Serotonin modulates various physiological processes and behaviors. This study investigates the role of 5-HT in locomotion and feeding behaviors as well as in modulation of sensory-motor circuits. The 5-HT biosynthesis was dysregulated by feeding Drosophila larvae 5-HT, a 5-HT precursor, or an inhibitor of tryptophan hydroxylase during early stages of development. The effects of feeding fluoxetine, a selective serotonin reuptake inhibitor, during early second instars were also examined. 5-HT receptor subtypes were manipulated using RNA interference mediated knockdown and 5-HT receptor insertional mutations. Moreover, synaptic transmission at 5-HT neurons was blocked or enhanced in both larvae and adult flies. The results demonstrate that disruption of components within the 5-HT system significantly impairs locomotion and feeding behaviors in larvae. Acute activation of 5-HT neurons disrupts normal locomotion activity in adult flies. To determine which 5-HT receptor subtype modulates the evoked sensory-motor activity, pharmacological agents were used. In addition, the activity of 5-HT neurons was enhanced by expressing and activating TrpA1 channels or channelrhodopsin-2 while recording the evoked excitatory postsynaptic potentials (EPSPs) in muscle fibers. 5-HT2 receptor activation mediates a modulatory role in a sensory-motor circuit, and the activation of 5-HT neurons can suppress the neural circuit activity, while fluoxetine can significantly decrease the sensory-motor activity.
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This work was funded by G. Ribble fellowship from Department of Biology, University of Kentucky (Esraa Abdeljaber), the Higher Committee for Education Development (HCED) scholarship in Iraq (Zana R. Majeed), Deutscher Akademischer Austausch Dienst (DAAD) German Academic Exchange Service, RISE Program (Research Internships in Science and Engineering) (Felicitas Koch), and personal funds (Robin L. Cooper).
Majeed, Zana R; Abdeljaber, Esraa; Soveland, Robin; Cornwell, Kristin; Bankemper, Aubrey; Koch, Felicitas; and Cooper, Robin L., "Modulatory Action by the Serotonergic System: Behavior and Neurophysiology in Drosophila melanogaster" (2016). Biology Faculty Publications. 107.