Related Experiment Videos
Melatonin mediates two distinct responses in vascular smooth muscle
S Doolen1, D N Krause, M L Dubocovich
1Department of Pharmacology, College of Medicine, University of California, Irvine 92697-4625, USA.
European Journal of Pharmacology
|May 21, 1998
Summary
The pineal hormone melatonin impacts vascular smooth muscle by potentially activating two receptor subtypes. Melatonin may cause vasoconstriction via one receptor and relaxation via the MT2 receptor.
Area of Science:
- Pharmacology
- Cardiovascular Physiology
- Endocrinology
Background:
- The pineal hormone melatonin is known for its role in circadian rhythms.
- Its effects on vascular smooth muscle are not fully understood.
- Vascular smooth muscle plays a critical role in regulating blood pressure.
Purpose of the Study:
- To investigate the distinct contractile responses of vascular smooth muscle to melatonin.
- To identify the potential receptor subtypes involved in melatonin's vascular effects.
Main Methods:
- Experiments were conducted on isolated rat caudal artery segments, denuded of endothelium.
- Phenylephrine was used to induce contractions.
- Melatonin was applied at various concentrations (10(-10) to 10(-5) M).
- The MT2 receptor antagonist 4-phenyl-2-acetamidotetraline (4P-ADOT) was used.
Main Results:
- Melatonin (10(-10)-10(-7) M) potentiated phenylephrine-induced contractions in a concentration-dependent manner.
- Higher melatonin concentrations (10(-7)-10(-5) M) attenuated this potentiating effect.
- The MT2 receptor antagonist 4P-ADOT selectively enhanced the attenuated constrictor responses.
Conclusions:
- Melatonin appears to activate at least two receptor subtypes in vascular smooth muscle.
- Activation of MT2 receptors may lead to vascular relaxation.
- A second, distinct receptor subtype likely mediates vasoconstriction by melatonin.