Electromyographic properties of the myometrium correlated with the endocrinology of the pre-partum and post-partum periods and parturition in pony mares.
A complete set of electromyographic recordings, plasma samples and behavioural observations were collected from 2 mares beginning 7 days pre partum, through parturition and into the early post-partum period. During the week pre partum, EMG activity was elevated, occurring 26-73% of the time. Activity was least during the day and greatest at night with no significant difference for the hours of the day or between days pre partum. During the 24 h before delivery, EMG activity was increased for 7-13 h (55-80%) during the daylight hours. EMG activity 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 fetal delivery there was a reduction in activity until placental delivery followed by very long (2-22 min) trains of potentials.
D000818:Animals; D004576:Electromyography; D005260:Female; D006736:Horses / Q000502:physiology*; D007743:Labor, Obstetric / Q000502:physiology; D009215:Myometrium / Q000502:physiology*; D049590:Postpartum Period / Q000502:physiology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*