Mapping the variability of in vivo rat uterine electrical properties throughout the oestrous cycle

After reaching sexual maturity, uterine function is driven by cyclical variations in hormone levels. The electrical and mechanical activity in the uterus varies during the menstrual cycle, contributing to essential functions such as sperm transport and shedding the menstrual lining. However, there is a lack of quantification of the variation in uterine function occurring over the course of the cycle. Female Wistar rats were used to quantify the changes in uterine electrical activity in vivo with respect to the oestrous cycle. Under anaesthesia, the uterus was exteriorised, and electrodes were placed on the dorsal and ventral sides of the organ to record spontaneous activity from the serosa. Electrical events were separated into slow and fast components based on frequency. The duration and interval between events were measured and propagation directions and velocities were mapped along the uterus using high spatial resolution electrode arrays. All stages of the oestrous cycle showed ovarian-cervical propagation, but cervical-ovarian propagation was also present in pro-oestrus and metoestrus. Ovarian-cervical propagation was dominant in oestrus and metoestrus. The interval between events showed significant differences with 40.2 ± 5.6 s (1.51 ± 0.25 cpm) and 60.5 ± 2.6 s (1.02 ± 0.05 cpm) during the dioestrus and metoestrus phases, respectively (P < 0.001). The slow and fast component durations were similar across the oestrous cycle (19.9 ± 2.2 s and 10.2 ± 3.0 s, respectively). This emphasizes the role of the oestrous cycle in guiding uterine function through modulation of the electrical activity and shows potential for estimating the oestrous cycle phases based on electrical characteristics.