ABSTRACT
The G-protein coupled receptors (GPCRs) generate a response by linking drug binding at the extracellular part of the receptor protein to activation of particular intracellular guanosine triphosphate (GTP) binding proteins (Brown, Chapter 7). Many GPCRs are hormone receptors and respond to changes in hormone concentration circulating in the blood. Many other GPCRs respond to the release of neurotransmitters at synapses in the brain or in the periphery. GPCRs may be located at a synapse; pre-, post-or perisynaptically; and mediate slow synaptic transmission (on a time scale of 100 ms to seconds) whose characteristics will depend on the particular G-protein that couples to the receptor.
