Rest-activity rhythm of the blind mole rat Spalax ehrenbergi under different lighting conditions

Irene Tobler, Miriam Herrmann, Howard M. Cooper, Julia Negroni, Eviatar Nevo, Peter Achermann

Research output: Contribution to journalArticlepeer-review

Abstract

The mole rat is a solitary, subterranean and photoperiodic rodent. We investigated its rest activity behavior under several lighting conditions, complemented our observations with light-induced c-fos expression, and compared the activity behavior of two chromosomal forms (2n = 58 and 60). The 26 mole rats had a clear overall preference for activity in the light or dark period, but prolonged recordings in five individuals showed that the initial preference was not stable in the nocturnal animals, they became diurnal. A 6- h advance of the light-dark (LD) cycle induced a shift of activity and the previous LD preference was reestablished. The large daily variability of activity onset did not allow this study to determine whether the animals were entrained to the LD cycle upon release into constant darkness (DD) or whether activity had been masked by light. The period of the motor activity rhythm in DD free ran in more than 50% of the animals. No differences in activity were observed between the two karyotypes. Immunohistochemistry for c-fos expression in the nucleus suprachiasmaticus at different circadian times showed that c-fos was induced only in animals exposed to a 1-h light pulse during the subjective night, but not during the subjective day or in control animals in the absence of a light pulse. The large intra- and inter- individual variability in daily motor activity both in LD and in DD suggest only a weak photic entrainment of the circadian clock to light of approximately 100 lux, and possibly a weak regulation of behavior by the circadian clock.

Original languageEnglish
Pages (from-to)173-183
Number of pages11
JournalBehavioural Brain Research
Volume96
Issue number1-2
DOIs
StatePublished - Nov 1998

Bibliographical note

Funding Information:
We thank Dr A. Borbély for critical reading of the manuscript, H. Heinrich for his help with the animal care and preparation of the figures, and C. Wüthrich for the construction of the running wheels. The study was supported by the Swiss National Science Foundation grants 31.32574.91 and 3100.042500.94, HFSPO grant No. RG 68/95 (HC, JN, EN) and the Israel Science Foundation, grant 21/94 (EN).

Keywords

  • Blind mole rat
  • c-fos
  • Circadian rhythm
  • Light-dark cycle
  • Motor activity
  • Running wheel
  • SCN
  • Subterranean

ASJC Scopus subject areas

  • Behavioral Neuroscience

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