Nagel Christina, Erber Regina, Ille Natascha, von Lewinski Mareike, Aurich Jörg, Möstl Erich, Aurich Christine
Graf Lehndorff Institute for Equine Science, Vienna University of Veterinary Sciences, Neustadt (Dosse), Germany.
Section for Artificial Insemination and Embryo Transfer, University of Veterinary Sciences, Vienna, Austria.
Theriogenology. 2014 Jul 1;82(1):160-8. doi: 10.1016/j.theriogenology.2014.03.015. Epub 2014 Mar 27.
External and internal stressors prolong parturition in different species. At parturition, sympathoadrenal activation should be avoided because an increased sympathetic tone may cause uterine atonia via β2-receptors. We hypothesized that at physiological parturition, horses are under parasympathetic dominance, and stress-response mechanisms are not activated during delivery of the foal. To evaluate stress responses, heart rate, heart rate variability, catecholamines, and cortisol were analyzed in mares (n = 17) throughout foaling. Heart rate decreased from 2 hours before (51 ± 1 beats/minute) to 2 hours after delivery (41 ± 2 beats/minute; P < 0.05). Heart rate variability variables, standard deviation of the beat-to-beat interval, and root mean square of successive beat-to-beat differences, changed over time (P < 0.05) with the highest values within 15 minutes after delivery. The number of mares with atrioventricular blocks and the number of atrioventricular blocks per mare increased over time (P < 0.01) and were significantly elevated from 15 minutes before to 45 minutes after birth of the foal. Salivary cortisol concentrations increased to a maximum at 30 minutes after delivery (25.0 ± 3.4 ng/mL; P < 0.01). Plasma epinephrine and norepinephrine concentrations showed significant fluctuations from rupture of the allantochorion to expulsion of the fetal membranes (P < 0.01) but were not markedly elevated at any time. In conclusion, mares give birth under high parasympathetic tone. Cortisol release during and after foaling is most likely part of the endocrine pathways regulating parturition and not a labor-associated stress response.
外部和内部应激源会延长不同物种的分娩时间。在分娩时，应避免交感肾上腺系统激活，因为交感神经张力增加可能通过β2受体导致子宫收缩乏力。我们推测，在生理性分娩时，马处于副交感神经主导状态，在驹分娩过程中应激反应机制未被激活。为了评估应激反应，在整个产驹过程中对17匹母马的心率、心率变异性、儿茶酚胺和皮质醇进行了分析。心率从分娩前2小时（51±1次/分钟）降至分娩后2小时（41±2次/分钟；P<0.05）。心率变异性变量、逐搏间期标准差和逐搏差异的均方根随时间变化（P<0.05），在分娩后15分钟内达到最高值。出现房室传导阻滞的母马数量和每匹母马的房室传导阻滞数量随时间增加（P<0.01），并且在驹出生前15分钟到出生后45分钟显著升高。唾液皮质醇浓度在分娩后30分钟升至最高（25.0±3.4 ng/mL；P<0.01）。从尿囊绒毛膜破裂到胎膜排出，血浆肾上腺素和去甲肾上腺素浓度出现显著波动（P<0.01），但在任何时候都没有明显升高。总之，母马在高副交感神经张力下分娩。产驹期间和之后的皮质醇释放很可能是调节分娩的内分泌途径的一部分，而不是与分娩相关的应激反应。
