Wegner Kirsten, Horais Kjersti A, Tozier Nicolle A, Rathbun Michael L, Shtaerman Yuri, Yaksh Tony L
Anesthesiology Research, Department of Anesthesiology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0818, USA.
J Neurosci Methods. 2008 Feb 15;168(1):88-97. doi: 10.1016/j.jneumeth.2007.09.019. Epub 2007 Sep 29.
Acute nociceptive models which have been validated for large animal species are limited, yet nociceptive assessment in non-rodent species is important in analgesic drug development where larger animals may be necessary because of the technical requirements of the study. Here we report development and validation of a canine hind paw thermal escape model and the effect of analgesics on withdrawal latencies. Individual focused projection bulbs were used as left and right voltage-adjusted thermal stimuli placed below a glass plate in a specifically designed canine holding apparatus. After acclimation, dogs were lightly restrained in a fabric sling while standing on the glass plate. The anterior center of the metatarsal pad of the left and right hind paw was positioned on the glass over each light, and duration of stimulation tolerance timed. For every trial, the escape latency from lamp actuation to paw withdrawal was recorded twice for each hind paw. The mean population baseline withdrawal latency of 9.3+/-1.7s (mean+/-S.D., n=12 dogs) was shown to be repeatable between paws, within and between individual animals, and between test days. This latency corresponded to a glass surface temperature of 49.5 degrees C. A cut-off time of 20s (corresponding to a glass surface temperature of 56.5 degrees C) was set to prevent tissue damage. Intravenous administration (mg/kg) of morphine (1.0), hydromorphone (0.2), butorphanol (0.4), fentanyl (0.01), and dexmedetomidine (0.01) significantly (p<0.05) increased withdrawal latency from baseline within 15-30 min of administration while buprenorphine (0.03) produced a delayed, modest but significant latency increase. Rank order of opioid analgesic duration was morphine=hydromorphone>butorphanol>bupenorphine>fentanyl=saline. A dose-effect curve for hydromorphone was generated and corresponded to previously described dose-effect relationships in other species. The non-analgesic tranquilizer acepromazine (0.1mg/kg) produced mild sedation, but no significant increase in latency from that of saline. The model yielded a clear distinction between analgesia and sedation for all agents tested. These studies provide validation of a canine thermal escape model and have demonstrated the efficacy of clinically relevant doses of analgesics in elevating escape latencies. This model will facilitate quantification of the effects of parenterally and neuraxially administered analgesics in dogs.
已在大型动物物种中得到验证的急性伤害性模型有限，但在镇痛药研发中，非啮齿类动物的伤害性评估很重要，因为研究的技术要求可能需要使用更大的动物。在此，我们报告犬后爪热逃避模型的开发与验证以及镇痛药对撤药潜伏期的影响。在专门设计的犬类固定装置中，使用单个聚焦投射灯泡作为置于玻璃板下方的左右电压可调热刺激源。适应环境后，让犬站立在玻璃板上，用织物吊带轻轻约束。将左右后爪跖垫的前中心置于每个灯泡上方的玻璃板上，并记录刺激耐受持续时间。每次试验时，记录每个后爪从灯泡启动到爪子撤回的逃避潜伏期两次。9.3±1.7秒（平均值±标准差，n = 12只犬）的平均群体基线撤药潜伏期在不同爪子之间、个体动物内部和个体动物之间以及不同测试日之间均可重复。该潜伏期对应于49.5℃的玻璃表面温度。设定20秒的截止时间（对应于56.5℃的玻璃表面温度）以防止组织损伤。静脉注射（mg/kg）吗啡（1.0）、氢吗啡酮（0.2）、布托啡诺（0.4）、芬太尼（0.01）和右美托咪定（0.01）在给药后15 - 30分钟内显著（p<0.05）增加了相对于基线的撤药潜伏期，而丁丙诺啡（0.03）产生了延迟的、适度但显著的潜伏期增加。阿片类镇痛药持续时间的排序为吗啡 = 氢吗啡酮>布托啡诺>丁丙诺啡>芬太尼 = 生理盐水。生成了氢吗啡酮的剂量 - 效应曲线，其与其他物种中先前描述的剂量 - 效应关系相符。非镇痛性镇静剂乙酰丙嗪（0.1mg/kg）产生轻度镇静作用，但相对于生理盐水，潜伏期无显著增加。该模型对所有测试药物在镇痛和镇静之间产生了明显区分。这些研究验证了犬热逃避模型，并证明了临床相关剂量的镇痛药在提高逃避潜伏期方面的有效性。该模型将有助于量化经胃肠外和神经轴给药的镇痛药对犬的作用。
