Immunoreactive orexin-A in human plasma

Zenei Arihara, Kazuhiro Takahashi, Osamu Murakami, Kazuhito Totsune, Masahiko Sone, Fumitoshi Satoh, Sadayoshi Ito, Toraichi Mouri

Research output: Contribution to journalArticlepeer-review

96 Citations (Scopus)


Orexin-A and orexin-B are newly discovered neuropeptides which are implicated in feeding behavior and arousal state. We studied immunoreactive(IR)-orexin-A concentrations in human plasma by radioimmunoassay. IR-orexin-A concentrations in plasma obtained from 17 healthy subjects in the morning were 1.94 ± 0.24 pmol/liter (mean ± SEM). IR-orexin-A levels in the plasma obtained at night were not significantly different from those obtained in the morning in 9 female subjects. The HPLC analysis of the plasma extract showed two immunoreactive peaks; one peak eluting in an identical position to synthetic orexin-A, and one eluting earlier. This study has shown for the first time the presence of orexin-A in human plasma.

Original languageEnglish
Pages (from-to)139-142
Number of pages4
Issue number1
Publication statusPublished - 2001


  • Diurnal variation
  • Orexin-A
  • Plasma
  • Radioimmunoassay


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