Cyclic adenosine-3,5-monophosphate is a nucleotide involved with intracellular signalling as a secondary messenger. It is formed from ATP by the action of the enzyme adenylate cyclase. Adenylate cyclase is regulated by hormone receptors in the plasma membrane of cells.
cAMP is degraded by specific phosphodiesterases. Inhibition of phosphodiesterase activity increases intracellular cAMP levels. Drugs which act in this way include theophylline, aminophylline and rolipram.