State-dependent effects of orexins on the serotonergic dorsal raphe neurons in the rat

The serotonergic dorsal raphe (DR) neurons play an important role in sleep–wakefulness regulation. Orexinergic neurons in the lateral hypothalamus densely project to the brainstem sites including the DR. To test the effects of orexins on the serotonergic DR neurons, we applied orexin A (0.1 mM) by p...

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Bibliographic Details
Published in:Regulatory peptides 2005-03, Vol.126 (1), p.43-47
Main Authors: Takahashi, Kazumi, Wang, Qing-Ping, Guan, Jian-Lian, Kayama, Yukihiko, Shioda, Seiji, Koyama, Yoshimasa
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Extracellular recording
Fundamental and applied biological sciences. Psychology
In vivo
Intracellular Signaling Peptides and Proteins - administration & dosage
Male
Neuronal activity
Neurons - drug effects
Neurons - physiology
Neuropeptides - administration & dosage
Orexins
Pressure injection
Raphe Nuclei - physiology
Rats
Rats, Sprague-Dawley
REM sleep
Serotonin - metabolism
Signal Transduction - drug effects
Sleep Stages - drug effects
Sleep Stages - physiology
Sleep. Vigilance
Sleep–wakefulness regulation
Vertebrates: endocrinology
Vertebrates: nervous system and sense organs
Wakefulness - drug effects
Wakefulness - physiology
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Summary:The serotonergic dorsal raphe (DR) neurons play an important role in sleep–wakefulness regulation. Orexinergic neurons in the lateral hypothalamus densely project to the brainstem sites including the DR. To test the effects of orexins on the serotonergic DR neurons, we applied orexin A (0.1 mM) by pressure to these neurons in unanesthetized and urethane anesthetized rats. Orexin A caused excitation in 10 of 15 neurons under unanesthetized condition. The excitation was characterized by slow onset (0–18 s), long lasting duration (15–150 s) and state-dependency. Orexin A applied during REM sleep or slow wave sleep induced significant excitation while during wakefulness, the similar amount of orexin A did not increase the firing rate any more. In the anesthetized animals, orexin A induced excitation in four of eight neurons. The excitation had slow onset and was long lasting. These results suggest that orexinergic neurons exert excitatory influence on the serotonergic DR neurons to maintain tonic activity of them, thereby participating in regulation of sleep–wakefulness cycles and other functions.
ISSN:0167-0115
1873-1686
DOI:10.1016/j.regpep.2004.08.009