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Peiris M, Hockley JR, Reed DE, Smith ESJ, Bulmer DC, Blackshaw LA. Peripheral K V7 channels regulate visceral sensory function in mouse and human colon. Mol Pain 2018; 13:1744806917709371. [PMID: 28566000 PMCID: PMC5456027 DOI: 10.1177/1744806917709371] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Background Chronic visceral pain is a defining symptom of many gastrointestinal disorders. The KV7 family (KV7.1–KV7.5) of voltage-gated potassium channels mediates the M current that regulates excitability in peripheral sensory nociceptors and central pain pathways. Here, we use a combination of immunohistochemistry, gut-nerve electrophysiological recordings in both mouse and human tissues, and single-cell qualitative real-time polymerase chain reaction of gut-projecting sensory neurons, to investigate the contribution of peripheral KV7 channels to visceral nociception. Results Immunohistochemical staining of mouse colon revealed labelling of KV7 subtypes (KV7.3 and KV7.5) with CGRP around intrinsic enteric neurons of the myenteric plexuses and within extrinsic sensory fibres along mesenteric blood vessels. Treatment with the KV7 opener retigabine almost completely abolished visceral afferent firing evoked by the algogen bradykinin, in agreement with significant co-expression of mRNA transcripts by single-cell qualitative real-time polymerase chain reaction for KCNQ subtypes and the B2 bradykinin receptor in retrogradely labelled extrinsic sensory neurons from the colon. Retigabine also attenuated responses to mechanical stimulation of the bowel following noxious distension (0–80 mmHg) in a concentration-dependent manner, whereas the KV7 blocker XE991 potentiated such responses. In human bowel tissues, KV7.3 and KV7.5 were expressed in neuronal varicosities co-labelled with synaptophysin and CGRP, and retigabine inhibited bradykinin-induced afferent activation in afferent recordings from human colon. Conclusions We show that KV7 channels contribute to the sensitivity of visceral sensory neurons to noxious chemical and mechanical stimuli in both mouse and human gut tissues. As such, peripherally restricted KV7 openers may represent a viable therapeutic modality for the treatment of gastrointestinal pathologies.
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Affiliation(s)
- Madusha Peiris
- 1 Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - James Rf Hockley
- 2 Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - David E Reed
- 3 GI Diseases Research Unit, Queen's University, Kingston, ON, Canada
| | | | - David C Bulmer
- 1 Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - L Ashley Blackshaw
- 1 Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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KCNQ potassium channels in sensory system and neural circuits. Acta Pharmacol Sin 2016; 37:25-33. [PMID: 26687932 DOI: 10.1038/aps.2015.131] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 11/10/2015] [Indexed: 12/15/2022] Open
Abstract
M channels, an important regulator of neural excitability, are composed of four subunits of the Kv7 (KCNQ) K(+) channel family. M channels were named as such because their activity was suppressed by stimulation of muscarinic acetylcholine receptors. These channels are of particular interest because they are activated at the subthreshold membrane potentials. Furthermore, neural KCNQ channels are drug targets for the treatments of epilepsy and a variety of neurological disorders, including chronic and neuropathic pain, deafness, and mental illness. This review will update readers on the roles of KCNQ channels in the sensory system and neural circuits as well as discuss their respective mechanisms and the implications for physiology and medicine. We will also consider future perspectives and the development of additional pharmacological models, such as seizure, stroke, pain and mental illness, which work in combination with drug-design targeting of KCNQ channels. These models will hopefully deepen our understanding of KCNQ channels and provide general therapeutic prospects of related channelopathies.
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Schauwecker PE. The relevance of individual genetic background and its role in animal models of epilepsy. Epilepsy Res 2011; 97:1-11. [PMID: 22001434 DOI: 10.1016/j.eplepsyres.2011.09.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Revised: 09/07/2011] [Accepted: 09/09/2011] [Indexed: 02/09/2023]
Abstract
Growing evidence has indicated that genetic factors contribute to the etiology of seizure disorders. Most epilepsies are multifactorial, involving a combination of additive and epistatic genetic variables. However, the genetic factors underlying epilepsy have remained unclear, partially due to epilepsy being a clinically and genetically heterogeneous syndrome. Similar to the human situation, genetic background also plays an important role in modulating both seizure susceptibility and its neuropathological consequences in animal models of epilepsy, which has too often been ignored or not been paid enough attention to in published studies. Genetic homogeneity within inbred strains and their general amenability to genetic manipulation have made them an ideal resource for dissecting the physiological function(s) of individual genes. However, the inbreeding that makes inbred mice so useful also results in genetic divergence between them. This genetic divergence is often unaccounted for but may be a confounding factor when comparing studies that have utilized distinct inbred strains. The purpose of this review is to discuss the effects of genetic background strain on epilepsy phenotypes of mice, to remind researchers that the background genetics of a knockout strain can have a profound influence on any observed phenotype, and outline the means by which to overcome potential genetic background effects in experimental models of epilepsy.
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Affiliation(s)
- P Elyse Schauwecker
- Department of Cell and Neurobiology, USC Keck School of Medicine, 1333 San Pablo Street, BMT 403, Los Angeles, CA 90089-9112, United States.
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Seizures and impairment of consciousness. HANDBOOK OF CLINICAL NEUROLOGY 2008. [PMID: 18631826 DOI: 10.1016/s0072-9752(07)01713-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Pinto D, Westland B, de Haan GJ, Rudolf G, da Silva BM, Hirsch E, Lindhout D, Trenité DGAKN, Koeleman BPC. Genome-wide linkage scan of epilepsy-related photoparoxysmal electroencephalographic response: evidence for linkage on chromosomes 7q32 and 16p13. Hum Mol Genet 2004; 14:171-8. [PMID: 15548544 DOI: 10.1093/hmg/ddi018] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Photoparoxysmal response (PPR) is an abnormal visual sensitivity of the brain in reaction to intermittent photic stimulation. It is an epilepsy-related electroencephalographic trait with high prevalence in idiopathic epilepsies, especially in common idiopathic generalized epilepsies (IGEs), such as childhood absence epilepsy and juvenile myoclonic epilepsy. This degree of co-morbidity suggests that PPR may be involved in the predisposition to IGE. The identification of genes for PPR would, therefore, aid the dissection of the genetic basis of IGE. Sixteen PPR-multiplex families were collected to conduct a genome-wide linkage scan using broad (all PPR types) and narrow (exclusion of PPR types I and II and the occipital epilepsy cases) models of affectedness for PPR. We found an empirical genome-wide significance for parametric (HLOD) and non-parametric (NPL) linkage (Pgw(HLOD)=0.004 and Pgw(NPL)=0.01) for two respective chromosomal regions, 7q32 at D7S1804 (HLOD=3.47 with alpha=1, P(NPL)=3.39x10(-5)) and 16p13 at D16S3395 (HLOD=2.44 with alpha=1, P(NPL)=7.91x10(-5)). These two genomic regions contain genes that are important for the neuromodulation of cortical dynamics and may represent good targets for candidate-gene studies. Our study identified two susceptibility loci for PPR, which may be related to the underlying myoclonic epilepsy phenotype present in the families studied.
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Affiliation(s)
- Dalila Pinto
- Complex Genetics Section, DBG-Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
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Buchhalter JR. EPILEPSY. Continuum (Minneap Minn) 2004. [DOI: 10.1212/01.con.0000293590.79518.31] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Anderson E, Berkovic S, Dulac O, Gardiner M, Jain S, Laue Friis M, Lindhout D, Noebels J, Ottman R, Scaramelli A, Serratosa J, Steinlein O, Avanzini G, Bailey-Wilson J, Cardon L, Fischbach R, Gwinn-Hardy K, Leppert M, Ott J, Lindblad-Toh K, Weiss K, Laue-Friis M. ILAE genetics commission conference report: molecular analysis of complex genetic epilepsies. Epilepsia 2002; 43:1262-7. [PMID: 12366744 DOI: 10.1046/j.1528-1157.2002.29502.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- E Anderson
- Noebels at Baylor College of Medicine, Department of Neurology, Houston, TX 77030, USA
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Schauwecker PE. Complications associated with genetic background effects in models of experimental epilepsy. PROGRESS IN BRAIN RESEARCH 2002; 135:139-48. [PMID: 12143336 DOI: 10.1016/s0079-6123(02)35014-3] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
To elucidate the genetic influences contributing to susceptibility to seizure disorders, researchers have long used selected lines and inbred strains of rodents. In recent years, the use of genetically altered mice as models of complex human disease has revolutionized biomedical research into the genetics of disease pathogenesis and potential therapeutic interventions. In particular, the study of transgenic and gene-deleted (knockout) mice can provide important insights into the in vivo function and interaction of specific gene products. While a variety of inbred mouse mutations have been used to directly evaluate the genetic basis of seizure disorders, data obtained from such genetically altered mice must be interpreted carefully. An increasing number of scientific articles have reported that the phenotype of a given single gene mutation in mice can be modulated by the genetic background of the inbred strain in which the mutation is maintained. This effect is attributable to so-called modifier genes, which act in combination with the causative gene. In this review, the author points out the importance of considering the genetic background of the strain used to create these animal models, the potential problems with interpretation of phenotype, and solutions to selecting an appropriate mouse model of experimental epilepsy. Despite these potential limitations, knockout mice provide a powerful tool for understanding the genetic and neurobiological mechanisms contributing to experimental epilepsy.
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Affiliation(s)
- P Elyse Schauwecker
- Department of Cell and Neurobiology, University of Southern California, Keck School of Medicine, BMT 401, 1333 San Pablo Street, Los Angeles, CA 90089-9112, USA.
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Kurtz BS, Lehman J, Garlick P, Amberg J, Mishra PK, Dailey JW, Weber R, Jobe PC. Penetrance and expressivity of genes involved in the development of epilepsy in the genetically epilepsy-prone rat (GEPR). J Neurogenet 2002; 15:233-44. [PMID: 12092906 DOI: 10.3109/01677060109167379] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
In order to understand the level of complexity of the epileptic phenotype in the two strains of Genetically Epilepsy-Prone Rats (GEPRs), we determined two important measures of genetic complexity, penetrance and expressivity. Penetrance is the percentage of animals of a specific genotype who express the phenotype associated with that underlying genotype. Expressivity refers to the degree that a particular genotype is expressed as a phenotype within an individual. Incomplete penetrance and variable expressivity are caused by genetic and environmental variation. In this paper we have studied the epileptic phenotype for 20,373 rats. Animals were tested on three occasions for audiogenic seizure and given an audiogenic response score (on a scale of 0-9, 0 being no seizure and 9 being the most severe). The GEPR-3 and GEPR-9 animals both show incomplete penetrance and variable expressivity of the underlying genetic predisposition. The GEPR-9 strain has more animals that have variable levels of seizure predisposition (as measured by a scoring system that denotes the severity of generalized tonic/clonic seizures) and a greater percentage of animals that exhibit no susceptibility to such seizures induced by sound. Both strains have a number of animals that are not susceptible to sound-induced GTCSs and that exhibit some variability in seizure severity. The GEPR-9 males show greater differences in expressivity and penetrance compared to GEPR-9 females. The GEPR-3 animals also show sex-associated variable penetrance and expressivity of the epileptic phenotype, although the differences are much smaller. These findings are the first step toward the mapping of the underlying quantitative trait loci (QTL) for seizure in these animals.
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Affiliation(s)
- B S Kurtz
- Biology Department, Bradley University, Peoria, IL 61625, USA.
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Affiliation(s)
- B S Meldrum
- GKT School of Biomedical Sciences, Henriette Raphael House, Guy's Campus, London, UK.
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Abstract
Humans have over 70 potassium channel genes, but only some of these have been linked to disease. In this respect, the KCNQ family of potassium channels is exceptional: mutations in four out of five KCNQ genes underlie diseases including cardiac arrhythmias, deafness and epilepsy. These disorders illustrate the different physiological functions of KCNQ channels, and provide a model for the study of the 'safety margin' that separates normal from pathological levels of channel expression. In addition, several KCNQ isoforms can associate to form heteromeric channels that underlie the M-current, an important regulator of neuronal excitability.
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Affiliation(s)
- T J Jentsch
- Zentrum für Molekulare Neurobiologie Hamburg, ZMNH, Hamburg University, Martinistrasse 85, D-20246 Hamburg, Germany.
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