Cases of Sprague-Dawley rats which did not respond to an 'alarm substance' in the forced swimming test.

The fact found by Abel and his group that rats produce an 'alarm substance' while swimming was examined by employing a single-subject approach. Sprague-Dawley rats were tested in the forced swimming test situation in fresh water and in water soiled by another rat. In Exp. 1, Sprague-Dawley rats from Japan SLC, Inc. were used. No evidence of responding to the 'alarm substance' was found. Then, further experiments were conducted employing methods similar to those of Abel and his group. In Exp. 2, Sprague-Dawley rats from Charles River, Japan, were used. In Exp. 3, the water depth and inner diameter in a cylinder used were the same as those used by Abel and his group, and the water was soiled more thoroughly. In Exp. 4, the level of water contamination was raised to four times that employed in Exps. 1 and 2. However, the series of experiments yielded no evidence of the 'alarm substance.' Breeder differences among subjects might explain the discrepancy in results.