The excitatory amino acid glutamate mediates reflexly increased tracheal blood flow and airway submucosal gland secretion.
In six decerebrated and in eight alpha-chloralose anesthetized, paralyzed and mechanically ventilated beagle dogs, we have studied involvement of glutamate and glutamate receptors in transmission of excitatory inputs from the airway sensory receptors to the nucleus tractus solitarius and from this site to airway-related vagal preganglionic cells that regulate the tracheal circulation and the submucosal gland secretion. Stimulation of airway sensory fibers by lung deflation-induced reflex increase in tracheal blood flow and submucosal gland secretion. These responses were diminished by prior administration of AMPA/kainate receptor antagonist CNQX into the fourth ventricle (n=6). Furthermore, topical application or microinjection of AMPA/kainate receptor blockers, into the region of the ventrolateral medulla, where airway-related vagal preganglionic neurons are located, abolished the reflex changes in tracheal submucosal gland secretion (n=8); in these dogs mucosal blood flow was not measured). These findings indicate that reflex increase in tracheal blood flow and submucosal gland secretions are mediated mainly via release of glutamate and activation of the AMPA/kainate subtype of glutamate receptors.
Haxhiu
M A
MA
Department of Pediatrics, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA. mah10@po.cwru.edu
Chavez
J C
JC
Pichiule
P
P
Erokwu
B
B
Dreshaj
I A
IA
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004285:Dogs; D005260:Female; D018698:Glutamic Acid / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D007276:Injections, Intraventricular; D008297:Male; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors; D018092:Kainic Acid Receptors / Q000037:antagonists & inhibitors; D012018:Reflex / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D012119:Respiration; D020545:Respiratory Mucosa / Q000187:drug effects / Q000378:metabolism*; D014132:Trachea / Q000098:blood supply*
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D018698:Glutamic Acid; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors