QS Study

Vasoconstrictor and Vasodilator Agents

Vasoconstrictor agents- They are an agent that causes narrowing of the blood vessels. Cold, fear, stress, and nicotine are common exogenous vasoconstrictors. Internally secreted epinephrine and norepinephrine cause blood vessels to contract by stimulating alpha-adrenergic receptors on the vascular smooth muscle.

(A) Circulating hormone

  • Epinephrine
  • Nor epinephrine
  • Angiotensin II
  • Vasopressin.

(B) Locally released substances

  • Serotonin
  • Thromboxane A2
  • Endothelin I.

Vasodilator agents – Vasodilation is the widening of blood vessels. It is the increase in the internal diameter of blood vessels that is caused by relaxation of smooth muscles within the wall of the vessels, thus causing an increase in blood flow. It is a nerve or agent that causes dilation of blood vessels by promoting the relaxation of the vascular smooth muscle. The process is the opposite of vasoconstriction, which is the narrowing of blood vessels.

(a) Histamine

(b) Bradykinin

(c) Prostaglandin.


(e) Adenosine

(f) Vasoactive peptide (VIP)

(g) Atrial natriuretic peptide (ANP)

(h) NO.