On-line detection of extracellular levels of serotonin in dorsal raphe nucleus and frontal cortex over the sleep/wake cycle in the freely moving rat

We used in vivo microdialysis coupled with polygraphic recording to monitor 5-hydroxytryptamine levels in the dorsal raphe nucleus and frontal cortex across waking, slow-wave sleep and rapid eye-movement sleep. Male Sprague–Dawley rats were prepared with electroencephalogram and electromyogram elect...

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Bibliographic Details
Published in:	Neuroscience Vol. 83; no. 3; pp. 807 - 814
Main Authors:	Portas, C.M, Bjorvatn, B, Fagerland, S, Grønli, J, Mundal, V, Sørensen, E, Ursin, R
Format:	Journal Article
Language:	English
Published:	Oxford Elsevier Ltd 01-01-1998 Elsevier
Subjects:	5-HT Animals Biological and medical sciences Chromatography, High Pressure Liquid dorsal raphe nucleus Electrochemistry - methods frontal cortex Frontal Lobe - metabolism Fundamental and applied biological sciences. Psychology HPLC-EC Male Microdialysis Monitoring, Physiologic - methods Raphe Nuclei - metabolism Rats Rats, Sprague-Dawley Serotonin - metabolism sleep Sleep Stages - physiology Sleep. Vigilance Vertebrates: nervous system and sense organs Wakefulness - physiology 5-HIAA, 5-hydroxy indolacetic acid FC, frontal cortex HPLC-EC, High-performance liquid chromatography–electrochemical detection EEG, electroencephalogram EMG, electromyogram REM, rapid eye-movement sleep dorsal raphe nucleus 5-HT, serotonin (5-hydroxytryptamine) frontal cortex microdialysis DRN, dorsal raphe nucleus W, waking 5-HT HPLC-EC SWS, slow-wave sleep Vertebrata Mammalia Rat Serotonin Rodentia Central nervous system Neurotransmitter Raphe nucleus Frontal cortex Sleep wake cycle Brain (vertebrata)
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Summary:	We used in vivo microdialysis coupled with polygraphic recording to monitor 5-hydroxytryptamine levels in the dorsal raphe nucleus and frontal cortex across waking, slow-wave sleep and rapid eye-movement sleep. Male Sprague–Dawley rats were prepared with electroencephalogram and electromyogram electrodes. Microdialysis probes were placed in dorsal raphe nucleus and/or frontal cortex. Dialysate samples were manually collected during polygraphically-defined behavioural states and the level of serotonin was assayed by means of microbore high-performance liquid chromatography separation and electrochemical detection. Samples from microdialysis probes histologically localized to the dorsal raphe nucleus and frontal cortex showed different levels of extracellular 5-hydroxytryptamine in waking, slow-wave sleep and rapid eye-movement sleep. In dorsal raphe nucleus the extracellular level of serotonin was highest in waking, decreased in slow-wave sleep to 69% and in rapid eye-movement sleep to 39% of waking mean level (waking 3.2±0.9; slow-wave sleep 2.2±0.8; rapid eye-movement sleep 1.3±0.4 fmol/sample). Mean extracellular levels of serotonin in frontal cortex displayed a similar pattern (waking 1.7±0.4; slow-wave sleep 1.0±0.3; rapid eye-movement 0.5±0.05 fmol/sample). In frontal cortex, rapid eye-movement sleep samples were only obtained in three animals. Our findings are consistent with previous results in cats, and suggest that in rats also, extracellular 5-hydroxytryptamine levels in dorsal raphe nucleus and frontal cortex across the sleep/wake cycle might reflect serotonergic neuronal activity. The findings stress the importance of controlling for behavioural state when investigating neurochemical correlates of serotonergic function.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0306-4522 1873-7544
DOI:	10.1016/S0306-4522(97)00438-7