In the course of studies concerning behavior and physiological characteristics of several inbred strains of rats, a technique was developed for periodic long-term recording of heart rate and body temperature in a freely moving rat. A method which has been reported earlier (Eisenstein and Woskow,1 1958) for obtaining heart rate involved the external use of surgical skin clips on the animal’s back. It has been found, however, that external clips are sloughed and require frequent replacement if long-term studies are to be undertaken.
The technique reported here involves the permanent placement of a Thermistor and two EKG leads into the body of the animal with an exposed miniature connector, to which recording leads can be attached.
Electrocardiographic leads consist of 2 in. lengths of EEG wire with surgical skin clips on the ends. The temperature probe which has been used in this case is a 4 in.