title: Phospholipase C-beta4 is essential for the progression of the normal sleep sequence and ultradian body temperature rhythms in mice.
abstract: BACKGROUND
  THE SLEEP SEQUENCE: i) non-REM sleep, ii) REM sleep, and iii) wakefulness, is stable and widely preserved in mammals, but the underlying mechanisms are unknown. It has been shown that this sequence is disrupted by sudden REM sleep onset during active wakefulness (i.e., narcolepsy) in orexin-deficient mutant animals. Phospholipase C (PLC) mediates the signaling of numerous metabotropic receptors, including orexin receptors. Among the several PLC subtypes, the beta4 subtype is uniquely localized in the geniculate nucleus of thalamus which is hypothesized to have a critical role in the transition and maintenance of sleep stages. In fact, we have reported irregular theta wave frequency during REM sleep in PLC-beta4-deficient mutant (PLC-beta4-/-) mice. Daily behavioral phenotypes and metabotropic receptors involved have not been analyzed in detail in PLC-beta4-/- mice, however.
  
  
  RESULTS
  Therefore, we analyzed 24-h sleep electroencephalogram in PLC-beta4-/- mice. PLC-beta4-/- mice exhibited normal non-REM sleep both during the day and nighttime. PLC-beta4-/- mice, however, exhibited increased REM sleep during the night, their active period. Also, their sleep was fragmented with unusual wake-to-REM sleep transitions, both during the day and nighttime. In addition, PLC-beta4-/- mice reduced ultradian body temperature rhythms and elevated body temperatures during the daytime, but had normal homeothermal response to acute shifts in ambient temperatures (22 degrees C-4 degrees C). Within the most likely brain areas to produce these behavioral phenotypes, we found that, not orexin, but group-1 metabotropic glutamate receptor (mGluR)-mediated Ca(2+) mobilization was significantly reduced in the dorsal lateral geniculate nucleus (LGNd) of PLC-beta4-/- mice. Voltage clamp recordings revealed that group-1 mGluR-mediated currents in LGNd relay neurons (inward in wild-type mice) were outward in PLC-beta4-/- mice.
  
  
  CONCLUSIONS
  These lines of evidence indicate that impaired LGNd relay, possibly mediated via group-1 mGluR, may underlie irregular sleep sequences and ultradian body temperature rhythms in PLC-beta4-/- mice.
authors.affiliation: Department of Chronobiology, Graduate School of Innovative Life Science, University of Toyama, Toyama, Japan. msikeda@sci.u-toyama.ac.jp
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ikeda
authors.forename: Moritoshi
authors.initials: M
authors.lastname: Hirono
authors.forename: Takashi
authors.initials: T
authors.lastname: Sugiyama
authors.forename: Takahiro
authors.initials: T
authors.lastname: Moriya
authors.forename: Masami
authors.initials: M
authors.lastname: Ikeda-Sagara
authors.forename: Naomi
authors.initials: N
authors.lastname: Eguchi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Urade
authors.forename: Tohru
authors.initials: T
authors.lastname: Yoshioka
mesh_terms: D000818:Animals; D001831:Body Temperature / Q000502:physiology*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006579:Heterozygote; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010641:Phenotype; D054799:Phospholipase C beta / Q000737:chemistry / Q000502:physiology*; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D012890:Sleep / Q000235:genetics / Q000502:physiology*; D012895:Sleep, REM; D013788:Thalamus / Q000378:metabolism; D014851:Wakefulness / Q000502:physiology
chemical_list: D018094:Receptors, Metabotropic Glutamate; C104077:metabotropic glutamate receptor type 1; D054799:Phospholipase C beta