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The Suprachiasmatic Nucleus (SCN) A Mammalian Pacemaker

The Suprachiasmatic Nucleus (SCN) A Mammalian Pacemaker. Joshua Gooley MCB 186: Circadian Biology October 19, 2005. The SCN is located in the anterior hypothalamus. Krieg, 1932. Location of the SCN in Human. Moore, 1991. The SCN receives direct retinal input. Hendrickson et al., 1972

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The Suprachiasmatic Nucleus (SCN) A Mammalian Pacemaker

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  1. The Suprachiasmatic Nucleus (SCN) A Mammalian Pacemaker Joshua Gooley MCB 186: Circadian Biology October 19, 2005

  2. The SCN is located in the anterior hypothalamus Krieg, 1932

  3. Location of the SCN in Human Moore, 1991

  4. The SCN receives direct retinal input Hendrickson et al., 1972 Moore and Lenn, 1972

  5. SCN lesions eliminate corticosteroid rhythm SCN Lesion Moore, 1972

  6. 0 0 12 12 24 24 SCN lesions disrupt circadian rhythms Drinking Rhythm Enucleated SCN-X Body Temperature Locomotor Activity Sham SCN-X Sham SCN-X Stephan and Zucker, 1972; Kittrell, 1988

  7. SCN lesions block circadian rhythm of sleep Solid line: Sham Dashed line: SCN-X Ibuka et al., 1977

  8. The SCN is shows diurnal rhythm of glucose utilization 0900 2100 DG Nissl Lights on: 0600-1800 Schwartz and Gainer, 1977

  9. Circadian rhythm of electrical activity persists in the SCN isolated in vivo – the “SCN island experiment” Inouye and Kawamura, 1979

  10. Circadian rhythms measured in hypothalamic slices Vasopressin Release Multiunit electrical activity Martha Gillette

  11. The Tau hamster displays a short circadian period Heterozygous Homozygous mutant Normal Ralph and Menaker

  12. Circadian period is genetically encoded in the SCN Ralph et al., 1990

  13. Individual SCN neurons show circadian rhythm of electrical activity and display different periods Welsh et al., 1995

  14. Light- and circadian-regulated expression of clock genes in the SCN Antle and Silver, 2005 Dunlap, 1999

  15. The SCN determines the circadian phase of behavior de la Iglesia, 2000

  16. Individual SCN neurons show circadian expression of Per1 in hypothalamic slices Per1-luciferase rhythm in individual SCN neurons Circadian rhythm of Per1 In four SCN neurons Wild Type: Per1 circadian rhythm is robust in individual SCN neurons Double Cry knockout: Per1 rhythm is lost in individual SCN neurons Yamaguchi et al., 2003

  17. Many genes are under circadian regulation in the SCN with broadly distributed circadian phases Panda et al., 2002

  18. The SCN is heterogeneously organized Gooley and Saper, 2004 Karatsoreos et al., 2004

  19. The SCN is functionally subdivided Antle and Silver, 2005

  20. VIP signaling is required for circadian expression of behavioral rhythms Harmar et al., 2004

  21. Inputs to the Suprachiasmatic Nucleus Gooley and Saper, 2004

  22. The intergeniculate leaflet and median raphe nucleus project to the suprachiasmatic nucleus IGL (retros from SCN) MRN (5-HT) MRN (retros from SCN) Morin et al., 2004; Leander et al., 1998

  23. Circadian entrainment by exogenous melatonin Melatonin binding in SCN Weaver, 1991 Cassone et al., 1996

  24. Efferent projections of the Suprachiasmatic Nucleus Gooley and Saper, 2004

  25. Circadian outflow pathways from the SCN Saper et al., 2005

  26. Diffusible factors can regulate behavioral rhythms Polymer-encapsulated SCN graft Silver et al., 1996

  27. EGF receptor signaling can regulate behavior Kramer et al., 2001

  28. Prokineticin 2 inhibits behavioral activity saline PK2 Cheng et al., 2002

  29. The SCN is a light entrainable circadian clock… Behavior Physiology …but it is not the only circadian clock

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