FEASIBILITY AND DURATION OF UNMYELINATED VAGAL NERVE BLOCKADE IN NEONATAL LAMB. 1991

Studies were performed on four cats to assess the role of extrinsic vagal innervation in the control of lower esophageal sphincter (LES) function. Both cervical vagal nerves were blocked transiently by cooling. LES pressure was measured using a multilumen manometry tube. LES relaxation was assessed during intraesophageal balloon distension in both the striated and smooth muscle portions of the esophagus. Bilateral vagal nerve blockade lowered the mean LES pressure from 58 +/- 17 to 29 +/- 9 mmHg (P less than 0.01). During vagal blockade, balloon distension in the striated muscle esophagus further reduced sphincter pressure to 16 +/- 4 mmHg (P less than 0.01) and that in the smooth muscle esophagus to 15 +/- 3 mmHg (P less than 0.01). Swallow-induced LES relaxation was abolished during bilateral vagal nerve blockade. During vagal blockade, atropine reduced LES pressure to 10 +/- 1 mmHg, phentolamine to 13 +/- 6 mmHg, and hexamethonium to 10 +/- 4 mmHg (all P less than 0.01). We conclude that 1) normal LES tone in the cat is mediated primarily by two separate neural mechanisms: a vagal cholinergic mechanism and a nonvagal mechanism that utilizes both alpha-adrenergic and cholinergic receptors; 2) local, intramural mechanisms of high threshold are present in the striated and smooth muscle cat esophagus to allow distension-induced reflex inhibition of the LES; and 3) swallow-induced LES relaxation is dependent on vagally mediated central nervous system connections.

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Oesophageal peristalsis in the cat: the role of central innervation assessed by transient vagal blockade

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y85-022 ◽

1985 ◽

Vol 63 (2) ◽

pp. 122-130 ◽

Cited By ~ 20

Author(s):

R. P. E. Reynolds ◽

T. Y. El-Sharkawy ◽

N. E. Diamant

Keyword(s):

Smooth Muscle ◽

Striated Muscle ◽

Vagal Nerve ◽

The Body ◽

Nerve Blockade ◽

Primary Peristalsis ◽

Vagal Blockade ◽

Central Innervation ◽

Secondary Peristalsis

Studies were performed on five cats to assess the role of extrinsic vagal innervation in the control of peristalsis in the smooth muscle oesophagus. Transient vagal nerve blockade was accomplished by cooling the cervical vagosympathetic nerve trunks previously isolated in skin loops on each side of the neck. Peristalsis throughout the body of the oesophagus was monitored using a continuously perfused multilumen manometry tube. Striated and smooth muscle portions of the esophagus were delineated by abolishing smooth muscle activity with atropine. Secondary peristalsis was assessed by intra-oesophageal balloon distension studies. The threshold volume for balloon-induced secondary peristalsis was lower in the smooth muscle oesophagus. Unilateral vagal blockade reduced the incidence of primary and secondary peristalsis in the striated muscle oesophagus but not in the smooth muscle oesophagus. Bilateral vagal nerve blockade abolished primary swallow-induced peristalsis and secondary peristalsis in both the smooth and striated muscle cat oesophagus. Administration of cholinergic agents or adrenergic blocking agents failed to restore secondary peristalsis in the smooth muscle oesophagus during vagal cooling. We conclude that connections to the central nervous system via the vagal nerve trunks are required for normal secondary as well as primary peristalsis in both the smooth and striated muscle portions of the cat oesophagus.

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The upper esophageal sphincter in the cat: the role of central innervation assessed by transient vagal blockade

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y87-019 ◽

1987 ◽

Vol 65 (1) ◽

pp. 96-99 ◽

Cited By ~ 17

Author(s):

R. P. E. Reynolds ◽

G. W. Effer ◽

M. P. Bendeck

Keyword(s):

Upper Esophageal Sphincter ◽

Vagal Nerve ◽

Sphincter Pressure ◽

Neural Pathways ◽

Cervical Nerve ◽

Nerve Blockade ◽

Acid Perfusion ◽

Balloon Distention ◽

Esophageal Sphincter

Studies were performed on four cats to assess the role of extrinsic innervation via the cervical nerve trunks in the control of upper esophageal sphincter function. Transient vagal nerve blockade was accomplished by cooling the cervical vagosympathetic nerve trunks previously isolated in skin loops on each side of the neck. Upper esophageal sphincter pressure was measured using a multilumen oval manometry tube and a rapid pull-through technique. The upper esophageal sphincter response to cervical intraesophageal balloon distention and acid perfusion was assessed. The feline upper esophageal sphincter has a distinct asymmetric pressure profile, whereby anterior pressure > posterior pressure > left pressure > right pressure. Bilateral vagal nerve blockade lowered the mean upper esophageal sphincter pressure from 18.5 ± 1.5 to 12.0 ± 2.8 mmHg (1 mmHg = 133.3 Pa) (p < 0.001), with a significant reduction in pressure in all four quadrants. Intraesophageal balloon distention and acid perfusion both produced a significant increase in upper esophageal sphincter pressure. Bilateral vagal nerve blockade completely abolished the response of the upper esophageal sphincter to balloon distention and acid perfusion. We conclude that (i) normal upper esophageal sphincter tone in the cat is partially mediated by excitatory neural input via the cervical nerve trunks, presumably via the recurrent laryngeal nerves; and (ii) cervical intraesophageal balloon distention and acid perfusion produce reflex contraction of the upper esophageal sphincter, which is dependent on neural pathways via the cervical vagal nerve trunks, but the relative contribution of afferent and efferent pathways remains unknown.

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