Effects of melatonin in isolated rat papillary muscle

Pasquale Abete, Sabatino Bianco, Claudio Calabrese, Claudio Napoli, Francesco Cacciatore, Nicola Ferrara, Franco Rengo

Research output: Contribution to journalArticle


Melatonin (N-acetyl-5-methoxytryptamine), the principal hormone of the vertebral pineal gland, elicits several neurobiological effects. However, the effects of melatonin on cardiac muscle are still unknown. The first goal of the study was to investigate the role of melatonin on myocardial contractility in isolated rat papillary muscle using dose-response curves to melatonin, to isoproterenol and calcium either in the presence or in the absence of melatonin (0.3 nM). Response curves to isoproterenol were additionally performed in the presence of melatonin plus the specific receptor antagonist N-acetyltryptamine (10 μM); the adenylate-cyclase stimulator forskolin (10 μM) was also used. Melatonin has no direct inotropic effect in isolated rat papillary muscle but counteracts isoproterenol but not [Ca2+] effects. In fact, the EC50 for isoproterenol was significantly higher in the presence than in the absence of melatonin (p <0.001). This antiadrenergic action occurs through an interaction to a specific cardiac receptor. Forskolin-stimulated adenylate cyclase induced an increase of contractile force (+118 ± 25%) which was reduced in the presence of melatonin (+26 ± 10%; p <0.01). In conclusion, we found that melatonin possess anti-adrenergic effect in isolated rat papillary muscle. This phenomenon was abolished in the presence of its receptor antagonist N-acetyltryptamine demonstrating that melatonin operates through a specific cardiac receptor. The reduction of contractility increase, induced by forskolin-stimulated adenylate cyclase, shows that melatonin may act through a reduction of cyclic AMP accumulation.

Original languageEnglish
Pages (from-to)79-85
Number of pages7
JournalFEBS Letters
Issue number1
Publication statusPublished - Jul 21 1997



  • Adreno-receptors
  • Calcium
  • Forskolin
  • Isoproterenol
  • Melatonin
  • Myocardial contractility
  • N-Acetyltryptamine
  • Papillary muscle

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology

Cite this

Abete, P., Bianco, S., Calabrese, C., Napoli, C., Cacciatore, F., Ferrara, N., & Rengo, F. (1997). Effects of melatonin in isolated rat papillary muscle. FEBS Letters, 412(1), 79-85. https://doi.org/10.1016/S0014-5793(97)00749-7