Opioid Receptors are G protein-coupled receptors (GPCRs). They mediate the human body's response to most hormones, neurotransmitters, drugs, and are involved in sensory perception of vision, taste, and olfaction. All GPCRs consists of seven transmembrane spanning proteins that couple to intracellular G proteins. There are different types of G proteins bound to receptors which are differentiated based on the signaling pathways activated intracellularly. Gs protein-coupled receptors are considered stimulatory due to their activation of the molecule adenylate cyclase, which increases cAMP production. The molecule cAMP activates Protein Kinase A (PKA) that is responsible for phosphorylation of numerous proteins, ion channels, and enzymes ultimately resulting in their activation/inhibition.
