Uterine electromyographic activity in horse mares as measured by radiotelemetry

The objective of this study was to determine if radiotelemetry could be used to measure myometrial electromyographic (EMG) activity. A radio transmitter with one pair of biopotential leads was implanted in the flank ipsilateral to the pregnant uterine horn at least five weeks prior to the expected date of parturition in two mares. The biopotential leads were implanted in the base of the pregnant uterine horn. Telemetered data were received by a pair of antennae placed at right angles in a 3.3 by 6.6-m stall. Data were recorded on VHS format videocassette tapes continuously for the 24h prior to and following parturition. Simultaneous physiograph recordings were made as a hard copy reference. In addition, 10 mg of prostaglandin F(2alpha) was administered to two mares in the luteal phase of the estrous cycle. Myometrial EMG during parturition was increased similarly to that of previously published reports that used myometrial electrodes wired directly to a physiograph. Prostaglandin F(2alpha) also caused an increase in myometrial EMG activity within 8 min of administration. This study demonstrated that radiotelemetry can be used for measuring myometrial EMG activity.