In-vivo myometrial electrical activity in the cyclic mare

Abstract

Uterine electromyography was performed by means of chronically implanted surface electrodes in 3 Pony mares during spontaneous oestrous cycles and following luteolysis induced by a prostaglandin analogue (fluprostenol). Three distinct patterns were recognized during the oestrous cycle. (1) During oestrus well defined phases of activity with closely grouped high-amplitude spikes were separated by long periods (10-45 min) of complete inactivity. (2) During dioestrus more diffuse phases of activity with low-amplitude spikes were separated by variable periods of relative inactivity. (3) During luteolysis, short and frequently occurring phases of activity were propagated between the two electrodes on one uterine horn; a similar pattern also occurred between 1 and 3 h after injection of fluprostenol. Peripheral plasma progesterone, but not total inconjugated oestrogen, concentrations were closely related to characteristics of the myographic activity during the cycle. Insemination during oestrus and injection of fluprostenol during dioestrus caused a marked and prolonged increase in myometrial electrical activity. Almost any non-specific environmental stimulus, including entry by palpation of the genital tract per rectum and vaginoscopic examination, but these were of brief duration and the normal resting pattern of activity was quickly re-established after completion of the manipulations.

Electromyographic properties of the myometrium of the pony mare during pregnancy

“…This indicates that the smooth muscle cells of the myometrium are better electro-coupled and are working as a syncytium rather than in a nonpropagating, asynchronous fashion, as characterized by long trains of low amplitude spike activity. Taverne et al (1979b) observed that EMG activity in the cyclic mare seems to be related to the peripheral concentrations of progesterone, with little apparent correlation with the concentration of oestrogen. It would seem that this situation also exists in the pregnant mare, since EMG activity for individual mares shows similar trends throughout pregnancy.…”

“…Electromyographic (EMG) activity of the uterus has been recorded from pregnant sheep (Harding era/., 1982;Krishnamurtieifl/., 1982;Toutaineera/., 1983), pregnant goats (Taverne &Sheerboom, 1984), pregnant sows (Taverne et al, 1979a), pregnant cows (Zerobin & Sporri, 1972) and from the non-pregnant cyclic mare (Taverne et al, 1979b). Despite the relatively unusual nature of the hormonal environment present in the mare during pregnancy, no attempt has been made previously to describe the electrical and contractile activity of the myometrium during this stage.…”

Experimental studies on uterine contractile activity in mares following insemination with cryopreserved sperm

“…Dieses Resultat bestätigt Ergebnisse aus vorangegangenen Arbeiten, bei denen mittels Elektromyographie nach konventioneller Besamung eine Frequenzsteigerung von EMG-Spikes verzeichnet wurden (Taverne et al 1979, Jones et al 1991, Troedsson et al 1998) beziehungsweise sich mit Hilfe dynamischer Szintigramme eine Zunahme der Stärke und Frequenz von Uteruskontraktionen nach Besamung mit radioaktiv markiertem Sperma aufzeigen ließ (Katila et al 2000).…”

The uterus, an organ of many roles

“…A further complication to this subject of venereal infection is the fact that some mares are more susceptible to infection than others. The conceot of the susceotible mare stems from work pedormed by Loy, 1969 andKenney et al, 1975; and has furlher expanded the clinical interest into immunology (Asbury et al, 1982;Widders et al, 1984;Cheung et al, 1985;Hansen, 1987, Watson et al, 1987;LeBlanc et al, 1991).Interest in myometrial activity (Taverne et al, 1979;Troedsson et al, 1995) and uterine drainage (fluid accumulation) (LeBlanc, 1994a(LeBlanc, , 1994b has become a recent focus of clinical interest.…”