Department of Zoology, Michigan State University, East Lansing, Michigan 48824, USA.
Physiol Behav. 2009 Dec 7;98(5):547-56. doi: 10.1016/j.physbeh.2009.08.012. Epub 2009 Sep 8.
A suite of changes in circadian rhythms have been described in nocturnal rodents as females go through pregnancy and lactation, but there is no information on such patterns in diurnal species. As the challenges faced by these two groups of animals are somewhat different, we characterized changes in activity and core body temperature (T(b)) in female diurnal Nile grass rats (Arvicanthis niloticus) as they went through a series of reproductive states: virgin, pregnant, pregnant and lactating, lactating only, and post-weaning. The phase of neither rhythm varied, but the amplitude did. Females increased their overall levels of daily activity from early to late pregnancy, regardless of whether they were also lactating. The pattern of activity was less rhythmic during early than mid-lactation, in both non-pregnant and pregnant females, as a consequence of a decrease in daytime relative to nighttime activity. The T(b) rhythm amplitude dropped from mid-pregnancy through mid-lactation, and there were rises in T(b) troughs during the mid-light and mid-dark phases of the day, though pregnancy and lactation affected T(b) at these times in somewhat different ways. This study demonstrates that rhythms in diurnal grass rats change during pregnancy and lactation in different ways than those of nocturnal species that have been studied to date and that the effects of pregnancy and lactation are not additive in any simple way.
昼夜节律的一系列变化已在夜间活动的啮齿动物中被描述，因为雌性经历怀孕和哺乳期，但在昼行性物种中没有关于这种模式的信息。由于这两组动物面临的挑战有些不同，我们描述了雌性昼行性尼罗河草鼠（Arvicanthis niloticus）在经历一系列生殖状态时活动和核心体温（T(b)）的变化：处女、怀孕、怀孕和哺乳期、仅哺乳期和断奶后。两种节律的相位都没有变化，但振幅有变化。无论是否同时处于哺乳期，雌性从怀孕早期到晚期都会增加日常活动的总体水平。在非怀孕和怀孕的雌性中，由于白天相对于夜间活动减少，早期哺乳期的活动模式比中期哺乳期的活动模式更不规律。从怀孕中期到哺乳期中期，T(b)节律的振幅下降，尽管怀孕和哺乳在白天和黑夜的中间阶段对 T(b)有影响，但 T(b)的低谷也有所上升。这项研究表明，昼夜草鼠的节律在怀孕和哺乳期的变化方式与迄今为止研究过的夜间物种不同，而且怀孕和哺乳的影响不是以任何简单的方式相加的。
