C. elegans express 6 different serotonin receptors and have only a few serotonergic neurons (NSM, HSN, and ADF).
NSM activity controls slowing in response to food but all 6 receptors are important for the full repertoire of behavioral responses to food.
Activation of NSM drives slowing, pharyngeal pumping and decreased head movements, which align with naturalistic foraging behaviors
Knocking out individual or combinations of the receptors reveals that there are 3 “driver” receptors (mod-1, ser4, and lgc-50) that have the strongest impact on foraging behavior, whereas the other 3 receptors only modulate the behavioral response.