Recording and analysis of uterine activity in pregnant guinea-pigs

Guinea-pigs are of considerable interest for the study of the physiology of parturition in view of their lack of placental 17-alpha hydroxylase, a property which they share with Man and monkeys. To allow long-term analysis of uterine activity, a chronic guinea pig model was developed carrying a uterine electromyogram (EMG) electrode array, intrauterine and intraabdominal balloon catheters and vascular catheters. Operative procedures and the characteristics of the hardware and software are described and evaluated. Quantitative analysis of uterine activity relies on the quasi-integrated EMG signal which is highly correlated with the raw EMG signal. Under optimal conditions of intrauterine pressure recording, the area of the quasi-integrated EMG signal is highly correlated with the area of the intrauterine pressure increment. The preparation is stable for at least four weeks, measurements are reproducible, and biologically meaningful results are obtained from the recordings.