Department of Animal Sciences, The Ohio State University, Wooster, OH 46691, USA.
Department of Animal Sciences, The Ohio State University, Columbus, OH 43210, USA.
Domest Anim Endocrinol. 2020 Jan;70:106379. doi: 10.1016/j.domaniend.2019.07.007. Epub 2019 Jul 24.
Changes in the physiological, psychological, and behavioral manifestations of stress have been observed in association with increases in circulating oxytocin (OXT). Providing OXT intranasally has been shown to attenuate stressor-induced hypothalamo-pituitary-adrenal (HPA) axis activation in humans and rodents; however, anxiolytic effects may be context and species specific. The present study aimed to investigate the effect of intranasal OXT supplementation on stressor-induced activation of the HPA axis in beef cattle. We hypothesized that OXT would attenuate activation of the HPA axis, ultimately decreasing plasma cortisol and adrenocorticotropic hormone (ACTH). Twenty-eight Bos taurus heifers were blocked by bodyweight and randomly allocated to one of four treatment groups, in a 2 × 2 factorial arrangement: (1) saline, isolated, standing, and unrestrained (S-isolation stress [IS], 0.015 mL/kg BW 0.9% isotonic saline, n = 7); (2) saline, isolated, and restrained (S-restraint and isolation stress [RIS]; 0.015 mL/kg BW 0.9% isotonic saline; n = 7); (3) OXT, IS (OXT-IS, 0.3 IU/kg BW oxytocin; n = 7); and (4) OXT and RIS (OXT-RIS, 0.3 IU/kg BW oxytocin; n = 7). Oxytocin and saline were administered intranasally. Intranasal treatments were given followed by a waiting time of 30 min when each of the stress treatments was applied for 2 h. Blood samples were collected via jugular catheters directly after stressor application and every 10 min thereafter, for 2 h. Cortisol concentrations increased over time in animals exposed to RIS (P < 0.01) and decreased over time in animals exposed to IS (P < 0.01). Concentrations of ACTH decreased over time for the IS-treated heifers but remained elevated for the RIS-treated heifers (P < 0.01). Under the conditions of the present study, OXT treatment did not affect measured indicators of HPA axis activation. A treatment × time interaction (P < 0.01) was detected for OXT, such that OXT heifers exhibited greater initial OXT concentrations followed by a decline; saline-treated heifers had consistently stable oxytocin concentrations. The RIS-treated heifers increased their glucose (P < 0.01) and lactate (P < 0.01) concentrations throughout the application of the stressors compared with the IS-treated heifers. Overall, restraint stress increased cortisol and oxytocin in B taurus heifers compared with heifers subjected only to isolation. Finding a more intermediate stress model may better allow for detection of the effects of oxytocin on the stress response.
应激时循环催产素（OXT）水平的变化与生理、心理和行为表现的变化有关。鼻内给予 OXT 已被证明可减轻人类和啮齿动物应激诱导的下丘脑-垂体-肾上腺（HPA）轴激活；然而，抗焦虑作用可能因环境和物种而异。本研究旨在探讨鼻内 OXT 补充对肉牛应激诱导的 HPA 轴激活的影响。我们假设 OXT 会减轻 HPA 轴的激活，最终降低血浆皮质醇和促肾上腺皮质激素（ACTH）。28 头荷斯坦小母牛按体重分组，随机分为四组，进行 2×2 析因设计：（1）盐水，隔离，站立，不受约束（S-隔离应激[IS]，0.015 mL/kg BW 0.9%等渗盐水，n=7）；（2）盐水，隔离和约束（S-约束和隔离应激[RIS]；0.015 mL/kg BW 0.9%等渗盐水；n=7）；（3）OXT，IS（OXT-IS，0.3 IU/kg BW 催产素；n=7）；和（4）OXT 和 RIS（OXT-RIS，0.3 IU/kg BW 催产素；n=7）。OXT 和盐水经鼻内给药。在每种应激处理应用 2 小时后，鼻内治疗后等待 30 分钟。应激后立即通过颈静脉导管采集血液样本，此后每 10 分钟采集一次，持续 2 小时。RIS 处理的牛皮质醇浓度随时间增加（P<0.01），IS 处理的牛皮质醇浓度随时间降低（P<0.01）。IS 处理的小母牛 ACTH 浓度随时间降低，但 RIS 处理的小母牛 ACTH 浓度仍升高（P<0.01）。在本研究的条件下，OXT 处理不影响 HPA 轴激活的测量指标。OXT 存在处理×时间的交互作用（P<0.01），即 OXT 处理的小母牛表现出更高的初始 OXT 浓度，随后下降；盐水处理的小母牛的催产素浓度始终稳定。与 IS 处理的小母牛相比，RIS 处理的小母牛在应激应用过程中增加了葡萄糖（P<0.01）和乳酸（P<0.01）浓度。总的来说，与仅隔离的小母牛相比，约束应激增加了 B 小母牛的皮质醇和催产素。寻找一种更中等强度的应激模型可能更有利于检测催产素对应激反应的影响。
