Modafinil more effectively induces wakefulness in orexin-null mice than in wild-type littermates

J. T. Willie, W. Renthal, R. M. Chemelli, M. S. Miller, T. E. Scammell, M. Yanagisawa, C. M. Sinton

Research output: Contribution to journalArticlepeer-review

77 Scopus citations

Abstract

Narcolepsy-cataplexy, a disorder of excessive sleepiness and abnormalities of rapid eye movement (REM) sleep, results from deficiency of the hypothalamic orexin (hypocretin) neuropeptides. Modafinil, an atypical wakefulness-promoting agent with an unknown mechanism of action, is used to treat hypersomnolence in these patients. Fos protein immunohistochemistry has previously demonstrated that orexin neurons are activated after modafinil administration, and it has been hypothesized that the wakefulness-promoting properties of modafinil might therefore be mediated by the neuropeptide. Here we tested this hypothesis by immunohistochemical, electroencephalographic, and behavioral methods using modafinil at doses of 0, 10, 30 and 100 mg/kg i.p. in orexin -/- mice and their wild-type littermates. We found that modafinil produced similar patterns of neuronal activation, as indicated by Fos immunohistochemistry, in both genotypes. Surprisingly, modafinil more effectively increased wakefulness time in orexin -/- mice than in the wild-type mice. This may reflect compensatory facilitation of components of central arousal in the absence of orexin in the null mice. In contrast, the compound did not suppress direct transitions from wakefulness to REM sleep, a sign of narcolepsy-cataplexy in mice. Spectral analysis of the electroencephalogram in awake orexin -/- mice under baseline conditions revealed reduced power in the θ band frequencies (8-9 Hz), an index of alertness or attention during wakefulness in the rodent. Modafinil administration only partly compensated for this attention deficit in the orexin null mice. We conclude that the presence of orexin is not required for the wakefulness-prolonging action of modafinil, but orexin may mediate some of the alerting effects of the compound.

Original languageEnglish (US)
Pages (from-to)983-995
Number of pages13
JournalNeuroscience
Volume130
Issue number4
DOIs
StatePublished - 2005

Keywords

  • amphetamine
  • arousal
  • dopamine
  • rebound hypersomnolence
  • sleep attacks
  • stimulants

ASJC Scopus subject areas

  • Neuroscience(all)

Fingerprint Dive into the research topics of 'Modafinil more effectively induces wakefulness in orexin-null mice than in wild-type littermates'. Together they form a unique fingerprint.

Cite this