Effects of vagal cooling on esophageal cardiovascular reflex responses in the rat.
Distension of the distal esophagus in the anesthetized rat causes a vagally-mediated arterial pressor and tachycardia response. To investigate the nature of viscerosensory fibers in the afferent limb of this reflex, the present study was carried out in urethane-anesthetized rats that were subjected to graded cooling of both cervical vagal trunks in situ. Distal esophageal distension was applied for 20 s by means of a water-filled high compliance balloon. Vagal cooling to 9 degrees C abolished pressor responses and unmasked a depressor component during maximal distension. Cooling to 7.5 degrees C blocked this inhibitory component, well above the temperature known to block C-fibers. We conclude that the cardiovascular response to esophageal distension is triggered via at least two subpopulations of A(delta) type vagal afferents that project to brain stem nuclei regulating central vasomotor tone.
Dong
H
H
Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Canada.
Loomis
C W
CW
Bieger
D
D
D000818:Animals; D001831:Body Temperature / Q000502:physiology*; D002319:Cardiovascular System / Q000294:innervation; D003080:Cold Temperature; D004947:Esophagus / Q000294:innervation*; D008297:Male; D009475:Neurons, Afferent / Q000502:physiology; D009619:Nociceptors / Q000502:physiology; D010146:Pain / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex / Q000502:physiology*; D013610:Tachycardia / Q000503:physiopathology; D014630:Vagus Nerve / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology