Caffeine leads to a vasoconstriction, raises the epinephrine levels, and increases nervous signaling. a metabolite of caffeine blocks phosphodiesterase. what is the most likely impact of caffeine on cell signaling?

Caffeine will block the action of phosphodiesterase and thus the enzyme will not be activated to break down cAMP.

Caffeine has some effects which are psychological in nature. At the cellular level, caffeine blocks the action of phosphodiesteerase. Phosphodiesterase is the one that break down the cAMP inside the cell.