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Role of spinal receptors for NMDA, NK-1 and CGRP in visceral pain response to colorectal distension (CRD)
Al148 AGA ABSTRACTS
GASTROENTEROLOGYVol. 114, No. 4 G4700
• G4698
EVIDENCE FOR ROLE OF VAGAL INNERVATION IN ACTIVATION OF OPIOIDERGIC ANTINOCICEPTIVE SYSTEMS IN RESPONSE TO COLORECTAL DISTENSION (CRD) IN RATS. JM Gschossmann, JC Miller and EA Mayer. UCLA/CURE Neuroenteric Disease Program, Depts. of Medicine and Physiology, and Brain Research Institute, UCLA and WLA VA Medical Center, Los Angeles, CA. BACKGROUND: In animals, activation of a subpopulation of vagal afferents engage antinociceptive systems. Patients with vagotomy exhibit symptoms of dyspepsia and show enhanced perceptual responses to duodenal distension (Gastroenterology 1996; 110: A680). AIMS: To determine the possible involvement of vagal afferents in the modulation of the pain response to CRD in male Sprague-Dawley (SD) rats, a strain with a strong opioid-influenced endogenous pain inhibition system. METHODS: CRD was performed in fasted, conscious male SD rats which had previously undergone either total vagotomy or sham surgical intervention (control). The number of abdominal contractions (behavioral pain response) during a test stimulus (10 rain tonic CRD to 60 mmHg) before (baseline) and following a Conditioning stimulus (10 repetitive 15 sec phasic CRDs to 80 mmHg) were determined. The effect of Naloxone (NAL; 25 mg/kg BW, i.p.) on pain responses was evaluated. RESULTS: Vagotomy enhanced pain responses during baseline and following conditioning stimulus. NAL enhanced pain responses during both conditions in sham operated but not vagotomized rats. study group
Baseline
Vagot. (n = 7) 8.2 ± 1.2 Sham (n = 6) 3.3 ± 0.4 Vagot. + NAL (n = 3) 7.3 ± 1.8 Sham + NAL (n = 7) 11.5 ± 0.6 *p < 0.05 (post cond. vs baseline);
Post-conditioning 16.8±2.3" 9.3±0.4* 11.6±2.4 21.7±3.6"
CONCLUSIONS: 1. Activation of vagal afferents innervating the left colon may play a role in activation of opioid-dependent antinociceptive systems by noxious CRD. 2. An alteration in these vagally-mediated mechanisms may play a role in the development of visceral hyperalgesia to repetitive sigmoid distension in IBS patients. Supported by NIH grants DK 48351 and DK 40919 (EAM), DK 41301 (CURE Center grant), by DFG grant Gs9/1-1 and by partial support from Astra Haessle • G4699
ROLE OF SPINAL RECEPTORS FOR NMDA, NK-1 AND CGRP IN VISCERAL PAIN RESPONSE TO COLORECTAL DISTENSION (CRD). JM Gschossmann and EA Mayer. UCLA/CURE Neuroenteric Disease Program, Depts. of Medicine and Physiology, and Brain Research Institute, UCLA and WLA VA Medical Center, Los Angeles, CA. BACKGROUND: Repetitive visceral distension produces central (spinal) sensitization in animals and induces visceral hyperalgesia in humans. We have previously shown that spinal NMDA receptors play a major role in mediation of the pain response to CRD in rats (Gastroenterology 1997; 112: Al152) and that presynaptic NMDA receptors control spinal substance P release (J Neuroscience 1997; 17: 8129). AIMS: To characterize the interactions of spinal NMDA receptors with CGRP and substance P receptors in the visceral pain transmission. METHODS: CRD was performed in fasted, conscious male Sprague-Dawley rats. The number of abdominal contractions (behavioral pain response) were determined during a test stimulus (10 min tonic CRD to 60 mmHg) before (baseline) and after a conditioning stimulus (10 repetitive 15 s phasic CRD to 80 mmHg). The effects of the NMDA receptor antagonist AP5, the NK1 antagonist CP-99,994 (Pfizer) and the CGRP receptor antagonist h-CGRPs_w, all given intrathecally (i.t.) on the visceromotor response to CRD were evaluated. RESULTS: All three antagonists for neuroreceptors reduced the numbers of abdominal contractions in response to CRD and prevented the development of sensitization: Compound
Baseline
post-conditioning
Control AP5 (50 nmol) CP-99,994 (100 nmol) h-CGRPs_37 (3 nmol)
6.5 - 2.5 4.0 _+1.7 3.0 ± 1.7 4.0 ± 1.5
14.1 ± 3.8* 6.2 ± 1.4 4.0 ± 1.5 6.0 ± 2.4
Combined application of AP5 with CP-99,994 or with h-CGRPs.37 did not enhance the analgesic effect of AP5 alone. CONCLUSIONS: 1. Spinally released glutamate, substance P and CGRP can independently contribute to the development of spinal sensitization. 2. The findings are consistent with a role of presynaptic NMDA receptors in the release of substance P and possibly CGRP in response to noxious CRD. Supported by NIH grants DK 48351 and DK 40919 (EAM), and by DFG grant Gs9/1-1 (JMG)
INFLAMATION-INDUCED IMPAIRMENT OF CHOLINERGIC NERVE FUNCTION IS CD-4 INDEPENDENT IN NEMATODE-INFECTED MICE. E.M. Haapala, P.A. Blennerhassett, B.A. Vallance and S.M.Collins. GI Division, IDRP, McMaster University, Hamilton, Ontario, Canada. Previous studies in the nematode-infected rat showed impaired release of acetylcholine (Ach) from myenteric nerves. We have subsequently focused attention on the mouse in order to utilize the broader array of immunological and molecular tools available in that species. In the present study we have applied a procedure for measuring the release of Ach from the intestinal myenteric plexus of C57BL/6 and knockout mice in which the CD4 ÷ T cells are inactive due to the deletion of the gene encoding for MHC II. C57BL/6 or MHC II knockout mice were infected with 375 T. spiralis larvae. Segments were removed from the jejunum, mounted on a glass rod and the longitudinal muscle plus myenteric plexus (LM-MP) carefully dissected. The LM-MP preparations were then pre-incubated with [3H]-choline and superfused with Krebs buffer containing hemicholinium-3. Tissues were stimulated electrically at 30V, 10Hz, 0.5ms or with 50mM KCI and the fractional release of [3H]Ach was measured. To determine whether observed changes in Ach release reflected the inflammatory response to nematode infection, a group of mice were treated with dexamethasone sodium phosphate (1 mg/kg/day i.p.), and inflammation monitored by measuring the activity of myeloperoxidase (MPO). A transient 40% increase in Ach release was seen on day 2 post-infection (PI). By day 6 PI, Ach release was significantly depressed by approximately 60%. Dexamethasone treatment prevented the increase in MPO seen in infected mice but had no impact on the transient increase in Ach release seen on day 2 PI. In contrast, steroid treatment prevented the suppression of Ach release on day 6 PI. Studies in the MHC II knockout mice revealed a profile of Ach release that was similar to that of the background strain C57BL/6 in the presence of infection. That is, both the transient increase and the subsequent suppression of Ach release were evident in infected MHC II knockout mice. This study demonstrates the feasibility of measuring enteric neural function in the mouse. Our results indicate that the suppression of cholinergic nerve function reflects the inflammatory response to infection, whereas the transient increase in Ach release seen early in the infection is independent of the inflammatory response and may reflect the effect of a parasite-derived product. Since the steroid-sensitive suppression of Ach release persisted in infected MCH II KO mice, we conclude that it does not require the activation of CD4 ÷ T lymphocytes. Supported by MRC Canada. G4701
INTRAVENOUS SECRETIN IMPROVES THE CANNULATION RATE OF THE PANCREATIC DUCT DURING ENDOSCOPIC RETROGRADE CHOLANGIO-PANCREATOGRAPHY. M. Hiifner, R. Sch~Sfl, F. Pfeffel, A. Gangl. Department of Gastroenterology and Hepatology, University of Vienna, Vienna, Austria Successful cannulation of the pancreatic duct during Endoscopic Retrograde Cholangio-Pancreatography (ERCP) is successful in approximately 90-95% of all cases when performed by an experienced investigator. However, success rate is lower in case of pancreas divisum. When cannulation fails tapered catheters, guidewires and papillotomes may be helpful in order to cannulate the pancreatic duct. We examined the value of secretin (Ferring, Sweden) in improving the cannulation rate of two experienced endoscopists. Patients and Methods: 887 ERCPs were performed between 8/1995 and 6/1997 with the aim of visualising the pancreatic duct. In 41 ERCPs cannulation of the pancreatic duct was not possible within 15 minutes although a guide-wire sphincterotome was applied. In 17 cases (16 patients) 75IU Secretin were given intravenously. The patients (8 females, 8 males, mean age 59, 31-74 years) were selected according to the examiner's opinion about the clinical importance of successful pancreatography. After ERCP the patient were admitted for at least 24 hours. Data was analysed retrospectively. Results: Cannulation of the pancreatic duct was successful in 12 out of 17 (71%) ERCPs within 10 minutes after i.v. application of 75IU of secretin. The 12 successfully obtained pancreatograms revealed chronic pancreatitis in 5 patients, pancreas divisum with dorsal duct pancreatogram in 5 cases and normal findings in 2 cases. As for the failed cannulations, pancreas divisum was suspected in 2 patients (although the minor papilla could not be cannulated), chronic pancreatitis in 3 patients. Within the study period chronic pancreatitis was found in 9% of all examinations (78/846 ERCPs), but in 42% of all cases with primary unsuccessful cannulation after administration of secretin. Pancreas divisum could be found in 36 of 846 examinations (4%), but in 5 of 12 (42%) in the secretin group. No major side effects were noted (including pancreatitis), although moderate pain was observed in 3 patients suffering from chronic pancreatitis. Discussion: Even when performed by experienced examiners pancreatography during ERCP fails in 5 to 10%. Especially in patients suffering from chronic pancreatitis or pancreas divisum cannulation may be difficult. Our findings suggest that intravenous application of secretin improves the cannulation rate and may help prevent ERCP-related pancreatitis when administered in time. However, further prospective evaluation is necessary. Introduction:
GASTROENTEROLOGYVol. 114, No. 4 G4700
• G4698
EVIDENCE FOR ROLE OF VAGAL INNERVATION IN ACTIVATION OF OPIOIDERGIC ANTINOCICEPTIVE SYSTEMS IN RESPONSE TO COLORECTAL DISTENSION (CRD) IN RATS. JM Gschossmann, JC Miller and EA Mayer. UCLA/CURE Neuroenteric Disease Program, Depts. of Medicine and Physiology, and Brain Research Institute, UCLA and WLA VA Medical Center, Los Angeles, CA. BACKGROUND: In animals, activation of a subpopulation of vagal afferents engage antinociceptive systems. Patients with vagotomy exhibit symptoms of dyspepsia and show enhanced perceptual responses to duodenal distension (Gastroenterology 1996; 110: A680). AIMS: To determine the possible involvement of vagal afferents in the modulation of the pain response to CRD in male Sprague-Dawley (SD) rats, a strain with a strong opioid-influenced endogenous pain inhibition system. METHODS: CRD was performed in fasted, conscious male SD rats which had previously undergone either total vagotomy or sham surgical intervention (control). The number of abdominal contractions (behavioral pain response) during a test stimulus (10 rain tonic CRD to 60 mmHg) before (baseline) and following a Conditioning stimulus (10 repetitive 15 sec phasic CRDs to 80 mmHg) were determined. The effect of Naloxone (NAL; 25 mg/kg BW, i.p.) on pain responses was evaluated. RESULTS: Vagotomy enhanced pain responses during baseline and following conditioning stimulus. NAL enhanced pain responses during both conditions in sham operated but not vagotomized rats. study group
Baseline
Vagot. (n = 7) 8.2 ± 1.2 Sham (n = 6) 3.3 ± 0.4 Vagot. + NAL (n = 3) 7.3 ± 1.8 Sham + NAL (n = 7) 11.5 ± 0.6 *p < 0.05 (post cond. vs baseline);
Post-conditioning 16.8±2.3" 9.3±0.4* 11.6±2.4 21.7±3.6"
CONCLUSIONS: 1. Activation of vagal afferents innervating the left colon may play a role in activation of opioid-dependent antinociceptive systems by noxious CRD. 2. An alteration in these vagally-mediated mechanisms may play a role in the development of visceral hyperalgesia to repetitive sigmoid distension in IBS patients. Supported by NIH grants DK 48351 and DK 40919 (EAM), DK 41301 (CURE Center grant), by DFG grant Gs9/1-1 and by partial support from Astra Haessle • G4699
ROLE OF SPINAL RECEPTORS FOR NMDA, NK-1 AND CGRP IN VISCERAL PAIN RESPONSE TO COLORECTAL DISTENSION (CRD). JM Gschossmann and EA Mayer. UCLA/CURE Neuroenteric Disease Program, Depts. of Medicine and Physiology, and Brain Research Institute, UCLA and WLA VA Medical Center, Los Angeles, CA. BACKGROUND: Repetitive visceral distension produces central (spinal) sensitization in animals and induces visceral hyperalgesia in humans. We have previously shown that spinal NMDA receptors play a major role in mediation of the pain response to CRD in rats (Gastroenterology 1997; 112: Al152) and that presynaptic NMDA receptors control spinal substance P release (J Neuroscience 1997; 17: 8129). AIMS: To characterize the interactions of spinal NMDA receptors with CGRP and substance P receptors in the visceral pain transmission. METHODS: CRD was performed in fasted, conscious male Sprague-Dawley rats. The number of abdominal contractions (behavioral pain response) were determined during a test stimulus (10 min tonic CRD to 60 mmHg) before (baseline) and after a conditioning stimulus (10 repetitive 15 s phasic CRD to 80 mmHg). The effects of the NMDA receptor antagonist AP5, the NK1 antagonist CP-99,994 (Pfizer) and the CGRP receptor antagonist h-CGRPs_w, all given intrathecally (i.t.) on the visceromotor response to CRD were evaluated. RESULTS: All three antagonists for neuroreceptors reduced the numbers of abdominal contractions in response to CRD and prevented the development of sensitization: Compound
Baseline
post-conditioning
Control AP5 (50 nmol) CP-99,994 (100 nmol) h-CGRPs_37 (3 nmol)
6.5 - 2.5 4.0 _+1.7 3.0 ± 1.7 4.0 ± 1.5
14.1 ± 3.8* 6.2 ± 1.4 4.0 ± 1.5 6.0 ± 2.4
Combined application of AP5 with CP-99,994 or with h-CGRPs.37 did not enhance the analgesic effect of AP5 alone. CONCLUSIONS: 1. Spinally released glutamate, substance P and CGRP can independently contribute to the development of spinal sensitization. 2. The findings are consistent with a role of presynaptic NMDA receptors in the release of substance P and possibly CGRP in response to noxious CRD. Supported by NIH grants DK 48351 and DK 40919 (EAM), and by DFG grant Gs9/1-1 (JMG)
INFLAMATION-INDUCED IMPAIRMENT OF CHOLINERGIC NERVE FUNCTION IS CD-4 INDEPENDENT IN NEMATODE-INFECTED MICE. E.M. Haapala, P.A. Blennerhassett, B.A. Vallance and S.M.Collins. GI Division, IDRP, McMaster University, Hamilton, Ontario, Canada. Previous studies in the nematode-infected rat showed impaired release of acetylcholine (Ach) from myenteric nerves. We have subsequently focused attention on the mouse in order to utilize the broader array of immunological and molecular tools available in that species. In the present study we have applied a procedure for measuring the release of Ach from the intestinal myenteric plexus of C57BL/6 and knockout mice in which the CD4 ÷ T cells are inactive due to the deletion of the gene encoding for MHC II. C57BL/6 or MHC II knockout mice were infected with 375 T. spiralis larvae. Segments were removed from the jejunum, mounted on a glass rod and the longitudinal muscle plus myenteric plexus (LM-MP) carefully dissected. The LM-MP preparations were then pre-incubated with [3H]-choline and superfused with Krebs buffer containing hemicholinium-3. Tissues were stimulated electrically at 30V, 10Hz, 0.5ms or with 50mM KCI and the fractional release of [3H]Ach was measured. To determine whether observed changes in Ach release reflected the inflammatory response to nematode infection, a group of mice were treated with dexamethasone sodium phosphate (1 mg/kg/day i.p.), and inflammation monitored by measuring the activity of myeloperoxidase (MPO). A transient 40% increase in Ach release was seen on day 2 post-infection (PI). By day 6 PI, Ach release was significantly depressed by approximately 60%. Dexamethasone treatment prevented the increase in MPO seen in infected mice but had no impact on the transient increase in Ach release seen on day 2 PI. In contrast, steroid treatment prevented the suppression of Ach release on day 6 PI. Studies in the MHC II knockout mice revealed a profile of Ach release that was similar to that of the background strain C57BL/6 in the presence of infection. That is, both the transient increase and the subsequent suppression of Ach release were evident in infected MHC II knockout mice. This study demonstrates the feasibility of measuring enteric neural function in the mouse. Our results indicate that the suppression of cholinergic nerve function reflects the inflammatory response to infection, whereas the transient increase in Ach release seen early in the infection is independent of the inflammatory response and may reflect the effect of a parasite-derived product. Since the steroid-sensitive suppression of Ach release persisted in infected MCH II KO mice, we conclude that it does not require the activation of CD4 ÷ T lymphocytes. Supported by MRC Canada. G4701
INTRAVENOUS SECRETIN IMPROVES THE CANNULATION RATE OF THE PANCREATIC DUCT DURING ENDOSCOPIC RETROGRADE CHOLANGIO-PANCREATOGRAPHY. M. Hiifner, R. Sch~Sfl, F. Pfeffel, A. Gangl. Department of Gastroenterology and Hepatology, University of Vienna, Vienna, Austria Successful cannulation of the pancreatic duct during Endoscopic Retrograde Cholangio-Pancreatography (ERCP) is successful in approximately 90-95% of all cases when performed by an experienced investigator. However, success rate is lower in case of pancreas divisum. When cannulation fails tapered catheters, guidewires and papillotomes may be helpful in order to cannulate the pancreatic duct. We examined the value of secretin (Ferring, Sweden) in improving the cannulation rate of two experienced endoscopists. Patients and Methods: 887 ERCPs were performed between 8/1995 and 6/1997 with the aim of visualising the pancreatic duct. In 41 ERCPs cannulation of the pancreatic duct was not possible within 15 minutes although a guide-wire sphincterotome was applied. In 17 cases (16 patients) 75IU Secretin were given intravenously. The patients (8 females, 8 males, mean age 59, 31-74 years) were selected according to the examiner's opinion about the clinical importance of successful pancreatography. After ERCP the patient were admitted for at least 24 hours. Data was analysed retrospectively. Results: Cannulation of the pancreatic duct was successful in 12 out of 17 (71%) ERCPs within 10 minutes after i.v. application of 75IU of secretin. The 12 successfully obtained pancreatograms revealed chronic pancreatitis in 5 patients, pancreas divisum with dorsal duct pancreatogram in 5 cases and normal findings in 2 cases. As for the failed cannulations, pancreas divisum was suspected in 2 patients (although the minor papilla could not be cannulated), chronic pancreatitis in 3 patients. Within the study period chronic pancreatitis was found in 9% of all examinations (78/846 ERCPs), but in 42% of all cases with primary unsuccessful cannulation after administration of secretin. Pancreas divisum could be found in 36 of 846 examinations (4%), but in 5 of 12 (42%) in the secretin group. No major side effects were noted (including pancreatitis), although moderate pain was observed in 3 patients suffering from chronic pancreatitis. Discussion: Even when performed by experienced examiners pancreatography during ERCP fails in 5 to 10%. Especially in patients suffering from chronic pancreatitis or pancreas divisum cannulation may be difficult. Our findings suggest that intravenous application of secretin improves the cannulation rate and may help prevent ERCP-related pancreatitis when administered in time. However, further prospective evaluation is necessary. Introduction: