AJP - Regulatory, Integrative and Comparative Physiology, Vol 249, Issue 4 402-R409, Copyright © 1985 by American Physiological Society
Resynchronization patterns for urinary rhythms in rats after light-dark shifts
J. Poulis, F. Roelfsema, D. van der Heide and D. Smeenk
Diurnal urinary rhythms during a fixed 12:12 light-dark cycle were studied
in male and female rats. After a control period of 9 days the light-dark
cycle was shifted either +6 or -6 h by delaying or advancing the light
period, respectively. Subsequently the resynchronization process was
studied for 19-21 days. In both male and female rats an asymmetry effect
was present: resynchronization was more rapid after a -6-h shift than after
a +6-h shift. However, female rats exhibited a rate of resynchronization
slower than male rats. During the process of resynchronization a state of
transient internal dissociation was found for all urinary constituents.
These results probably point to different control systems rather than to
different circadian pacemakers. Further analysis of the role of sex steroid
hormones is required in view of the sex variations reported.
