Ovariectomy influences the circadian rhythm of locomotor activity and the photic phase shifts in the volcano mouse

• Published in: Physiology & behavior Vol. 182; pp. 77 - 85
• Main Authors: Juárez-Tapia, Cinthia, Miranda-Anaya, Manuel
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-12-2017
• Subjects: Analysis of Variance; Animals; Circadian locomotor activity; Circadian Rhythm - physiology; Estradiol - blood; Female; Locomotion - physiology; Mice; Neotomodon alstoni; Ovariectomy; Ovary; Photic phase shifting; Photic Stimulation; Species Specificity; Time Factors; Photic phase shifting; Ovary; Circadian locomotor activity; Neotomodon alstoni
• ISSN: 0031-9384; 1873-507X
• DOI: 10.1016/j.physbeh.2017.10.002

Recently, the relationship between the circadian system and female reproduction has been of great interest; ovarian hormones can modify the amount and distribution of daily activity differently in rodent species. The volcano mouse Neotomodon alstoni is a species in which it is possible to study the circadian rhythm of locomotion, and it offers comparative information about the influence of ovaries on the circadian system. In this study, we used infrared crossings to compare free movement in intact and sham-operated or ovariectomized mice. We analyzed behavioral and endocrine changes related to the estrous cycle and locomotor circadian rhythm in free-running mice and photic phase shifting. Evidence shows that intact mice present a scalloped pattern of daily activity during the estrous cycle. In constant darkness, the ovariectomy reduces the total amount of activity, shortens the free-running circadian period of locomotion and increases photic phase shifts during the early subjective night. During entrainment, the ovariectomized mice increased the amplitude of total activity during the scotophase, and delay the time of activity onset. These results suggest that ovarian hormones in N. alstoni modulate the circadian rhythm of locomotor activity in a species-specific manner.
•Ovariectomy produces species-specific changes in Neotomodon alstoni in an environment without running wheel.•In intact females, locomotor activity presents “scalloping” that disappears in ovariectomized mice.•Ovariectomy reduces the period and intensity of locomotor activity in darkness but increases photic phase shifting.•In LD  cycles ovariectomy delays the onset of locomotor activity, increases its amplitude and shortens its duration.