Electromyographic properties of the myometrium correlated with the endocrinology of the pre-partum and post-partum periods and parturition in pony mares
Haluska, G.J.; Lowe, J.E.; Currie, W.B.
Journal of Reproduction and Fertility. Supplement 35: 553-564
1987
ISSN/ISBN: 0449-3087 PMID: 3479609 Document Number: 302414
A complete set of electromyographic recordings, plasma samples and behavioural observations were collected from 2 mares beginning 7 days before parturition, through parturition and into the early postpartum period. Electromyographical (EMG) activity was elevated during the week before parturition, occurring 26-73% of the time. Activity was lowest during the day and highest at night, with no significant difference among the hours of the day or among days before parturition. In the 24 h before delivery, EMG activity was increased for 7-13 h (55-80%) during the daylight hours. It decreased 2-4 h immediately preceding delivery of the foal, with an abrupt increase at rupture of the chorioallantois. At delivery, EMG activity consisted of events containing a series of 10-13 discrete bursts of increasing amplitude occurring in rapid succession. After foetal delivery there was a reduction in activity until placental delivery, followed by very long (2-22 min) trains of potentials.