Sedation or Inhalant Anesthesia before Euthanasia with CO2 Does Not Reduce Behavioral or Physiologic Signs of Pain and Stress in Mice
Abstract:CO2 administration is a common euthanasia method for research mice, yet questions remain regarding whether CO2 euthanasia is associated with pain and stress. Here we assessed whether premedication with acepromazine, midazolam, or anesthetic induction with isoflurane altered behavioral and physiologic parameters that may reflect pain or stress during CO2 euthanasia. Mice were assigned to 1 of 6 euthanasia groups: CO2 only at a flow rate of 1.2 L/min which displaces 20% of the cage volume per minute (V/min; control group); premedication with acepromazine (5 mg/kg), midazolam (5 mg/kg), or saline followed by 20% V/min CO2; induction with 5% isoflurane followed by greater than 100% V/min CO2 (>6L/min); and 100% V/min CO2 only (6 L/min). Measures included ultrasonic sound recordings, behavioral analysis of video record- ings, plasma ACTH and corticosterone levels immediately after euthanasia, and quantification of c-fos from brain tissue. Compared with 20% V/min CO2 alone, premedication with acepromazine or midazolam did not significantly alter behavior but did induce significantly higher c-fos expression in the brain. Furthermore, the use of isoflurane induction prior to CO2 euthanasia significantly increased both behavioral and neuromolecular signs of stress. The data indicate that compared with other modalities, 20% V/min CO2 alone resulted in the least evidence of stress in mice and therefore was the most humane euthanasia method identified in the current study.
Document Type: Research Article
Affiliations: 1: Cornell Center for Animal Resources and Education, School of Veterinary Medicine, Cornell University, Ithaca, New York, USA; Department of Biomedical Sciences, School of Veterinary Medicine, Cornell University, Ithaca, New York, USA 2: Cornell Center for Animal Resources and Education, School of Veterinary Medicine, Cornell University, Ithaca, New York, USA 3: Cornell Center for Animal Resources and Education, School of Veterinary Medicine, Cornell University, Ithaca, New York, USA; Department of Biomedical Sciences, School of Veterinary Medicine, Cornell University, Ithaca, New York, USA. km429@Cornell.edu
Publication date: 2012-01-01
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