Sleep Arrhythmia in the Eusocial Naked Mole-Rat

Psychology Department, McMaster University, Hamilton, Ontario, Canada.
The Science of Nature (Impact Factor: 2.1). 07/1994; 81(6):272-5. DOI: 10.1007/BF01131581
Source: PubMed
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    • "The study of activity patterns in subterranean mammals has been traditionally addressed to rodent species (see among the others Nevo et al. 1982, Bennet 1992, Rado et al. 1993, Davis-Walton & Sherman 1994, Ben-Shlomo et al. 1995, Lovegrove & Papenfus 1995, Oster et al. 2002, Zelová et al. 2009, Lövy et al. 2013), while little is known about the activity patterns of subterranean insectivores (Godfrey 1955, Mellanby 1967, Harvey 1976, Gorman & Stone 1990, Loy et al. 1992, Hennicke 1997, Macdonald et al. 1997, Borroni et al. 1999). This lack of data is mostly related to the many difficulties in capturing, handling and monitoring subterranean insectivores. "
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    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.
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