Chapter Two - Molecular Signalling, Pharmacology, and Physiology of Octopamine and Tyramine Receptors as Potential Insect Pest Control Targets

Octopamine (OA) and tyramine (TA) are phenolamines that are synthesised from tyrosine and are widely distributed in insects. These amines play vital roles as neurotransmitters, neuromodulators, and neurohormones in a wide variety of physiological processes in insects. G protein-coupled receptors (GPCRs) mediate the signal transduction of OA and TA by modifying intracellular Ca2+ and cAMP levels. Since the first discovery of a phenolamine GPCR, two main types of OA GPCRs and three types of TA GPCRs have been revealed by studies of various insect species over the past two decades. The OA receptors have been studied as targets of classical amidine acaricide/insecticides, even though these GPCRs are not well understood at the molecular level; however, new discoveries have recently provided more information regarding these GPCRs. This chapter reviews the recent progress that has been made in the understanding of the molecular signalling, pharmacology, and physiology of OA and TA GPCRs, which may lead to the increased study of OA and TA GPCRs as insect pest control targets.