Dopaminergic Modulation of Mushroom Body Output Neurons Mediates Nociception-Induced Escape in Drosophila

Abstract

In Drosophila, noxious heat is detected by peripheral nociceptors expressing transient receptor potential (TRP) channels, including Painless and TrpA1, and rapidly triggers escape behavior. Although peripheral transduction has been defined in detail, the central circuits and neuromodulatory mechanisms that translate nociceptor activity into escape decisions remain poorly understood. Here, we combine targeted behavioral perturbations with anatomical tracing to delineate a nociception-to-escape pathway that engages dopaminergic modulation of mushroom body (MB) output. Kir2.1-mediated silencing across candidate neurotransmitter systems revealed a specific requirement for MB-innervating dopaminergic neurons (DANs)--particularly subsets within the protocerebral posterior lateral 1 (PPL1) and protocerebral anterior medial (PAM) clusters--for robust nociception-induced escape. Anterograde trans-Tango tracing from painless- and trpA1-expressing nociceptors labeled these MB dopaminergic neurons as direct postsynaptic partners, consistent with convergence of distinct nociceptor inputs onto a shared dopaminergic pathway. Finally, silencing a subset of mushroom body output neurons (MBONs) delayed escape without overtly disrupting baseline locomotion, supporting a model in which dopaminergic signaling recruits MB output to shape defensive action selection. Together, our results define a multi-layer circuit motif linking peripheral nociception to MB-dependent escape and provide a framework for dissecting how neuromodulation gates rapid defensive behaviors.