College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G61 1QH, UK.
Physiol Behav. 2011 Oct 24;104(5):728-37. doi: 10.1016/j.physbeh.2011.07.018. Epub 2011 Jul 23.
The consequences of tail-docking (at 2-4 days) and prenatal stress (maternal social stress during the 2nd third of pregnancy) on baseline nociceptive thresholds and responses to acute inflammatory challenge were investigated in juvenile pigs in two studies. Nociceptive thresholds were assessed on the tail root and on the hind foot using noxious mechanical and cold stimulation before and after acute inflammatory challenge by intradermal injection of 30 μg capsaicin (study 1) or 3% carrageenan (study 2) into the tail root. Four groups of 8 (study 1, n=14-16 pigs/treatment) or 5 (study 2, n=6 pigs/treatment/sex) week-old pigs were exposed to the main factors: maternal stress and treatment (docked vs. intact tails). In study 1, tail docking did not significantly alter thresholds to noxious mechanical stimulation, whilst prenatally stressed pigs had significantly higher baseline thresholds to noxious mechanical stimulation on the tail root and on the hind foot than unstressed pigs, whether tail-docked or intact. Capsaicin injection induced localised mechanical allodynia around the tail root in all treatment groups, but had no effect on noxious plantar mechanical responses; however prenatally stressed offspring exhibited significantly attenuated response thresholds to capsaicin compared to controls. In study 2 tail docking did not alter thresholds to either mechanical or noxious cold stimulation. Baseline response durations to noxious cold stimulation of the tail root were significantly shorter in both sexes of prenatally stressed pigs, whilst male but not female prenatally stressed pigs exhibited significantly higher baseline thresholds to mechanical stimulation than controls, although results in female pigs tended towards significance. Carrageenan injection into the tail root induced localised mechanical and cold allodynia in all treatment groups, effects that were attenuated in prenatally stressed pigs. Collectively, these findings indicate that prenatal stress can induce long-term alterations in nociceptive responses, manifest as a reduced sensitivity to noxious mechanical and cold stimulation and evoked inflammatory allodynia. Neonatal tail-docking does not lead to long-term alterations in nociception in pigs.
在两项研究中，研究人员调查了在幼年猪中，在 2-4 天大时进行断尾（tail-docking）和在妊娠中期进行产前应激（maternal social stress）对基础痛觉阈值和急性炎症反应的影响。在急性炎症反应前，使用有害机械和冷刺激评估尾根和后脚的痛觉阈值，急性炎症反应通过在尾根皮内注射 30μg 辣椒素（研究 1）或 3%角叉菜胶（研究 2）来引发。将 8 只（研究 1，每组 14-16 只猪/处理）或 5 只（研究 2，每组 6 只猪/处理/性别）周龄的猪暴露于主要因素：母体应激和处理（断尾与完整尾巴）。在研究 1 中，断尾并未显著改变对有害机械刺激的阈值，而产前应激的猪在尾根和后脚的有害机械刺激的基础阈值显著高于未应激的猪，无论是否断尾。辣椒素注射在所有处理组中均在尾根周围引起局部机械性痛觉过敏，但对足底机械性痛觉反应没有影响；然而，与对照组相比，产前应激的后代对辣椒素的反应阈值明显降低。在研究 2 中，断尾未改变对机械或有害冷刺激的阈值。尾根有害冷刺激的基础反应持续时间在产前应激的公猪和母猪中均显著缩短，而雄性但不是雌性产前应激的猪对机械刺激的基础阈值显著高于对照组，尽管在雌性猪中结果趋于显著。角叉菜胶注射到尾根在所有处理组中均引起局部机械和冷性痛觉过敏，这些效应在产前应激的猪中减弱。总的来说，这些发现表明产前应激可引起痛觉反应的长期改变，表现为对有害机械和冷刺激的敏感性降低以及诱发的炎症性痛觉过敏。新生仔猪断尾不会导致猪的长期痛觉改变。
