Small, nonprotein, water-soluble molecules or ions involved in pathways initiated by G-protein linked receptor andreceptor tyrosine-kinase. They spread throughout the cell by diffusion. The two most widely used second messengersare cAMP (cyclic AMP) and calcium ions, Ca .

Other molecules that act as second messengers are: cGMP, DAG(diacyglycerol) and IP3 (inositol triphosphate).These molecules are regulated by extracellular signaling agents such as neurotransmitters and hormones (firstmessengers). Second messengers typically operate by activating protein kinases that phosphorylate carious targetproteins, thereby altering the functioning of these proseins.

Such functional effects are subsequently reversed by proteinphosphotase-mediated dephosphorylation. Second messengers modulate a wide range of both rapid and long-termneuronal processes.First messengersONcurotransmittersand oilierextracellular messenger-—ISecond messengersProtein phosphatase.

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Second messengers .-::70962::-.