The influence of alpha-adrenergic receptors stimulator and blockers and beta-blocker on the ovary and endocrinological activity in heifers during superovulation.

ABSTRACT

Twenty five Holstein-Friesian heifers, clinically normal and with regular oestrous cycles, were used for induction of superovulation (PMSG-PGF(2)alpha-Neutra-PMSG). Animals were divided into 5 groups receiving I - detomidine (40 microg/kg b.w.), II - doxazosin (0.2 mg/kg b.w.), III - yohimbine HCL 1% (1 ml/50 kg b.w.), IV - carazolol (0.01 mg/ kg b.w., i.v.), and V - physiological saline (1 ml/50 kg b.w.). The heifers with PGF2 alpha-induced cycles were treated with the substances 88 hrs after being given a single i.m. injection of 2500 IU PMSG. All animals were examined by ultrasonography, and by the number and size of ovarian follicles > 3 mm in diameter. The follicles were divided into 3 groups according to the diameter. Blood plasma was stored at -20 degrees C until LH, P4, E2 and PGFM analyses. In the control (V) group, two waves of follicle growth were observed. Yohimbine produced a significant blockage of ovulation. The mean number of corpora lutea in the group III was significantly lower than that in the control group (p< 0.02). No significant differences in the number of corpora lutea were observed between the groups I, II and III. The increase in E2 concentrations could be the response to the PMSG treatment with two waves of growth of large follicles before and after ovulation. Pulsatile LH release was altered by yohimbinum injection, however, the greater amplitude of pulses immediately following yohimbinum administration are suggestive of a positive influence of the alpha-2 adrenergic receptors antagonist. Yohimbinum administration did not affect plasma concentration of examined hormones. There was a difference between the plasma levels of LH after the doxazosin injection. Single injection of the stimulators and blockers of adrenergic receptors did not affect superovulatory response in terms of the numbers of CL, unruptured follicles and embryos recovered. The affectivity of artificial insemination was not significantly different between the control group and the detomidinum groups, while in the yohimbinum group it was significantly lower.