Mapping the Neural Circuits That Modulates the Molecular Switch Between Alternative Interval Timing Behaviours in Drosophila Melanogaster

Abstract

Neuropeptides are central modulators of many functions including male-specific mating behaviours. Understanding how these chemical messengers modulate the neural substrates are still not well understood but remains important for biological research. In Drosophila melanogaster, two well-defined microcircuits (Longer-Mating-Duration (LMD) and Shorter-Mating-Duration (SMD)), are used to understand the underlying mechanisms of how neuropeptide interactions modulate temporal information in mating behaviours. In our study, we investigated the influence of SIFamide receptor-mediated signaling and its association to both LMD and SMD. We performed several RNAi-based screens where we identified and mapped out seven different types of neuropeptidergic neurons which were found to be important to either LMD and/or SMD. Following this analysis, we highlight three independent signaling pathways which are necessary to describe the cellular mechanics of the neuropeptides involved. Firstly, we infer that synaptic contacts between proctolin and SIFamide neurons in the subesophageal ganglion mediate inhibition in SMD whereas proctoclin as a neuropeptide modulates both LMD and SMD in a non-synaptic manner. Secondly, we describe an existing insulin-related microcircuit that is modulated by the inputs of Dimmed (DIMM), a transcription factor, through adipokinetic hormone, allatostatin A, and leucokinin to exhibit SMD. Thirdly and lastly, we discuss our interpretations of how capability neurons in the central brain resolves a potential disinhibition microcircuit in LMD via olfactory based signaling in the antennae lobe. In summary, our results contribute to establishing a model system to study neuropeptidergic microcircuits in complex mating behaviours.