Vasodilation is where blood vessels in the body become wider following the relaxation of the smooth muscle in the vessel wall. This will reduce blood pressure - since there is more room for the blood. The opposite physiological process is vasoconstriction.

Vasomotor refers to the muscles and nerves controlling the process of vasodilation.

A vasodilator is a substance that causes vasodilation. Several vasodilators are used as drugs which may, for example, allow blood to flow more easily around a clot.

Flushing may be a physiological response to vasodilators.

Natural vasodilators and Drugs that Exploit Them

• Absence of high levels of environmental noise
• Adenosine
  • Adenocard - this is primarily used as an anti-arrhythmic.
• Adrenaline and noradrenaline vasodilate arterioles of the skeletal muscles. (By acting on beta-2 adrenergic receptors.) These chemicals cause vasoconstriction elsewhere.
  • Alpha blockers (block the constricting effect of adrenaline).
• Atrial natriuretic peptide (ANP) - a weak vasodilator.
• Bradykinin
• Histamine
  • Complement proteins C3a, C4a and C5a work by triggering histamine release from mast cells and basophil granulocytes.
• L-Arginine
• Niacin (aka nicotinic acid)
• Nitric oxide
  • Glyceryl trinitrate (commonly known as Nitroglycerin)
  • Isosorbide mononitrate & Isosorbide dinitrate
  • Pentaerythritol Tetranitrate (PETN)
  • Sodium nitroprusside
  • PDE5 inhibitors: these agents indirectly increase the effects of nitric oxide
    • Sildenafil
    • Tadalafil
    • Vardenafil
• Platelet activating factor (PAF)
• Prostacyclin (PGI₂) as well as other prostaglandins.
• Tetrahydrocannabinol (THC) - the major active chemical in marijuana. Its mild vasodilating effects redden the eyes of cannabis smokers.
• Papaverine an alkaloid found in the opium poppy papaver somniferum

Vasodilators

Vasodilatation | Vasodilatateur | Vasodilatatie | Vazodilatör