Calbindin neurons in the hamster suprachiasmatic nucleus do not exhibit a circadian variation in spontaneous firing rate

Erin E. Jobst, Charles N. Allen

Research output: Contribution to journalArticle

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The role of the mammalian suprachiasmatic nuclei (SCN) in generating circadian rhythms in behaviours and other physiological processes is well established. A prominent feature of SCN neurons is the circadian oscillation in action potential firing frequency, with a peak near midday. A subset of calbindin-immunoreactive (CB+) neurons form a compact subnucleus (CBsn) in the hamster SCN. Restoration of rhythmicity using fetal SCN grafts in SCN-lesioned hamsters is critically dependent upon the presence of CB+ neurons within the transplanted grafts [LeSauter & Silver (1999) J. Neurosci., 5574-5585]. The aim of the current study was to determine whether CB+ neurons within the CBsn of the hamster SCN fire action potentials in a circadian pattern as part of their output signal. Using patch-clamp recording, we demonstrated that CB+ neurons in the CBsn do not express a circadian rhythm in spontaneous firing frequency under diurnal conditions in vitro. Furthermore, the percentage of silent CB- cells varies with zeitgeber time, whereas the percentage of silent CB+ cells does not. Immunohistochemical analysis revealed that the CBsn is a nonhomogeneous nucleus, containing many more CB- than CB+ cells. Our results reveal that CB+ neurons within the CBsn represent a functionally distinct neuronal subpopulation in which rhythmic action potential output may not be necessary for the restoration of behavioural circadian rhythmicity.

Original languageEnglish (US)
Pages (from-to)2469-2474
Number of pages6
JournalEuropean Journal of Neuroscience
Issue number12
StatePublished - Jan 1 2002



  • Cell-attached patch-clamp recording
  • Circadian rhythm

ASJC Scopus subject areas

  • Neuroscience(all)

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