The use of telemetry to record electrocardiogram and heart rate in freely swimming rats.

Measurement of parameters from the circulatory system of laboratory animals can play an important role in pharmacological or toxicological research. To study the mutual interaction between physical exercise and antioxidant systems in rats, we selected swimming as a model for exercise performance. Swimming belongs to the natural behavior of the rat, and under proper experimental conditions, it primarily involves physical exercise with little emotional arousal. Therefore, we developed a swimming basin in which the intensity of exercise could be manipulated through speed and duration of swimming. A laser beam interruption system enables the rat to be followed during each swimming session. A motor-controlled following device, consisting of a rail and sledge connected to a position sensor, contains an antenna mounted in a receiver board. In this way, we can record the electrocardiogram (ECG) and heart rate (HR) with a commercially available telemetry transmitter implanted in the peritoneal cavity of freely swimming rats and evaluate the physical fitness (condition) of the swim-trained rats.