Physiological and behavioral effects of dextroamphetamine on Beagle dogs

The purpose of the study was to measure the effects of a dose of 0.2 mg/kg dextroamphetamine on body temperature, heart rate, motor activity, and associated behavior changes in Beagle dogs. Reliability of a collar-mounted accelerometer as an objective measure of motor activity was also investigated by comparing motor activity with that observed using video recordings. A total of 12 research colony Beagle dogs (13-20-months-old) served as their own control in this placebo-controlled crossover design, receiving both placebo and 0.2 mg/kg dextroamphetamine as treatment. Baseline and posttreatment values for body temperature, heart rate, and motor activity were obtained using a rectal temperature, heart rate monitor, and a collar-mounted accelerometer, respectively. Behavior sequences were filmed and analyzed. Repeated measures model indicated that dogs receiving a dose of 0.2 mg/kg dextroamphetamine had a significantly (P = 0.044) reduced heart rate as compared with placebo. There was no effect of treatment on the dogs’ body temperature, motor activity, or other behaviors such as “lip-licking,” “panting,” and “yawning.” There was a significant linear and positive relationship between the gross motor activity as measured by observational video and the accelerometer counts (P < 0.0001). Several behavioral textbooks used in clinical practice distinguish canine hyperactivity–hyperkinesis from overactivity by physiological and behavioral responses to amphetamines in a clinical setting. The authors of these textbooks suggest that true hyperactive–hyperkinetic dogs provided with oral amphetamines will paradoxically calm down, and have >15% reduction in heart rate. However, no data exist on the various effects of a low dose (0.2 mg/kg) of oral dextroamphetamine in dogs. The results of this study indicate that although as a group the medicated dogs showed a significantly lower heart rate than the placebo group, individual Beagle dogs showed variability in changes of heart rate. The use of the accelerometer in this study is a reliable tool for measuring motor activity in the dog.