What is the physiological effect of pertussis toxin on GPCR signaling?

• A. It enhances adenylate cyclase activity, reducing cAMP levels
• B. It overstimulates the stimulatory G protein, leading to decreased cAMP levels
• C. It inhibits the inhibitory G protein, leading to increased cAMP levels
• D. It blocks GPCR binding, preventing signal transduction

Answer: (C)