PKA acts on downstream targets to bring about cellular changes that are required for learning and memory.
G proteins activate and inhibit elements in the learning pathway.
Heterotrimeric G proteins transduce signals from cell surface 7 pass transmembrane serpentine receptors to downstream effectors, such as ion channels, cytoskeletal elements and other signal transduction proteins. Classification of G proteins is based historically on the functional interaction of G protein alpha subunits with specific effector proteins. For example, transducins are responsible for the activation of the cGMP phosphodiesterase in the retina. Gs alpha stimulates adenylate cyclase, while Gi alpha acts as an inhibitor. In eukaryotic cells, serpentine receptors, excited by neurotransmitters are coupled to the activation of adenylyl cyclase by the heterotrimeric GTP binding protein complex Gs.