Ans. is 'd' i.e. Fenoldopam FenoldopamFenoldopam is a selective dopamine -1 receptor agonist.Administered parenterally it acts predominantly as a vasodilator in peripheral arteries and diuretic in kidney.It has been approved by FDA for short term a management of hypertensive emergency.Nitric Oxide (NO) is recognized as a mediator in a bewildering array of biologic systems.Nitric oxide is identical to endothelium derived relaxing factor (EDRF) which causes vasodilation by relaxing vascular smooth muscle.* NO also acts as neurotransmitter, prevents platelet aggregation and plays an essential role in macrophage function.Synthesis of NONo is synthesized by the action of NO synthase on Arginine.Arginine O2 and NADPH are substrates.FMN, FAD, heme and tetrahydrobiopterin are coenzymes for the enzymes.NO and citrulline are products of the reaction.Actions of NO on vascular endotheliumNitric oxide is an important mediator in the control of vascular smooth muscle tone.Nitric oxide is synthesized in endothelial cells and diffuses to vascular smooth muscle, where it activates the cytosolic form of guanylate cyclase.The resultant rise in cGMP causes muscle relaxation possibly through activation of protein kinase G(Note : Vasodilator nitrates such as nitroglycerin and nitroprusside are metabolized to nitric oxide, which causes relaxation of vascular smooth muscle, presumably by the above mechanism. Thus NO can be envisioned as an endogenous nitrovasodilator)Role of NO in mediating macrophage bactericidal activityIn macrophages, NO synthetase activity is normally low, but synthesis of the enzyme is markedly stimulated by bacterial lipopolysaccharide and g interferon release in response to infection.Activated macrophages form oxygen free radicals that combine with NO to form compounds that are more bactericidal than NO itself.Drugs generating Nitric oxide i) Nitric oxide level is increased by increased release of donorsAcetylcholineGlyceryl trinitrateSodium nitroprussideCalcium ionsHydralazineAspirin (No releasing aspirin)ACE inhibitorGlyceryl trinitrate (recently been recognized as Nitric oxide donor)ii) Drugs which inhibits phosphodiesterase enzymeSlidenaphilAminophyllineTheophyllineAmrinoneMilrinoneCilostazol