Effect of the denervation of porcine ovaries on dexamethasone-induced cyst formation

Previously, we have shown that the activity of noradrenergic nerve fibres increased and the steroid content changed in porcine ovaries with dexamethasone-(DXM-) induced polycystic status. To better understand the role of the ovarian nerves in the formation of cystic status, the morphology and steroidogenic activity of the ovaries of DXM-treated gilts after denervation of the gonads were investigated in this study. Ovarian denervation was performed on day 3 of the first studied oestrous cycle and then, on days 7–21 of the cycle, DXM was administered. Following neurectomy and DXM treatment, cysts, medium-sized follicles and corpora lutea were not present, while the number of small-sized follicles increased. Denervation and DXM application led to a reduction in the number of dopamine-β-hydroxylase- and/or neuropeptide Y-immunoreactive nerve fibres. The concentrations of progesterone, androstenedione, testosterone and oestradiol-17β in the follicular fluid and/or in the wall of small-sized follicles of the experimental gilts were lower than in the controls. A similar result was demonstrated for P450scc, 3β-HSD and P450arom protein contents in the small follicles. Our data showed that DXM was not able to stimulate the formation of cysts in denervated porcine ovaries, indicating that the ovarian peripheral nerves might participate in the aetiopathogenesis of polycystic status.

Surgical denervation of porcine ovaries during the middle luteal phase of the oestrous cycle changes their morphology and steroidogenic activity

Changes in both the morphology and the steroidogenic activity of porcine ovaries denervated surgically on day 12 of the oestrous cycle were studied. Neurectomy of the plexus and the superior ovarian nerves caused a dramatic reduction in the number (or even a disappearance) of dopamine-β-hydroxylase- and/or neuropeptide tyrosine-immunoreactive nerve terminals. On day 20 of the subsequent oestrous cycle, the number of small follicles increased (P < 0.01) and that of large follicles decreased (P < 0.05) in the denervated ovaries, as compared to the controls. Neurectomy led to a decrease in the level of progesterone (P 4 ; P < 0.001) and androstenedione (A 4 ; P < 0.01) in the fluid from small follicles, A 4 (P < 0.001) and testosterone (T; P < 0.05) in the fluid from medium-sized follicles, as well as in the content of all these steroids in the fluid from large-sized follicles (P < 0.001 for P 4 and P < 0.05 for A 4 and T). Denervation also caused a decrease in the content of A 4 (P < 0.01) and T (P < 0.001) in the wall of follicles. Neurectomy resulted in a significant increase in the immunoexpression of cholesterol side-chain cleavage cytochrome P450 in the follicles and a decrease of 3β-hydroxysteroid dehydrogenase. After denervation, plasma levels of LH, P 4 , A 4 , T, oestrone and oestradiol-17β were lower (P < 0.05–0.001) on the particular days of the study than in the control group. Our data revealed that the denervation of ovaries during the middle luteal phase of the oestrous cycle in gilts caused distinct changes in both the morphology and the steroidogenic activity of the organ, confirming an important role of the peripheral nervous system in the control of the gonad in this species.

Uterine arterial vasoconstrictions mediated by ovarian nerves in virgin and postpartum rats

In most mammals, including humans, pregnancy results in the loss of most uterine vasomotor fibers. These experiments determined whether, despite this denervation, sympathetic nerves mediated uterine vasoconstrictions in the rat 24 h after delivery. Both virgin and uniparous postpartum rats were anesthetized with urethan. Femoral vessels were cannulated for measurement of arterial pressure and intravenous administration of fluids and drugs. Blood flow was measured in a uterine artery after ligation of all anastomotic ovarian vessels. Electrical stimulation of ovarian nerve efferents elicited frequency-dependent uterine vasoconstrictions in both virgin and postpartum rats. Vasoconstrictions in postpartum rats were not significantly different from those observed in virgins. In both virgin and postpartum rats, neurogenic vasoconstrictions were reduced by combined alpha 1- and alpha 2-adrenergic blockade. We conclude that the uterine branches of the ovarian nerve mediate adrenergic uterine vasoconstrictions. In the largely denervated uterus of the postpartum rat, these vasoconstrictions may be mediated by surviving innervation of the uterine artery and its major branches. Sympathetic vasoconstriction acting at these sites would constitute an effective defense against postpartum hemorrhage.

Control of ovarian innervation

The presence of intra-ovarian nerves was reported more than a century ago and successive investigations have demonstrated that the mammalian ovary is innervated by both sympathetic and sensory fibres distributed to the different compartments of the gland, such as blood vessels, ovarian stroma and follicle wall. Despite the extensive ovarian innervation and the experimental evidence indicating that neuromediators can influence sex steroid production, the role of the nervous system in the control of ovarian activity is still largely unknown.

Sympathetic innervation of guinea pig uterus and ovary

The relative contribution of the ovarian nerves and hypogastric plexus in the innervation of the guinea pig uterus and ovary was assessed. Chronic section of the hypogastric nerve did not reduce norepinephrine (NE) concentration in either organ. Localization of the hypogastric plexus in female guinea pigs was unsuccessful. Crushing the ovarian nerves 1) lowered the NE concentration in the ovary (70%) and in all portions of the uterus (86%), 2) decreased by 80-90% the uterine retention of [3H]NE, and 3) decreased the intensity of fluorescent adrenergic fibers in the uterus. However, the denervated uterus failed to exhibit supersensitivity to NE. In conclusion, sympathetic innervation of the guinea pig uterus and ovary is predominantly via the ovarian nerves, and a minor pathway of innervation may come from hypogastric plexus.