Effects of ambient temperature on sleep and cardiovascular regulation in mice: the role of hypocretin/orexin neurons

PLoS One. 2012;7(10):e47032. doi: 10.1371/journal.pone.0047032. Epub 2012 Oct 8.

Abstract

The central neural pathways underlying the physiological coordination between thermoregulation and the controls of the wake-sleep behavior and cardiovascular function remain insufficiently understood. Growing evidence supports the involvement of hypocretin (orexin) peptides in behavioral, cardiovascular, and thermoregulatory functions. We investigated whether the effects of ambient temperature on wake-sleep behavior and cardiovascular control depend on the hypothalamic neurons that release hypocretin peptides. Orexin-ataxin3 transgenic mice with genetic ablation of hypocretin neurons (n = 11) and wild-type controls (n = 12) were instrumented with electrodes for sleep scoring and a telemetric blood pressure transducer. Simultaneous sleep and blood pressure recordings were performed on freely-behaving mice at ambient temperatures ranging between mild cold (20°C) and the thermoneutral zone (30°C). In both mouse groups, the time spent awake and blood pressure were higher at 20°C than at 30°C. The cold-related increase in blood pressure was significantly smaller in rapid-eye-movement sleep (REMS) than either in non-rapid-eye-movement sleep (NREMS) or wakefulness. Blood pressure was higher in wakefulness than either in NREMS or REMS at both ambient temperatures. This effect was significantly blunted in orexin-ataxin3 mice irrespective of ambient temperature and particularly during REMS. These data demonstrate that hypocretin neurons are not a necessary part of the central pathways that coordinate thermoregulation with wake-sleep behavior and cardiovascular control. Data also support the hypothesis that hypocretin neurons modulate changes in blood pressure between wakefulness and the sleep states. These concepts may have clinical implications in patients with narcolepsy with cataplexy, who lack hypocretin neurons.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Ataxin-3
  • Blood Pressure / genetics
  • Blood Pressure / physiology
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Male
  • Mice
  • Mice, Transgenic
  • Neurons / metabolism*
  • Neuropeptides / genetics
  • Neuropeptides / metabolism*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Orexins
  • Sleep / physiology*
  • Temperature*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism

Substances

  • Intracellular Signaling Peptides and Proteins
  • Neuropeptides
  • Nuclear Proteins
  • Orexins
  • Transcription Factors
  • Ataxin-3
  • Atxn3 protein, mouse

Grants and funding

This work was funded by the University of Bologna (RFO 10 and RFO 11; http://www.unibo.it/Portale/Ricerca/ServiziDocentiRicercatori/finanziamentinaz/RFO-Finanziamentoallaricercadibase.htm), Ministry of Instruction, University and Research, Italy (PRIN 2008, prot. 2008FY7K9S; http://prin.miur.it/), and Fondazione Cassa di Risparmio di Bologna (http://www.fondazionecarisbo.it/fondazionecarisbo/page.do?idc=2&grp=2&ord=01&idt=3). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.