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Clock mutation lengthens the circadian period without damping rhythms in individual SCN neurons

Nature Neuroscience volume 5, pages 399400 (2002) | Download Citation



Spontaneous discharges of individual neurons in the suprachiasmatic nucleus (SCN) of Clock mutant mice were recorded for over 5 days in organotypic slice cultures and dispersed cell cultures using a multi-electrode dish. Circadian rhythms with periods of about 27 hours were detected in 77% of slice cultures and 15% of dispersed cell cultures derived from Clock/Clock homozygotes. These findings indicate that the Clock mutation lengthens the circadian period but does not abolish the circadian oscillation, and suggest an important role of intercellular communication in the expression of circadian rhythm in the SCN.

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We thank J. S. Takahashi and N. Ishida for generous gifts of Clock mutant mice, and T. Yasuda for technical assistance. This work was supported in part by a Grant-in-Aid for scientific research from the Ministry of Education, Science, Culture, Sports and Technology of Japan (nos. 11233201 and 12557005).

Author information


  1. Department of Physiology, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan

    • Wataru Nakamura
    • , Sato Honma
    •  & Ken-ichi Honma
  2. Department of Oral Functional Science, Hokkaido University Graduate School of Dentistry, Sapporo 060-8586, Japan

    • Wataru Nakamura
    •  & Tetsuo Shirakawa


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Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Sato Honma.

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Image files

  1. 1.

    Supplementary Fig. 1.

    Representative wheel-running activities of Clock mutant and wild-type mice. Wheel-running activities were measured under DD after recording under light/dark (LD) cycle for 10 d. White and black bars indicated times of lights-on and lights-off, respectively. Detection of a circadian rhythm and calculation of a period were done by a χ-square periodogram using a record of every 10 d under DD. The circadian periods of these mice in the first, second and third 10-d periods mice were 24.1, 24.5 and 24.9 h for Clock/+ and 23.5, 23.6 and 23.5 h for +/+, respectively. Clock/Clock showed significant circadian rhythm with a period of 28.0 h in the first 10 d under DD and then became arrhythmic.

  2. 2.

    Supplementary Fig. 2.

    A phase-contrast photomicrograph of a cultured SCN slice on a multi-electrode dish after 14 d in culture. A pair of the SCN was recognized as densely packed neuronal areas located immediately above the degenerated optic chiasm together with electrodes. The black squares indicated the 64 electrodes with a size of 20 µm square arranged in an 8 × 8 pattern with 100 µm separation. V, third ventricle; OC, optic chiasm; SCN, suprachiasmatic nucleus. Scale bar, 150 µm

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