This study was undertaken to clarify the effect of aggregate life on the adrenocortical function. Adrenal weight, and 11-OHCS concentration in the adrenal gland and the serum were measured on Wistar rats. The experiment consists of the following two parts.
Experiment 1. The influences of group size and occupied space per rat on the adrenocortical function were observed. Immediately after weaning, the rats were divided into five groups by the group size and the occupied space, and then were reared for 50 days. The following results were obtained.
The aggregate life caused an increase in the adrenocortical function. The group size had more influence on this increase than on the occupied space, especially in a small occupied space. And females showed the adrenocortical function to be higher than males. And furthermore, as for the group size, the adrenocortical function in two rats per cage was lowest in females.
Experiment 2. The relationship between the adrenocortical function and the social rank in a group was investigated. This experiment was carried out on 3 rats per cage. The social rank in a group was evaluated by the profiles based on the number of fights and the rate of victory.
From the results, subordinate rats showed the adrenocortical function higher than dominant rats.