Project Details
Projekt
The circadian clock of the Madeira cockroach
Subject Area
Cognitive, Systems and Behavioural Neurobiology
Term
from 2020 to 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 444683199
The nocturnal Madeira cockroach is an established model in chronobiology. Its circadian clock is the accessory medulla (AME) that releases specific neuropeptides at specific times of the day to time rhythms in physiology and behavior. Our preliminary studies suggested that peaks of neuropeptide release occur every 6 h at dusk and dawn, at the middle of day and night, activating neuropeptide-dependent neuronal ensembles. However, it is still unknown which neuropeptides are released at what time over the course of the 24 h daily cycle. We focus our analysis on the clock´s control of rest-activity cycles via its neuropeptide pigment-dispersing factor (PDF). PDF keeps two neuronal circuits in antiphase, activating ipsilateral AME neurons, while inhibiting contralateral projecting AME neurons that are known to activate locomotor activity rhythms. Therefore, we hypothesize that the circadian clock rhythmically releases the neuropeptide PDF activated by (entrained to) light at dawn. Thus, during the day PDF release activates ipsilateral sleep maintaining ensembles (morning cells) and suppresses at the same time contralateral activity promoting neuronal ensembles (evening cells). At dusk, another putative neuropeptide is released that will antagonize PDF. To challenge our hypothesis, here, we want to test every 6 h by mass spectrometry when PDF and which other neuropeptides are released by the circadian clock. With single cell transcriptomics, calcium imaging and intracellular recordings we want to identify PDF-sensitive morning and evening cells to determine their respective morphology, their neuropeptide equipment and their neuropeptide/neurotransmitter receptors. Then, with 3D reconstruction and implementation of the neuropeptidergic clock neurons in our standard cockroach brain including modeling of their connectivity pattern at specific times of the day, we are able to identify rest-activity controlling circadian clock circuits in this basal insect. With this comparative approach we expect to identify general schemes of neuropeptidergic information encoding and timing invented early in evolution and possibly maintained also in mammalian brains.
DFG Programme
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