Calcium modulates circadian variation in cAMP-stimulated melatonin in chick pineal cells

Selene S. Nikaido, Joseph S. Takahashi

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

In chick pineal cells, melatonin synthesis is regulated by both calcium and cAMP. Calcium-dependent regulation of melatonin is suggested by the monotonic decrease in melatonin observed with decreasing extracellular calcium ion concentrations ([Ca2+](o)), the stimulation of melatonin with Bay K8644, and the inhibition of nocturual melatonin by several calmodulin antagonists. At submicromolar [Ca2+](o), a stimulation of melatonin was observed in the presence of 8-Br cAMP, but not with Bay K8644, suggesting that this amount of stimulation of melatonin by 8-Br cAMP is independent of Ca2+ influx through dihydropyridine-sensitive Ca2+ channels. At micromolar [Ca2+](o), there was a further increase in the stimulation of melatonin by 8-Br cAMP that was not blocked by nifedipine, a dihydropyridine-sensitive Ca2+ channel antagonist. Micromolar [Ca2+](o) is required for the greater stimulation of melatonin by 8-Br cAMP during the night than during the day. Melatonin was stimulated by 8-Br cAMP to higher levels during the night than during the subjective day under normal [Ca2+](o) (1.3 mM). This difference in the amount of melatonin stimulated by 8-Br cAMP during the subjective night versus the subjective day was blocked by lowering [Ca2+](o) to a submicromolar concentration (0.2 μM). Both nifedipine and calmidazolium partially blocked nocturnal increases in melatonin, but were ineffective during the day. These results suggest that Ca2+ plays an important role in the differential ability of cAMP to stimulate melatonin during the night versus the day.

Original languageEnglish (US)
Pages (from-to)1-10
Number of pages10
JournalBrain Research
Volume716
Issue number1-2
DOIs
StatePublished - Apr 15 1996

Keywords

  • calcium ion
  • chick pineal
  • circadian rhythm
  • cyclic adenosine monophosphate
  • diurnal rhythm
  • melatonin

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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