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LOS Relaxation (los + relaxation)

Distribution by Scientific Domains
Medical Sciences100%

Selected Abstracts

Opiate-induced oesophageal dysmotility

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 5 2010
R. E. KRAICHELY
Aliment Pharmacol Ther,31, 601,606 Summary Background, Opiates have well characterized (troublesome) untoward effects on the gastrointestinal tract. Opioid bowel dysfunction has been a subject of research and even drug design, but surprisingly little is known with regard to clinical effects of opiates on the oesophagus. Aim, To characterize opiate effects on motor function of the oesophagus in patients presenting with dysphagia. Methods, Retrospective review of 15 patients with dysphagia referred for oesophageal manometry while on chronic opiates. Manometry was completed during opiate use and in three cases, after opiates were discontinued. Results, All patients demonstrated motility abnormalities. Incomplete lower oesophageal sphincter (LOS) relaxation (11.5 ± 1.6 mmHg) was seen in most cases. Ten patients demonstrated nonperistaltic contractions in ,3 of 10 swallows. Additional abnormalities included high amplitude contractions; triple peaked contractions; and increased velocity. The average resting lower oesophageal sphincter (LOSP) met criteria for hypertensive LOS in three patients. These features were suggestive of spasm or achalasia. Repeat manometry off opiates was performed in three cases. LOS relaxation was noted to be complete upon repeat manometry in these cases. There was also improved peristalsis and normal velocity. Conclusions, A range of manometric abnormalities were seen in patients with dysphagia in the setting of opiate use: impaired LOS relaxation, high amplitude/velocity and simultaneous oesophageal waves. These data suggest that the oesophagus is susceptible to the effects of opiates and care must be taken before ascribing dysphagia to a primary oesophageal motility disorder in patients taking opiates. [source]

Lower oesophageal sphincter relaxation evoked by stimulation of the dorsal motor nucleus of the vagus in ferrets

NEUROGASTROENTEROLOGY & MOTILITY, Issue 3 2002
T. P. Abrahams
Abstract, An understanding of the neural control of lower oesophageal sphincter (LOS) relaxation is clinically relevant because transient LOS relaxations (TLOSRs) are a mechanism of acid reflux into the oesophagus. Preganglionic motor neurones innervating the LOS are localized in the dorsal motor nucleus of the vagus (DMV). Based on a single study in cats, it is now widely accepted that these neurones are functionally organized into two separate populations, such that stimulation of the caudal and rostral DMV evokes LOS relaxation and contraction, respectively. Our goal was to map the functional LOS responses to chemical stimulation in the DMV and nucleus tractus solitarius (NTS) of ferrets, an animal model commonly used for conscious studies on TLOSRs, and to test whether DMV-evoked LOS relaxation is mediated through hexamethonium-sensitive vagal-inhibitory pathways to the LOS. We used miniaturized manometry with Dentsleeve to monitor LOS and oesophageal pressures in decerebrate unanaesthetized ferrets. LOS relaxation was evoked readily in response to gastric insufflation, which shows that the vago,vagal reflex was intact in this preparation. Microinjections of l -glutamate (12.5 nmol L,1in 25 nL) were made into the DMV from approximately ,,1.5 to +,2.0 mm relative to the obex. Microinjections into the caudal (, 1.5 to +,0.0 mm behind obex) and intermediate (+ 0.1 to +,1.0 mm rostral to obex) DMV both significantly decreased LOS pressure, and complete LOS relaxation was noted in 28/32 and 11/18 cases, respectively. LOS relaxation responses to DMV microinjection were highly reproducible and abolished by bilateral vagotomy or hexamethonium (15 mg kg,1intravenously). A nitric oxide synthase inhibitor (l -NAME 100 mg kg,1intramuscularly) significantly increased the time taken to reach the maximal response. Increases in LOS pressure (24 ± 4 mmHg; n = 3) were obtained only when stimulation sites were located equal to greater than 1.5 mm rostral to the obex. LOS relaxation (, 78 ± 10%; n = 6) was evoked by stimulation of the NTS but not immediately outside of the NTS (11 ± 27%; n = 5). We conclude that there is a very extensive population of ,inhibitory' motor neurones in the DMV that may account for the predominant vagal-inhibitory tone in ferrets. As NTS stimulation evokes LOS relaxation and the predominant response to DMV stimulation is also LOS relaxation, this vago,vagal reflex may involve an excitatory interneurone between the NTS and DMV vagal inhibitory output. [source]

Effect of endotoxin on opossum oesophageal motor function

NEUROGASTROENTEROLOGY & MOTILITY, Issue 3 2000
H. Park
Endotoxin induces nitric oxide (NO,) synthase and alters gastrointestinal functions. We explored the effect of lipopolysaccharide (LPS) on oesophageal motor function at 6, 12, 24, and 48 h. The effects of inhibiting inducible NO, synthase (iNOS) were studied 12 h after administration of LPS with/without aminoguanidine (AG). Oesophageal manometry was performed and tissue bath studies were performed with muscle strips from the oesophagus and lower oesophageal sphincter (LOS). Plasma nitrite/nitrate concentrations were determined. The amplitudes of peristaltic pressure waves, resting LOS pressure and the percentage LOS relaxations were diminished by LPS. AG attenuated the decrease in amplitude of oesophageal pressure waves, LOS pressure, and percentage relaxation of LOS brought about by LPS. LPS decreased electrical field stimulation (EFS)-induced relaxation of LOS muscle. AG attenuated this decrease in LOS relaxation. The off-response of transverse oesophageal muscle strips was decreased, and AG antagonized this effect. Plasma concentrations of nitrite/nitrate were increased. The increase in plasma nitrite/nitrate was attenuated by AG. These studies support the hypothesis that endotoxin modulates oesophageal motor function by increasing NO production and suggest that this results from the induction of iNOS. [source]

Lower oesophageal sphincter relaxation evoked by stimulation of the dorsal motor nucleus of the vagus in ferrets

NEUROGASTROENTEROLOGY & MOTILITY, Issue 3 2002
T. P. Abrahams
Abstract, An understanding of the neural control of lower oesophageal sphincter (LOS) relaxation is clinically relevant because transient LOS relaxations (TLOSRs) are a mechanism of acid reflux into the oesophagus. Preganglionic motor neurones innervating the LOS are localized in the dorsal motor nucleus of the vagus (DMV). Based on a single study in cats, it is now widely accepted that these neurones are functionally organized into two separate populations, such that stimulation of the caudal and rostral DMV evokes LOS relaxation and contraction, respectively. Our goal was to map the functional LOS responses to chemical stimulation in the DMV and nucleus tractus solitarius (NTS) of ferrets, an animal model commonly used for conscious studies on TLOSRs, and to test whether DMV-evoked LOS relaxation is mediated through hexamethonium-sensitive vagal-inhibitory pathways to the LOS. We used miniaturized manometry with Dentsleeve to monitor LOS and oesophageal pressures in decerebrate unanaesthetized ferrets. LOS relaxation was evoked readily in response to gastric insufflation, which shows that the vago,vagal reflex was intact in this preparation. Microinjections of l -glutamate (12.5 nmol L,1in 25 nL) were made into the DMV from approximately ,,1.5 to +,2.0 mm relative to the obex. Microinjections into the caudal (, 1.5 to +,0.0 mm behind obex) and intermediate (+ 0.1 to +,1.0 mm rostral to obex) DMV both significantly decreased LOS pressure, and complete LOS relaxation was noted in 28/32 and 11/18 cases, respectively. LOS relaxation responses to DMV microinjection were highly reproducible and abolished by bilateral vagotomy or hexamethonium (15 mg kg,1intravenously). A nitric oxide synthase inhibitor (l -NAME 100 mg kg,1intramuscularly) significantly increased the time taken to reach the maximal response. Increases in LOS pressure (24 ± 4 mmHg; n = 3) were obtained only when stimulation sites were located equal to greater than 1.5 mm rostral to the obex. LOS relaxation (, 78 ± 10%; n = 6) was evoked by stimulation of the NTS but not immediately outside of the NTS (11 ± 27%; n = 5). We conclude that there is a very extensive population of ,inhibitory' motor neurones in the DMV that may account for the predominant vagal-inhibitory tone in ferrets. As NTS stimulation evokes LOS relaxation and the predominant response to DMV stimulation is also LOS relaxation, this vago,vagal reflex may involve an excitatory interneurone between the NTS and DMV vagal inhibitory output. [source]

Prolonged recording of oesophageal and lower oesophageal sphincter pressure using a portable water-perfused manometric system

NEUROGASTROENTEROLOGY & MOTILITY, Issue 2 2001
M. A. Van Herwaarden
The aim of our study was to investigate the recording fidelity of a water-perfused micromanometric catheter with incorporated sleeve combined with a newly developed portable water-perfused manometric system for pharyngeal, oesophageal and lower oesophageal sphincter (LOS) pressure recording. The system's performance was assessed in prolonged recordings in ambulant gastro-oesophageal reflux disease (GORD) patients. Eighty 24-h studies in GORD patients, carried out with the perfused portable manometric system, were evaluated. Twelve of these recordings were analysed in detail in order to compare oesophageal and LOS motor patterns with those described previously. Paired 2-h manometric recordings of the pharynx, oesophagus, LOS and stomach, using the new system and a conventional perfused stationary manometric system, were performed in eight healthy subjects. With the portable manometric system oesophageal contractions, transient LOS relaxations, swallow-associated prolonged LOS relaxations and LOS pressures were recorded with equal fidelity to the conventional manometric system. Recordings obtained with the portable system showed meal-related and diurnal variations in oesophageal and LOS variables that were similar to these found in studies using conventional equipment. The new manometric system, consisting of a perfused micromanometric catheter with incorporated sleeve and a portable perfusion system, enables prolonged studies on oesophageal and LOS motor patterns in ambulant subjects. [source]

Effect of endotoxin on opossum oesophageal motor function

NEUROGASTROENTEROLOGY & MOTILITY, Issue 3 2000
H. Park
Endotoxin induces nitric oxide (NO,) synthase and alters gastrointestinal functions. We explored the effect of lipopolysaccharide (LPS) on oesophageal motor function at 6, 12, 24, and 48 h. The effects of inhibiting inducible NO, synthase (iNOS) were studied 12 h after administration of LPS with/without aminoguanidine (AG). Oesophageal manometry was performed and tissue bath studies were performed with muscle strips from the oesophagus and lower oesophageal sphincter (LOS). Plasma nitrite/nitrate concentrations were determined. The amplitudes of peristaltic pressure waves, resting LOS pressure and the percentage LOS relaxations were diminished by LPS. AG attenuated the decrease in amplitude of oesophageal pressure waves, LOS pressure, and percentage relaxation of LOS brought about by LPS. LPS decreased electrical field stimulation (EFS)-induced relaxation of LOS muscle. AG attenuated this decrease in LOS relaxation. The off-response of transverse oesophageal muscle strips was decreased, and AG antagonized this effect. Plasma concentrations of nitrite/nitrate were increased. The increase in plasma nitrite/nitrate was attenuated by AG. These studies support the hypothesis that endotoxin modulates oesophageal motor function by increasing NO production and suggest that this results from the induction of iNOS. [source]