Identification of myoelectric signals of pregnant rat uterus: new method to detect myometrial contraction

Abstract

AimTo develop an electromyography method for pregnant rat uterus in vivo and to separate myometrial signals from the gastrointestinal tract signals.MethodsPregnant Sprague-Dawley rats (n = 8) were anaesthetized and their stomach, small intestine, and large intestine were removed from the abdomen. A pair of thread electrodes was inserted into the uterus, while a pair of disk electrodes was placed subcutaneously above the myometrium. Additionally, a strain gauge sensor was fixed on the surface of the myometrium and cecum for the parallel detection of mechanical contractions in rats (n = 18) with intact gastrointestinal tract. The filtered electric signals were amplified and recorded by an online computer system and analyzed by fast Fourier transformation. The frequency of the electric activity was characterized by cycle per minute (cpm), the magnitude of the activity was described as power spectrum density maximum (PsDmax).ResultsThe frequency of the pregnant uterine activity was 1-3 cpm, which falls within the same range as that of cecum. Measuring by both electrodes, oxytocin (1 µg/kg) increased and terbutaline (50 µg/kg) decreased the PsDmax by 25%-50% (P < 0.001) and 25%-40% (P < 0.01), respectively. We found a strong positive correlation between the alterations of PsDmax values and the strain gauge sensor-detected mechanical contractions (area under curve). The GI specific compounds (neostigmine, atropine) mainly affected the cecal activity, while myometrium specific drugs (oxytocin, terbutaline) influenced the myometrial signals only.ConclusionOur method proved to be able to detect the myoelectric activity that reflects the mechanical contraction. The overlapping myometrial and cecal signals are not separable, but they can be distinguished based on the much higher activity and different pharmacological reactivity of the pregnant uterus. Thus, the early signs of contractions can be detected and labor may be predicted in a fast and sensitive way.

Combined uterorelaxant effect of magnesium sulfate and terbutaline: Studies on late pregnant rat uteri in vitro and in vivo

“…In each dose, the animals were treated with constant intravenous MgSO 4 (0.3 mg/kg) while increasing doses of terbutaline (from 0.05 to 50 μg/kg every 15 min) were added in a cumulative manner. The myoelectric signals of the pregnant uterus, representing the strength of contractions, 14 were detected by an online computer system (SPEL Advanced ISOSYS Data Acquisition System). Uterine contractility was evaluated by fast Fourier transformation (FFT).…”

The combined uterorelaxant effect of sildenafil and terbutalin in the rat: The potential benefit of co-administration of low doses

“…All analogue signals were filtered with a first-order bandpass Bessel-type filter with a frequency of 1–3 cycles per minute (cpm) and were digitized at a sample rate of 2 Hz. Uterine contractility was evaluated by fast Fourier transformation (FFT), then the power spectrum density maximum (PsD max , the highest peak of PsD) of the SMEMG activity was determined as previously described [ 17 ] ( Fig. 1 .).…”

Non-genomic uterorelaxant actions of corticosteroid hormones in rats: An in vitro and in vivo study

“…The recorded mechanical and myoelectric signals of the in vivo experiments were analyzed by AUC and fast Fourier transformation, respectively. The AUC and PsD max values were determined and compared statistically (Szucs et al, 2016(Szucs et al, , 2017.…”

“…In pregnant rats, the electromyographic responses were evaluated by fast Fourier transformation (FFT) and the maximum of power spectrum density (PsD max ) values were compared in the frequency range of 1-3 cpm, which is characteristic for late pregnant uteri (Fig. 3) (Szucs et al, 2017).…”