What are the common second messengers?

Common second messengers include: calcium ions, cyclic nucleotides, nitric oxide, and IP3. Calcium ions are the most common second messenger in neurons. Information is transmitted by a rise in the cytoplasmic calcium concentration, which allows for Ca2+ to bind to a large number of Ca2+ binding proteins. Examples of cyclic nucleotides include cAMP and cGMP, which serve as second messengers in both ion-channel and hormone signaling in eukaryotes. Nitric oxide is a gas which permeates the plasma membrane, and thus can travel through the extracellular medium and act within other adjacent cells. NO reacts nonspecifically with many other molecules and decays shortly after reacting with oxygen to produce inactive nitrogen oxides. Thus, the gas only lasts for a short amount of time. IP3 is a molecule that leaves the cell membrane and diffuses within the cytosol. IP3 binds to IP3 receptors, which are channels that release calcium from the ER. Therefore, the function of IP3 is to produce another second messenger, and triggers many reactions within the cytosol.