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bioRxiv · 10.1101/2020.07.24.219725

Independently Regulated Multi-compartment Neuropeptide Release from a Clock Neuron Controls Circadian Behavior

Klose, M. K.·Bruchez, M. P.·Deitcher, D. L.·Levitan, E. S.
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Abstract

Neuropeptides control rhythmic behaviors, but the timing and location of their release within circuits is unknown. Here imaging in the brain shows that synaptic neuropeptide release by Drosophila clock neurons is diurnal, peaking at times of day that were not anticipated by prior electrical and Ca2+ data. Furthermore, hours before peak synaptic neuropeptide release, neuropeptide release occurs at the soma, a neuronal compartment that has not been implicated in peptidergic transmission. The timing disparity between release at the soma and terminals results from independent and compartmentalized mechanisms for daily rhythmic release: consistent with conventional electrical activity-triggered synaptic transmission, terminals require Ca2+ influx, while somatic neuropeptide release is triggered by the biochemical signal IP3. Upon disrupting the somatic mechanism, the rhythm of terminal release and locomotor activity period are unaffected, but the number of flies with rhythmic behavior and sleep-wake balance are reduced. These results support the conclusion that somatic neuropeptide release controls specific features of clock neuron dependent behaviors. Thus, compartment specific mechanisms within individual clock neurons produce temporally and spatially partitioned neuropeptide release to expand the peptidergic connectome underlying daily rhythmic behaviors. Significance StatementIt is believed that electrical activity simultaneously stimulates widespread release sites in single neurons to elicit neuropeptide dependent behaviors. However, optically detecting neuropeptide release in the intact brain shows that clock neurons release neuropeptides from different sites at different times of the day. This is possible because one neuronal compartment, the soma, uses biochemical signaling instead of electrical activity to evoke release. Disrupting somatic release affects specific features of circadian locomotor activity and sleep. Thus, neuropeptide release is elicited by independent triggers from distinct parts of clock neurons to engage different regions of behavior regulating circuitry. This strategy for expanding the connectome may be used for other neuropeptide dependent behaviors, such as feeding and pain perception.

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Klose, M. K., Bruchez, M. P., Deitcher, D. L., Levitan, E. S.. 2020-07-26. Independently Regulated Multi-compartment Neuropeptide Release from a Clock Neuron Controls Circadian Behavior. https://doi.org/10.1101/2020.07.24.219725

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