Assessment of Routine Procedure Effect on Breathing Parameters in Mice by Using Whole-Body Plethysmography

Handling, restraint, identification methods, and blood or tissue sampling are regarded as routine procedures in animal experiments. This aspect is particularly important when working with transgenic animals, where the need for genotyping demands the frequent use of these procedures, which can readily yield DNA samples.5 The effect of routine procedures on physiologic parameters varies depending on method, frequency, and duration, but these procedures generally are considered to be acute stressors.2,5,26,27 A large body of research has focused on the effect of routine procedures on animals’ physiology. These effects were assessed by studying changes in behavior,1,23,36,37 body weight,29,37 food and water intake,29,37 body temperature35 and heart rate by radiotelemetry,5,10,19,26,27 corticosterone11,12,24,25,29 and glucose levels,33 and blood variables.29,36 Several differences in the response of laboratory animals to stress have been correlated to breed,2,33 strain,11,14,37 age,24 and sex.12,23,24 Some authors24 have noted that female mice show a lower overall stress level due to the modest effect of social competition. Another study12 showed a different, sex-specific response to hypoxic ventilation in rats, which was higher in male than female rats. In addition, these authors12 suggested that female ovarian hormones are prime candidates for stress regulation. Whole-body plethysmography is a noninvasive, indirect method of studying respiratory function in conscious, unrestrained animals. This method has been used particularly in pharmacologic and toxicologic studies in diverse animal species including mice,3,9,14,15,38 rats,8,20 cats,22 dogs,16,34 and pigs.13 The present study was designed to investigate the extent to which routine procedures affect breathing parameters in a transgenic mouse colony. Male and female mice were exposed to 4 routine procedures that are used for DNA sampling and identification of transgenic mice (ear marking, tail clipping, and tail vein and retroorbital blood sampling). Respiratory parameters were recorded by whole-body plethysmography immediately and at 4, 24, and 48 h after the procedure. Handling and restraint were used as control procedures.