Accurate and precise circadian locomotor activity rhythms in male and female Indian pygmy field mice, Mus terricolor

Abstract

We report some basic circadian characteristics in Mus terricolor, the nocturnal pygmy field mouse. Both male and female M. terricolor entrain well to a 12:12 light:dark schedule. Activity is completely nocturnal in distribution in LD. ρ and α in LD differ significantly between males and females. Free-running circadian locomotor activity rhythm in DD was 23.69 h (males) and 23.46 h (females). In LD, ψ was −0.20 h and −0.15 h in males and females, respectively. Rhythms were accurate (6.02 in males/7.30 in females [h⁻¹]) and precise (4.83 in males /4.74 in females [h⁻¹]). Fifteen-minute perturbations with ∼70 lux white light in DD led to predictable phase advances and delays. Mus terricolor took ∼7 days to re-entrain to a 6 h advance in the ambient light schedule, with rapid resynchronization to a 6 h phase delay. These results indicate that M. terricolor is a good model animal for in-depth research in circadian biology.

Keywords:

• Mus terricolor
• wheel running
• circadian properties
• accuracy
• precision
• simulated jet lag

Acknowledgments

Financial aid to MS vide grant no. (F (A) 1-14(G)/3449) and University Grants Commission (Junior and Senior Research Fellowship grant to PB) are highly acknowledged. The authors are thankful to Mr. Punit Kumar for his help with animal handling and maintenance.