[Campbell Biology P.273] The text explains how the compound known as Viagra is used to treat... | Practice Question

The text explains how the compound known as Viagra is used to treat erectile dysfunction. Which of the following statements best describes its mechanism of action?

  • A: Viagra directly stimulates the production of cyclic AMP (cAMP), leading to muscle relaxation.
  • B: Viagra inhibits the hydrolysis of cyclic GMP (cGMP) to GMP, thereby prolonging vasodilation.
  • C: Viagra acts as a first messenger, directly activating G protein-coupled receptors.
  • D: Viagra increases the intracellular concentration of calcium ions, promoting muscle contraction.

Explanation

The text states that cGMP acts as a second messenger causing relaxation of muscles in artery walls. Viagra prolongs this signal by inhibiting the hydrolysis of cGMP to GMP. This leads to sustained muscle relaxation and vasodilation, increasing blood flow and treating erectile dysfunction.