Effect of flow rate on aversion to gradual-fill carbon dioxide exposure in rats
Effect of flow rate on aversion to gradual-fill carbon dioxide exposure in rats
复制标题
DOI：
10.1016/j.applanim.2007.02.004
复制
发表时间：
2008-01-01
影响因子：
2.3
通讯作者：
Weary, Daniel A.
中科院分区：
文献类型：
--
作者：
Niel, Lee;Stewart, Sarah A.;Weary, Daniel A.
实验室大鼠通常通过逐渐增加的二氧化碳浓度（CO2）杀死，但在此过程中减少痛苦的最佳流速尚未确定。虽然快的流速可以缩短动物失去意识的时间，但慢的流速可能会让动物在二氧化碳浓度足以引起疼痛和呼吸困难之前失去意识。为了确定老鼠对逐渐充满二氧化碳的二氧化碳暴露的厌恶程度是否随着流速的变化而变化，我们使用了一种方法回避测试，在该测试中，获得食物奖励取决于进入一个逐渐充满二氧化碳的房间。在测试过程中，暴露室充满空气或二氧化碳，我们检测了二氧化碳的流速，范围为室体积/分钟的3%至27%。在各种流速下，老鼠在失去意识之前离开了房间，在较高的流速下，它们离开房间的速度更快。最大的二氧化碳耐受浓度是在中等流速下，但即使在14%/分钟的最佳流速下，一旦二氧化碳浓度达到15.9%，大鼠就离开了房间，并且没有大鼠留在房间里直到失去意识。当流量高低时，大鼠耐受更低的浓度，但这种反应函数并不陡峭。例如，在最高流速为27%/min时，大鼠在CO2浓度为13%时离开室。综上所述，大鼠对二氧化碳流速敏感，当二氧化碳流速在15%左右时，大鼠对二氧化碳的耐受性最强。尽管流速的影响不大，但在所有流速测试中，逐渐填充的二氧化碳暴露对老鼠仍然是厌恶的，现在迫切需要研究安乐死的替代方法。(c) 2007 Elsevier B.V.版权所有
Laboratory rats are commonly killed by a gradually increasing concentration of carbon dioxide (CO2), but an optimal flow rate for minimizing distress during this procedure has not yet been identified. While fast flow rates minimize time to unconsciousness, slow flow rates may allow an animal to lose consciousness before CO2 concentrations become sufficient to cause pain and dyspnoea. We used an approach-avoidance test, where access to a food reward was contingent on entering a chamber that was gradually filling with CO2, in order to determine whether rats' aversion to gradual-fill CO2 exposure varies with flow rate. During testing, the exposure chamber was filled with either air or CO2, and we examined CO2 flow rates ranging from 3% to 27% of the chamber volume/min. The rats left the chamber before loss of consciousness at all flow rates, and at higher flow rates they left the chamber more quickly. The maximum CO2 Concentrations tolerated were at intermediate flow rates, but even at the optimal flow rate of 14%/min rats left the chamber once the CO2 concentration reached just 15.9%, and no rats remained in the chamber until they lost consciousness. Rats tolerated even lower concentrations when flow rates were higher and lower, but this response function was not steep. For example, at the highest flow rate of 27%/min rats left the chamber at a CO2 concentration of 13%. In conclusion rats are sensitive to CO2 flow rate and are most tolerant Of CO2 when introduced at a flow rate of around 15%. Despite this modest effect of flow rate, gradual-fill CO2 exposure is still aversive to rats over all flow rates tested and research into alternative methods of euthanasia is now urgently required. (c) 2007 Elsevier B.V. All rights reserved.