Relaxant innervation of the guinea-pig trachealis: demonstration of capsaicin-sensitive and -insensitive vagal pathways
1. The guinea-pig trachea was isolated with its extrinsic innervation intact and placed in a water-jacketed dissecting dish containing warmed, oxygenated Krebs solution. The trachea was not separated from the oesophagus. Two adjacent cartilage rings of the rostral portion of the trachea were cut ope...
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Veröffentlicht in: | The Journal of physiology 1993-01, Vol.460 (1), p.719-739 |
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Sprache: | eng |
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Zusammenfassung: | 1. The guinea-pig trachea was isolated with its extrinsic innervation intact and placed in a water-jacketed dissecting dish
containing warmed, oxygenated Krebs solution. The trachea was not separated from the oesophagus. Two adjacent cartilage rings
of the rostral portion of the trachea were cut open opposite the trachealis and prepared for isometric tension measurements.
2. Following the addition of atropine and contraction of the trachealis with prostaglandin F2 alpha (PGF2 alpha), stimulation
of the cervical sympathetic trunks elicited relaxations that were abolished by propranolol or hexamethonium. Stimulation of
the vagus nerves caudal to the nodose ganglia also elicited relaxations. These vagally mediated relaxations were unaffected
by propranolol but were abolished by hexamethonium or by cutting the recurrent laryngeal nerves. 3. After cutting the vagi
caudal to the nodose ganglia, stimulation of the vagi rostral to the nodose ganglia elicited relaxations of the trachealis
that were not significantly affected by either propranolol or hexamethonium but were abolished by cutting the superior laryngeal
nerves. Stimulation of right vagi which had undergone supranodose vagotomy 14 days prior to experimentation was without effect
on the smooth muscle of the guinea-pig trachea while the response to stimulation of the left vagus was unchanged. 4. Acute
capsaicin desensitization abolished relaxations of the guinea-pig trachealis elicited by stimulation of the vagal fibres carried
by the superior laryngeal nerves. In contrast, capsaicin desensitization only modestly inhibited relaxations elicited by stimulation
of the preganglionic parasympathetic fibres carried by the recurrent laryngeal nerves and had no effect on sympathetic nerve-induced
relaxations. 5. Removing the oesophagus selectively abolished relaxations elicited by stimulation of both vagal pathways of
non-adrenergic relaxant innervation. Non-adrenergic relaxations of the trachealis elicited by electrical field stimulation
were unaffected by removing the oesophagus. Oesophagus removal also had no effect on the parasympathetic-cholinergic contractile
innervation or the sympathetic relaxant innervation of the trachealis. 6. The results indicate that the guinea-pig trachealis
receives non-adrenergic relaxant innervation from both parasympathetic and capsaicin-sensitive vagal pathways. The results
also suggest that the neurones mediating non-adrenergic relaxations of the trachea are sensitive to oesoph |
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ISSN: | 0022-3751 1469-7793 |
DOI: | 10.1113/jphysiol.1993.sp019496 |