Pierce B N, Hemsworth P H, Rivalland E T A, Wagenmaker E R, Morrissey A D, Papargiris M M, Clarke I J, Karsch F J, Turner A I, Tilbrook A J
Department of Physiology, Monash University, Victoria, 3800, Australia.
Horm Behav. 2008 Aug;54(3):424-34. doi: 10.1016/j.yhbeh.2008.04.005. Epub 2008 Apr 23.
Various stressors suppress pulsatile secretion of luteinizing hormone (LH) in ewes and cortisol has been shown to be a mediator of this effect under various conditions. In contrast, little is known about the impact of stress and cortisol on sexual behavior in the ewe. Therefore, we tested the hypothesis that both psychosocial stress and stress-like levels of cortisol will reduce the level of attractivity, proceptivity and receptivity in addition to suppressing LH secretion in the ewe. In Experiment 1, a layered stress paradigm of psychosocial stress was used, consisting of isolation for 4 h with the addition of restraint, blindfold and noise of a barking dog (predator stress) at hourly intervals. This stress paradigm reduced LH pulse amplitude in ovariectomized ewes. In Experiment 2, ovariectomized ewes were artificially induced into estrus with progesterone and estradiol benzoate treatment and the layered stress paradigm was applied. LH was measured and sexual behavior was assessed using T-mazes and mating tests. Stress reduced pulsatile LH secretion, and also reduced attractivity and proceptivity of ewes but had no effect on receptivity. In Experiment 3, ewes artificially induced into estrus were infused with cortisol for 30 h. Cortisol elevated circulating plasma concentrations of cortisol, delayed the onset of estrus and resulted in increased circling behavior of ewes (i.e. moderate avoidance) during estrus and increased investigation and courtship from rams. There was no effect of cortisol on attractivity, proceptivity or receptivity during estrus. We conclude that psychosocial stress inhibits LH secretion, the ability of ewes to attract rams (attractivity) and the motivation of ewes to seek rams and initiate mating (proceptivity), but cortisol is unlikely to be the principal mediator of these effects.
多种应激源会抑制母羊促黄体生成素（LH）的脉冲式分泌，并且在各种条件下，皮质醇已被证明是这种效应的介导物。相比之下，关于应激和皮质醇对母羊性行为的影响知之甚少。因此，我们检验了以下假设：社会心理应激和类似应激水平的皮质醇除了会抑制母羊的LH分泌外，还会降低其吸引力、主动求偶行为和接受能力。在实验1中，使用了一种社会心理应激的分层应激范式，包括隔离4小时，并每隔一小时增加束缚、蒙眼和吠叫狗的噪音（捕食者应激）。这种应激范式降低了去卵巢母羊的LH脉冲幅度。在实验2中，对去卵巢母羊用孕酮和苯甲酸雌二醇处理人工诱导发情，并应用分层应激范式。测量LH，并使用T迷宫和交配试验评估性行为。应激降低了LH的脉冲式分泌，也降低了母羊的吸引力和主动求偶行为，但对接受能力没有影响。在实验3中，对人工诱导发情的母羊输注皮质醇30小时。皮质醇提高了循环血浆皮质醇浓度，延迟了发情开始，并导致母羊在发情期间的转圈行为增加（即适度回避），以及公羊的调查和求偶行为增加。皮质醇对发情期间的吸引力、主动求偶行为或接受能力没有影响。我们得出结论，社会心理应激会抑制LH分泌、母羊吸引公羊的能力（吸引力）以及母羊寻找公羊并开始交配的动机（主动求偶行为），但皮质醇不太可能是这些效应的主要介导物。
