Comparing the Effect of Methods of Rat Euthanasia on the Brain of Wistar Rats: Cervical Dislocation, Chloroform Inhalation, Diethyl Ether Inhalation and Formalin Inhalation

Contentions still exist as to the most humane method of sacrificing experimental animals. Beyond humaneness, there is also the issue of appropriateness of a method of sacrifice with regards to organ safety. This study compared four common methods of rodent sacrifice used in Nigeria and their effects on the brain. Twenty male Wistar rats weighing 150 to 180g were randomly separated into four groups of five rats each. After a two week period of acclimatization, the animals were sacrificed; Group A by Cervical dislocation (CD) which also served as control, Group B by chloroform inhalation (CI), Group C by diethyl ether inhalation (DEI) and group D by Formalin inhalation (FI). The time taken for the animals to pass out was documented and the brains were harvested. Four of the brains from rats in each group were homogenized in phosphate buffer solution and centrifuged at 10000rpm. The supernatant were used for antioxidant studies. The remaining one brain from each group were fixed in 10% formal saline and after 48 hours, the cerebellum (CB) and hippocampus (Hp) were used for histological studies using the H & E method. Our results show although CD was the quickest, it gave the least quantity of blood. Meanwhile CI was the most humane, gave the most blood and saved time compared to DEI and FI. None of the methods of sacrifice showed adverse effect on the antioxidant parameters of the rats. However, histological studies showed that while CD and CI showed no adverse effects on the hippocampus, only CD was completely safe for the CB. The other methods showed various levels of cell death. It is therefore expedient to consider these factors in making the choice of an appropriate method of sacrifice and to use the most humane and safest method with reference to the organ studied.