Melatonin reduces nitric oxide synthase activity in rat hypothalamus

Ilham Bettahi, David Pozo, Carmen Osuna, Russel J. Reiter, Dario Acuña-Castroviejo, Juan M. Guerrero

Research output: Contribution to journalArticlepeer-review

209 Scopus citations


In this report, rat hypothalamic nitric oxide synthase (NOS) activity is shown to be partially inhibited by physiological concentrations of the pineal hormone melatonin. In vitro studies demonstrate that 1 nM melatonin, which approximates the physiological concentration of the hormone at night, significantly inhibited NOS activity. In vivo studies show that administering melatonin or collecting the hypothalamus from animals at night, when endogenous melatonin levels are elevated, results in a significant decrease of NOS activity. Results also show that calmodulin may be involved in this process since its presence in the incubation medium prevents the inhibitory effect of melatonin on NOS activity.

Original languageEnglish (US)
Pages (from-to)205-210
Number of pages6
JournalJournal of pineal research
Issue number4
StatePublished - May 1996
Externally publishedYes


  • Calmodulin
  • Hypothalamus
  • Melatonin
  • Nitric oxide
  • Pineal

ASJC Scopus subject areas

  • Endocrinology


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