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Brian M Davis - One of the best experts on this subject based on the ideXlab platform.
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optogenetic activation of the distal Colon epithelium engages enteric nervous system circuits to initiate Motility patterns
American Journal of Physiology-gastrointestinal and Liver Physiology, 2021Co-Authors: Sarah A Najjar, Brian S Edwards, Kathryn M Albers, Brian M Davis, Kristen M SmithedwardsAbstract:Digestive functions of the Colon depend on sensory-motor reflexes in the enteric nervous system (ENS), initiated by intrinsic primary afferent neurons (IPANs). IPAN terminals project to the mucosal layer of the Colon, allowing communication with epithelial cells comprising the Colon lining. The chemical nature and functional significance of this epithelial-neural communication in regard to secretion and Colon Motility are of high interest. Colon epithelial cells can produce and release neuroactive substances such as ATP and 5-hydroxytryptamine (5-HT), which can activate receptors on adjacent nerve fibers, including IPAN subtypes. In this study, we examined if stimulation of epithelial cells alone is sufficient to activate neural circuits that control Colon Motility. Optogenetics and calcium imaging were used in ex vivo preparations of the mouse Colon to selectively stimulate the Colon epithelium, measure changes in Motility, and record activity of neurons within the myenteric plexus. Light-mediated activation of epithelial cells lining the distal, but not proximal, Colon caused local contractions and increased the rate of Colonic migrating motor complexes. Epithelial-evoked local contractions in the distal Colon were reduced by both ATP and 5-HT receptor antagonists. Our findings indicate that Colon epithelial cells likely use purinergic and serotonergic signaling to initiate activity in myenteric neurons, produce local contractions, and facilitate large-scale coordination of ENS activity responsible for whole Colon Motility patterns.NEW & NOTEWORTHY Using an all-optical approach to measure real-time cell-to-cell communication responsible for Colon functions, we show that selective optogenetic stimulation of distal Colon epithelium produced activity in myenteric neurons, as measured with red genetically encoded calcium indicators. The epithelial-induced neural response led to local contractions, mediated by both purinergic and serotonergic signaling, and facilitated Colonic motor complexes that propagate from proximal to distal Colon.
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extrinsic primary afferent neurons link visceral pain to Colon Motility through a spinal reflex in mice
Gastroenterology, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Marthe J Howard, Kathryn M Albers, Brian M DavisAbstract:Background & Aims Proper Colon function requires signals from extrinsic primary afferent neurons (ExPANs) located in spinal ganglia. Most ExPANs express the vanilloid receptor TRPV1, and a dense plexus of TRPV1-positive fibers is found around myenteric neurons. Capsaicin, a TRPV1 agonist, can initiate activity in myenteric neurons and produce muscle contraction. ExPANs might therefore form Motility-regulating synapses onto myenteric neurons. ExPANs mediate visceral pain, and myenteric neurons mediate Colon Motility, so we investigated communication between ExPANs and myenteric neurons and the circuits by which ExPANs modulate Colon function. Methods In live mice and Colon tissues that express a transgene encoding the calcium indicator GCaMP, we visualized levels of activity in myenteric neurons during smooth muscle contractions induced by application of capsaicin, direct Colon stimulation, stimulation of ExPANs, or stimulation of preganglionic parasympathetic neuron (PPN) axons. To localize central targets of ExPANs, we optogenetically activated TRPV1-expressing ExPANs in live mice and then quantified Fos immunoreactivity to identify activated spinal neurons. Results Focal electrical stimulation of mouse Colon produced phased-locked calcium signals in myenteric neurons and produced Colon contractions. Stimulation of the L6 ventral root, which contains PPN axons, also produced myenteric activation and contractions that were comparable to those of direct Colon stimulation. Surprisingly, capsaicin application to the isolated L6 dorsal root ganglia, which produced robust calcium signals in neurons throughout the ganglion, did not activate myenteric neurons. Electrical activation of the ganglia, which activated even more neurons than capsaicin, did not produce myenteric activation or contractions unless the spinal cord was intact, indicating that a complete afferent-to-efferent (PPN) circuit was necessary for ExPANs to regulate myenteric neurons. In TRPV1-channel rhodopsin-2 mice, light activation of ExPANs induced a pain-like visceromotor response and expression of Fos in spinal PPN neurons. Conclusions In mice, ExPANs regulate myenteric neuron activity and smooth muscle contraction via a parasympathetic spinal circuit, linking sensation and pain to Motility.
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extrinsic primary afferent neurons link visceral pain to Colon Motility through a spinal reflex in mice
Gastroenterology, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Marthe J Howard, Kathryn M Albers, Brian M DavisAbstract:Background & Aims Proper Colon function requires signals from extrinsic primary afferent neurons (ExPANs) located in spinal ganglia. Most ExPANs express the vanilloid receptor TRPV1, and a dense plexus of TRPV1-positive fibers is found around myenteric neurons. Capsaicin, a TRPV1 agonist, can initiate activity in myenteric neurons and produce muscle contraction. ExPANs might therefore form Motility-regulating synapses onto myenteric neurons. ExPANs mediate visceral pain, and myenteric neurons mediate Colon Motility, so we investigated communication between ExPANs and myenteric neurons and the circuits by which ExPANs modulate Colon function. Methods In live mice and Colon tissues that express a transgene encoding the calcium indicator GCaMP, we visualized levels of activity in myenteric neurons during smooth muscle contractions induced by application of capsaicin, direct Colon stimulation, stimulation of ExPANs, or stimulation of preganglionic parasympathetic neuron (PPN) axons. To localize central targets of ExPANs, we optogenetically activated TRPV1-expressing ExPANs in live mice and then quantified Fos immunoreactivity to identify activated spinal neurons. Results Focal electrical stimulation of mouse Colon produced phased-locked calcium signals in myenteric neurons and produced Colon contractions. Stimulation of the L6 ventral root, which contains PPN axons, also produced myenteric activation and contractions that were comparable to those of direct Colon stimulation. Surprisingly, capsaicin application to the isolated L6 dorsal root ganglia, which produced robust calcium signals in neurons throughout the ganglion, did not activate myenteric neurons. Electrical activation of the ganglia, which activated even more neurons than capsaicin, did not produce myenteric activation or contractions unless the spinal cord was intact, indicating that a complete afferent-to-efferent (PPN) circuit was necessary for ExPANs to regulate myenteric neurons. In TRPV1-channel rhodopsin-2 mice, light activation of ExPANs induced a pain-like visceromotor response and expression of Fos in spinal PPN neurons. Conclusions In mice, ExPANs regulate myenteric neuron activity and smooth muscle contraction via a parasympathetic spinal circuit, linking sensation and pain to Motility.
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225 extrinsic Colon afferents influence enteric neuron activity and Colon Motility by engaging spinal reflexes
The Journal of Pain, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Kathryn M Albers, Brian M DavisAbstract:Abdominal pain and bowel dysMotility are hallmark symptoms of functional bowel disorders, yet it is unclear how pain and dysMotility are correlated mechanistically. Extrinsic Colon afferents (EPANs) provide sensory input to the CNS, and visceral pain is thought to be due to hypersensitivity of these afferents. The enteric nervous system (ENS) acts autonomously to control Motility reflexes, but extrinsic nerve pathways coordinate activity between distant regions of the GI tract, and importantly, allow the central nervous system (CNS) to regulate GI functioning. To test whether EPANs can directly influence ENS activity, we used an ex vivo Colon-pelvic nerve-L6 DRG preparation, in which the roots were cut from the spinal cord, that allowed selective activation of EPANs via dorsal root stimulation and simultaneous calcium imaging (GCaMP6s) of myenteric neurons in the Colon. Electrical stimulation of the dorsal root activated the majority of L6 DRG neurons, but produced no GCaMP responses in myenteric neurons of the Colon in any of the visual fields tested (n=8). By contrast, ventral root stimulation led to GCaMP responses in ∼20% of myenteric neurons, followed by smooth muscle contraction, as indicated by movement of the imaging field. Interestingly, when the spinal cord was left intact, dorsal root stimulation produced responses in 12% of myenteric neurons (n=5), suggesting the presence of a sensory-parasympathetic spinal reflex. To elucidate this reflex in vivo, we used optogenetic stimulation to produce visceromotor responses and then processed spinal cord tissue for the immediate early gene, c-fos. There were significantly greater numbers of parasympathetic preganglionic neurons (PPNs) with c-fos staining in lumbosacral spinal segments from TRPV1-ChR2 mice (n=3) compared to controls (n=3), and TRPV1 central terminals were observed in close apposition to PPN. Overall, our data suggests that Colon afferents influence ENS activity and Colon Motility by engaging parasympathetic pathways through a spinal reflex.
Kristen M Smithedwards - One of the best experts on this subject based on the ideXlab platform.
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optogenetic activation of the distal Colon epithelium engages enteric nervous system circuits to initiate Motility patterns
American Journal of Physiology-gastrointestinal and Liver Physiology, 2021Co-Authors: Sarah A Najjar, Brian S Edwards, Kathryn M Albers, Brian M Davis, Kristen M SmithedwardsAbstract:Digestive functions of the Colon depend on sensory-motor reflexes in the enteric nervous system (ENS), initiated by intrinsic primary afferent neurons (IPANs). IPAN terminals project to the mucosal layer of the Colon, allowing communication with epithelial cells comprising the Colon lining. The chemical nature and functional significance of this epithelial-neural communication in regard to secretion and Colon Motility are of high interest. Colon epithelial cells can produce and release neuroactive substances such as ATP and 5-hydroxytryptamine (5-HT), which can activate receptors on adjacent nerve fibers, including IPAN subtypes. In this study, we examined if stimulation of epithelial cells alone is sufficient to activate neural circuits that control Colon Motility. Optogenetics and calcium imaging were used in ex vivo preparations of the mouse Colon to selectively stimulate the Colon epithelium, measure changes in Motility, and record activity of neurons within the myenteric plexus. Light-mediated activation of epithelial cells lining the distal, but not proximal, Colon caused local contractions and increased the rate of Colonic migrating motor complexes. Epithelial-evoked local contractions in the distal Colon were reduced by both ATP and 5-HT receptor antagonists. Our findings indicate that Colon epithelial cells likely use purinergic and serotonergic signaling to initiate activity in myenteric neurons, produce local contractions, and facilitate large-scale coordination of ENS activity responsible for whole Colon Motility patterns.NEW & NOTEWORTHY Using an all-optical approach to measure real-time cell-to-cell communication responsible for Colon functions, we show that selective optogenetic stimulation of distal Colon epithelium produced activity in myenteric neurons, as measured with red genetically encoded calcium indicators. The epithelial-induced neural response led to local contractions, mediated by both purinergic and serotonergic signaling, and facilitated Colonic motor complexes that propagate from proximal to distal Colon.
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extrinsic primary afferent neurons link visceral pain to Colon Motility through a spinal reflex in mice
Gastroenterology, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Marthe J Howard, Kathryn M Albers, Brian M DavisAbstract:Background & Aims Proper Colon function requires signals from extrinsic primary afferent neurons (ExPANs) located in spinal ganglia. Most ExPANs express the vanilloid receptor TRPV1, and a dense plexus of TRPV1-positive fibers is found around myenteric neurons. Capsaicin, a TRPV1 agonist, can initiate activity in myenteric neurons and produce muscle contraction. ExPANs might therefore form Motility-regulating synapses onto myenteric neurons. ExPANs mediate visceral pain, and myenteric neurons mediate Colon Motility, so we investigated communication between ExPANs and myenteric neurons and the circuits by which ExPANs modulate Colon function. Methods In live mice and Colon tissues that express a transgene encoding the calcium indicator GCaMP, we visualized levels of activity in myenteric neurons during smooth muscle contractions induced by application of capsaicin, direct Colon stimulation, stimulation of ExPANs, or stimulation of preganglionic parasympathetic neuron (PPN) axons. To localize central targets of ExPANs, we optogenetically activated TRPV1-expressing ExPANs in live mice and then quantified Fos immunoreactivity to identify activated spinal neurons. Results Focal electrical stimulation of mouse Colon produced phased-locked calcium signals in myenteric neurons and produced Colon contractions. Stimulation of the L6 ventral root, which contains PPN axons, also produced myenteric activation and contractions that were comparable to those of direct Colon stimulation. Surprisingly, capsaicin application to the isolated L6 dorsal root ganglia, which produced robust calcium signals in neurons throughout the ganglion, did not activate myenteric neurons. Electrical activation of the ganglia, which activated even more neurons than capsaicin, did not produce myenteric activation or contractions unless the spinal cord was intact, indicating that a complete afferent-to-efferent (PPN) circuit was necessary for ExPANs to regulate myenteric neurons. In TRPV1-channel rhodopsin-2 mice, light activation of ExPANs induced a pain-like visceromotor response and expression of Fos in spinal PPN neurons. Conclusions In mice, ExPANs regulate myenteric neuron activity and smooth muscle contraction via a parasympathetic spinal circuit, linking sensation and pain to Motility.
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extrinsic primary afferent neurons link visceral pain to Colon Motility through a spinal reflex in mice
Gastroenterology, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Marthe J Howard, Kathryn M Albers, Brian M DavisAbstract:Background & Aims Proper Colon function requires signals from extrinsic primary afferent neurons (ExPANs) located in spinal ganglia. Most ExPANs express the vanilloid receptor TRPV1, and a dense plexus of TRPV1-positive fibers is found around myenteric neurons. Capsaicin, a TRPV1 agonist, can initiate activity in myenteric neurons and produce muscle contraction. ExPANs might therefore form Motility-regulating synapses onto myenteric neurons. ExPANs mediate visceral pain, and myenteric neurons mediate Colon Motility, so we investigated communication between ExPANs and myenteric neurons and the circuits by which ExPANs modulate Colon function. Methods In live mice and Colon tissues that express a transgene encoding the calcium indicator GCaMP, we visualized levels of activity in myenteric neurons during smooth muscle contractions induced by application of capsaicin, direct Colon stimulation, stimulation of ExPANs, or stimulation of preganglionic parasympathetic neuron (PPN) axons. To localize central targets of ExPANs, we optogenetically activated TRPV1-expressing ExPANs in live mice and then quantified Fos immunoreactivity to identify activated spinal neurons. Results Focal electrical stimulation of mouse Colon produced phased-locked calcium signals in myenteric neurons and produced Colon contractions. Stimulation of the L6 ventral root, which contains PPN axons, also produced myenteric activation and contractions that were comparable to those of direct Colon stimulation. Surprisingly, capsaicin application to the isolated L6 dorsal root ganglia, which produced robust calcium signals in neurons throughout the ganglion, did not activate myenteric neurons. Electrical activation of the ganglia, which activated even more neurons than capsaicin, did not produce myenteric activation or contractions unless the spinal cord was intact, indicating that a complete afferent-to-efferent (PPN) circuit was necessary for ExPANs to regulate myenteric neurons. In TRPV1-channel rhodopsin-2 mice, light activation of ExPANs induced a pain-like visceromotor response and expression of Fos in spinal PPN neurons. Conclusions In mice, ExPANs regulate myenteric neuron activity and smooth muscle contraction via a parasympathetic spinal circuit, linking sensation and pain to Motility.
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225 extrinsic Colon afferents influence enteric neuron activity and Colon Motility by engaging spinal reflexes
The Journal of Pain, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Kathryn M Albers, Brian M DavisAbstract:Abdominal pain and bowel dysMotility are hallmark symptoms of functional bowel disorders, yet it is unclear how pain and dysMotility are correlated mechanistically. Extrinsic Colon afferents (EPANs) provide sensory input to the CNS, and visceral pain is thought to be due to hypersensitivity of these afferents. The enteric nervous system (ENS) acts autonomously to control Motility reflexes, but extrinsic nerve pathways coordinate activity between distant regions of the GI tract, and importantly, allow the central nervous system (CNS) to regulate GI functioning. To test whether EPANs can directly influence ENS activity, we used an ex vivo Colon-pelvic nerve-L6 DRG preparation, in which the roots were cut from the spinal cord, that allowed selective activation of EPANs via dorsal root stimulation and simultaneous calcium imaging (GCaMP6s) of myenteric neurons in the Colon. Electrical stimulation of the dorsal root activated the majority of L6 DRG neurons, but produced no GCaMP responses in myenteric neurons of the Colon in any of the visual fields tested (n=8). By contrast, ventral root stimulation led to GCaMP responses in ∼20% of myenteric neurons, followed by smooth muscle contraction, as indicated by movement of the imaging field. Interestingly, when the spinal cord was left intact, dorsal root stimulation produced responses in 12% of myenteric neurons (n=5), suggesting the presence of a sensory-parasympathetic spinal reflex. To elucidate this reflex in vivo, we used optogenetic stimulation to produce visceromotor responses and then processed spinal cord tissue for the immediate early gene, c-fos. There were significantly greater numbers of parasympathetic preganglionic neurons (PPNs) with c-fos staining in lumbosacral spinal segments from TRPV1-ChR2 mice (n=3) compared to controls (n=3), and TRPV1 central terminals were observed in close apposition to PPN. Overall, our data suggests that Colon afferents influence ENS activity and Colon Motility by engaging parasympathetic pathways through a spinal reflex.
Sarah A Najjar - One of the best experts on this subject based on the ideXlab platform.
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optogenetic activation of the distal Colon epithelium engages enteric nervous system circuits to initiate Motility patterns
American Journal of Physiology-gastrointestinal and Liver Physiology, 2021Co-Authors: Sarah A Najjar, Brian S Edwards, Kathryn M Albers, Brian M Davis, Kristen M SmithedwardsAbstract:Digestive functions of the Colon depend on sensory-motor reflexes in the enteric nervous system (ENS), initiated by intrinsic primary afferent neurons (IPANs). IPAN terminals project to the mucosal layer of the Colon, allowing communication with epithelial cells comprising the Colon lining. The chemical nature and functional significance of this epithelial-neural communication in regard to secretion and Colon Motility are of high interest. Colon epithelial cells can produce and release neuroactive substances such as ATP and 5-hydroxytryptamine (5-HT), which can activate receptors on adjacent nerve fibers, including IPAN subtypes. In this study, we examined if stimulation of epithelial cells alone is sufficient to activate neural circuits that control Colon Motility. Optogenetics and calcium imaging were used in ex vivo preparations of the mouse Colon to selectively stimulate the Colon epithelium, measure changes in Motility, and record activity of neurons within the myenteric plexus. Light-mediated activation of epithelial cells lining the distal, but not proximal, Colon caused local contractions and increased the rate of Colonic migrating motor complexes. Epithelial-evoked local contractions in the distal Colon were reduced by both ATP and 5-HT receptor antagonists. Our findings indicate that Colon epithelial cells likely use purinergic and serotonergic signaling to initiate activity in myenteric neurons, produce local contractions, and facilitate large-scale coordination of ENS activity responsible for whole Colon Motility patterns.NEW & NOTEWORTHY Using an all-optical approach to measure real-time cell-to-cell communication responsible for Colon functions, we show that selective optogenetic stimulation of distal Colon epithelium produced activity in myenteric neurons, as measured with red genetically encoded calcium indicators. The epithelial-induced neural response led to local contractions, mediated by both purinergic and serotonergic signaling, and facilitated Colonic motor complexes that propagate from proximal to distal Colon.
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extrinsic primary afferent neurons link visceral pain to Colon Motility through a spinal reflex in mice
Gastroenterology, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Marthe J Howard, Kathryn M Albers, Brian M DavisAbstract:Background & Aims Proper Colon function requires signals from extrinsic primary afferent neurons (ExPANs) located in spinal ganglia. Most ExPANs express the vanilloid receptor TRPV1, and a dense plexus of TRPV1-positive fibers is found around myenteric neurons. Capsaicin, a TRPV1 agonist, can initiate activity in myenteric neurons and produce muscle contraction. ExPANs might therefore form Motility-regulating synapses onto myenteric neurons. ExPANs mediate visceral pain, and myenteric neurons mediate Colon Motility, so we investigated communication between ExPANs and myenteric neurons and the circuits by which ExPANs modulate Colon function. Methods In live mice and Colon tissues that express a transgene encoding the calcium indicator GCaMP, we visualized levels of activity in myenteric neurons during smooth muscle contractions induced by application of capsaicin, direct Colon stimulation, stimulation of ExPANs, or stimulation of preganglionic parasympathetic neuron (PPN) axons. To localize central targets of ExPANs, we optogenetically activated TRPV1-expressing ExPANs in live mice and then quantified Fos immunoreactivity to identify activated spinal neurons. Results Focal electrical stimulation of mouse Colon produced phased-locked calcium signals in myenteric neurons and produced Colon contractions. Stimulation of the L6 ventral root, which contains PPN axons, also produced myenteric activation and contractions that were comparable to those of direct Colon stimulation. Surprisingly, capsaicin application to the isolated L6 dorsal root ganglia, which produced robust calcium signals in neurons throughout the ganglion, did not activate myenteric neurons. Electrical activation of the ganglia, which activated even more neurons than capsaicin, did not produce myenteric activation or contractions unless the spinal cord was intact, indicating that a complete afferent-to-efferent (PPN) circuit was necessary for ExPANs to regulate myenteric neurons. In TRPV1-channel rhodopsin-2 mice, light activation of ExPANs induced a pain-like visceromotor response and expression of Fos in spinal PPN neurons. Conclusions In mice, ExPANs regulate myenteric neuron activity and smooth muscle contraction via a parasympathetic spinal circuit, linking sensation and pain to Motility.
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extrinsic primary afferent neurons link visceral pain to Colon Motility through a spinal reflex in mice
Gastroenterology, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Marthe J Howard, Kathryn M Albers, Brian M DavisAbstract:Background & Aims Proper Colon function requires signals from extrinsic primary afferent neurons (ExPANs) located in spinal ganglia. Most ExPANs express the vanilloid receptor TRPV1, and a dense plexus of TRPV1-positive fibers is found around myenteric neurons. Capsaicin, a TRPV1 agonist, can initiate activity in myenteric neurons and produce muscle contraction. ExPANs might therefore form Motility-regulating synapses onto myenteric neurons. ExPANs mediate visceral pain, and myenteric neurons mediate Colon Motility, so we investigated communication between ExPANs and myenteric neurons and the circuits by which ExPANs modulate Colon function. Methods In live mice and Colon tissues that express a transgene encoding the calcium indicator GCaMP, we visualized levels of activity in myenteric neurons during smooth muscle contractions induced by application of capsaicin, direct Colon stimulation, stimulation of ExPANs, or stimulation of preganglionic parasympathetic neuron (PPN) axons. To localize central targets of ExPANs, we optogenetically activated TRPV1-expressing ExPANs in live mice and then quantified Fos immunoreactivity to identify activated spinal neurons. Results Focal electrical stimulation of mouse Colon produced phased-locked calcium signals in myenteric neurons and produced Colon contractions. Stimulation of the L6 ventral root, which contains PPN axons, also produced myenteric activation and contractions that were comparable to those of direct Colon stimulation. Surprisingly, capsaicin application to the isolated L6 dorsal root ganglia, which produced robust calcium signals in neurons throughout the ganglion, did not activate myenteric neurons. Electrical activation of the ganglia, which activated even more neurons than capsaicin, did not produce myenteric activation or contractions unless the spinal cord was intact, indicating that a complete afferent-to-efferent (PPN) circuit was necessary for ExPANs to regulate myenteric neurons. In TRPV1-channel rhodopsin-2 mice, light activation of ExPANs induced a pain-like visceromotor response and expression of Fos in spinal PPN neurons. Conclusions In mice, ExPANs regulate myenteric neuron activity and smooth muscle contraction via a parasympathetic spinal circuit, linking sensation and pain to Motility.
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225 extrinsic Colon afferents influence enteric neuron activity and Colon Motility by engaging spinal reflexes
The Journal of Pain, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Kathryn M Albers, Brian M DavisAbstract:Abdominal pain and bowel dysMotility are hallmark symptoms of functional bowel disorders, yet it is unclear how pain and dysMotility are correlated mechanistically. Extrinsic Colon afferents (EPANs) provide sensory input to the CNS, and visceral pain is thought to be due to hypersensitivity of these afferents. The enteric nervous system (ENS) acts autonomously to control Motility reflexes, but extrinsic nerve pathways coordinate activity between distant regions of the GI tract, and importantly, allow the central nervous system (CNS) to regulate GI functioning. To test whether EPANs can directly influence ENS activity, we used an ex vivo Colon-pelvic nerve-L6 DRG preparation, in which the roots were cut from the spinal cord, that allowed selective activation of EPANs via dorsal root stimulation and simultaneous calcium imaging (GCaMP6s) of myenteric neurons in the Colon. Electrical stimulation of the dorsal root activated the majority of L6 DRG neurons, but produced no GCaMP responses in myenteric neurons of the Colon in any of the visual fields tested (n=8). By contrast, ventral root stimulation led to GCaMP responses in ∼20% of myenteric neurons, followed by smooth muscle contraction, as indicated by movement of the imaging field. Interestingly, when the spinal cord was left intact, dorsal root stimulation produced responses in 12% of myenteric neurons (n=5), suggesting the presence of a sensory-parasympathetic spinal reflex. To elucidate this reflex in vivo, we used optogenetic stimulation to produce visceromotor responses and then processed spinal cord tissue for the immediate early gene, c-fos. There were significantly greater numbers of parasympathetic preganglionic neurons (PPNs) with c-fos staining in lumbosacral spinal segments from TRPV1-ChR2 mice (n=3) compared to controls (n=3), and TRPV1 central terminals were observed in close apposition to PPN. Overall, our data suggests that Colon afferents influence ENS activity and Colon Motility by engaging parasympathetic pathways through a spinal reflex.
Brian S Edwards - One of the best experts on this subject based on the ideXlab platform.
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optogenetic activation of the distal Colon epithelium engages enteric nervous system circuits to initiate Motility patterns
American Journal of Physiology-gastrointestinal and Liver Physiology, 2021Co-Authors: Sarah A Najjar, Brian S Edwards, Kathryn M Albers, Brian M Davis, Kristen M SmithedwardsAbstract:Digestive functions of the Colon depend on sensory-motor reflexes in the enteric nervous system (ENS), initiated by intrinsic primary afferent neurons (IPANs). IPAN terminals project to the mucosal layer of the Colon, allowing communication with epithelial cells comprising the Colon lining. The chemical nature and functional significance of this epithelial-neural communication in regard to secretion and Colon Motility are of high interest. Colon epithelial cells can produce and release neuroactive substances such as ATP and 5-hydroxytryptamine (5-HT), which can activate receptors on adjacent nerve fibers, including IPAN subtypes. In this study, we examined if stimulation of epithelial cells alone is sufficient to activate neural circuits that control Colon Motility. Optogenetics and calcium imaging were used in ex vivo preparations of the mouse Colon to selectively stimulate the Colon epithelium, measure changes in Motility, and record activity of neurons within the myenteric plexus. Light-mediated activation of epithelial cells lining the distal, but not proximal, Colon caused local contractions and increased the rate of Colonic migrating motor complexes. Epithelial-evoked local contractions in the distal Colon were reduced by both ATP and 5-HT receptor antagonists. Our findings indicate that Colon epithelial cells likely use purinergic and serotonergic signaling to initiate activity in myenteric neurons, produce local contractions, and facilitate large-scale coordination of ENS activity responsible for whole Colon Motility patterns.NEW & NOTEWORTHY Using an all-optical approach to measure real-time cell-to-cell communication responsible for Colon functions, we show that selective optogenetic stimulation of distal Colon epithelium produced activity in myenteric neurons, as measured with red genetically encoded calcium indicators. The epithelial-induced neural response led to local contractions, mediated by both purinergic and serotonergic signaling, and facilitated Colonic motor complexes that propagate from proximal to distal Colon.
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extrinsic primary afferent neurons link visceral pain to Colon Motility through a spinal reflex in mice
Gastroenterology, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Marthe J Howard, Kathryn M Albers, Brian M DavisAbstract:Background & Aims Proper Colon function requires signals from extrinsic primary afferent neurons (ExPANs) located in spinal ganglia. Most ExPANs express the vanilloid receptor TRPV1, and a dense plexus of TRPV1-positive fibers is found around myenteric neurons. Capsaicin, a TRPV1 agonist, can initiate activity in myenteric neurons and produce muscle contraction. ExPANs might therefore form Motility-regulating synapses onto myenteric neurons. ExPANs mediate visceral pain, and myenteric neurons mediate Colon Motility, so we investigated communication between ExPANs and myenteric neurons and the circuits by which ExPANs modulate Colon function. Methods In live mice and Colon tissues that express a transgene encoding the calcium indicator GCaMP, we visualized levels of activity in myenteric neurons during smooth muscle contractions induced by application of capsaicin, direct Colon stimulation, stimulation of ExPANs, or stimulation of preganglionic parasympathetic neuron (PPN) axons. To localize central targets of ExPANs, we optogenetically activated TRPV1-expressing ExPANs in live mice and then quantified Fos immunoreactivity to identify activated spinal neurons. Results Focal electrical stimulation of mouse Colon produced phased-locked calcium signals in myenteric neurons and produced Colon contractions. Stimulation of the L6 ventral root, which contains PPN axons, also produced myenteric activation and contractions that were comparable to those of direct Colon stimulation. Surprisingly, capsaicin application to the isolated L6 dorsal root ganglia, which produced robust calcium signals in neurons throughout the ganglion, did not activate myenteric neurons. Electrical activation of the ganglia, which activated even more neurons than capsaicin, did not produce myenteric activation or contractions unless the spinal cord was intact, indicating that a complete afferent-to-efferent (PPN) circuit was necessary for ExPANs to regulate myenteric neurons. In TRPV1-channel rhodopsin-2 mice, light activation of ExPANs induced a pain-like visceromotor response and expression of Fos in spinal PPN neurons. Conclusions In mice, ExPANs regulate myenteric neuron activity and smooth muscle contraction via a parasympathetic spinal circuit, linking sensation and pain to Motility.
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extrinsic primary afferent neurons link visceral pain to Colon Motility through a spinal reflex in mice
Gastroenterology, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Marthe J Howard, Kathryn M Albers, Brian M DavisAbstract:Background & Aims Proper Colon function requires signals from extrinsic primary afferent neurons (ExPANs) located in spinal ganglia. Most ExPANs express the vanilloid receptor TRPV1, and a dense plexus of TRPV1-positive fibers is found around myenteric neurons. Capsaicin, a TRPV1 agonist, can initiate activity in myenteric neurons and produce muscle contraction. ExPANs might therefore form Motility-regulating synapses onto myenteric neurons. ExPANs mediate visceral pain, and myenteric neurons mediate Colon Motility, so we investigated communication between ExPANs and myenteric neurons and the circuits by which ExPANs modulate Colon function. Methods In live mice and Colon tissues that express a transgene encoding the calcium indicator GCaMP, we visualized levels of activity in myenteric neurons during smooth muscle contractions induced by application of capsaicin, direct Colon stimulation, stimulation of ExPANs, or stimulation of preganglionic parasympathetic neuron (PPN) axons. To localize central targets of ExPANs, we optogenetically activated TRPV1-expressing ExPANs in live mice and then quantified Fos immunoreactivity to identify activated spinal neurons. Results Focal electrical stimulation of mouse Colon produced phased-locked calcium signals in myenteric neurons and produced Colon contractions. Stimulation of the L6 ventral root, which contains PPN axons, also produced myenteric activation and contractions that were comparable to those of direct Colon stimulation. Surprisingly, capsaicin application to the isolated L6 dorsal root ganglia, which produced robust calcium signals in neurons throughout the ganglion, did not activate myenteric neurons. Electrical activation of the ganglia, which activated even more neurons than capsaicin, did not produce myenteric activation or contractions unless the spinal cord was intact, indicating that a complete afferent-to-efferent (PPN) circuit was necessary for ExPANs to regulate myenteric neurons. In TRPV1-channel rhodopsin-2 mice, light activation of ExPANs induced a pain-like visceromotor response and expression of Fos in spinal PPN neurons. Conclusions In mice, ExPANs regulate myenteric neuron activity and smooth muscle contraction via a parasympathetic spinal circuit, linking sensation and pain to Motility.
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225 extrinsic Colon afferents influence enteric neuron activity and Colon Motility by engaging spinal reflexes
The Journal of Pain, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Kathryn M Albers, Brian M DavisAbstract:Abdominal pain and bowel dysMotility are hallmark symptoms of functional bowel disorders, yet it is unclear how pain and dysMotility are correlated mechanistically. Extrinsic Colon afferents (EPANs) provide sensory input to the CNS, and visceral pain is thought to be due to hypersensitivity of these afferents. The enteric nervous system (ENS) acts autonomously to control Motility reflexes, but extrinsic nerve pathways coordinate activity between distant regions of the GI tract, and importantly, allow the central nervous system (CNS) to regulate GI functioning. To test whether EPANs can directly influence ENS activity, we used an ex vivo Colon-pelvic nerve-L6 DRG preparation, in which the roots were cut from the spinal cord, that allowed selective activation of EPANs via dorsal root stimulation and simultaneous calcium imaging (GCaMP6s) of myenteric neurons in the Colon. Electrical stimulation of the dorsal root activated the majority of L6 DRG neurons, but produced no GCaMP responses in myenteric neurons of the Colon in any of the visual fields tested (n=8). By contrast, ventral root stimulation led to GCaMP responses in ∼20% of myenteric neurons, followed by smooth muscle contraction, as indicated by movement of the imaging field. Interestingly, when the spinal cord was left intact, dorsal root stimulation produced responses in 12% of myenteric neurons (n=5), suggesting the presence of a sensory-parasympathetic spinal reflex. To elucidate this reflex in vivo, we used optogenetic stimulation to produce visceromotor responses and then processed spinal cord tissue for the immediate early gene, c-fos. There were significantly greater numbers of parasympathetic preganglionic neurons (PPNs) with c-fos staining in lumbosacral spinal segments from TRPV1-ChR2 mice (n=3) compared to controls (n=3), and TRPV1 central terminals were observed in close apposition to PPN. Overall, our data suggests that Colon afferents influence ENS activity and Colon Motility by engaging parasympathetic pathways through a spinal reflex.
Kathryn M Albers - One of the best experts on this subject based on the ideXlab platform.
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optogenetic activation of the distal Colon epithelium engages enteric nervous system circuits to initiate Motility patterns
American Journal of Physiology-gastrointestinal and Liver Physiology, 2021Co-Authors: Sarah A Najjar, Brian S Edwards, Kathryn M Albers, Brian M Davis, Kristen M SmithedwardsAbstract:Digestive functions of the Colon depend on sensory-motor reflexes in the enteric nervous system (ENS), initiated by intrinsic primary afferent neurons (IPANs). IPAN terminals project to the mucosal layer of the Colon, allowing communication with epithelial cells comprising the Colon lining. The chemical nature and functional significance of this epithelial-neural communication in regard to secretion and Colon Motility are of high interest. Colon epithelial cells can produce and release neuroactive substances such as ATP and 5-hydroxytryptamine (5-HT), which can activate receptors on adjacent nerve fibers, including IPAN subtypes. In this study, we examined if stimulation of epithelial cells alone is sufficient to activate neural circuits that control Colon Motility. Optogenetics and calcium imaging were used in ex vivo preparations of the mouse Colon to selectively stimulate the Colon epithelium, measure changes in Motility, and record activity of neurons within the myenteric plexus. Light-mediated activation of epithelial cells lining the distal, but not proximal, Colon caused local contractions and increased the rate of Colonic migrating motor complexes. Epithelial-evoked local contractions in the distal Colon were reduced by both ATP and 5-HT receptor antagonists. Our findings indicate that Colon epithelial cells likely use purinergic and serotonergic signaling to initiate activity in myenteric neurons, produce local contractions, and facilitate large-scale coordination of ENS activity responsible for whole Colon Motility patterns.NEW & NOTEWORTHY Using an all-optical approach to measure real-time cell-to-cell communication responsible for Colon functions, we show that selective optogenetic stimulation of distal Colon epithelium produced activity in myenteric neurons, as measured with red genetically encoded calcium indicators. The epithelial-induced neural response led to local contractions, mediated by both purinergic and serotonergic signaling, and facilitated Colonic motor complexes that propagate from proximal to distal Colon.
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extrinsic primary afferent neurons link visceral pain to Colon Motility through a spinal reflex in mice
Gastroenterology, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Marthe J Howard, Kathryn M Albers, Brian M DavisAbstract:Background & Aims Proper Colon function requires signals from extrinsic primary afferent neurons (ExPANs) located in spinal ganglia. Most ExPANs express the vanilloid receptor TRPV1, and a dense plexus of TRPV1-positive fibers is found around myenteric neurons. Capsaicin, a TRPV1 agonist, can initiate activity in myenteric neurons and produce muscle contraction. ExPANs might therefore form Motility-regulating synapses onto myenteric neurons. ExPANs mediate visceral pain, and myenteric neurons mediate Colon Motility, so we investigated communication between ExPANs and myenteric neurons and the circuits by which ExPANs modulate Colon function. Methods In live mice and Colon tissues that express a transgene encoding the calcium indicator GCaMP, we visualized levels of activity in myenteric neurons during smooth muscle contractions induced by application of capsaicin, direct Colon stimulation, stimulation of ExPANs, or stimulation of preganglionic parasympathetic neuron (PPN) axons. To localize central targets of ExPANs, we optogenetically activated TRPV1-expressing ExPANs in live mice and then quantified Fos immunoreactivity to identify activated spinal neurons. Results Focal electrical stimulation of mouse Colon produced phased-locked calcium signals in myenteric neurons and produced Colon contractions. Stimulation of the L6 ventral root, which contains PPN axons, also produced myenteric activation and contractions that were comparable to those of direct Colon stimulation. Surprisingly, capsaicin application to the isolated L6 dorsal root ganglia, which produced robust calcium signals in neurons throughout the ganglion, did not activate myenteric neurons. Electrical activation of the ganglia, which activated even more neurons than capsaicin, did not produce myenteric activation or contractions unless the spinal cord was intact, indicating that a complete afferent-to-efferent (PPN) circuit was necessary for ExPANs to regulate myenteric neurons. In TRPV1-channel rhodopsin-2 mice, light activation of ExPANs induced a pain-like visceromotor response and expression of Fos in spinal PPN neurons. Conclusions In mice, ExPANs regulate myenteric neuron activity and smooth muscle contraction via a parasympathetic spinal circuit, linking sensation and pain to Motility.
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extrinsic primary afferent neurons link visceral pain to Colon Motility through a spinal reflex in mice
Gastroenterology, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Marthe J Howard, Kathryn M Albers, Brian M DavisAbstract:Background & Aims Proper Colon function requires signals from extrinsic primary afferent neurons (ExPANs) located in spinal ganglia. Most ExPANs express the vanilloid receptor TRPV1, and a dense plexus of TRPV1-positive fibers is found around myenteric neurons. Capsaicin, a TRPV1 agonist, can initiate activity in myenteric neurons and produce muscle contraction. ExPANs might therefore form Motility-regulating synapses onto myenteric neurons. ExPANs mediate visceral pain, and myenteric neurons mediate Colon Motility, so we investigated communication between ExPANs and myenteric neurons and the circuits by which ExPANs modulate Colon function. Methods In live mice and Colon tissues that express a transgene encoding the calcium indicator GCaMP, we visualized levels of activity in myenteric neurons during smooth muscle contractions induced by application of capsaicin, direct Colon stimulation, stimulation of ExPANs, or stimulation of preganglionic parasympathetic neuron (PPN) axons. To localize central targets of ExPANs, we optogenetically activated TRPV1-expressing ExPANs in live mice and then quantified Fos immunoreactivity to identify activated spinal neurons. Results Focal electrical stimulation of mouse Colon produced phased-locked calcium signals in myenteric neurons and produced Colon contractions. Stimulation of the L6 ventral root, which contains PPN axons, also produced myenteric activation and contractions that were comparable to those of direct Colon stimulation. Surprisingly, capsaicin application to the isolated L6 dorsal root ganglia, which produced robust calcium signals in neurons throughout the ganglion, did not activate myenteric neurons. Electrical activation of the ganglia, which activated even more neurons than capsaicin, did not produce myenteric activation or contractions unless the spinal cord was intact, indicating that a complete afferent-to-efferent (PPN) circuit was necessary for ExPANs to regulate myenteric neurons. In TRPV1-channel rhodopsin-2 mice, light activation of ExPANs induced a pain-like visceromotor response and expression of Fos in spinal PPN neurons. Conclusions In mice, ExPANs regulate myenteric neuron activity and smooth muscle contraction via a parasympathetic spinal circuit, linking sensation and pain to Motility.
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225 extrinsic Colon afferents influence enteric neuron activity and Colon Motility by engaging spinal reflexes
The Journal of Pain, 2019Co-Authors: Kristen M Smithedwards, Sarah A Najjar, Brian S Edwards, Kathryn M Albers, Brian M DavisAbstract:Abdominal pain and bowel dysMotility are hallmark symptoms of functional bowel disorders, yet it is unclear how pain and dysMotility are correlated mechanistically. Extrinsic Colon afferents (EPANs) provide sensory input to the CNS, and visceral pain is thought to be due to hypersensitivity of these afferents. The enteric nervous system (ENS) acts autonomously to control Motility reflexes, but extrinsic nerve pathways coordinate activity between distant regions of the GI tract, and importantly, allow the central nervous system (CNS) to regulate GI functioning. To test whether EPANs can directly influence ENS activity, we used an ex vivo Colon-pelvic nerve-L6 DRG preparation, in which the roots were cut from the spinal cord, that allowed selective activation of EPANs via dorsal root stimulation and simultaneous calcium imaging (GCaMP6s) of myenteric neurons in the Colon. Electrical stimulation of the dorsal root activated the majority of L6 DRG neurons, but produced no GCaMP responses in myenteric neurons of the Colon in any of the visual fields tested (n=8). By contrast, ventral root stimulation led to GCaMP responses in ∼20% of myenteric neurons, followed by smooth muscle contraction, as indicated by movement of the imaging field. Interestingly, when the spinal cord was left intact, dorsal root stimulation produced responses in 12% of myenteric neurons (n=5), suggesting the presence of a sensory-parasympathetic spinal reflex. To elucidate this reflex in vivo, we used optogenetic stimulation to produce visceromotor responses and then processed spinal cord tissue for the immediate early gene, c-fos. There were significantly greater numbers of parasympathetic preganglionic neurons (PPNs) with c-fos staining in lumbosacral spinal segments from TRPV1-ChR2 mice (n=3) compared to controls (n=3), and TRPV1 central terminals were observed in close apposition to PPN. Overall, our data suggests that Colon afferents influence ENS activity and Colon Motility by engaging parasympathetic pathways through a spinal reflex.