Johnson Craig B, Sylvester Shauna P, Stafford Kevin J, Mitchinson Sheryl L, Ward R Neil, Mellor David J
Institute of Veterinary, Animal and Biomedical Sciences, Animal Welfare Science and Bioethics Centre, Massey University, Palmerston North, New Zealand.
Vet Anaesth Analg. 2009 May;36(3):273-9. doi: 10.1111/j.1467-2995.2009.00448.x.
To characterize changes in the cerebro-cortical response of lambs to rubber-ring castration during the first 6 weeks of postnatal life.
Coopworth-Texel cross ram lambs between 3 hours and 44 days of age.
The electroencephalogram (EEG) and heart rate responses to rubber ring castration were compared. Anaesthesia was induced via a face mask and maintained with halothane in oxygen (e'(Hal) = 1.2%). Once a stable plane of anaesthesia had been achieved, data collection of EEG and electrocardiogram (ECG) commenced, and the lambs were castrated 15 minutes later, using rubber rings. Heart rate was derived from the ECG and the median frequency (F(50)), spectral edge frequency (F(95)) and total power (p(tot)) were derived from the EEG.
Castration-induced changes in F(50) increased from 2 +/- 1.8% in the youngest lambs to a maximum of 33 +/- 8.9% in the 36 +/- 0.5 day-old lambs. Changes in F(95) increased from -7 +/- 3% in the youngest lambs to a maximum of 16 +/- 11% in the 36 +/- 0.5 day-old lambs. Linear regression analysis in lambs up to 10 days of age demonstrated a change in the response with age that was significantly different from zero for F(50) (r(2) = 0.28, p = 0.007) and F(95) (r(2) = 0.38, p = 0.001), but not for p(tot) or heart rate.
This study identified significant changes in the responsiveness of the lambs' cerebral cortex to the noxious stimulation of castration over the first 7-10 days of postnatal life. The results suggest that mechanisms that suppress responses of the fetus to noxious stimulation may still be active in the first few days after birth.
This study documents changes in central nociceptive processing which may reflect the ability of neonatal animals to perceive pain.
描述出生后6周内羔羊对橡胶环去势术的脑皮质反应变化。
3小时至44日龄的库泊沃思-特克塞尔杂交公羔羊。
比较脑电图（EEG）和心率对橡胶环去势术的反应。通过面罩诱导麻醉，并用氧气和氟烷维持麻醉（e'（Hal）=1.2%）。一旦达到稳定的麻醉平面，开始收集EEG和心电图（ECG）数据，15分钟后用橡胶环给羔羊去势。心率由ECG得出，EEG得出中位频率（F（50））、频谱边缘频率（F（95））和总功率（p（tot））。
去势引起的F（50）变化从最年幼羔羊的2±1.8%增加到36±0.5日龄羔羊的最大33±8.9%。F（95）的变化从最年幼羔羊的-7±3%增加到36±0.5日龄羔羊的最大16±11%。对10日龄以内羔羊的线性回归分析表明，F（50）（r² = 0.28，p = 0.007）和F（95）（r² = 0.38，p = 0.001）随年龄的反应变化与零有显著差异，但p（tot）或心率无此差异。
本研究发现羔羊出生后7 - 10天内，其大脑皮质对去势有害刺激的反应性有显著变化。结果表明，抑制胎儿对有害刺激反应的机制在出生后的头几天可能仍然活跃。
本研究记录了中枢伤害性处理的变化，这可能反映新生动物感知疼痛的能力。
