Document Type
Article
Publication Date
6-2012
Publication Title
Journal of Biological Rhythms
Abstract
The impact of ovarian hormones on hamster ultradian rhythms (URs) is unknown. We concurrently monitored URs and circadian rhythms (CRs) of home cage locomotor activity during the estrous cycle, pregnancy, and lactation of Syrian hamsters. URs with a mean period of 4–5 h were evident during the dark phase in more than 90% of females on days 1 and 2 of the estrous cycle but were significantly less prevalent on cycle days 3 and 4. The period of the UR did not vary as a function of estrous cycle stage, but at all stages, the UR period was longer in the dark than the light phase. The UR acrophase occurred significantly earlier on cycle day 4 than on days 1 and 2, and UR robustness and amplitude were reduced on days 3 and 4. Robustness, mesor, and amplitude of CRs were greater during cycle days 3 and 4; timing of the CR acrophase was delayed on day 4 relative to all other cycle days. Effects of the estrous cycle on URs were evident only during the dark phase. The proportion of hamsters displaying dark phase URs increased significantly during early and late gestation and decreased during lactation. Pregnancy significantly increased UR complexity, robustness, and amplitude. The emergence of URs over gestation was paralleled by decrements in the robustness and amplitude of CRs, which also were absent in a significant proportion of dams during lactation but re-emerged at weaning of litters. The changing endocrine profile of the estrous cycle, hormonal dynamics of pregnancy and lactation, and nursing demands placed on dams are each associated with alterations in the expression of ultradian and circadian locomotor rhythms. Diminution of CRs and augmentation of URs may afford greater behavioral flexibility during life stages when interactions with mates and offspring are less predictable.
Keywords
locomotor activity, gonadal steroids, estrous cycle, pregnancy, lactation
Volume
27
Issue
3
First Page
246
Last Page
256
DOI
doi:10.1177/0748730412441315
Rights
© 2012 The Author(s)
Recommended Citation
Prendergast, Brian J.; Beery, Annaliese K.; Paul, Matthew J.; and Zucker, Irving, "Enhancement and Suppression of Ultradian and Circadian Rhythms Across the Female Hamster Reproductive Cycle" (2012). Neuroscience: Faculty Publications, Smith College, Northampton, MA.
https://scholarworks.smith.edu/nsc_facpubs/14
Comments
Peer reviewed accepted manuscript.
Supplementary material is available on the journal’s website at http://jbr.sagepub.com/supplemental.