Circadian and ultradian rhythms in normal mice and in a mouse model of Huntington’s disease

ABSTRACT

Circadian rhythms in core body temperature (CBT) have been widely studied, but fewer studies have explored higher-frequency (ultradian) rhythms in detail. We analyzed CBT recordings from young and middle-aged wild-type mice as well as from the Q175 model of Huntington’s disease (HD), at sufficient temporal resolution to address the question of ultradian rhythms. We used model selection methods to show that the overall circadian pattern was better fit by a square wave than a sine wave. Then, using Fourier analysis of the CBT rhythms, we identified the spectral signature of an 8-hour oscillation that occurs in the night but not the day, an observation that can be confirmed by direct inspection of the rhythms. This diurnal amplitude modulation of the 8-hour rhythm was lost with aging as well as in the HD model. Thus, the impact of aging and disease is seen here in the loss of the ability to separate rhythms into a daytime phase and a nighttime phase. These findings raise the possibility that ultradian rhythms in CBT may be a useful biomarker for the pathology within the central nervous system.

KEYWORDS:

• Aging
• biomarker
• core body temperature
• circadian
• Fourier analysis
• Huntington’s disease
• Q175 mice
• ultradian

Acknowledgements

We are grateful to Aram Derbedrossian, Se-Young (Myki) Lee, Natalia Vargas, Sarah Popelka, and Lauryn Robinson for technical assistance in assembling and processing the data. The data were originally collected in the UCLA cardiovascular core headed by Dr. K. Roos.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.