Alpha2-adrenoceptors coordinate swallowing and respiration.
Because the discoordination between swallowing and respiration may cause severe respiratory disorders such as aspiration pneumonia, understanding the neuronal mechanisms underlying such coordination is important. Recently, it was reported that medullary noradrenergic neurons are involved in evoking esophageal-gastric relaxation reflex, leading to a hypothesis that such neurons are also involved in swallowing-respiration coordination. We tested this hypothesis using an in vitro brain-stem preparation obtained from neonatal rats. A temporal inhibition of respiratory rhythm was consistently observed when swallowing activity was induced by electrical stimulations to the supralaryngeal nerve. We found that a broad adrenergic receptor agonist, norepinephrine, markedly blocked the swallowing-induced temporal inhibition of respiration. Further studies revealed that swallowing-induced respiratory inhibition is blocked by an alpha2-adrenergic receptor agonist and enhanced by an alpha2-adrenergic receptor antagonist, indicating an important role of alpha2-adrenergic receptors in regulation of the coordination between swallowing and respiration in vitro.
Yamanishi
T
T
First Department of Oral and Maxillofacial Surgery, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka, Japan. yaman2@dent.osaka-u.ac.jp
Takao
K
K
Koizumi
H
H
Ishihama
K
K
Nohara
K
K
Komaki
M
M
Enomoto
A
A
Yokota
Y
Y
Kogo
M
M
D018663:Adrenergic Agents / Q000494:pharmacology; D000818:Animals; D001933:Brain Stem / Q000187:drug effects / Q000502:physiology; D003679:Deglutition / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D009434:Neural Pathways / Q000187:drug effects; D009474:Neurons / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000187:drug effects / Q000502:physiology*; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*; D013116:Spinal Cord / Q000187:drug effects
D018663:Adrenergic Agents; D018341:Receptors, Adrenergic, alpha-2; D009638:Norepinephrine