title: Extracellular levels of serotonin in the medial pontine reticular formation in relation to sleep-wake cycle in cats: a microdialysis study.
abstract: Extracellular levels of endogenous serotonin (5-hydroxytryptamine; 5-HT) and its major metabolite, 5-hydroxyindoleacetic acid (5-HIAA) were measured in the medial pontine reticular formation (medial PRF) of intact cats. A microdialysis probe was inserted through a guide cannula into the medial PRF. At least 12 h after the probe insertion, in vivo brain microdialysis was initiated. The perfusion rate was 1 microliters/min, and perfusate fractions at regular intervals of 20 min were collected. Changes in extracellular 5-HT levels were compared across sleep-wake states of the animals, such as waking (W), slow wave sleep (SWS) and rapid eye movement (REM) sleep. To assess sleep-wake states, EEG, EMG, EOG and PGO waves were simultaneously recorded in parallel with microdialysis of the medial PRF. Extracellular 5-HT levels were highest (20-28 fmol/20 microliters) during W. As the animals entered SWS, 5-HT levels decreased to about 90% of those during W. The state of REM sleep usually interrupted SWS for 3-8 min. During the longer periods of REM sleep, during the 20 min periods in which the perfusates were collected, we observed the lowest 5-HT levels (60-50%).
authors.affiliation: Department of Otolaryngology, Asahikawa Medical College, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Iwakiri
authors.forename: K
authors.initials: K
authors.lastname: Matsuyama
authors.forename: S
authors.initials: S
authors.lastname: Mori
mesh_terms: D000818:Animals; D002415:Cats; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004576:Electromyography; D004585:Electrooculography; D005110:Extracellular Space / Q000378:metabolism; D005260:Female; D006719:Homovanillic Acid / Q000378:metabolism; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D017286:Polysomnography; D011149:Pons / Q000378:metabolism*; D012154:Reticular Formation / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D012890:Sleep / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology; D014851:Wakefulness / Q000502:physiology*
chemical_list: D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D006719:Homovanillic Acid