Acetic acid induced painful endogenous infliction in writhing test on mice

Writhing test is a chemical method used to induce pain of peripheral origin by injection of irritant principles like phenylquinone, acetic acid in mice. Analgesic activity of the test compound is inferred from decrease in the frequency of writhings. The manifestations of abdominal writhings in mice were first described by Sigmund et al.[1] as an arching of back, extension of hind limbs and contraction of abdominal musculature. The writhing response is considered as a reflexive test and is without clinical counterparts as it cannot be performed in human and sensations involved are unknown. Further, authors pointed out that the writhing test produced severe pain in mice which raises ethical concern regarding its use. Stevens[2] has commented on the report of one pharmaceutical company, Warner –Lambert Research Institute, Morris Plains N.J. which company has conducted about 100 experiments on 5000 mice. 0.1 ml of phenylquinone was injected intraperitoneally to induce writhing and animals began stretching their abdomen in few minutes. He wrote that ‘writhing, of course, means agony, a standard test that should not be tolerated in any civilized country’.