This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
The mechanism of action of sodium nitroprusside is? 
Select and explain. 
A. Increased cAMP, B. Increased guanylate cyclase, C. Calcium channel blockage, D. IC channel opener
B: Increased guanylate cyclase
Answer: B: Increased guanylate cyclase 
Explanation: Ans. is 'b' i.e., Increases Guanyl Cyclase o "Nitroprusside dilates both aerial and venous vessels, resulting in reduced peripheral vascular resistance and venous return. The action occurs as a result of activation of guanylyl cyclase, either release of nitric oxide or by direct stimulation of enzyme. The result is increased intracellular cGMP, which relaxes vascular smooth muscle".