The effects of routine cage-changing on cardiovascular and behavioral parameters in male Sprague-Dawley rats

The objective of this study was to determine whether the blood pressure and heart rate of adult male Sprague-Dawley rats are affected by the routine animal husbandry procedure of moving animals to clean cages. Cardiovascular parameters were obtained by using radiotelemetry; behavior in the home cage also was evaluated. Each rat had a radiotelemetry transmitter implanted in the peritoneal cavity, with the attached catheter placed in the femoral artery. After a 7- to 9-day recovery period, half of the rats were moved to clean cages with fresh wood-chip bedding; the other animals were left undisturbed. Systolic, diastolic, and mean arterial blood pressures; heart rate; and cage behavior (movement, rearing, grooming) increased promptly and significantly when animals were placed in clean cages. These cardiovascular and behavioral responses lasted for 45 to 60 min. Those animals not moved to clean cages but present in the animal room when this procedure was done did not show significant increases in blood pressure, heart rate, or activity. When rats were moved to clean cages that contained new bedding plus a small quantity of the soiled bedding from their previous cage, the cardiovascular and behavioral responses were similar to those of animals exposed to completely fresh bedding. The responses of rats being moved to new cages did not diminish between the first and fourth weekly cage change. Rats whose cages were not changed for 2 weeks showed small, but significant, increases in cardiovascular and behavioral responses above the responses in animals with weekly cage changes. We conclude that ordinary animal husbandry procedures such as moving rats to a clean cage can induce transient, but significant, cardiovascular and behavioral changes. Investigators and animal care staff should recognize that such routine procedures could confound experiments conducted shortly thereafter.