Pigment-dispersing factor and GABA synchronize cells of the isolated circadian clock of the cockroach Leucophaea maderae.
Pigment-dispersing factor-immunoreactive circadian pacemaker cells, which arborize in the accessory medulla, control circadian locomotor activity rhythms in Drosophila as well as in the cockroach Leucophaea maderae via unknown mechanisms. Here, we show that circadian pacemaker candidates of the accessory medulla of the cockroach produce regular interspike intervals. Therefore, the membrane potential of the cells oscillates with ultradian periods. Most or all oscillating cells within the accessory medulla are coupled via synaptic and nonsynaptic mechanisms, forming different assemblies. The cells within an assembly share the same ultradian period (interspike interval) and the same phase (timing of spikes), whereas cells between assemblies differ in phase. Apparently, the majority of these assemblies are formed by inhibitory GABAergic synaptic interactions. Application of pigment-dispersing factor phase locked and thereby synchronized different assemblies. The data suggest that pigment-dispersing factor inhibits GABAergic interneurons, resulting in disinhibition and phase locking of their postsynaptic cells, which previously belonged to different assemblies. Our data suggest that phase control of action potential oscillations in the ultradian range is a main task of the circadian pacemaker network. We hypothesize that neuropeptide-dependent phase control is used to gate circadian outputs to locomotor control centers.
Schneider
Nils-Lasse
NL
Department of Biology, Animal Physiology, Philipps University of Marburg, D-35032 Marburg, Germany.
Stengl
Monika
M
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D003058:Cockroaches; D018756:GABA Antagonists / Q000494:pharmacology; D019476:Insect Proteins / Q000378:metabolism*; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D008954:Models, Biological; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009479:Neuropeptides / Q000494:pharmacology; D010852:Picrotoxin / Q000494:pharmacology; D013493:Suprachiasmatic Nucleus / Q000166:cytology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D002118:Calcium; D018756:GABA Antagonists; D019476:Insect Proteins; D009479:Neuropeptides; D010852:Picrotoxin; D005680:gamma-Aminobutyric Acid