Involved in diverse biological roles including regulating aspects of gut function, satiety and food ingestion, hyperactivity, and aggression (PubMed:17632121, PubMed:24142897, PubMed:25187989). Regulates gut muscle contraction in adults but not in larvae (PubMed:17632121). Functions downstream of TfAP-2 and twz in octopamine signaling pathways to modulate feeding and male aggression (PubMed:24142897, PubMed:25187989). Inhibits consummatory behavior in adults and functions as part of a negative feedback loop with TfAP-2 and twz to prevent overeating; TfAP-2 and twz regulate octopamine signaling to initiate feeding, then octopamine activates expression of Dsk in insulin-producing cells (IPCs) to inhibit feeding (PubMed:25187989). Expressed in larval brain tissue localizing to cells in the anterior and medial protocerebrum. Expressed in cells in the brain lobe, optic lobe, subesophageal ganglion, thoracic ganglia and the eighth abdominal neuromere. Drosulfakinin-0 is expressed in the central nervous system including the subesophageal ganglion and an abdominal ganglion. Expressed at all developmental stages. Up-regulated 24 hours after starvation and then appears to return to normal expression levels 48 hours after nutritional starvation. In adults, RNAi-mediated knockdown in insulin-producing cells or all Dsk-expressing cells, increases total food intake and the number of feeding bouts over a 24 hour period (PubMed:25187989). However, feeding them the CCK antagonist SR 27897 does not result in a further increase in total food intake and feeding bouts, as in wild-type adults (PubMed:25187989). Belongs to the gastrin/cholecystokinin family.