The role of myoinhibitory peptides (MIPs) in the circadian system of the Madeira cockroach Rhyparobia maderae
Final Report Abstract
To summarize findings: MIP receptors are involved in parallel light entrainment pathways to the AME. - MIPs control locomotor activity rhythms via M and E oscillator circuits. - Not MIPs alone, but an interplay of MIPs, PDF, and at least one more peptide control the rhythmicity and regularity of locomotor activity rhythms. - Simultaneous knockdown of mip-precursor and mip-receptor decreased weight and body size of female Madeira cockroaches, but not of males. - Mating-dependently decreases of activity and decline of rhythmicity of female cockroaches was not affected by mip-precursor RNAi. - Sexual receptivity of female cockroaches was not affected by mip-precursor RNAi. - Sleep-deprived cockroaches reduced general activity levels and shifted their activity patterns from the night to the day, but this was not exclusively determined via MIP signaling. - Arena assays were developed to study the role of MIPs for food preferences. No mating-dependent switch in food preference was found. Preliminary MIP-injection studies did not reveal any significant affect on food preferences. - Y-maze assays were developed to study food preferences after starvation with/without MIP-receptor-RNAi in mated/non-mated cockroaches. Results are still preliminary and need further experiments. - Running wheel assays combined with mip-precursor knockdowns or with double knockdowns of mip-precursor and pdf-precursor. We found changes in the amplitude and rhythmicity of rest-activity cycles that were maximal in the doubleknockdowns. Thus, both MIPs and PDF control sleep-wake rhythms. In summary, we conclude that MIPs together with other neuropeptides control various clock outputs such as sleep-wake cycles and different metabolic routes. MIPs were shown to control the general metabolism of females, but no decisive role for stimulation of mating or mating-dependent behavioral changes were found. Preliminary sleep deprivation studies hint further roles of MIPs but need to be continued since the number of experiments is too low for reliable statistical conclusions.
Publications
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(2017) Functions of corazonin and histamine in light entrainment of the circadian pacemaker in the Madeira cockroach, Rhyparobia maderae. J Comp Neurol 525(5): 1250-1272
Arendt A, Baz ES, Stengl M
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(2018) Circadian pacemaker neurons of the Madeira cockroach are inhibited and activated by GABAA and also by GABAB receptors. Eur J Neurosci 51(1):282-299
Giese M, Wei HY, Stengl M
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(2018) GABA- und serotonin-expressing neurons take part in inhibitory as well as excitatory input pathways to the circadian clock of the Madeira cockroach Rhyparobia maderae. Eur J Neurosci 47(9):1067-1080
Giese M, Gestrich J, Massah A, Peterle J, Wei HY, Stengl M
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(2020) Candidates for photic entrainment pathways to the circadian clock via optic lobe neuropils in the Madeira cockroach. J Comp Neurol.; 528: 1754–1774
Arnold T, Korek S, Massah A, Eschstruth D, Stengl M
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Morphological and functional examination of neuropeptides in the circadian system of Rhyparobia maderae with special focus on myoinhibitory peptides. Dissertation, Univ. of Kassel, April 2021
Thordis Arnold
