Dept. of Biology, Portland State University, 1719 SW 10(th) Ave, Portland, OR 97201, United States.
Dept. of Biology, Western Oregon University, 345 N. Monmouth Ave, Monmouth, OR 97361, United States.
Horm Behav. 2018 Apr;100:1-11. doi: 10.1016/j.yhbeh.2018.02.004. Epub 2018 Feb 23.
When opportunities to feed and reproduce are limited, females are often unable to recover sufficient energy stores to reproduce in consecutive years. Body condition has been used as a proxy for recent reproductive history in such species. We previously found that glucocorticoid responses to capture stress vary with body condition in female red-sided garter snakes (Thamnophis sirtalis parietalis), a species with limited seasonal breeding opportunities. Because variation in glucocorticoid receptor (GR) protein in the brain could explain these differences, we first assessed GR protein content in females in different body conditions. To investigate if body condition during the spring mating season accurately reflects recent reproductive history, we measured glucocorticoid responses to stress in females with different body conditions, assessed their mating behavior and brought mated females to our lab to determine which females would give birth during the summer (i.e., were parturient). Female red-sided garter snakes reproduce biennially, and therefore mated females that did not give birth were deemed non-parturient. In this study, glucocorticoid stress responses and mating behavior did not vary with body condition, nor was body condition related to brain GR or reproductive condition (parturient vs non-parturient). Only unreceptive females showed a significant stress-induced increase in glucocorticoids, suggesting that reduced stress responsiveness is associated with receptivity. Parturient females mated faster (were more proceptive) than non-parturient females. These data suggest that HPA axis activity modulates receptivity, while proceptivity is related primarily to reproductive condition.
当觅食和繁殖的机会受到限制时，雌性通常无法恢复足够的能量储备，无法在连续的年份里进行繁殖。在这些物种中，身体状况常被用作近期繁殖历史的替代指标。我们之前发现，在繁殖机会有限的红边束带蛇（Thamnophis sirtalis parietalis）中，雌性对被捕猎应激的糖皮质激素反应会随着身体状况的不同而变化。由于大脑中的糖皮质激素受体（GR）蛋白的变化可能解释了这些差异，我们首先评估了不同身体状况的雌性体内的 GR 蛋白含量。为了研究春季交配季节的身体状况是否能准确反映近期的繁殖历史，我们测量了不同身体状况的雌性对压力的糖皮质激素反应，评估了它们的交配行为，并将交配后的雌性带到实验室，以确定哪些雌性会在夏季分娩（即，是分娩的）。红边束带蛇每两年繁殖一次，因此没有分娩的交配雌性被认为是非分娩的。在这项研究中，糖皮质激素应激反应和交配行为与身体状况无关，身体状况也与大脑中的 GR 或繁殖状况（分娩与非分娩）无关。只有未受孕的雌性在受到压力时才会出现明显的糖皮质激素增加，这表明应激反应的降低与接受度有关。分娩的雌性比非分娩的雌性交配速度更快（更具求偶性）。这些数据表明，HPA 轴活动调节接受度，而求偶性主要与繁殖状况有关。
