Affiliation: Salk Institute for Biological Studies, La Jolla, CA
Keywords: r. circuits; i. aggression
All animals must process and respond accordingly to both internal and external stimuli. Modifying behavior is an essential strategy animals employ to respond to a changing environment. Octopamine(OA)–the insect equivalent of norepinephrine–functions as a neurotransmitter, neurohormone, and neuromodulator involved in modulating various behaviors based on sensory input and internal states. The relationship between OA and aggression has been well studied in insects and other arthropods. Because of its expansive genetic toolkit, Drosophila is one of the most useful model organisms for exploring the mechanisms employed by OA neurons to influence aggression. Past studies using Drosophila have demonstrated OA’s role in modulating aggression based on various sensory inputs, such as sleep, gut microbiome health, and social experience. Importantly, OA neurons in Drosophila are known to consist of up to 27 anatomically distinct subtypes. Aside from a few examples, it remains in question whether each subtype modulates a specific behavioral process (including context-dependent modulation of aggressive behavior), and if so, which of these OA neurons is responsible for each process. Genetic reagents (such as GAL4 lines) that label specific subtypes of OA neurons will help advance our understanding of the circuits driving octopaminergic modulation of behavior. Currently, only a few OA subtypes are genetically accessible. To investigate the functions of the remaining OA neuronal subtypes, we are isolating split GAL4 lines that label specific subtypes of OA neurons in the central brain. After using immunohistochemistry to visualize the labeling patterns of 367 combinations of split GAL4 Drosophila lines, we have so far found 24 candidates that partially or completely isolate several octopaminergic cell types. Our new genetic reagents will enable further investigation of not only OA’s role in aggression circuitry but also cell-type specific control of other behaviors modulated by OA. With more refined access to the circuits underpinning behavior modulation, we can achieve a better understanding of how animals process and respond to the barrage of stimuli they constantly encounter.