Date of Award
Master of Science
Mark C. Ospeck
David A. Freeman
The suprachiasmatic nuclei (SCN), the principal mammalian circadian oscillator, contain several thousand clock neurons that oscillate spontaneously with ~24-hour periods in its ventrolateral region. Without light, this network synchronizes through action potentials releasing VIP, compromising on a free-running period near 24 hours. We entrained Siberian hamsters to various light-dark cycles and tracked their activity into constant darkness showing that they retain memory for a particular light-dark cycle to which they were entrained before returning to their own free-running period. Using Leloup-Goldbeter mammalian clock neurons, we model the ventrolateral SCN network and show that light acting weakly upon a strongly rhythmic VIP oscillation can explain the light-dark cycle memory that we observe. Additionally, light is known to initiate a MAP kinase signaling cascade that induces transcription of both per and mpk1 phosphatase. We show that the ensuing phosphatase-kinase interaction can account for the dead zone in the mammalian phase response curve.
dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.
Coffey, Benjamin L., "Modeling Light-Dark Cycle Memory in the Mammalian SCN" (2010). Electronic Theses and Dissertations. 141.