THE ROLE OF OCTOPAMINERGIC AND TYRAMINERGIC CIRCUITS IN INNATE VALENCE

Abstract

Valence is a property of brain activity that represents the pleasantness of a cue as an instruction for either approach or avoidance response. Thus, the process by which distinct neural circuits assign valence to internal or external cues is a crucial step in innate behaviors and is believed to be one of the evolutionary and adaptive properties of emotion. Octopamine (OA) and its precursor tyramine (TA) are often considered to be the invertebrate counterparts of the vertebrate adrenergic transmitter, as they play a key role in a variety of innate behaviors such as aggression, feeding and sleep in invertebrates. I hypothesized that distinct octopaminergic and tyraminergic (OATA) circuits encode innate valence. Here, to dissect OATA circuits that encode innate valence, I optogenetically targeted OATA cells in fruit flies for optogenetic self-stimulation experiments. I found that flies sought out repeated stimulation of OATA-VM cells located in SEZ of the adult fly brain through octopamine and tyramine receptors (Oct-TyrRs). Epistasis experiments revealed that TA but not OA is required for this repeated self-stimulation behavior. Nevertheless, OA induced hyperactivity and reduced the positive valence effect.