Ruvkun hopes that serotonin pathways in the worm might yield valuable drug targets. Worms can be conveniently grown in microwell plates and are already being used in primary screens by a Belgian company that has licensed some of his technology. Granted, the backbone of molecular pathways provided by C. elegans unites previous data on serotonin and metabolism under the umbrella of food signaling. Yet evolution has added flesh to this backbone as complex animals expanded their genomes and diversified their behavior. For example, worms eat constantly while humans eat intermittently, requiring more sophisticated regulation.
Worms have no leptin, a hormone that controls eating.
And the diversity of serotonin receptors in mammals far exceeds that in worms, accounting for the neurotransmitter's powerful role in mood control and its disorders and myriad other functions.