Inhibition of trigeminal respiratory activity by suckling.
The trigeminal motor system is involved in many rhythmic oral-motor behaviors, such as suckling, mastication, swallowing, and breathing. Despite the obvious importance of functional coordination among these rhythmic activities, the system is not well-understood. In the present study, we examined the hypothesis that an interaction between suckling and breathing exists in the brainstem, by studying the respiratory activity in trigeminal motoneurons (TMNs) during fictive suckling using a neonatal rat in vitro brainstem preparation. The results showed that fictive suckling, which was neurochemically induced by bath application of N-methyl-D,L-aspartate and bicuculline-methiodide, or by local micro-injection of the same drugs to the trigeminal motor nucleus, inhibited the inspiratory activities in both respiration TMNs and respiratory rhythm-generating neurons. Under patch-clamp recording, fictive suckling caused membrane potential hyperpolarization of respiration TMNs. We conclude that the brainstem preparation contains an inhibitory circuit for respiratory activity in the trigeminal motor system via the rhythm-generating network for suckling.


BACKGROUND
BIC, bicuculline methiodide; GABA, gamma aminobutyric acid; NMA, N-methyl-D,L-aspartate; NMDA, N-methyl-D-aspartate; and TMN, trigeminal motoneuron.
Koizumi
H
H
The First Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871 Japan. koizumi@dent.osaka-u.ac.jp
Nomura
K
K
Ishihama
K
K
Yamanishi
T
T
Enomoto
A
A
Kogo
M
M
D000818:Animals; D000833:Animals, Suckling; D001640:Bicuculline / Q000494:pharmacology; D019069:Cell Respiration / Q000187:drug effects / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D008564:Membrane Potentials; D009046:Motor Neurons / Q000502:physiology; D016202:N-Methylaspartate / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D012119:Respiration / Q000187:drug effects; D012125:Respiratory Center / Q000187:drug effects / Q000502:physiology*; D013391:Sucking Behavior / Q000502:physiology*; D014278:Trigeminal Nuclei / Q000187:drug effects / Q000502:physiology*
D018690:Excitatory Amino Acid Agonists; D018756:GABA Antagonists; D016202:N-Methylaspartate; D001640:Bicuculline