TY - JOUR TI - MDN brain descending neurons coordinately activate backward and inhibit forward locomotion AU - Carreira-Rosario, Arnaldo AU - Zarin, Aref Arzan AU - Clark, Matthew Q AU - Manning, Laurina AU - Fetter, Richard D AU - Cardona, Albert AU - Doe, Chris Q A2 - Calabrese, Ronald L A2 - Marder, Eve VL - 7 PY - 2018 DA - 2018/08/02 SP - e38554 C1 - eLife 2018;7:e38554 DO - 10.7554/eLife.38554 UR - https://doi.org/10.7554/eLife.38554 AB - Command-like descending neurons can induce many behaviors, such as backward locomotion, escape, feeding, courtship, egg-laying, or grooming (we define ‘command-like neuron’ as a neuron whose activation elicits or ‘commands’ a specific behavior). In most animals, it remains unknown how neural circuits switch between antagonistic behaviors: via top-down activation/inhibition of antagonistic circuits or via reciprocal inhibition between antagonistic circuits. Here, we use genetic screens, intersectional genetics, circuit reconstruction by electron microscopy, and functional optogenetics to identify a bilateral pair of Drosophila larval ‘mooncrawler descending neurons’ (MDNs) with command-like ability to coordinately induce backward locomotion and block forward locomotion; the former by stimulating a backward-active premotor neuron, and the latter by disynaptic inhibition of a forward-specific premotor neuron. In contrast, direct monosynaptic reciprocal inhibition between forward and backward circuits was not observed. Thus, MDNs coordinate a transition between antagonistic larval locomotor behaviors. Interestingly, larval MDNs persist into adulthood, where they can trigger backward walking. Thus, MDNs induce backward locomotion in both limbless and limbed animals. KW - neural circuit KW - locomotor KW - command neuron KW - behavior KW - backward crawl KW - descending neuron JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -