Induced changes on uterine myoelectrical activity around oestrous in the ewe by progesterone antagonist Onapristone and superovulation treatments - preliminary results Alterações na actividade mioeléctrica uterina na ovelha induzidas durante o estro por tratamentos de superovulação e pelo antagonista da progesterona Onapristone - resultados preliminares

Summary: Uterine myoelectrical activity (EMG) was measured with a computerised modular system in one adult Merino ewe previously fitted with three pairs of electrodes embedded in the myometrium of the uterine body (UB), the medium horn (MH) and proximal horn (PH). EMG was recorded for 30 minutes periods during follicular (F) and luteal (L) phases of normal oestrus cycle, and 24 and 28 hours after sponge withdrawal in synchronized and eCG superovulated oestrus cycles associated (treatment SZK) or not (treatment S) with the progesterone antagonist Onapristone. To evaluate uterine myoelectrical total activity the bursts of spike potentials (events) taken in each 30 minutes record were counted. The number of events in each uterine portion was expressed as a percentage of the total activity in each treatment (F, L, S and SZK). Frequency represents the number of events recorded over a 10 minute period. F and L treatments exhibited different patterns of EMG, with F presenting a significant higher activity on the posterior portions of genital tract (UB), and L presenting higher activity on the anterior portions (PH and MH). Pattern of uterine myoelectrical activity during normal follicular phase (treatment F) was modified both by eCG (S) and Onapristone (SZK) treatments. In both treatments it was observed not only an increase on frequency, but also a different pattern of percentage of total activity, with PH presenting the highest percentage of total activity on both treatments. In this work important changes on both quality and quantity of ewe uterine myoelectrical activity were found, associated with eCG and Onapristone. Although needing further confirmation on a larger number of animals, these changes may explain the reduction or absence of fertilization previously associated with superovulatory protocols and Onapristone administration. Resumo: A actividade mioelectrica uterina (EMG) foi medida, utilizando um sistema modular computorizado, numa ovelha adulta com 3 pares de electrodos previamente implantados no miometrio da regiao do corpo uterino (UB), do corno medio (MH) e do corno proximal (PH).