Estrous cycle‐dependent differences in responsiveness to prostaglandins and contractile agents in sheep (Ovis aries) cervical smooth muscle

Abstract

We investigated the influence of the phase of the estrous cycle on mechanical responses elicited in sheep cervix by potassium chloride (KCl), acetylcholine chloride (ACh), prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E1 (PGE1). The cervix of adult ewes (n = 48) were classified according to the presence or absence of corpora lutea (luteal or follicular phase, respectively). Muscle strips of the circular and longitudinal layers were prepared in an organ bath and coupled to an isometric force transducer. Concentration-response curves were obtained noncumulatively. KCl and ACh produced concentration-dependent contractions in all preparations in both phases of the estrous cycle. However, maximum effect, EC50 and slope values of KCl and ACh were not significantly different between muscle layers, as well as between the phases of the estrous cycle. The prostanoid, PGF2 alpha, produced a significant reduction in the amplitude of spontaneous contractions for all preparations. The depressant effect of PGF2 alpha on spontaneous contractions of circular smooth muscle was significantly greater during the follicular than the luteal phase, whilst the depressant effect of PGF2 alpha on the longitudinal layer did not differ between phases of the estrous cycle. PGE1 significantly reduced the amplitude of spontaneous contractions on circular but not on longitudinal preparations. In conclusion, we have characterized with in vitro preparations of circular and longitudinal muscle layers of ewes during the follicular and luteal phases of the estrous cycle, the parameters of the K- and ACh-induced contractions on cervix and the efficacy of PGF2 alpha and PGE1 on inhibition spontaneous contractile activity.

Relaxant effect of the essential oil of Croton nepetifolius on ovine cervix

“…Previously, we found that 10 μM prostaglandin E 1 reduced the spontaneous contractions of the circular layer in sheep cervix, but had no significant effect on the longitudinal layer in concentrations varying of 0.1-10 μM (Pereira et al, 2007). In the same study, prostaglandin F 2α (0.5-30.0 μM) produced a maximum inhibitory effect of 100% on spontaneous contractions of longitudinal segments and only 30% in the circular layers.…”

“…In this establishment, sheep management (reception, maintenance and slaughter by captive bolt) follows the standard rules for humane slaughter of animals (Normative n. 3: 17/01/2000-Ministério de Agricultura Pecuária e Abastecimento-MAPA). The cervix was removed and transported to the laboratory in modified Tyrode's solution (in mM: NaCl 136.0, KCl 5.0, CaCl 2 2.0, MgCl 2 0.98, NaH 2 PO 4 0.36, NaHCO 3 11.9 and glucose 5.5, pH 7.4), at 5 °C within 2-3 h. After confirming the absence of pregnancy, the ovaries were removed and macroscopically examined to determine the phase of the estrous cycle (Pereira et al, 2007). The only tissues used were those from animals showing at least one corpus luteum, thereby characterizing the luteal phase.…”

“…The tissue strips were prepared according to methods previously described by Pereira et al (2007). Thus, muscle segments (4-5 mm wide, 9-10 mm long and 1 mm thick) corresponding to circular and longitudinal fibers were suspended vertically in an organ bath containing 5 mL modified Tyrode's solution, at 37 °C, bubbled continuously with air.…”

Improvement of Fertility in Artificially Inseminated Ewes Following Vaginal Treatment with Misoprostol Plus Terbutaline Sulphate

“…During oestrus, cervical electrical activity is increased (Cavaco‐Gonçalves et al. 2006a), and PGE1 was found to significantly reduce the amplitude of spontaneous contractions on circular but not on longitudinal cervical muscle strips in the ewe (Pereira et al. 2007).…”

An in vitro investigation of the actions of reproductive hormones on the cervix of the ewe in the follicular stage: The effects of 17β-estradiol, oxytocin, FSH, and arachidonic acid on the cervical pathway for the synthesis of prostaglandin E2

“…The immediate cause of cervical relaxation is thought to be prostaglandin E 2 (PGE 2 ) that acts on cervical collagen causing it to disperse [6,7] and on cervical smooth muscle [7,8] thus allowing the cervical canal to dilate. It has been previously reported that in the bovine [9] and ovine cervix [5,10], during the follicular phase of the estrous cycle, there is an increase in the expression of the FSH receptors suggesting that the gonadotrophic hormone might play a role in the pathway of PGE 2 synthesis and final cervical relaxation.…”