The role of G-proteins in neurotransmission

The role of G-proteins in neurotransmission
 An excitatory neurotransmitter such as noradrenaline or serotonin acts on its receptor and activates the intermembrane G-protein by converting GDP to GTP thereby linking the receptor to the second messenger system, usually adenylate cyclase.
 The second messenger, for example cyclic adenosine monophosphate (cAMP), then activates cAMP-dependent protein kinase which modulates the function of a broad range of membrane receptors, intracellular enzymes, ion channels and transcription factors.
 An inhibitory neurotransmitter activates an inhibitory G-protein thereby leading to a reduction in cAMP synthesis.
 The termination of signal transduction results from the hydrolysis of GTP to GDP by GTPase thereby returning the G-protein to its inactive form.