Cortical arousal induced by microinjection of orexins into the paraventricular nucleus of the rat.
Orexin-A is a neuropeptide which has been suggested to be involved in sleep and arousal mechanisms. Orexin-A, for example, stimulates arousal when administrated intracerebroventricularly to rats. We attempted to identify specific neural sites of orexin-A and orexin-B action. Orexin-A and orexin-B were microinjected into the medial parvocellular subdivision of the paraventricular nucleus (PVN) in anesthetized, spontaneously breathing rats, and cortical arousal and yawning responses were assessed. Cortical arousal responses were monitored with the electrocorticogram (ECoG), and yawning responses were evaluated by monitoring intercostal electromyograms as an index of inspiratory activity and digastric electromyograms as an indicator of mouth opening. We also measured blood pressure and heart rate during yawning responses, since yawning is accompanied by changes in autonomic activity. Microinjection of orexin-A into the PVN elicited an arousal shift in the ECoG to lower voltage and faster rhythms. This cortical arousal response was followed by a single large inspiration with mouth opening, i.e. a yawning response. On the other hand, microinjection of orexin-B into the PVN elicited an arousal shift in the ECoG without yawning responses. These results demonstrate that an orexin receptive site for triggering arousal/yawning responses exists in the PVN, and suggest that the PVN is involved in arousal mechanisms.
Sato-Suzuki
Ikuko
I
Department of Physiology, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan.
Kita
Ichiro
I
Seki
Yoshinari
Y
Oguri
Mitsugu
M
Arita
Hideho
H
D000818:Animals; D001143:Arousal / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects; D002352:Carrier Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000187:drug effects*; D004562:Electrocardiography / Q000187:drug effects; D004576:Electromyography / Q000187:drug effects; D018698:Glutamic Acid / Q000008:administration & dosage / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008845:Microinjections; D009479:Neuropeptides / Q000008:administration & dosage / Q000494:pharmacology*; D000068797:Orexins; D010286:Paraventricular Hypothalamic Nucleus / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013239:Stereotyped Behavior / Q000187:drug effects; D013566:Sympathomimetics / Q000494:pharmacology*; D015000:Yawning / Q000187:drug effects
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins; D013566:Sympathomimetics; D018698:Glutamic Acid