BIOTELEMETRY - ADJUSTMENT OF A TELEMETRY SYSTEM FOR SIMULTANEOUS MEASUREMENTS OF ACUTE HEART-RATE CHANGES AND BEHAVIORAL EVENTS IN UNRESTRAINED RATS

The radiotelemetry system described in this paper consists of an impla ntable transmitter and a receiver, connected to a microcomputer. The h ardware and software belonging to Mini-Mitters, for the collection and analysis of heart rate (HR), core temperature (CT), and gross activit y data, do not possess the flexibility to detect acute changes in HR n or to discriminate among simultaneously occurring different types of b ehavior. In order to study short-term changes in HR in response to str ess or drugs, in relation to behavioral responses, an inexpensive comp uter interface and a software program (CARDIAQ) were developed to coll ect data from Mini-Mitters. The interface conveys the QRS signal, whic h is converted to a TTL pulse train, to the parallel printer adapter ( LPT1) of an IBM-compatible computer. Heart rate is determined by measu ring single interbeat intervals (IBI). The software controls the sampl ing schedule and stores the collected data in a format compatible with a commercial spreadsheet package. The program calculates the median I BI per s, mean +/- SD IBI, variance, skewness, and kurtosis of the IBI distribution. In addition, it enables simultaneous recording of behav ior by entering data through the keyboard at the occurrence of each ev ent. In this paper, we describe the CARDIAQ program and provide sample s of its application together with the implantable transmitters in fre ely moving rats.