Neuropeptidergic input pathways to the circadian pacemaker center of the Madeira cockroach analysed with an improved injection technique. Issue 6 (27th June 2013)

• Record Type: Journal Article
• Authors: Schulze, Julia; Schendzielorz, Thomas; Neupert, Susanne; Predel, Reinhard; Stengl, Monika
• Is Part Of: European journal of neuroscience. Volume 38:Issue 6(2013:Sep.)
• Page Start: 2842
• Page End: 2852
• Publication Date: 2013-06-27
• Subjects: Nervous system -- Periodicals; 612.8
• DOI: 10.1111/ejn.12285
• Languages: English
• ISSNs: 0953-816X

Abstract

<abstract abstract-type="main" id="ejn12285-abs-0001"> <title>Abstract</title> <p>Light entrainment pathways synchronize the circadian clock of almost all species of the animal and plant kingdom to the daily light dark cycle. In the Madeira cockroach <italic>Rhyparobia (Leucophaea) maderae</italic>, the circadian clock is located in the accessory medulla of the brain's optic lobes. The clock has abundant neuropeptides with unknown functions. Previous studies suggested that myoinhibitory peptides (MIPs), orcokinins (ORCs), and allatotropin (AT) take part in light input pathways to the circadian clock. As the sequences of AT and ORCs of <italic>R. maderae</italic> have not yet been determined, with matrix‐assisted laser desorption/ionization–time of flight mass spectrometry, the respective <italic>Rhyparobia</italic> peptides were characterized. To search for light‐like phase‐shifting inputs to the circadian clock, <italic>Rhyparobia</italic>‐MIP‐1, <italic>Rhyparobia</italic>‐AT, and <italic>Rhyparobia</italic>‐ORC were injected at different circadian times, combined with locomotor activity assays. An improved, less invasive injection method was developed that allowed for the analysis of peptide effects within <2 weeks after injection. <italic>Rhyparobia</italic>‐MIP‐1 and <italic>Rhyparobia</italic>‐AT injections resulted in dose‐dependent monophasic phase response curves with maximum delays at the beginning of the subjective night, similar to light‐dependent phase delays. In contrast to <italic>Manduca sexta</italic>‐AT, <italic> Rhyparobia</italic>‐AT did not phase advance locomotor activity rhythms. Only injections of <italic>Rhyparobia</italic>‐ORCs resulted in a biphasic light‐like phase response curve. Thus, it is hypothesized that <italic>Rhyparobia</italic>‐MIP‐1 and ‐AT are candidates for relaying light‐dependent delays and/or non‐photic inputs to the clock, whereas <italic>Rhyparobia</italic>‐ORCs might be part of the light‐entrainment pathways relaying phase delays and advances to the circadian clock of the Madeira cockroach.</p> </abstract>