title: Postnatal changes in vagal control of esophageal muscle contractions in rats.
abstract: OBJECTIVE
  Replacement of smooth muscles by striated muscles occurs in the esophagus during the early postnatal period. The aim of this study was to clarify postnatal changes in vagal control of esophageal muscle contractions in rats.
  
  
  METHODS
  An isolated segment of the neonatal rat esophagus was placed in an organ bath and the contractile responses were recorded using a force transducer.
  
  
  RESULTS
  Electrical stimulation of the vagus trunk evoked a biphasic contractile response in the neonatal esophageal segment. The first and second components of the contractions were inhibited by α-bungarotoxin and atropine, respectively. Ganglion blockers, hexamethonium and mecamylamine, did not affect vagally mediated contractions. The first component gradually enlarged with age in days, whereas the second component declined during the first week after birth. Application of d-tubocurarine or acetylcholine caused an apparent contraction in the esophageal striated muscle at postnatal day 0, but responses to these drugs were not observed at 1 week after birth. The neonatal esophagus expressed the γ-subunit of nicotinic acetylcholine receptors. In contrast, the ε-subunit was dominantly expressed in the adult esophagus.
  
  
  CONCLUSIONS
  The vagus nerves directly innervate both the esophageal striated muscles and smooth muscles in the early neonatal period. During the process of muscle rearrangement, the property of the striated muscles is altered substantially. The specific features of striated muscles in the neonatal rat esophagus might compensate for immature formation of neuromuscular junctions. Unsuccessful conversion of the striated muscle property during postnatal muscle rearrangement would be related to disorders of esophageal motility.
authors.affiliation: Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Nakamori
authors.forename: Takahiko
authors.initials: T
authors.lastname: Shiina
authors.forename: Yasutake
authors.initials: Y
authors.lastname: Shimizu
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001285:Atropine / Q000494:pharmacology; D004558:Electric Stimulation; D004947:Esophagus / Q000187:drug effects / Q000294:innervation* / Q000502:physiology*; D005260:Female; D005730:Ganglionic Blockers / Q000494:pharmacology; D006321:Heart / Q000502:physiology; D018738:Hexamethonium / Q000494:pharmacology; D008464:Mecamylamine / Q000494:pharmacology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D011247:Pregnancy; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism; D014403:Tubocurarine / Q000494:pharmacology; D014630:Vagus Nerve / Q000187:drug effects / Q000502:physiology*
chemical_list: D005730:Ganglionic Blockers; D018727:Muscarinic Antagonists; D018733:Nicotinic Antagonists; D021122:Protein Subunits; D011978:Receptors, Nicotinic; D018738:Hexamethonium; D008464:Mecamylamine; D001285:Atropine; D000109:Acetylcholine; D014403:Tubocurarine