National Institute of Agrobiological Sciences, Tsukuba 305-8602, Japan.
Physiol Behav. 2010 Mar 3;99(3):362-9. doi: 10.1016/j.physbeh.2009.11.016. Epub 2009 Dec 5.
Oxytocin and prolactin are potential candidates for the regulation of behavioral and physiological stress responses in the brain. To investigate the neurobiological basis of individual differences in stress responses in cattle, we examined the association of behavioral and hypothalamo-pituitary-adrenal axis reactivity to acute stressors and basal and stimulated levels of oxytocin and prolactin. Twenty Holstein heifer calves aged 2 weeks were subjected to a 10 min open-field test (OFT) followed by presentation of a feeding bucket for 15 min in the OF. If the calf contacted the bucket, a blast of air was applied to its muzzle (surprise test). Jugular blood samples collected before and after both tests were analyzed for oxytocin, prolactin, and cortisol. Relationships of basal and percent change in oxytocin or prolactin with behavioral responses in each test and percent change in cortisol were analyzed using principal components analysis and Spearman rank correlations. Plasma cortisol and prolactin concentrations were significantly elevated by the tests (p<0.005), but plasma oxytocin concentration did not significantly change (p>0.1). Four principal components explained 56.1% of the total variation: curiosity, general activity, fearfulness, and dependence on humans. Curiosity was inversely correlated with basal oxytocin level (rS=-0.683, p<0.05). General activity was positively correlated with prolactin reactivity (rS=0.448, p<0.05) and inversely with oxytocin reactivity to the novel environment (rS=-0.717, p<0.05). Fearfulness tended to correlate positively with basal oxytocin level (rS=0.583, p<0.1). Dependence on humans correlated with none of the hormonal parameters. The relationships of basal oxytocin level with curiosity and fearfulness for novel environments are of particular interest for future study.
催产素和催乳素是调节大脑行为和生理应激反应的潜在候选物质。为了研究牛对压力反应的个体差异的神经生物学基础，我们研究了行为和下丘脑-垂体-肾上腺轴对急性应激源的反应性以及催产素和催乳素的基础和刺激水平之间的关联。20 头 2 周龄的荷斯坦小母牛接受了 10 分钟的开放场测试（OFT），随后在 OF 中展示了 15 分钟的饲料桶。如果小牛接触到桶，就会向它的口鼻部吹一口气（惊喜测试）。在两项测试前后采集的颈静脉血样用于分析催产素、催乳素和皮质醇。使用主成分分析和 Spearman 等级相关分析，分析了基础和催产素或催乳素变化百分比与每个测试中的行为反应以及皮质醇变化百分比之间的关系。测试（p<0.005）显著提高了血浆皮质醇和催乳素浓度，但血浆催产素浓度没有显著变化（p>0.1）。四个主成分解释了总变异的 56.1%：好奇心、一般活动、恐惧和对人类的依赖。好奇心与基础催产素水平呈负相关（rS=-0.683，p<0.05）。一般活动与催乳素反应性呈正相关（rS=0.448，p<0.05），与新环境中的催产素反应性呈负相关（rS=-0.717，p<0.05）。恐惧倾向于与基础催产素水平呈正相关（rS=0.583，p<0.1）。对人类的依赖与任何激素参数都没有关系。基础催产素水平与对新环境的好奇心和恐惧之间的关系是未来研究的特别关注点。
