Possible involvement of neurons in locus coeruleus in inhibitory effect on glossopharyngeal expiratory activity in a neonatal rat brainstem-spinal cord preparation in vitro.
In this study, we found that a certain motor branch of glossopharyngeal (IX) motor nerves stably exhibits not only inspiratory activity but also expiratory activity with pons removal in neonatal rat brainstem-spinal cord preparations in vitro. Because this finding indicates that IX expiratory activity is masked by an inhibitory mechanism operating in the pons, we sought to determine the candidate neurons that exert an inhibitory effect on IX expiratory activity. IX expiratory activity was observed when only the pons was perfused with noradrenaline (NA) or clonidine (alpha2 adrenergic receptor agonist), but not when NA and yohimbine (alpha2 adrenergic receptor antagonist) were perfused together. IX expiratory activity was also observed following the removal of the dorsal pons but not the ventral pons. The local administration of clonidine into the bilateral locus coeruleus (LC) evoked burst discharges during the expiratory phase in the IX motor rootlet. These results suggest that neurons in the LC that possess an alpha2 adrenergic receptor on the membrane surface exert a tonic inhibitory effect on IX expiratory activity in neonatal rat brainstem-spinal cord preparations.
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
Tadashi
T
Yamanishi
Hidehiko
H
Koizumi
Masashi
M
Komaki
Kohji
K
Ishihama
Tadafumi
T
Adachi
Akifumi
A
Enomoto
Kana
K
Takao
Seiji
S
Iida
Mikihiko
M
Kogo
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D058647:Adrenergic alpha-2 Receptor Agonists; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D045853:Exhalation / Q000187:drug effects / Q000502:physiology*; D005930:Glossopharyngeal Nerve / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008125:Locus Coeruleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009434:Neural Pathways / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D009638:Norepinephrine / Q000378:metabolism; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism; D012125:Respiratory Center / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D058647:Adrenergic alpha-2 Receptor Agonists; D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D018341:Receptors, Adrenergic, alpha-2; D009638:Norepinephrine