Evaluation of Mice Undergoing Serial Oral Gavage While Awake or Anesthetized

Although oral gavage is the most straightforward approach to achieve precise enteric administration in rodents, it is associated with potential adverse consequences. Here we compare the effects of serial oral gavage in awake compared with anesthetized mice. Female C57BL/6J mice (n = 20 per group) were assigned to 1 of 3 treatment groups (control, awake gavage, or anesthetized gavage) and gavaged daily with 0.2 mL of saline (with no manipulation on weekends) for a total of 18 treatment days. Body weight and clinical appearance were monitored throughout the treatment period, after which mice were euthanized and necropsied. Endpoints evaluated included adrenal gland weight, plasma corticosterone, lymphocyte:neutrophil ratio, and esophageal histopathology. Mean body weight did not differ between groups. Compared with other groups, the awake gavage group had more mice removed (3 of 20) prior to study completion due to body weight loss greater than 10%, with corresponding gross and histopathologic lesions attributed to the gavage procedure. Mice gavaged when awake had an over 20-fold higher incidence of incomplete retention of the administered saline than did anesthetized mice. Of the mice that completed the study, esophageal inflammation was not apparent at necropsy regardless of treatment, with the exception of a single mouse in the awake gavage group. Although WBC and lymphocyte counts were lower in mice in the anesthetized gavage group compared with other groups, none of the endpoints measured to evaluate stress (adrenal gland weight, neutrophil:lymphocyte ratio, plasma corticosterone) differed. These findings support the use of brief isoflurane anesthesia when performing serial oral gavage in mice.