Synaptically activated second messengers act through G protein coupled receptors. Either the G protein or the second messenger then act on a channel to modify ionic across the cell membrane. Protein kinases The second messenger can also activate a secondary effector, such as a protein kinase, which acts on the channel. The addition of a phosphate group to a channel protein can provide the energy needed for opening or closing. The kinase can also phosphorylate regulatory proteins which then act on the channel.
Kinases have regulatory and catalytic subunits.
Exposure or cleavage of the catalytic subunits frees them to phosphorylate proteins. Back to sensitization The process of facilitation involves activation of seretonergic inputs from facilitating interneurons which are stimulated by sensory input. Long-term facilitation acts through the same cAMP signalling system. Second messengers can induce new protein synthesis by regulating gene expression. Segue to gene regulation Genes are typically made up of two regions.