GABAergic signaling shapes multiple aspects of Drosophila courtship motor behavior

Inhibitory neurons are essential for nervous system function. GABA is the most important neurotransmitter for fast neuronal inhibition in vertebrates and invertebrates. GABAergic signaling in sex specific, fruitless expressing neuronal circuits of Drosophila is required for multiple aspects of male courtship behavior. RNAi mediated knockdown of the GABA producing enzyme Gad1 and the ionotropic receptor Rdl in the ventral nerve cord causes uncoordinated and futile copulation attempts, defects in wing extension choice and severe alterations of courtship song. Altered song of GABA depleted males fails to stimulate female receptivity, but rescue of song patterning alone is not sufficient to rescue male mating success. Knockdown of Gad1 and Rdl in brain circuits abolishes courtship conditioning. We characterize the around 220 neurons coexpressing Gad1 and Fruitless in the Drosophila male nervous system and propose inhibitory circuit motifs underlying key features of courtship behavior based on the observed phenotypes.