Machado Filho L C, Hurnik J F, Ewing K K
Department of Animal and Poultry Science, University of Guelph, Ontario.
Can J Vet Res. 1998 Jul;62(3):218-23.
A thermal threshold measurer (TTM) apparatus was developed and tested in 12 dry, nonpregnant, culled cows with the purpose of measuring the thermal nociceptive threshold and of finding the response to morphine sulphate dosages. The cows received a cumulative dose (from 0.00 to 0.40 mg/kg BW) of morphine sulphate through a catheter in the jugular vein. The interval between doses was 20 min, and a nociceptive test was performed 15 min after each injection. The TTM device consisted of a 60 W halogen bulb mounted in a 15 cm PVC tube, with a 0.6 s response time probe attached to its end, connected to a thermocouple. The probe measured the response temperature on the skin over the middle phalanges on the dorsum of the forefoot. The radiating heat stimulus from the bulb was instantaneously terminated with the foot-lift response of the tested animal. The nociceptive response to the 0.00 mg/kg dose was considered the baseline and subsequent measurements were expressed in difference from it. Data were evaluated in a regression analysis using the GLM procedure. A significant elevation (P < 0.0001) in the nociceptive threshold of the cows with cumulative dosing of morphine sulphate was noticed. A high variability (P < 0.0001) in the response among animals was also detected, suggesting that a 2-step dose of morphine sulphate is necessary to achieve a certain degree of induced analgesia in all cows. The nociceptive assay described, using the TTM device, was able to detect an elevation of the thermal threshold of cows due to morphine sulphate induced analgesia. An increase in locomotory behaviour or other side effects due to morphine sulphate were not noticed.
研发了一种热阈值测量仪（TTM）设备，并在12头非妊娠、已被淘汰的干奶牛身上进行了测试，目的是测量热伤害性感受阈值并找出对硫酸吗啡剂量的反应。奶牛通过颈静脉导管接受了累积剂量（从0.00至0.40 mg/kg体重）的硫酸吗啡。剂量之间的间隔为20分钟，每次注射后15分钟进行一次伤害性感受测试。TTM设备由一个安装在15厘米PVC管中的60瓦卤素灯泡组成，其末端连接有一个响应时间为0.6秒的探头，该探头与一个热电偶相连。该探头测量前足背中节指骨上方皮肤的反应温度。当受试动物出现举足反应时，灯泡发出的辐射热刺激立即终止。将对0.00 mg/kg剂量的伤害性反应视为基线，后续测量结果以与基线的差异表示。使用GLM程序在回归分析中对数据进行评估。注意到随着硫酸吗啡累积给药，奶牛的伤害性感受阈值显著升高（P < 0.0001）。还检测到动物之间的反应存在高度变异性（P < 0.0001），这表明需要分两步给予硫酸吗啡剂量才能在所有奶牛中实现一定程度的诱导镇痛。所描述的使用TTM设备的伤害性感受测定能够检测到由于硫酸吗啡诱导的镇痛而导致的奶牛热阈值升高。未注意到由于硫酸吗啡导致的运动行为增加或其他副作用。
