In the treatment of asthma, how do cyclic AMP and cyclic GMP differ in their effects on smooth muscle contraction?

• A. Cyclic AMP stimulates smooth muscle contraction, while cyclic GMP relaxes it; asthma treatment involves increasing cyclic GMP to open airways.
• B. Both cyclic AMP and cyclic GMP stimulate smooth muscle contraction; asthma treatment involves decreasing both to open airways.
• C. Both cyclic AMP and cyclic GMP relax smooth muscle; asthma treatment involves increasing both to open airways.
• D. Cyclic AMP relaxes smooth muscle, while cyclic GMP stimulates contraction; asthma treatment involves increasing cyclic AMP to open airways.

Answer: (D)