Which of the following causes vasodilation?
(A) Thromboxane A2 (B) Prostaglandin E2 (C) Histamine (D) Serotonin
(C) Major vasoactive amine responsible for vasodilation is Histamine. It causes dilation of aerioles and increases the permeability of venules. Prostaglandins can also cause vasodilation but major chemical responsible is histamine. Serotonin (5hydroxytryptamine) is a preformed vasoactive mediator present in platelets and ceain neuroendocrine cells, such as in the gastrointestinal tract, and in mast cells in rodents but not humans.