. Transduction by low threshold stretch-sensitive muscle mechanoreceptors does not appear to involve exocytotic synaptic transmission since it occurs in Ca2+-free (with 1 mM EDTA and 6 mM Mg2+) Krebs solution. The data suggest that the endogenous transmitter ATP is not involved in mechanotransduction by this specific class of low threshold muscle mechanoreceptors in the guinea pig bladder; rather they appear to transduce mechanical stimuli directly, possibly via stretch-activated ion channels. Mechanisms of activation of other classes of mechanoreceptors and chemoreceptors remain to be established.
Collapse
Affiliation(s)
- Vladimir P Zagorodnyuk
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, GPO Box 2100, Adelaide 5001, South Australia.
| | | | | |
Collapse
|
28
|
Zagorodnyuk VP, Lynn P, Costa M, Brookes SJH. Mechanisms of mechanotransduction by specialized low-threshold mechanoreceptors in the guinea pig rectum. Am J Physiol Gastrointest Liver Physiol 2005; 289:G397-406. [PMID: 15933221 DOI: 10.1152/ajpgi.00557.2004] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The guinea pig rectum, but not the colon, is innervated by a specialized class of distension-sensitive mechanoreceptors that have transduction sites corresponding to rectal intraganglionic laminar endings (rIGLEs). Rectal mechanoreceptors recorded in vitro had low threshold to circumferential stretch, adapted slowly, and could respond within 2 ms to mechanical stimulation by a piezo-electric probe. Antagonists to ionotropic N-methyl-D-aspartate (NMDA; CGS 19755, memantine) and non-NMDA (6,7-dinitroquinoxaline-2,3-dione) glutamate receptors did not affect mechanotransduction. In normal Krebs solution, the P2X purinoreceptor agonist alpha,beta-methylene ATP reduced mechanoreceptor firing evoked by distension but simultaneously relaxed circular smooth muscle and inhibited stretch-induced contractions. Neither ATP nor alpha,beta-methylene ATP affected mechanotransduction when transduction sites were directly compressed with von Frey hairs. The P2 purinoreceptor antagonist pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid did not affect stretch-induced firing but reduced the inhibitory effect of alpha,beta-methylene ATP on stretch-induced firing. Under isometric conditions, blocking synaptic transmission in Ca2+-free solution reduced stretch-evoked firing but not when basal tension was restored to control levels. Under isotonic condition, Ca2+-free solution did not significantly affect load-evoked firing. The blockers of mechanogated and/or transient receptor potential channels, benzamil, Gd3+, SKF 96365, and ruthenium red inhibited stretch-induced firing but, in parallel, significantly reduced stretch-induced contractions. Benzamil and SKF 96365 were able to inhibit mechanotransduction when transduction sites were compressed with von Frey hairs. The results show that mechanotransduction is rapid but does not depend on fast exocytotic release of mediators. It is likely that stretch-activated ion channels on rIGLEs are involved in direct, physical mechanotransduction by rectal low-threshold mechanoreceptors.
Collapse
Affiliation(s)
- Vladimir P Zagorodnyuk
- Dept. of Human Physiology, Flinders Univ., GPO Box 2100, Adelaide, South Australia 5001.
| | | | | | | |
Collapse
|
29
|
Zagorodnyuk VP, Chen BN, Costa M, Brookes SJH. Mechanotransduction by intraganglionic laminar endings of vagal tension receptors in the guinea-pig oesophagus. J Physiol 2003; 553:575-87. [PMID: 14500769 PMCID: PMC2343564 DOI: 10.1113/jphysiol.2003.051862] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Vagal mechanoreceptors to the guinea-pig oesophagus, recorded extracellularly, in vitro, fired spontaneously at 3.3 +/- 0.2 Hz, (n = 75, from 57 animals), and had low thresholds to circumferential stretch. In this study, we have investigated whether mechanotransduction by intraganglionic laminar endings (IGLEs) directly relies on mechano-gated ion channels, or whether it is due to chemical activation by neurotransmitters (glutamate or ATP) released from other cells during mechanical distortion. Rapid distortion of focal transduction sites (IGLEs) evoked action potentials with a latency of < 10 ms. Antagonists to ionotropic (AP5, memantine and 6,7-dinitroquinoxaline-2,3-dione (DNQX)) and metabotropic glutamate receptors (N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide (PHCCC) and (RS)-a-methyl-4-phosphono-phenylglycine (MPPG)) did not affect mechano-transduction. Glutamate, NMDA and the selective mGluR group II and III agonists, (2R, 4R)-APDC and L-AP4, had no effect on spontaneous or stretch-induced firing. The P2X purinoreceptor agonist, alpha,beta-methylene ATP, caused concentration-dependent excitation of vagal mechanoreceptors (EC50 = 22.2 microM) which was blocked by the non-selective P2 antagonist PPADS (30 microM). On its own, PPADS affected neither stretch-induced firing nor spontaneous firing. Neither Ca(2+)-free solution (1 mM EDTA, 3.6 mM Mg(2+)) solution nor Cd(2+) (100 microM) blocked stretch-induced firing. Thus chemical transmission is not involved in activation of vagal mechanoreceptors. The blocker of stretch-activated channels, Gd(3+) (300 microM), did not inhibit stretch-induced firing. However, benzamil (100 microM) significantly inhibited spontaneous and distension-evoked firing in a stretch-dependent manner; proportionally greater inhibition was seen with larger stretches. The results suggest that IGLEs of vagal tension receptors directly transduce mechanical stimuli probably via benzamil-sensitive, Gd3+-insensitive, stretch-activated ion channels, and that chemical transmission is not involved in transduction.
Collapse
Affiliation(s)
- Vladimir P Zagorodnyuk
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, GPO Box 2100, Adelaide, South Australia.
| | | | | | | |
Collapse
|
30
|
Zagorodnyuk VP, Chen BN, Costa M, Brookes SJH. 4-aminopyridine- and dendrotoxin-sensitive potassium channels influence excitability of vagal mechano-sensitive endings in guinea-pig oesophagus. Br J Pharmacol 2002; 137:1195-206. [PMID: 12466228 PMCID: PMC1573601 DOI: 10.1038/sj.bjp.0704964] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Distension-sensitive vagal afferent fibres from the guinea-pig oesophagus were recorded extracellularly in vitro. Most recorded units were spontaneously active firing at 3.2+/-0.3 Hz (n=41, N=41) and had low thresholds (less than 1 mm) to circumferential stretch. Dynamic and adapted phases of stretch-evoked firing, as well as a silent period were linearly dependent on the amplitude of stretch. 2. High K+ (7-12 mM) Krebs solution dose-dependently increased both spontaneous and stretch-evoked firing and reduced the duration of the silent period. 3. Charybdotoxin (ChTX, 100 nM) slightly increased spontaneous and stretch-evoked firing and decreased the silent period, while neither iberiotoxin (100 nM) nor apamin (0.5 microM) had significant effects. omega-Conotoxin GVIA (0.5 microM) did not significantly affect firing of vagal mechanoreceptors. 4. In the majority of single units, 4-aminopyridine (4-AP) concentration-dependently (EC(50) approximately 28 microM) increased spontaneous firing, strongly reduced the silent period but did not affect stretch (3 mm)-induced firing. Firing evoked by 1-2 mm was increased by 4-AP. 5. Alpha-dendrotoxin (DnTX, 300 nM) and DnTX K (30 nM) slightly increased spontaneous and stretch-evoked firing. There was no additive effect on spontaneous firing when ChTX and DnTX K were applied simultaneously. 6. Barium (100 microM) increased stretch-induced firing, probably due to an increase in intramural tension. Glibenclamide (10 microM) had no effect on spontaneous or stretch-induced firing. 7. The results indicate that voltage-gated 4-AP- and dendrotoxin-sensitive K+ channels are the main type of K+ channels that influence excitability of vagal mechano-sensitive endings of the guinea-pig oesophagus. They were involved in control of spontaneous firing and in stretch-induced firing evoked by moderate stretch, but none of the K+ channels appeared to be involved in adaptation to maintained stretch by their slowly adapting vagal mechanoreceptors.
Collapse
Affiliation(s)
- Vladimir P Zagorodnyuk
- Department of Human Physiology and Centre for Neuroscience, Flinders University, GPO Box 2100, Adelaide, South Australia, Australia.
| | | | | | | |
Collapse
|
31
|
Zagorodnyuk VP, D'Antona G, Brookes SJH, Costa M. Functional GABAB receptors are present in guinea pig nodose ganglion cell bodies but not in peripheral mechanosensitive endings. Auton Neurosci 2002; 102:20-9. [PMID: 12492132 DOI: 10.1016/s1566-0702(02)00183-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The effects of the GABAB-selective agonist baclofen were studied on guinea pig nodose ganglion neurones using grease gap and intracellular recording techniques, and on peripheral mechanosensitive endings in the guinea pig oesophagus and stomach with extracellular recordings. GABA dose-dependently reduced the amplitude of the compound action potential of C-type neurones (C spikes, EC50 = 30.9 microM), which was prevented by the GABAA antagonist bicuculline (10 microM). The GABAB agonist baclofen (1-300 microM) did not produce any significant effect on the amplitude of C spikes. In microelectrode studies, baclofen (100 microM) evoked hyperpolarisation (by 2.53 +/- 0.51 mV, n = 6, N = 5) in a subset of nodose neurones (6 out of 26, N = 18). In seven out of eight neurones (N = 8) with a slow after-hyperpolarisation following action potentials, baclofen significantly inhibited its amplitude by 19 +/- 4% (n = 7, p < 0.05). GABA (100 microM) evoked a depolarisation of 9.3 +/- 2.4 mV (10 nodose neurones, N = 9, p < 0.05) associated with a decrease in input impedance of 49 +/- 12% (N = 4, p < 0.05). Baclofen (100-200 microM) did not affect either spontaneous or stretch-evoked firing of distension-sensitive vagal mechanoreceptors of the guinea pig oesophagus and stomach but did inhibit mechanoreceptors in the ferret oesophagus. Antibodies to GABAB receptor 1a splice variants labelled most of the neurones and numerous fibres in the guinea pig nodose ganglion while antibodies to GABAB receptor 1b splice variants stained only nerve cell bodies. There were numerous nerve fibres showing GABAB receptor 1a- and 1b-like immunoreactivity in the myenteric plexus in the guinea pig oesophagus and stomach but not in anterogradely labelled extrinsic vagal nerve fibres. The result indicates that most guinea pig C-type nodose ganglion neurones have GABAB receptors on their cell bodies but their density on distension-sensitive peripheral endings is too low to allow modulation of mechanotransduction. There is a significant species-dependent difference in the expression of GABAB receptors on peripheral vagal mechanosensitive endings.
Collapse
Affiliation(s)
- Vladimir P Zagorodnyuk
- Department of Human Physiology, Centre for Neuroscience, Flinders University of South Australia, GPO Box 2100, Adelaide, South Australia, Australia.
| | | | | | | |
Collapse
|
32
|
Brookes SJ, D'Antona G, Zagorodnyuk VP, Humphreys CM, Costa M. Propagating contractions of the circular muscle evoked by slow stretch in flat sheets of guinea-pig ileum. Neurogastroenterol Motil 2001; 13:519-31. [PMID: 11903913 DOI: 10.1046/j.1365-2982.2001.00290.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Flat sheet preparations of guinea-pig ileum were stretched circumferentially and the propagation of circular muscle contractions along the preparation was investigated. Slow stretch, at 100 microm s-1, of a 50-mm long flat sheet of intestine, evoked circular muscle contraction orally, which propagated, without decrement, for up to 30 mm. This occurred despite circular muscle shortening being prevented, and in the absence of propulsion of contents. Thus, propagation in this flat sheet preparation could not explained on the basis of neuro-mechanical interactions, as previously proposed. Irrespective of the length of preparations, contraction amplitude decreased significantly in the most aboral 10-15 mm of intestine. This was not due to descending inhibitory pathways, but was associated with interruption of ascending excitatory pathways near the aboral end. Slow waves were not detected in circular muscle cells in any preparation (n=8). Smooth muscle action potentials evoked in circular muscle cells, in the presence of tetrodotoxin (TTX, 0.6 micromol L-1), did not propagate for more than 1 mm in the longitudinal axis. Propagation of circular muscle activity, evoked by slow stretch of flat sheet preparations, reveals the presence of a mechanism other than myogenic spread or the neuro-mechanical interactions previously proposed to account for propagation; the nature of this mechanism remains to be determined.
Collapse
Affiliation(s)
- S J Brookes
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, South Australia.
| | | | | | | | | |
Collapse
|
33
|
Abstract
1. Distension-sensitive vagal afferent fibres from the cardiac region of the guinea-pig stomach were recorded extracellularly, then filled with biotinamide, using an anterograde tracing technique. 2. Most of the stretch-sensitive units of the guinea-pig stomach (41 out of 47; number of animals N = 26) had low thresholds (less than 1 mm) to circumferential stretch and showed slow adaptation. Twenty of these units fired spontaneously under resting conditions (mean: 1.9 +/- 0.3 Hz, n = 20, N = 14). 3. Adaptation of firing during slow or maintained stretch correlated closely with accommodation of intramural tension, but tension-independent adaptation was also present. 4. Nicardipine (3 microM) with hyoscine (3 microM) reduced stretch-evoked firing of gastric vagal afferents, by inhibiting smooth muscle contraction. Gadolinium (1 mM) blocked distension-evoked firing. 5. Focal stimulation of the stomach muscle wall with a von Frey hair (0.4 mN) identified one to six punctate receptive fields in each low threshold vagal distension-sensitive afferent. These were marked on the serosal surface of the stomach wall. 6. Anterograde filling of recorded nerve trunks revealed intraganglionic laminar endings (IGLEs) within 142 +/- 34 microm (n = 38; N = 10) of marked receptive fields. The mean distance from randomly generated sites to the nearest IGLE was significantly greater (1500 +/- 48 microm, n = 380, N = 10, P < 0.0001). Viscerofugal nerve cell bodies, intramuscular arrays and varicose axons were not associated with receptive fields. The results indicate that IGLEs are the mechanotransduction sites of low threshold, slowly adapting vagal tension receptors in the guinea-pig upper stomach.
Collapse
Affiliation(s)
- V P Zagorodnyuk
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, GPO Box 2100, Adelaide, South Australia.
| | | | | |
Collapse
|
34
|
Zagorodnyuk VP, Brookes SJ. Transduction sites of vagal mechanoreceptors in the guinea pig esophagus. J Neurosci 2000; 20:6249-55. [PMID: 10934275 PMCID: PMC6772604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023] Open
Abstract
Extrinsic afferent neurons play an essential role in both sensation and reflex control of visceral organs, but their specialized morphological peripheral endings have never been functionally identified. Extracellular recordings were made from fine nerve trunks running between the vagus nerve and esophagus of the guinea pig. Mechanoreceptors, which responded to esophageal distension, fired spontaneously, had low thresholds to circumferential stretch, and were slowly adapting. Calibrated von Frey hairs (0.12 mN) were used to probe the serosal surface at 100-200 sites, which were mapped on a video image of the live preparation. Each stretch-sensitive unit had one to three highly localized receptive fields ("hot spots"), which were marked with Indian ink applied on the tip of the von Frey hair. Recorded nerve trunks were then filled anterogradely, using biotinamide in an artificial intracellular solution. Receptive fields were consistently associated with intraganglionic laminar endings (IGLEs) in myenteric ganglia, but not with other filled neuronal structures. The average distance of receptive fields to IGLEs was 73 +/- 14 microm (24 receptive fields, from 12 units; n = 5), compared to 374 +/- 17 microm for 240 randomly generated sites (n = 5; p < 0.001). After maintained probing on a single receptive field, spontaneous discharge of units was inhibited, as were responses to distension. During adapted discharge to maintained distension, interspike intervals were distributed in a narrow range. This indicates that multiple receptive fields interact to encode mechanical distortion in a graded manner. IGLEs are specialized transduction sites of mechanosensitive vagal afferent neurons in the guinea pig esophagus.
Collapse
Affiliation(s)
- V P Zagorodnyuk
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide, South Australia 5001
| | | |
Collapse
|
35
|
Zagorodnyuk VP, Hoyle CH, Burnstock G. An electrophysiological study of developmental changes in the innervation of the guinea-pig taenia coli. Pflugers Arch 1993; 423:427-33. [PMID: 8394567 DOI: 10.1007/bf00374937] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A sucrose-gap technique was used to study the development of neuromuscular transmission in the taenia coli of fetal, 1- to 2-day-old, 3- to 4-week-old and 3-month-old guinea-pigs. In addition, the effects of exogenous, alpha,beta-methylene adenosine 5'-triphosphate (ATP), noradrenaline, vasoactive intestinal polypeptide (VIP) and carbachol were examined. Taking the response to a single pulse of electrical field stimulation as the index of a developed neuromuscular junction, it was apparent that the non-adrenergic inhibitory system arose before, and matured more quickly than, the cholinergic system. The inhibitory system was present by 8 weeks of gestation in some fetuses, but, in contrast, excitatory cholinergic transmission was not seen until birth. As evidenced by responses to carbachol, alpha,beta-methylene ATP and VIP, cholinergic, purinergic and VIP receptors were present on the smooth muscle at the earliest ages studied. No changes in sensitivity to these agents were noted throughout development, although in adults the level of the maximum responses increased.
Collapse
Affiliation(s)
- V P Zagorodnyuk
- Department of Anatomy and Developmental Biology, University College London, UK
| | | | | |
Collapse
|
36
|
Zagorodnyuk VP, Vladimirova IA, Vovk EV, Shuba MF. Studies of the inhibitory non-adrenergic neuromuscular transmission in the smooth muscle of the normal human intestine and from a case of Hirschsprung's disease. J Auton Nerv Syst 1989; 26:51-60. [PMID: 2708784 DOI: 10.1016/0165-1838(89)90107-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A modified sucrose-gap method was used to study both non-adrenergic inhibitory neuromuscular transmission and effects of adenosine 5'-triphosphate (ATP) on isolated smooth muscle preparations from the human intestine. It was found that non-adrenergic inhibition in the circular smooth muscle layer was of larger amplitude than in the longitudinal layer. Study of the ionic mechanisms underlying non-adrenergic inhibition indicated that an increase in K+ conductance was responsible for the generation of non-adrenergic inhibitory junction potentials (IJPs). The results suggest that the inhibitory actions of the endogenous neurotransmitter and exogenous ATP are due to increases in Ca2+-dependent K+ conductance. The K+-channel blockers tetraethylammonium and 4-aminopyridine had no effect on IJPs or ATP, while apamin slightly decreased both the amplitude of the IJP and the hyperpolarization of the circular smooth muscle caused by ATP. These results are consistent with the purinergic hypothesis of non-adrenergic inhibition. In addition to inhibitory purinoceptors, the existence of excitatory purinoceptors was identified in the longitudinal muscle, activation of which probably caused an increase in Na+-conductance. The excitatory purinoceptor-mediated contraction in the longitudinal muscle from the constricted region of large intestine from patients with Hirschsprung's disease was greater than that found in control specimens. It is possible that excitatory purinoceptors play a role in the pathophysiology of Hirschsprung's disease.
Collapse
Affiliation(s)
- V P Zagorodnyuk
- A.A. Bogomoletz Institute of Physiology, Ukr. Academy of Sciences, Kiev, U.S.S.R
| | | | | | | |
Collapse
|