RT Journal Article SR Electronic T1 Octopaminergic neurons have multiple targets in Drosophila larval mushroom body calyx and regulate behavioral odor discrimination JF bioRxiv FD Cold Spring Harbor Laboratory SP 295659 DO 10.1101/295659 A1 Alex D McLachlan A1 J Y Hilary Wong A1 Bo Angela Wan A1 Cahir J O’Kane A1 Marcella Montagnese A1 Shuo Wei Zhang A1 Liria M Masuda-Nakagawa YR 2018 UL http://biorxiv.org/content/early/2018/04/09/295659.abstract AB The insect mushroom bodies (MBs) are essential for associative olfactory learning, and their sensory input region, the MB calyx, is organized in discrete glomeruli, most of which receive stereotypic input from olfactory projection neurons (PNs). Odors are represented by activity of MB neurons, the Kenyon Cells (KCs) using a sparse code that allows odor discrimination during learning. Octopamine (OA) is a neurotransmitter that signals reward in associative learning and arousal, in insects including Drosophila. The calyx receives OA innervation from two neurons, sVUMmd1 and sVUMmx1, originating from their respective neuromeres in the suboesophageal zone (SEZ). To understand how these OA inputs might influence odor discrimination in the MBs, we analyzed their pattern of innervation of the MB calyx, their connectivity with the other neurons that innervate the calyx, and their influence on sensory discrimination during learning.Clonal labeling of multiple single neurons showed that the two sVUM1 neurons innervated all regions of the calyx. GRASP (GFP Reconstitution Among Synaptic Partners) revealed contacts of sVUM1 neurons in the calyx with olfactory PNs, the inhibitory neuron APL, a pair of extrinsic neurons with dendrites throughout the calyx, but only few contacts with KCs. A GFP protein trap of the OA receptor Oamb, a Drosophila alpha-1-adrenergic receptor ortholog, localized to PN terminals in the calyx. In a behavioral odor discrimination assay, activating a set of 5 OA neurons, including the sVUM1 neurons, compromised the ability to discriminate similar odors.Our results support a model, in which OA release from sVUM1 neurons can increase sensitivity but decrease discrimination in the olfactory learning pathway, either by modifying release from PN terminals, or interacting with the negative feedback look that comprises Kenyon cells and the APL.