Technical Brief: A comparison of two methods of euthanasia on retinal dopamine levels

PURPOSE: Mice are commonly used in biomedical research, and euthanasia is an important part of mouse husbandry. Approved, humane methods of euthanasia are designed to minimize the potential for pain or discomfort, but may also influence the measurement of experimental variables. METHODS: We compared the effects of two approved methods of mouse euthanasia on the levels of retinal dopamine. We examined the level of retinal dopamine, a commonly studied neuromodulator, following euthanasia by carbon dioxide (CO(2))-induced asphyxiation or by cervical dislocation. RESULTS: We found that the level of retinal dopamine in mice euthanized through CO(2) overdose substantially differed from that in mice euthanized through cervical dislocation. CONCLUSIONS: The use of CO(2) as a method of euthanasia could result in an experimental artifact that could compromise results when studying labile biologic processes.