The effect of administration of buserelin acetate (GNRH analogue) on in vivo bovine myometrial contractility at estrus

In this PhD dissertation, it was aimed that the determination of the in vivo effect of buserelin acetate, a commonly used a GnRH analogue for ovulation induction in artificial insemination, on myometrial contractility in cows at estrus. As a material, 26 cow at estrus were used. After the setup of intrauterine pressure measurement system with open-ended catheter technique (IUP), a blood sampling done for the determination of serum progesterone (P4) level. After the recording of spontaneous uterine contractility for 30 min (T1,3), in first group (n=7, KON) 5 ml saline solution, in second group (n=6, BUS1) 0,01 mg buserelin acetate, in third group (n=6, BUS2) 0,02 mg buserelin acetate and in fourth group (n=7, OXT) 50 IU oxytocin were injected intravenously. After the injection of drugs, uterine contractility recorded for 60 minutes (T4-9). Spontaneous and drug-induced contraction patterns of uterus were evaluated in terms of contraction frequency (number of contraction /10 min), amplitude (mmHg), duration (sec) and area under the curve (AUC) (mmHg X sec). Spontaneous contractility of uterus (T1-3) was severe and regular in cows at estrus. In contraction frequency and duration, no significant difference was found compared spontaneous and drug-induced contractions (P>0.05). In KON, BUS1 and BUS2 groups, no effect were seen in amplitude after the administration of the drugs (P>0.05), but in OXT group, after the administration of 50 IU oxytocin, the amplitude increased as a significant degree (P<0.05). It was concluded that the two dosages of buserelin acetate (0,01; 0,02 mg) had no effect on uterine contractility in cows at estrus and on the other side oxytocin was known as a good uterotonic, enhanced amplitude and area under the curve, but no effect on frequency and duration of uterine contractions. Keywords: Buserelin acetate, Contractility, Uterus, In Vivo, Cow