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Euthanasia efficacy and plasma biochemical implications of intraperitoneal thiamylal sodium in three rat strains
Takeru Sasaki1, Masaki Watanabe1, Tomoki Omori1
1Laboratory of Laboratory Animal Science and Medicine, School of Veterinary Medicine, Kitasato University, Aomori, Japan.
Abstract:
Acceptable euthanasia methods must rapidly induce unconsciousness and death without pain or distress. We evaluated intraperitoneal thiamylal sodium (TM; 150 mg/kg; hereafter TM150) in male Sprague-Dawley, Wistar, and Fischer 344 rats. TM produced immobilization, loss of righting reflex, respiratory arrest, and cardiac arrest in all strains, with the shortest latencies in Fischer 344. Plasma chemistry showed strain-dependent shifts, including aspartate aminotransferase (AST) increases and variable alanine aminotransferase (ALT) responses; chloride and calcium showed small, non-uniform changes across strains, and most values remained within commonly cited reference ranges. These findings most likely reflect perimortem physiology and methodological factors superimposed on strain baselines rather than primary organ injury. TM150 is therefore effective for rat euthanasia, although post-TM plasma biochemistry should be interpreted cautiously.
Insights
Thiamylal sodium (TM) at 150 mg/kg effectively euthanized rats across three strains by causing rapid unconsciousness and death. Post-euthanasia plasma chemistry changes were observed but likely reflect physiological responses rather than organ damage.
Area of Science:
- Veterinary Medicine
- Toxicology
- Animal Science
Background:
- Establishing humane and effective euthanasia methods is critical in animal research.
- Thiamylal sodium (TM) is a barbiturate used for anesthesia and euthanasia.
Purpose of the Study:
- To evaluate the efficacy and physiological effects of intraperitoneal thiamylal sodium (TM) at 150 mg/kg for rat euthanasia.
- To assess strain-specific responses in Sprague-Dawley, Wistar, and Fischer 344 rats.
Main Methods:
- Male rats of three strains (Sprague-Dawley, Wistar, Fischer 344) were administered intraperitoneal thiamylal sodium (TM) at 150 mg/kg.
- Euthanasia endpoints including immobilization, loss of righting reflex, respiratory arrest, and cardiac arrest were recorded.
- Plasma chemistry was analyzed to assess physiological changes post-administration.
Main Results:
- Thiamylal sodium (TM) effectively induced euthanasia in all rat strains tested.
- Fischer 344 rats exhibited the shortest latencies to euthanasia endpoints.
- Plasma chemistry revealed strain-dependent shifts, including aspartate aminotransferase (AST) increases, with most values within reference ranges, suggesting perimortem physiological changes.
Conclusions:
- Intraperitoneal thiamylal sodium (TM) at 150 mg/kg is an effective method for rat euthanasia.
- Interpreting post-euthanasia plasma biochemistry requires consideration of strain-specific physiology and potential methodological influences.
