Chronic restraint via tail immobilization of mice: effects on corticosterone levels and other physiologic indices of stress

Chronic venous cannulation in mice is an acceptable and useful technique for repeated blood sampling or continuous intravenous administration of substances, for which mild restraint of the animal may be necessary. Because chronic restraint has drawn considerable attention in the animal welfare community, the purpose of this study was to evaluate physiologic indices of stress in mice restrained by using an established tail restraint method. Serum corticosterone levels and body, thymus, adrenal, and spleen weights on days 2, 5, 8, and 12 were compared between tail-restrained and unrestrained mice. There were no significant differences between the two groups at the time points evaluated. Corticosterone levels were highest on day 8 for both groups and were significantly different from those on days 2 (P