title: Candidates for the light entrainment pathway to the circadian clock of the Madeira cockroach Rhyparobia maderae.
abstract: The circadian pacemaker controlling locomotor activity rhythms in the Madeira cockroach is located at the accessory medulla (AMe). The ipsi- and contralateral compound eyes provide light input to the AMe, possibly via the γ-aminobutyric acid (GABA)-immunoreactive (-ir) distal tract, which connects the glomeruli of the AMe to the ipsilateral medulla and lamina. To identify possible light-entrainment pathways, double-label immunocytochemistry was performed employing antibodies against GABA, myoinhibitory peptide (MIP), allatotropin (AT) and orcokinin (ORC). While all antisera tested, except the anti-ORC, prominently stained the glomeruli of the AMe, colocalization with anti-GABA was detected neither in the glomeruli nor in the distal tract. However, one median neuron that colocalized GABA-, AT- and MIP-immunoreactivity appeared to connect all glomeruli of the AMe to the medulla and lamina. Furthermore, one distal-frontoventral local neuron with arborizations in all glomeruli of the AMe colocalized anti-AT- and anti-MIP immunoreactivity. As candidates for contralateral light entrainment pathways, one ventromedian and one ventral neuron colocalized MIP- and ORC immunoreactivity, projecting via posterior and anterior commissures. Both branched in the interglomerular region of the AMe, where arborizations co-labeled with anti-ORC- and anti-MIP antisera. A possible role for MIP in light entrainment is supported also by injections of Rhyparobia maderae-specific MIP-2, which generated an all-advance phase-response curve late at night. Future experiments will challenge our hypothesis that GABA-, MIP- and AT-ir neurons provide ipsilateral light entrainment to all glomeruli, while MIP- and ORC-ir neurons carry contralateral light entrainment to the AMe's interglomerular region, either delaying or advancing AMe neurons light-dependently.
authors: Department of Biology, Animal Physiology, University of Kassel, Heinrich-Plett-Str. 40, 34132, Kassel, Germany.
authors: Julia
authors: J
authors: Schendzielorz
authors: Monika
authors: M
authors: Stengl
mesh_terms: D000825:Animal Structures / Q000166:cytology / Q000294:innervation / Q000378:metabolism / Q000528:radiation effects; D000818:Animals; D057906:Circadian Clocks / Q000528:radiation effects*; D002940:Circadian Rhythm / Q000187:drug effects; D003058:Cockroaches / Q000502:physiology* / Q000528:radiation effects*; D007267:Injections; D008027:Light; D008297:Male; D008954:Models, Biological; D009043:Motor Activity / Q000187:drug effects; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009479:Neuropeptides / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D019581:Neuropil / Q000187:drug effects / Q000378:metabolism; D009899:Optic Lobe, Nonmammalian / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D012044:Regression Analysis; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D009479:Neuropeptides; C079067:orcokinin; D005680:gamma-Aminobutyric Acid