The spinal cord has both vasodilation and vasoconstriction nerves. Chemoreceptors are responsible for signaling vasoconstriction, vasodilation, bronchoconstriction, and bronchodilation. Inhaled nitric oxide (iNO) acts on vascular smooth muscle causing selective pulmonary vasodilation. Affected arteries develop endothelial dysfunction and impairment of normal vasodilation, which alter kidney autoregulation. Nitric oxide results in vasodilation of blood vessels. Sublingual administration of nifedipine promotes a hypotensive effect via peripheral vasodilation. Endogenous substances and drugs that cause vasodilation are termed vasodilators. Excessive vasodilation, or insufficient constriction of the blood vessels (mostly arterioles), causes hypotension. This stimulates vasodilation and vascular remodelling. The collective effects of decreased blood volume and vasodilation decrease blood pressure and ameliorate edema. Exercise or dipyridamole induces widening (vasodilation) of normal coronary arteries. Endothelial cells induce expression of endothelin-1, which leads to NO production and vasodilation. The neurons that control vascular vasodilation originate in the hypothalamus. Cutaneous vasodilation and skin flushing may be noted due to decreased capillary tone. The main factor involved in causing vasodilation is histamine.