Light-Dark Cycle Memory in the Mammalian Suprachiasmatic Nucleus
AUTOR(ES)
Ospeck, Mark C.
FONTE
The Biophysical Society
RESUMO
The mammalian circadian oscillator, or suprachiasmatic nucleus (SCN), contains several thousand clock neurons in its ventrolateral division, many of which are spontaneous oscillators with period lengths that range from 22 to 28 h. In complete darkness, this network synchronizes through the exchange of action potentials that release vasoactive intestinal polypeptide, striking a compromise, free-running period close to 24 h long. We entrained Siberian hamsters to various light-dark cycles and then tracked their activity into constant darkness to show that they retain a memory of the previous light-dark cycle before returning to their own free-running period. Employing Leloup-Goldbeter mammalian clock neurons we model the ventrolateral SCN network and show that light acting weakly upon a strongly rhythmic vasoactive intestinal polypeptide oscillation can explain the observed light-dark cycle memory. In addition, light is known to initiate a mitogen-activated protein kinase signaling cascade that induces transcription of both per and mkp1 phosphatase. We show that the ensuing phosphatase-kinase interaction can account for the dead zone in the mammalian phase response curve and hypothesize that the SCN behaves like a lock-in amplifier to entrain to the light edges of the circadian day.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2741590Documentos Relacionados
- Synaptic input from the retina to the suprachiasmatic nucleus changes with the light-dark cycle in the Syrian hamster.
- Light-Dark Regulation of Starch Metabolism in Chloroplasts: I. Levels of Metabolites in Chloroplasts and Medium during Light-Dark Transition 1
- Carbon Partitioning in Eelgrass (Regulation by Photosynthesis and the Response to Daily Light-Dark Cycles).
- Kinetics of light-dark CO2 fixation and glucose assimilation by Aphanocapsa 6714.
- Growth, molt and survival of Palaemonetes argentinus (Decapoda, Caridea) under different light-dark conditions