Department of Biology, University of California, Riverside, CA 92521, United States.
Physiol Behav. 2011 Sep 1;104(3):446-53. doi: 10.1016/j.physbeh.2011.05.005. Epub 2011 May 11.
In several mammalian species, hypothalamic-pituitary-adrenal (HPA) and behavioral responses to stressors are down-regulated in lactating females, possibly preventing stress-induced disruptions of maternal care. Experimental elevations of HPA axis hormones have been found to inhibit maternal behavior in lactating common marmoset monkeys (Callithrix jacchus), raising the question of whether lactating female marmosets also have blunted endogenous responses to stress. Therefore, we compared HPA and behavioral responses to standardized stressors in reproductively experienced female common marmosets that were undergoing ovulatory cycles and that either were (N=7) or were not lactating (N=8). Each marmoset underwent (1) a restraint stressor during the early follicular phase of the ovarian cycle (approximately 5 weeks postpartum for lactating females) and (2) exposure to a simulated hawk predator during the early to mid-luteal phase (approximately 7 weeks postpartum for lactating females). Lactating females were tested in the presence of one of their infants. Blood samples were collected before, during, and immediately after each test for determination of plasma adrenocorticotropic hormone (ACTH) and cortisol concentrations. Both stressors caused significant elevations in plasma ACTH and cortisol levels, and significant decreases in cortisol:ACTH ratios; however, lactating and non-lactating females showed no significant differences in their endocrine or behavioral responses to either stressor, or in baseline ACTH or cortisol levels. These findings suggest that in contrast to several other mammalian species, lactating female marmosets maintain full behavioral and HPA responsiveness to stress, at least in the presence of their infants.
在一些哺乳动物物种中，下丘脑-垂体-肾上腺（HPA）轴和对压力源的行为反应在哺乳期雌性动物中被下调，这可能防止了应激引起的母性照顾中断。实验性地升高 HPA 轴激素已被发现会抑制哺乳期普通狨猴（Callithrix jacchus）的母性行为，这引发了一个问题，即哺乳期雌性狨猴是否也对压力的内源性反应减弱。因此，我们比较了经历过繁殖周期的正在经历排卵周期的哺乳期和非哺乳期（N=7）的雌性普通狨猴对标准化压力源的 HPA 和行为反应。每只狨猴都经历了（1）在卵巢周期的卵泡早期进行的束缚应激源（对于哺乳期雌性大约是产后 5 周）和（2）在黄体早期至中期暴露于模拟的鹰类捕食者（对于哺乳期雌性大约是产后 7 周）。哺乳期雌性在其婴儿的存在下进行测试。在每个测试之前、期间和之后立即采集血液样本，以测定血浆促肾上腺皮质激素（ACTH）和皮质醇浓度。这两种压力源都导致血浆 ACTH 和皮质醇水平显著升高，皮质醇：ACTH 比值显著降低；然而，哺乳期和非哺乳期雌性在对这两种压力源的内分泌或行为反应、或基础 ACTH 或皮质醇水平方面均无显著差异。这些发现表明，与其他几种哺乳动物不同，哺乳期雌性狨猴至少在其婴儿存在的情况下，维持了对压力的完全行为和 HPA 反应能力。
