Neuromodulatory State and Sex Specify Alternative Behaviors through Antagonistic Synaptic Pathways in C. elegans

Pheromone responses are highly context dependent. For example, the C. elegans pheromone ascaroside C9 (ascr#3) is repulsive to wild-type hermaphrodites, attractive to wild-type males, and usually neutral to “social” hermaphrodites with reduced activity of the npr-1 neuropeptide receptor gene. We show here that these distinct behavioral responses arise from overlapping push-pull circuits driven by two classes of pheromone-sensing neurons. The ADL sensory neurons detect C9 and, in wild-type hermaphrodites, drive C9 repulsion through their chemical synapses. In npr-1 mutant hermaphrodites, C9 repulsion is reduced by the recruitment of a gap junction circuit that antagonizes ADL chemical synapses. In males, ADL sensory responses are diminished; in addition, a second pheromone-sensing neuron, ASK, antagonizes C9 repulsion. The additive effects of these antagonistic circuit elements generate attractive, repulsive, or neutral pheromone responses. Neuronal modulation by circuit state and sex, and flexibility in synaptic output pathways, may permit small circuits to maximize their adaptive behavioral outputs. ► Behavioral responses to a pheromone are modified by sex and neuromodulatory state ► Two sensory neurons promote attraction or repulsion via a gap junction circuit ► Antagonistic circuit outputs interact to determine pheromone responses Behavioral responses elicited by pheromones depend on sex and physiological state. Jang et al. find that overlapping push-pull circuits modulated by neuropeptidergic signaling and sex determine whether pheromones are attractive, neutral, or repulsive.