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W1729 Volume Dependent Recruitment of Adaptive Esophageal Peristaltic and Upper Esophageal Sphincter Contractile Reflexes Is Preserved in Sleep State in Healthy Premature Infants
W1727
We tested the hypothesis that the frequency recruitment of esophageal provocation induced peristaltic and upper esophageal sphincter contractile reflexes (UESCR) is dependent on media type (air, water, apple juice), volume, and activity state (sleep vs. awake). Methods: Ethical requirements were fulfilled. Neonates (N=16) born at 29±1 wks were evaluated at 37±1 wks corrected age using concurrent esophageal manometry and video-polysomnography. At evaluation, subjects were healthy and orally fed, and did not have neurological or lung disease. Abrupt mid esophageal infusions of graded volumes (0.1 to 5 ml) of air, water and apple juice were given during sleep and awake-states (as defined by synchronized videopolysomnography). The frequency recruitment of esophageal peristaltic reflexes and UESCR were evaluated by observers blinded to sleep state. Polysomnography was scored by observers blinded to esophageal manometry. Multiple logistic regression models with repeated measurements, were used to test for significance (P < 0.05), data shown as mean ± SEM, Odds Ratio (95% CI). Results: A total of 489 infusions (200 air, 144 water, and 145 apple juice) were given; of which 95 infusions were in awake and 394 in sleep state. The relationship between the stimulus (media, volume) and the response (peristaltic reflex and UESCR) characteristics are described in the table. Unit volume increment in the dose resulted in corresponding Odds Ratio increment in the recruitment of the reflex (Table). Conclusions: In healthy premature infants, 1. Volume dependent recruitment of peristaltic and UES contractile reflexes remains to be preserved in sleep as much as in the awake state. 2. There were no differences between the media and between sleep vs. awake states for the reflexes studied. *Supported by NIH- RO1 DK 068158 Graded stimulus-response relationship between awake and sleep states
AGA Abstracts
Analgesic Effect of Tegaserod in Visceral Pain Is Not Peripheral, But via the Central Opioidergic System Jyoti N. Sengupta, Aaron D. Mickle, Zhihong Zhang, Bidyut K. Medda, Reza Shaker, Russell Spruell, John McRorie, Adrian Miranda Background: Serotonin (5-HT) plays a major role in gastrointestinal (GI) functions. Of several subtypes of 5-HT receptors, 5-HT3 and 5-HT4 are involved in GI motility and pain. 5-HT4 receptor agonist tegaserod (TEG) has been shown to modulate visceral pain in both humans and animals. However, its underlying mechanism of action remains unknown. Aim: The objective of the present study is to examine the site of action of this drug in colorectal distension (CRD)-induced visceral pain in naïve and post-inflamed sensitized rats. Methods: In each of 47 male Sprague-Dawley rats under fully anesthetized state, a bipolar electrode was implanted surgically into the external oblique muscle of the abdomen to measure the visceromotor response (VMR) represented as electrical activity (EMG) of the muscle to graded CRD (10-80mmHg). VMR was recorded in fully awake rats 72 hours following the surgery. To induce colonic inflammation, 0.5ml of tri-nitrobenzene sulfonic acid (TNBS) in 50% ethanol was infused into the colon under the influence of anesthesia and rats were tested 7days after TNBS injection. Drugs were injected either intraperitoneally (ip), intravenously (iv) or subcutaneously (sc). Electrophysiological recordings were made from the S1 sacral dorsal root receiving pelvic nerve innervating the colon. Responses of pelvic afferents to CRD were recorded before and after TEG injection. Results: Rats exhibited linear increasing VMR to graded CRD. TNBS-treated rats exhibited significantly (p<0.05 vs naive) greater VMR suggesting the sensitization following inflammation. High doses of TEG (5 and 10mg/ kg, ip) resulted in severe CNS effect including agitation, motor impairment and sedation (n=4). CNS effects were delayed in atropine (5mg/kg, ip) pretreated rats (n=4). Lower doses (0.5 and 1mg/kg, ip) of TEG did not produce any visible CNS effect. TEG (1mg/kg) significantly attenuated VMR in both naïve and post-inflamed rats. Atropine failed to block the effect of TEG, suggesting that visceral analgesia was not mediated via muscariniccholinergic system. Selective 5-HT4 antagonist GR113808 (5mg/kg, sc) significantly reversed the effect of TEG. Similarly, opioid receptor antagonist naloxone (5mg/kg, iv) significantly reversed the effect of TEG. In electrophysiology experiments, TEG (1mg/kg, ip) did not attenuate the mechanotransduction of colonic pelvic nerve afferents in either naïve or postinflamed rats. Conclusion: Results suggest that TEG produces visceral analgesia via the activation of central 5-HT4 receptors. Since opioid antagonist naloxone blocks the effect of TEG, it suggests that the central opioidergic system is linked to 5-HT4 mediated visceral analgesia.
W1730 Attenuation of Colonic Afferent Nerve Recordings But Not Visceromotor Response in Acute Citrobacter rodentium Colitis Marcela Miranda-Morales, Walter E. Sipe, Ian Spreadbury, Nigel W. Bunnett, Stephen J. Vanner
W1728 Activation of MAPK and TRPV1 Contribute to Primary Afferent Sensitization in a Rat Model of Chronic Visceral Hypersensitivity Guang-Yin Xu, Pankaj J. Pasricha, John H. Winston
The evidence for visceral hyperalgesia in models of intestinal inflammation has varied considerably depending upon the type of inflammation, timing of the measurement and the methodology. C. rodentium causes a self-limiting colitis in mice, similar to E. coli infection in humans, and may serve as a model of post-infectious IBS. As a first step towards understanding visceral hyperalgesia in this model, we examined visceral motor responses (VMR) induced by colorectal distension and compared these responses to multi-unit recordings from splanchnic nerves, during acute infection. C57BL/6N mice were gavaged with C. rodentium or saline and studied during active infection at day 10 - 14. VMR EMG was recorded using a bioamplifier, stored by Spike 2, and colorectal distensions (15-60 mmHg) were pre-regulated and gated by a customized valve. Animals were acclimatized to the apparatus for 5 days prior to measurements. Colonic afferent recordings were obtained from splanchnic mesenteric afferents of In Vitro segments (4 cm long) of descending colon attached to input and outlet ports. Via a syringe pump, the input port allowed continuous intra-luminal perfusion of physiological Krebs solution through the segments (0.2 ml/min). Periodic distensions (0 35 mmHg) were performed by closing this port and simultaneous pressure and afferent discharge measurements obtained. VMRs did not differ between C. rodentium infected and control animals (n = 8 for both groups). Acute application of zymosan intra-rectally produced hyperalgesia (~ 50 - 80 % increase) compared to controls (n = 8 for each group; p<0.05) at day 10. Colonic afferent nerve recordings displayed a pressure-dependent biphasic response to distension in controls (0 - 35 mmHg). Multi-unit responses (spikes/s) were significantly attenuated (maximum mean decrease ~ 30 %) in C. rodentium animals (p<0.02; n = 5 per group). Volume-pressure relationship did not differ between the groups. The afferent nerve response to 5HT (10 μM) also did not differ between infected and control animals. The results demonstrate that C. rodentium does not induce visceral hyperalgesia during the acute infection based on VMRs. Moreover, the colonic afferent nerve recordings demonstrate an attenuated response at the intestinal-sensory nerve interface. This may reflect desensitization, and/or altered smooth muscle properties (e.g. ability to induce tension) due to the inflammatory milieu. The lack of correlation between multi-unit and VMR recordings (i.e. reduced responses vs. no change observed) may suggest a contribution from other nociceptive mechanisms in the VMR measurements.
Primary afferent sensitization is associated with persistent visceral hypersensitivity both in irritable bowel syndrome and in animal models, but the mechanisms underlying primary afferent sensitization are not known. We have developed an animal model of persistent visceral sensitization produced by neonatal exposure to mild acid that is associated with sensitization of colon-specific DRG sensory neurons. We tested the hypothesis that MAPK activation in colon DRG neurons as a consequence of infusion of acetic acid into the colon in neonates contributes to the development of both behavioral and primary afferent sensitization. Since antagonism of TRPV1 prior to neonatal administration of acetic acid attenuates the development of sensitivity to CRD, we also tested the hypothesis that TRPV1 activation on colon DRG neurons contributes to persistent sensitization of these neurons. Results: In LS DRG, we observed significant increases in p-p38 at one hour (3-fold, p<0.05) and 4 hours (2-fold, p<0.05) after colonic acetic acid infusion compared to saline controls. At one hour, there was a seven-fold increase in ERK p-p44 in LS DRG from acetic acid treated pups (p<0.05). In TL DRG, there was a significant 2-fold increase in p-p38 in acetic acid treated rats compared to controls at 1 hour (p<0.05). P-p42 and p-p44 were increased 3-5 fold in both saline and acetic acid treated pups (p<0.05) compared to untreated controls. Pretreatment with either p38 MAPK antagonist SB-203580 (10 mg /kg) or with ERK1/2 antagonist U0126 (30 mg /kg) prior to acetic acid infusion in 10 days old pups reduced hypersensitivity of eight weeks old rats to graded CRD (p<0.002). Treatment with the ERK inhibitor U1026 (30 mg/kg) prior to acetic acid infusion as neonates significantly reduced the increase in the number of action potentials produced at 2X rheobase (p<0.05) and prevented the decline in rheobase of both TL and LS neurons observed in acetic acid treated rats (p<0.05). Treatment with the TRPV1 antagonist SB36679 prevented the decline in rheobase of both TL (p<0.05) and LS (p<0.05) neurons and reduced action potential generation but this was not statistically significant. Conclusions: Colonic infusion of acetic acid activates MAPK in DRG containing colon afferents. Neonatal pretreatment with pERK inhibitor blocked persistent hypersensitivity in adults. Neonatal systemic pre-treatment with either aTRPV1 or an ERK antagonist prevents increases in colon DRG neuron excitability in adults. These data support the hypothesis that both TRPV1 and ERK ½ activation are involved in neonatal acetic acid induced increases in the excitability of both TL and LS colon afferent neurons.
W1731 The Cannabinoid Receptor Agonist Delta-9-Tetrahydrocannabinol Increases Rectal Sensitivity in IBS Patients and Healthy Volunteers Tamira Klooker, Karolien Leliefeld, Rene M. van den Wijngaard, Guy E. Boeckxstaens
W1729 Volume Dependent Recruitment of Adaptive Esophageal Peristaltic and Upper Esophageal Sphincter Contractile Reflexes Is Preserved in Sleep State in Healthy Premature Infants Alankar Gupta, Vanessa N. Parks, Mansen Wang, Samuel Dzodzomenyo, Soledad A. Fernandez, Mark Splaingard, Reza Shaker, Sudarshan R. Jadcherla
BACKGROUND/AIM: Visceral hypersensitivity to distention is thought to play an important role in the pathophysiology of the irritable bowel syndrome (IBS). Cannabinoïds are known to decrease somatic pain perception, but their effect on visceral sensitivity remains unclear. Therefore, we evaluated the effect of the mixed CB1/CB2 receptor agonist delta-9-tetrahydrocannabinol (Δ9-THC, dronabinol) on rectal sensitivity in IBS patients and healthy volunteers (HV). METHODS Twelve HV (32 ± 4 yr, 7F) and ten IBS patients (33 ± 3 yr, 8F) underwent a barostat study to assess rectal sensitivity using an intermittent pressure-controlled distention protocol before and after sigmoid stimulation. Repetitive sigmoid stimulation is a validated method to induce visceral hypersensitivity in IBS patients, consisting of
Background and Aims: Infants spend a significant time in sleep. Assessment of aerodigestive pathologies during sleep is important in clarifying aerodigestive protective mechanisms; failure of such may be the cause of apparent life threatening events (ALTE). The role of sleep in modulating the volume dependent esophageal adaptive reflex responses is not clear.
AGA Abstracts
A-726
We tested the hypothesis that the frequency recruitment of esophageal provocation induced peristaltic and upper esophageal sphincter contractile reflexes (UESCR) is dependent on media type (air, water, apple juice), volume, and activity state (sleep vs. awake). Methods: Ethical requirements were fulfilled. Neonates (N=16) born at 29±1 wks were evaluated at 37±1 wks corrected age using concurrent esophageal manometry and video-polysomnography. At evaluation, subjects were healthy and orally fed, and did not have neurological or lung disease. Abrupt mid esophageal infusions of graded volumes (0.1 to 5 ml) of air, water and apple juice were given during sleep and awake-states (as defined by synchronized videopolysomnography). The frequency recruitment of esophageal peristaltic reflexes and UESCR were evaluated by observers blinded to sleep state. Polysomnography was scored by observers blinded to esophageal manometry. Multiple logistic regression models with repeated measurements, were used to test for significance (P < 0.05), data shown as mean ± SEM, Odds Ratio (95% CI). Results: A total of 489 infusions (200 air, 144 water, and 145 apple juice) were given; of which 95 infusions were in awake and 394 in sleep state. The relationship between the stimulus (media, volume) and the response (peristaltic reflex and UESCR) characteristics are described in the table. Unit volume increment in the dose resulted in corresponding Odds Ratio increment in the recruitment of the reflex (Table). Conclusions: In healthy premature infants, 1. Volume dependent recruitment of peristaltic and UES contractile reflexes remains to be preserved in sleep as much as in the awake state. 2. There were no differences between the media and between sleep vs. awake states for the reflexes studied. *Supported by NIH- RO1 DK 068158 Graded stimulus-response relationship between awake and sleep states
AGA Abstracts
Analgesic Effect of Tegaserod in Visceral Pain Is Not Peripheral, But via the Central Opioidergic System Jyoti N. Sengupta, Aaron D. Mickle, Zhihong Zhang, Bidyut K. Medda, Reza Shaker, Russell Spruell, John McRorie, Adrian Miranda Background: Serotonin (5-HT) plays a major role in gastrointestinal (GI) functions. Of several subtypes of 5-HT receptors, 5-HT3 and 5-HT4 are involved in GI motility and pain. 5-HT4 receptor agonist tegaserod (TEG) has been shown to modulate visceral pain in both humans and animals. However, its underlying mechanism of action remains unknown. Aim: The objective of the present study is to examine the site of action of this drug in colorectal distension (CRD)-induced visceral pain in naïve and post-inflamed sensitized rats. Methods: In each of 47 male Sprague-Dawley rats under fully anesthetized state, a bipolar electrode was implanted surgically into the external oblique muscle of the abdomen to measure the visceromotor response (VMR) represented as electrical activity (EMG) of the muscle to graded CRD (10-80mmHg). VMR was recorded in fully awake rats 72 hours following the surgery. To induce colonic inflammation, 0.5ml of tri-nitrobenzene sulfonic acid (TNBS) in 50% ethanol was infused into the colon under the influence of anesthesia and rats were tested 7days after TNBS injection. Drugs were injected either intraperitoneally (ip), intravenously (iv) or subcutaneously (sc). Electrophysiological recordings were made from the S1 sacral dorsal root receiving pelvic nerve innervating the colon. Responses of pelvic afferents to CRD were recorded before and after TEG injection. Results: Rats exhibited linear increasing VMR to graded CRD. TNBS-treated rats exhibited significantly (p<0.05 vs naive) greater VMR suggesting the sensitization following inflammation. High doses of TEG (5 and 10mg/ kg, ip) resulted in severe CNS effect including agitation, motor impairment and sedation (n=4). CNS effects were delayed in atropine (5mg/kg, ip) pretreated rats (n=4). Lower doses (0.5 and 1mg/kg, ip) of TEG did not produce any visible CNS effect. TEG (1mg/kg) significantly attenuated VMR in both naïve and post-inflamed rats. Atropine failed to block the effect of TEG, suggesting that visceral analgesia was not mediated via muscariniccholinergic system. Selective 5-HT4 antagonist GR113808 (5mg/kg, sc) significantly reversed the effect of TEG. Similarly, opioid receptor antagonist naloxone (5mg/kg, iv) significantly reversed the effect of TEG. In electrophysiology experiments, TEG (1mg/kg, ip) did not attenuate the mechanotransduction of colonic pelvic nerve afferents in either naïve or postinflamed rats. Conclusion: Results suggest that TEG produces visceral analgesia via the activation of central 5-HT4 receptors. Since opioid antagonist naloxone blocks the effect of TEG, it suggests that the central opioidergic system is linked to 5-HT4 mediated visceral analgesia.
W1730 Attenuation of Colonic Afferent Nerve Recordings But Not Visceromotor Response in Acute Citrobacter rodentium Colitis Marcela Miranda-Morales, Walter E. Sipe, Ian Spreadbury, Nigel W. Bunnett, Stephen J. Vanner
W1728 Activation of MAPK and TRPV1 Contribute to Primary Afferent Sensitization in a Rat Model of Chronic Visceral Hypersensitivity Guang-Yin Xu, Pankaj J. Pasricha, John H. Winston
The evidence for visceral hyperalgesia in models of intestinal inflammation has varied considerably depending upon the type of inflammation, timing of the measurement and the methodology. C. rodentium causes a self-limiting colitis in mice, similar to E. coli infection in humans, and may serve as a model of post-infectious IBS. As a first step towards understanding visceral hyperalgesia in this model, we examined visceral motor responses (VMR) induced by colorectal distension and compared these responses to multi-unit recordings from splanchnic nerves, during acute infection. C57BL/6N mice were gavaged with C. rodentium or saline and studied during active infection at day 10 - 14. VMR EMG was recorded using a bioamplifier, stored by Spike 2, and colorectal distensions (15-60 mmHg) were pre-regulated and gated by a customized valve. Animals were acclimatized to the apparatus for 5 days prior to measurements. Colonic afferent recordings were obtained from splanchnic mesenteric afferents of In Vitro segments (4 cm long) of descending colon attached to input and outlet ports. Via a syringe pump, the input port allowed continuous intra-luminal perfusion of physiological Krebs solution through the segments (0.2 ml/min). Periodic distensions (0 35 mmHg) were performed by closing this port and simultaneous pressure and afferent discharge measurements obtained. VMRs did not differ between C. rodentium infected and control animals (n = 8 for both groups). Acute application of zymosan intra-rectally produced hyperalgesia (~ 50 - 80 % increase) compared to controls (n = 8 for each group; p<0.05) at day 10. Colonic afferent nerve recordings displayed a pressure-dependent biphasic response to distension in controls (0 - 35 mmHg). Multi-unit responses (spikes/s) were significantly attenuated (maximum mean decrease ~ 30 %) in C. rodentium animals (p<0.02; n = 5 per group). Volume-pressure relationship did not differ between the groups. The afferent nerve response to 5HT (10 μM) also did not differ between infected and control animals. The results demonstrate that C. rodentium does not induce visceral hyperalgesia during the acute infection based on VMRs. Moreover, the colonic afferent nerve recordings demonstrate an attenuated response at the intestinal-sensory nerve interface. This may reflect desensitization, and/or altered smooth muscle properties (e.g. ability to induce tension) due to the inflammatory milieu. The lack of correlation between multi-unit and VMR recordings (i.e. reduced responses vs. no change observed) may suggest a contribution from other nociceptive mechanisms in the VMR measurements.
Primary afferent sensitization is associated with persistent visceral hypersensitivity both in irritable bowel syndrome and in animal models, but the mechanisms underlying primary afferent sensitization are not known. We have developed an animal model of persistent visceral sensitization produced by neonatal exposure to mild acid that is associated with sensitization of colon-specific DRG sensory neurons. We tested the hypothesis that MAPK activation in colon DRG neurons as a consequence of infusion of acetic acid into the colon in neonates contributes to the development of both behavioral and primary afferent sensitization. Since antagonism of TRPV1 prior to neonatal administration of acetic acid attenuates the development of sensitivity to CRD, we also tested the hypothesis that TRPV1 activation on colon DRG neurons contributes to persistent sensitization of these neurons. Results: In LS DRG, we observed significant increases in p-p38 at one hour (3-fold, p<0.05) and 4 hours (2-fold, p<0.05) after colonic acetic acid infusion compared to saline controls. At one hour, there was a seven-fold increase in ERK p-p44 in LS DRG from acetic acid treated pups (p<0.05). In TL DRG, there was a significant 2-fold increase in p-p38 in acetic acid treated rats compared to controls at 1 hour (p<0.05). P-p42 and p-p44 were increased 3-5 fold in both saline and acetic acid treated pups (p<0.05) compared to untreated controls. Pretreatment with either p38 MAPK antagonist SB-203580 (10 mg /kg) or with ERK1/2 antagonist U0126 (30 mg /kg) prior to acetic acid infusion in 10 days old pups reduced hypersensitivity of eight weeks old rats to graded CRD (p<0.002). Treatment with the ERK inhibitor U1026 (30 mg/kg) prior to acetic acid infusion as neonates significantly reduced the increase in the number of action potentials produced at 2X rheobase (p<0.05) and prevented the decline in rheobase of both TL and LS neurons observed in acetic acid treated rats (p<0.05). Treatment with the TRPV1 antagonist SB36679 prevented the decline in rheobase of both TL (p<0.05) and LS (p<0.05) neurons and reduced action potential generation but this was not statistically significant. Conclusions: Colonic infusion of acetic acid activates MAPK in DRG containing colon afferents. Neonatal pretreatment with pERK inhibitor blocked persistent hypersensitivity in adults. Neonatal systemic pre-treatment with either aTRPV1 or an ERK antagonist prevents increases in colon DRG neuron excitability in adults. These data support the hypothesis that both TRPV1 and ERK ½ activation are involved in neonatal acetic acid induced increases in the excitability of both TL and LS colon afferent neurons.
W1731 The Cannabinoid Receptor Agonist Delta-9-Tetrahydrocannabinol Increases Rectal Sensitivity in IBS Patients and Healthy Volunteers Tamira Klooker, Karolien Leliefeld, Rene M. van den Wijngaard, Guy E. Boeckxstaens
W1729 Volume Dependent Recruitment of Adaptive Esophageal Peristaltic and Upper Esophageal Sphincter Contractile Reflexes Is Preserved in Sleep State in Healthy Premature Infants Alankar Gupta, Vanessa N. Parks, Mansen Wang, Samuel Dzodzomenyo, Soledad A. Fernandez, Mark Splaingard, Reza Shaker, Sudarshan R. Jadcherla
BACKGROUND/AIM: Visceral hypersensitivity to distention is thought to play an important role in the pathophysiology of the irritable bowel syndrome (IBS). Cannabinoïds are known to decrease somatic pain perception, but their effect on visceral sensitivity remains unclear. Therefore, we evaluated the effect of the mixed CB1/CB2 receptor agonist delta-9-tetrahydrocannabinol (Δ9-THC, dronabinol) on rectal sensitivity in IBS patients and healthy volunteers (HV). METHODS Twelve HV (32 ± 4 yr, 7F) and ten IBS patients (33 ± 3 yr, 8F) underwent a barostat study to assess rectal sensitivity using an intermittent pressure-controlled distention protocol before and after sigmoid stimulation. Repetitive sigmoid stimulation is a validated method to induce visceral hypersensitivity in IBS patients, consisting of
Background and Aims: Infants spend a significant time in sleep. Assessment of aerodigestive pathologies during sleep is important in clarifying aerodigestive protective mechanisms; failure of such may be the cause of apparent life threatening events (ALTE). The role of sleep in modulating the volume dependent esophageal adaptive reflex responses is not clear.
AGA Abstracts
A-726