Octopamine receptors in Drosophila larvae: expression, development, and behavior.

Octopamine is involved in a variety of physiological and behavioral mechanisms throughout the Drosophila melanogaster life cycle. Octopaminergic neurons in both the central and the peripheral nervous system target a multitude of neurons and even non-neuronal tissues, making it challenging to analyze individual mechanisms of octopamine function. One approach to deconstructing this complex system is to examine the postsynaptic components of signal transmission, the six distinct G-protein-coupled octopamine receptors. Here, we compiled and validated a complete set of potential mutant lines of all known octopamine receptors (Oamb, Octα2R, Octβ1R, Octβ2R, Octβ3R, and Oct-TyrR) that were generated using the same genetic tool: the recently established Trojan Exon system. It integrates the Gal4/UAS binary expression strategy while simultaneously impairing receptor function. We generated a comprehensive anatomical map of receptor expression in the larva and, at the same time, analyzed the function of individual octopamine receptors during larval development, chemosensory perception, and locomotion. All octopamine receptors are expressed in the central and peripheral nervous system. Octβ2R stands out with a pronounced expression in the somatic muscles. We also observed a previously undescribed role of Octβ1R, Octβ3R, and Oct-TyrR in larval hatching and in the survival of larvae and pupae. Combined with tissue- and stage-specific gene expression data, this validated set of transgenic lines provides a basis for further functional studies of the octopaminergic system.