The inhibitory action of melatonin on the contractile response to 5-hydroxytryptamine in various isolated vascular smooth muscles

Gen Pharmacol. 1986;17(5):553-8. doi: 10.1016/0306-3623(86)90092-3.


The effects of melatonin on the contractile responses to 5-hydroxytryptamine (5-HT), norepinephrine (NE), angiotensin-1 (AT-1) and potassium were determined on the rabbit isolated aorta, iliac and renal arteries. Melatonin, at 10(-4) or 10(-3) M inhibited the response to 5-HT in the aorta, iliac and renal arteries. Melatonin, at 10(-3) M, had a negligible effect on the responses to NE and AT-1 in all preparations used. The potassium-induced contraction of all 3 preparations used was slightly inhibited by only the high concentration of melatonin (10(-3) M). In a Ca+-free medium with EGTA (0.1 mM), the residual response to 5-HT (10(-5) or 10(-4) M) were inhibited by melatonin (10(-4) or 10(-3) M) in all preparations used. In a Ca2+-free medium with EGTA (0.01 mM), nifedipine (10(-6) M) and 5-HT (5 X 10(-7) M), application of Ca2+ (2 mM) resulted in a tonic contraction, related to receptor operated channels, of all preparations. This Ca2+ dependent, nifedipine insensitive contraction was markedly inhibited or abolished by melatonin at 10(-5) and 10(-4) M. These results demonstrated that melatonin had a generally greater inhibitory effect on the response to 5-HT than those to NE, AT-1 and potassium in vascular smooth muscles. Also the results suggest that action of melatonin on the 5-HT induced contraction is more related to interference with Ca2+ influx through receptor operated channels than release of intracellular Ca2+ from the store site.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiotensin I / pharmacology
  • Animals
  • Calcium / metabolism
  • Calcium / pharmacology
  • In Vitro Techniques
  • Male
  • Melatonin / pharmacology*
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / physiology
  • Norepinephrine / pharmacology
  • Potassium / pharmacology
  • Rabbits
  • Serotonin / pharmacology*
  • Vasoconstriction / drug effects*


  • Serotonin
  • Angiotensin I
  • Melatonin
  • Potassium
  • Calcium
  • Norepinephrine