Opioid Receptors

Opioid receptor, being a member of the superfamily of membrane proteins that transduces its signals via the heterotrimeric G proteins, has myriad of activities upon activation by exogenous alkaloid and endogenous peptide ligands. The most important of these functions is the modulation of pain perception. The many side effects that associated with the receptor activation, especially those that can lead to addiction to the exogenous alkaloid ligands, mandate the investigation into the mechanism of opioid receptor action in order to develop an ideal analgesic agent. The synaptic location of the receptor, the presence of multiple opioid receptor, the multiple pathways that the receptor could transduce its signal, and the probability that the receptors could form oligomeric protein complexes add to the complexity of the opioid receptor signal mechanism. In this chapter, we examine some of the opioid receptor signaling complexity.