Morphological demonstration of a vagal inhibitory pathway to the lower esophageal sphincter via nitrergic neurons in the rat esophagus

Studies were performed in anesthetized opossums to investigate the nature of vagal-stimulated sphincter relaxation, which is resistant to antagonism by a combination of hexamethonium and atropine. The sphincter pressures were measured with water-filled and continuously perfused catheters anchored in the lower esophageal sphincter. Neither increase in the doses of hexamethonium and atropine nor addition of diphenhydramine further modified the vagal response. However, administration of 5-methoxydimethyltryptamine in the presence of hexamethonium and atropine abolished vagally stimulated sphincter relaxation. In animals pretreated with parachlorophenylalanine, addition of atropine and hexamethonium also abolished vagally stimulated sphincter relaxation. In the experiments in which lower esophageal sphincter relaxation on vagal stimulation was abolished, the local stimulation of intramural neurons still produced normal lower esophageal sphincter relaxation. These studies suggest that 5-hydroxytryptamine may participate in the vagal inhibitory pathway to the lower esophageal sphincter.

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Baclofen blocks LES relaxation and crural diaphragm inhibition by esophageal and gastric distension in cats

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00080.2002 ◽

2002 ◽

Vol 283 (6) ◽

pp. G1276-G1281 ◽

Cited By ~ 16

Author(s):

Jianmin Liu ◽

Nonko Pehlivanov ◽

Ravinder K. Mittal

Keyword(s):

Lower Esophageal Sphincter ◽

Receptor Agonist ◽

Gastric Distension ◽

Emg Activity ◽

Inhibitory Pathway ◽

Surgical Implantation ◽

Esophageal Sphincter ◽

Adult Cats ◽

Crural Diaphragm

Esophageal distension and transient lower esophageal sphincter (LES) relaxation (TLESR) are accompanied by simultaneous relaxation of the LES and inhibition of crural diaphragm. Recent studies indicate that baclofen decreases the frequency of TLESR; however, its effect on the crural diaphragm is not known. We evaluated the effects of baclofen on LES relaxation and crural diaphragm inhibition induced by gastric distension and esophageal distension in cats. Five adult cats underwent surgical implantation of wire electrodes into the crural and costal diaphragm for measurement of their EMG activity, respectively. One week after the surgery, animals were lightly sedated and recordings were performed using a manometry catheter equipped with a 2.5-cm balloon. The effects of baclofen (10 μmol/kg iv) on the graded esophageal distension and gastric distension-induced LES and crural diaphragm responses were studied. Distension of the esophagus and stomach induces relaxation of the LES and inhibition of the crural diaphragm, simultaneously. Baclofen blocks both the esophageal and the gastric distension-induced relaxation of the LES and inhibition of the crural diaphragm. The magnitude of response to baclofen was significantly larger for the crural diaphragm inhibition than for the LES relaxation. Baclofen, a GABABreceptor agonist, blocks the reflex inhibitory pathway to the LES and crural diaphragm. The reflex inhibitory pathway to the crural diaphragm is more sensitive to blockade by baclofen than the reflex LES inhibitory pathway.

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Subtypes of muscarinic receptors in vagal inhibitory pathway to the lower esophageal sphincter of the opossum

Digestive Diseases and Sciences ◽

10.1007/bf01300200 ◽

1987 ◽

Vol 32 (10) ◽

pp. 1130-1135 ◽

Cited By ~ 4

Author(s):

Richard J. Gilbert ◽

Wylie J. Dodds

Keyword(s):

Lower Esophageal Sphincter ◽

Muscarinic Receptors ◽

Inhibitory Pathway ◽

Esophageal Sphincter

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Pharmacological characterization of lower esophageal sphincter relaxation induced by swallowing, vagal efferent nerve stimulation, and esophageal distention

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y92-139 ◽

1992 ◽

Vol 70 (7) ◽

pp. 1011-1015 ◽

Cited By ~ 53

Author(s):

W. G. Paterson ◽

M. A. B. Anderson ◽

N. Anand

Keyword(s):

Nitric Oxide ◽

Lower Esophageal Sphincter ◽

Vagal Stimulation ◽

Inhibitory Pathway ◽

Efferent Nerve ◽

Balloon Distention ◽

Esophageal Sphincter ◽

Ganglionic Transmission ◽

Oxide Synthase ◽

Vagal Efferent Nerve

To characterize the neural pathways involved in lower esophageal sphincter relaxation, intraluminal pressures from the lower esophageal sphincter of the opossum were monitored during swallowing, vagal efferent nerve stimulation, and intraluminal balloon distention in the presence and absence of pharmacologic antagonism of putative neurotransmitters. The combination of atropine, hexamethonium, and 5-methoxydimethyltryptamine, which is known to block ganglionic transmission in the vagal inhibitory pathway to the lower esophageal sphincter, significantly antagonized LES relaxation induced by both swallowing and vagal stimulation, but did not affect the LES relaxation induced by balloon distention. Administration of the nitric oxide synthase inhibitor Nωnitro-L-arginine methyl ester, on the other hand, markedly inhibited LES relaxation induced by vagal stimulation, swallowing, and balloon distention, and this effect was reversed by administration of the nitric oxide synthase substrate L-arginine. These studies indicate that the distension-induced intramural pathway mediating LES relaxation does not involve ganglionic transmission similar to that of the vagal inhibitory pathway to the LES. However, the LES relaxation induced by all forms of stimuli appears to depend on nitric oxide as a final mediator.Key words: ganglionic transmission, muscarinic, nicotinic, serotonergic, nitric oxide.

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