Two neighbouring neurons simultaneously receive two different primary messengers; one neuron receives adenosine and the other caffeine. Adenosine binding to its receptors leads to inhibition of adenylate cyclase. Caffeine raises camp levels which increases (by activating ac) or stays the same (if ac is already active) cellular activity and adenosine decreases camp and decreases cellular activity. You have synthesized a new drug and when you finally get to investigate what the compound you have synthesized does is cells. You realize that it greatly reduces the cell s ability to hydrolyse atp.