Blocking of ß-adrenergic receptors during the subfertile period inhibits spontaneous ovarian cyst formation in rats.

As aging proceeds, fertility problems arise, and the success rate of in vitro fertilization declines. During reproductive aging, rat ovaries present spontaneous formation of cysts, followed by a concomitant increase in sympathetic nerve activity, causing infertility and cessation of ovarian function. ß2-Adrenergic receptors, which are activated by noradrenaline (NA), modify follicular development and steroid secretions; thus, increased nerve activity has been associated with the development and maintenance of cystic structures. The purpose of this work was to block the effect of this sympathetic activity through in vivo administration of propranolol (a ß-adrenergic receptor antagonist) to determine whether it delays cyst formation and cessation of the ovarian function in rats that had reached the subfertile period. Propranolol was administrated daily to 8- and 10-month-old rats for 2 months. Estrous cycling activity was monitored by vaginal smear, serum concentration of the steroidal hormones was determined by enzyme-immune assay and morphological analysis of the ovaries was performed using 6 µm tissue slices stained with hematoxylin-eosin. Propranolol increased the number of healthy follicles, the ovulation rate, and levels of serum sexual steroids (androstenedione, testosterone, and estradiol) and recovered estrous cycling activity. It also decreased the number of follicular cysts. These results suggest that the blockade of ß-adrenergic receptors recovered ovarian function during reproductive aging. It is suggested that propranolol induces a time-dependent extension of the subfertile window, and it could be used to increase the success rate of fertility programs in aging woman.

In vivo ß-adrenergic blockade by propranolol prevents isoproterenol-induced polycystic ovary in adult rats.

Increasing evidence in animal models and in humans shows that sympathetic nerve activity controls ovarian androgen biosynthesis and follicular development. Thus, sympathetic nerve activity participates in the follicular development and the hyperandrogenism characteristics of polycystic ovary syndrome, which is the most prevalent ovarian pathology in women during their reproductive years. In this study, we mimic sympathetic nerve activity in the rat via "in vivo" stimulation with isoproterenol (ISO), a ß-adrenergic receptor agonist, and test for the development of the polycystic ovary condition. We also determine whether this effect can be reversed by the administration of propranolol (PROP), a ß-adrenergic receptor antagonist. Rats were treated for 10 days with 125 µg/kg ISO or with ISO plus 5 mg/kg PROP. The ovaries were examined 1 day or 30 days following drug treatment. While ISO was present, the ovaries had an increased capacity to secrete androgens; ISO + PROP reversed this effect on androgen secretory activity. 30 days after treatment, androstenedione secretion reverted to normal levels, but an increase in the intra-ovarian nerve growth factor (NGF) concentration and luteinizing hormone (LH) plasma levels was detected. ISO treatment resulted in follicular development characterized by an increased number of pre-cystic and cystic ovarian follicles; this was reversed in the ISO + PROP group. The lack of change in the plasma levels of progesterone, androstenedione, testosterone, or estradiol and the increased LH plasma levels strongly suggests a local intra-ovarian effect of ISO indicating that ß-adrenergic stimulation is a definitive component in the rat polycystic ovary condition.

Hormonal programming across the lifespan.

Hormones influence countless biological processes across an animal's lifespan. Many hormone-mediated events occur within developmental sensitive periods, during which hormones have the potential to cause permanent tissue-specific alterations in anatomy and physiology. There are numerous selective critical periods in development with different targets being affected during different periods. This review outlines the proceedings of the Hormonal Programming in Development session at the US-South American Workshop in Neuroendocrinology in August 2011. Here we discuss how gonadal steroid hormones impact various biological processes within the brain and gonads during early development and describe the changes that take place in the aging female ovary. At the cellular level, hormonal targets in the brain include neurons, glia, or vasculature. On a genomic/epigenomic level, transcription factor signaling and epigenetic changes alter the expression of critical hormone receptor genes across development and following ischemic brain insult. In addition, organizational hormone exposure alters epigenetic processes in specific brain nuclei and may be an important mediator of sexual differentiation of the neonatal brain. Brain targets of hormonal programming, such as the paraventricular nucleus of the hypothalamus, may be critical in influencing the development of peripheral targets, such as the ovary. Exposure to excess hormones can cause abnormalities in the ovary during development leading to polycystic ovarian syndrome (PCOS). Exposure to excess androgens during fetal development also has a profound effect on the development of the male reproductive system. In addition, increased activity of the sympathetic nerve and stress during early life have been linked to PCOS symptomology in adulthood. Finally, we describe how age-related decreases in fertility are linked to high levels of nerve growth factor (NGF), which enhances sympathetic nerve activity and alters ovarian function.

Neonatal exposure to estradiol valerate reprograms the rat ovary androgen receptor and anti-Müllerian hormone to a polycystic ovary phenotype.

To understand the impact of exposure to steroids in the early step of ovary development (a stage occurring in uterus in humans), we studied neonatal exposure to estradiol valerate (EV) in rats regarding polycystic ovary (PCO) development as well as expression of androgen receptor (Ar) and anti-Müllerian hormone (AMH), a marker of ovarian follicular development. Rats exposed to one dose of EV (10mg/kg, sc) during their first 12h of life were euthanized at 2, 30 and 60days of age. Gene array and real-time PCR studies showed Ar and AMH up regulation in the ovary at 2days of age and persisted at 60days of age, when a PCO phenotype was evident with increased levels of Ar and AMH proteins. The single neonatal exposure in rats suggests participation of EV in developing PCO syndrome. Its persistence also suggests that estradiol reprograms ovarian function and disease during adulthood.

Role of RFRP-3 in the development of cold stress-induced polycystic ovary phenotype in rats

RFamide-related peptide (RFRP-3) is a regulator of GnRH secretion from the brain, but it can also act in human ovary to influence steroidogenesis. We aimed to study the putative local role of RFRP-3 in the ovary and its potential participation in the development of a polycystic ovary phenotype induced by chronic sympathetic stress (cold stress). We used adult Sprague­Dawley rats divided into control and stressed groups. In both groups, we studied the effect of intraovarian exposure to RFRP-3 on follicular development and plasma ovarian steroid concentrations. We also tested the effect of RFRP-3 on ovarian steroid production in vitro. Chronic in vivo intraovarian exposure to RFRP-3 decreased basal testosterone concentrations and cold stress-induced progesterone production by the ovary. In vitro, RFRP-3 decreased hCG-induced ovarian progesterone and testosterone secretion. Immunohistochemistry and mRNA expression analysis showed a decrease in Rfrp and expression of its receptor in the ovary of stressed rats, a result which is in line with the increased testosterone levels found in stressed rats. In vivo application of RFRP-3 recovered the low levels of secondary and healthy antral follicles found in stressed rats. Taken together, our data indicate a previously unknown response of hypothalamic and ovarian RFRP-3 to chronic cold stress, influencing ovarian steroidogenesis and follicular dynamics. Thus, it is likely that RFRP-3 modulation in the ovary is a key component of development of the polycystic ovary phenotype.

Metformin increases norepinephrine transporter expression in placenta of patients with polycystic ovary syndrome.

OBJECTIVE: To evaluate the norepinephrine (NE) and placental NE transporter (NET) in women with polycystic ovary syndrome (PCOS) non-treated and treated with metformin during pregnancy. PATIENTS AND METHODS: We studied sixteen pregnant women with PCOS: 8 without metformin treatment during pregnancy (PCOS-M) and 8 treated with metformin during pregnancy (PCOS+M). Sixteen pregnant women of similar age without PCOS were included as controls (Control). At 24th and 35th weeks of pregnancy, blood samples were obtained. Placentas from full-term pregnancies were collected immediately after delivery. They were divided into two samples representative from the region near the chorionic plate (fetal side) and from the region near the basal plate (maternal side). NE plasma concentrations were measured by HPLC with electrochemical detection, and placental NET protein levels were determined by Western blot. RESULTS: At week 24 of gestation, PCOS-M had higher NE plasma levels compared to control women (p < 0.001). Moreover, NET expression was lower in the maternal side of the placenta of PCOS-M compared to controls (p < 0.05). Metformin treatment normalized NE plasma levels at week 24 of gestation and NET expression in the maternal side of the placenta. In the fetal side of the placenta, NET expression was lower in PCOS-M and PCOS+M compared to control women (p < 0.001 and < 0.01, respectively). CONCLUSIONS: Our results strongly suggest that norepinephrine homeostasis is altered in pregnant women with PCOS. Remarkably, metformin administration during pregnancy decreases circulating norepinephrine levels and increases NET expression in the maternal side of placentas from PCOS women.

Nerve growth factor-dependent activation of trkA receptors in the human ovary results in synthesis of follicle-stimulating hormone receptors and estrogen secretion.

CONTEXT: Previous studies showed that nerve growth factor (NGF) induces the expression of functional FSH receptors (FSHR) in preantral follicles of the developing rat ovary. OBJECTIVE: The objective of this study was to determine whether NGF can affect granulosa cell (GC) function in human periovulatory follicles using intact human ovaries and isolated human GCs. PATIENTS AND INTERVENTIONS: Human GCs were obtained from in vitro fertilization patients and normal ovaries from women with elective pelvic surgery for nonovarian indications. RESULTS: In normal ovaries, NGF and trkA (NGF's high-affinity receptor) were detected by immunohistochemistry in GCs of preantral and antral follicles. NGF and trkA are also present in thecal cells of antral follicles. Both freshly collected and cultured GCs contained immunoreactive NGF and trkA in addition to their respective mRNAs. Human GCs respond to NGF with increased estradiol (E(2)) secretion and a reduction in progesterone output. Exposure of human GCs to NGF increased FSHR mRNA content within 18 h of treatment, and this effect was blocked by the trk tyrosine kinase blocker K-252a. Also, cells preexposed to NGF released significantly more E(2) in response to hFSH than cells not pretreated with the neurotropin, showing that the NGF-induced increase in FSHR gene expression results in the formation of functional FSHRs. CONCLUSIONS: These results suggest that one of the functions of NGF in the preovulatory human ovary is to increase the secretion of E(2) while preventing early luteinization via an inhibitory effect on progesterone secretion. NGF stimulates E(2) secretion both directly and by increasing the formation of FSHRs.

Cold stress induces metabolic activation of thyrotrophin-releasing hormone-synthesising neurones in the magnocellular division of the hypothalamic paraventricular nucleus and concomitantly changes ovarian sympathetic activity parameters.

Recent studies suggest thyrotrophin-releasing hormone (TRH) serves as a neurotransmitter and thereby provides a functional vegetative connection between the brain and the ovary. In the present study, magnocellular neurones of the paraventricular nucleus (PVN) in animals subjected to cold exposure were studied to determine the hypothalamic origin of the TRH involved in this pathway. In situ hybridisation analysis of hypothalamic tissue showed that cold exposure causes a two-fold increase in the total number of neurones expressing TRH mRNA in the PVN. Immunohistochemical studies showed that TRH peptide is localised to the magnocellular PVN and that the number of TRH immunoreactive cells increases two-fold following 64 h of cold exposure. Double-immunostaining for MAP-2 and TRH revealed that TRH peptide is localised in the perikarya of the magnocellular neurones. TRH release was measured in vivo from the magnocellular portion of the PVN using push-pull perfusion. Although controls exhibited a very low level of TRH release, animals subjected to cold showed a pulsatile-like TRH release profile with two different patterns of release: (i) low basal level with small bursts of TRH release and (ii) a profile with an up to seven-fold increase in TRH release compared to controls. The colocalisation of TRH with the specific somato-dendritic marker MAP-2 in processes of the magnocellular neurones suggested a local release of TRH. Additional studies demonstrated a reduction in ovarian noradrenaline content after 48 h of cold exposure, a feature indicative of nerve activation at the terminal organ. After 64 h of cold exposure, the ovarian noradrenaline returned to control values but the noradrenaline content of the coeliac ganglia was increased, suggesting a compensatory effect originating in the cell bodies of the sympathetic neurones that innervate the ovary. The correlation between the local release of TRH from dendrites within the magnocellular PVN in conditions of cold and the activation of the sympathetic nerves supplying the ovary raises the possibility that TRH contributes to the processing regulating sympathetic outflow and may thereby impact on the functional activity of the ovary.

Kisspeptin is involved in ovarian follicular development during aging in rats.

We have previously reported that kisspeptin (KP) may be under the control of the sympathetic innervation of the ovary. Considering that the sympathetic activity of the ovary increases with aging, it is possible that ovarian KP also increases during this period and participates in follicular development. To evaluate this possibility, we determined ovarian KP expression and its action on follicular development during reproductive aging in rats. We measured ovarian KP mRNA and protein levels in 6-, 8-, 10- and 12-month-old rats. To evaluate follicular developmental changes, intraovarian administration of KP or its antagonist, peptide 234 (P234), was performed using a mini-osmotic pump, and to evaluate FSH receptor (FSHR) changes in the senescent ovary, we stimulated cultured ovaries with KP, P234 and isoproterenol (ISO). Our results shows that KP expression in the ovary was increased in 10- and 12-month-old rats compared with 6-month-old rats, and this increase in KP was strongly correlated with the increase in ovarian norepinephrine observed with aging. The administration of KP produced an increase in corpora lutea and type III follicles in 6- and 10-month-old rats, which was reversed by P234 administration at 10 months. In addition, KP decreased the number and size of antral follicles in 6- and 10-month-old rats, while P234 administration produced an increase in these structures at the same ages. In ovarian cultures KP prevented the induction of FSHR by ISO. These results suggest that intraovarian KP negatively participates in the acquisition of FSHR, indicating a local role in the regulation of follicular development and ovulation during reproductive aging.

Developmental and Functional Effects of Steroid Hormones on the Neuroendocrine Axis and Spinal Cord.

This review highlights the principal effects of steroid hormones at central and peripheral levels in the neuroendocrine axis. The data discussed highlight the principal role of oestrogens and testosterone in hormonal programming in relation to sexual orientation, reproductive and metabolic programming, and the neuroendocrine mechanism involved in the development of polycystic ovary syndrome phenotype. Moreover, consistent with the wide range of processes in which steroid hormones take part, we discuss the protective effects of progesterone on neurodegenerative disease and the signalling mechanism involved in the genesis of oestrogen-induced pituitary prolactinomas.

Study of luminescence, color and paramagnetic centers properties of albite.

A sample of natural albite, NaAlSi3O8, from the state of Minas Gerais, Brazil, has been investigated. The mineral is a solid solution of K-feldspar (4600 ppm--K) and Ca-feldspar (1100 ppm--Ca). The TL spectra of natural and the pre-annealed at high temperature albite presented a very intense band around 275 nm and weaker bands around 400 and 560 nm. Other TL properties have been investigated through monochromatic (275 nm and 400 nm) glow curves. The EPR spectrum measured at low temperature (77K) shows the typical 11 lines signal due to Al-O(-)-Al center superposed on Fe(3+) signal around g=2.0. The EPR spectra above 260 K show only g=2.0 signal due to Fe(3+) ions.

Involvement of nerve growth factor in female sexual development.

The ovary is innervated by noradrenergic and peptidergic fibers. Treatment of neonatal rats with antibodies to nerve growth factor (NGF Ab) resulted in failure of the sympathetic (noradrenergic and neuropeptide-Y) nerves to develop. Partial loss of sensory innervation, represented by calcitonin gene-related peptide fibers, was also observed. Follicular growth was stunted, and production of androgens and estradiol was reduced. The timing of first ovulation was delayed, estrous cyclicity was disrupted, and fertility was compromised. Plasma LH levels were elevated, and LH pulsatility was enhanced, suggesting primary ovarian failure. A normal appearance of tyrosine hydroxylase-, LHRH-, and neuropeptide-Y-immunoreactive neurons in the hypothalamus, as determined by immunocytochemistry, suggested that neonatal immunosympathectomy did not directly affect hypothalamic reproductive function. In vitro release of LHRH from median eminence nerve terminals in response to prostaglandin E2 was, however, reduced in NGF Ab-treated rats. Normalization of the response by prior in vivo exposure of the animals to physiological estradiol levels, suggested that the diminished LHRH output was due at least in part to estrogen deficiency. Although ovarian dysfunction induced by immunosympathectomy may be related to alterations in vascular tone, the striking loss of perifollicular noradrenergic innervation caused by NGF Ab suggests that the absence of the nonvascular norepinephrine stimulus to follicular steroidogenesis is a primary factor responsible for the alterations observed. The results indicate that development of the sympathetic innervation of the ovary is NGF dependent and that NGF, by supporting the differentiation and survival of the innervating neurons, contributes to the acquisition of mature ovarian function.

Norepinephrine release in the immature ovary is regulated by autoreceptors and neuropeptide-Y.

Experiments were undertaken to study the role that neuropeptide-Y (NPY) and adrenergic autoreceptors may play in the regulation of norepinephrine (NE) release from the rat ovary. Ovaries from 28- to 32-day-old rats were preincubated with [3H]NE, and the release of the recently taken up catecholamine in response to electric field stimulation was assessed. The release was strictly dependent on the presence of extracellular calcium and decreased when the frequency of stimulation was increased. This drop in [3H]NE release was significantly reversed by exposure of the ovaries during stimulation to yohimbine, a selective alpha 2-adrenoreceptor blocker. The existence of prejunctional alpha 2-adrenergic autoreceptors in ovarian nerves was further suggested by the ability of exogenous NE to mimic the inhibitory effect of high frequency stimulation. NPY inhibited by 40% the release of [3H]NE induced by electrical stimulation. The specificity of this effect and its prejunctional nature were demonstrated by the finding that avian pancreatic polypeptide, a structural homolog of NPY that is not recognized by prejunctional NPY receptors of the Y2 subtype, failed to alter the induced release of [3H]NE. Neither NPY, avian pancreatic polypeptide, nor peptide-YY, another member of the pancreatic polypeptide fold family, altered progesterone or estradiol secretion from whole ovaries or granulosa cells in culture, suggesting that NPY (and its structural homologs) does not directly affect ovarian steroidogenesis. The results suggest that 1) the release of NE from ovarian sympathetic nerves is subjected to a dual modulatory influence provided by NE itself and NPY; and 2) this regulatory effect is exerted via specific prejunctional receptors. Such NE/NPY actions are likely to regulate the availability of NE to its postsynaptic receptors during ovarian development and adult function. The fact that NPY is mostly released during high frequency stimulation raises the possibility of NPY involvement in ovarian dysfunctions associated with situations of enhanced sympathetic discharge, such as strenuous exercise and psychogenic amenorrhea.

Ovarian steroidal response to gonadotropins and beta-adrenergic stimulation is enhanced in polycystic ovary syndrome: role of sympathetic innervation.

Experimental induction of a polycystic ovarian syndrome (PCOS) in rodents by the administration of a single dose of estradiol valerate (EV) results in activation of the peripheral sympathetic neurons that innervate the ovary. This activation is evidenced by an increased capacity of ovarian nerve terminals to incorporate and release norepinephrine (NE), an increase in ovarian NE content, and a decrease in ovarian beta-adrenergic receptor number in the ovarian compartments receiving catecholaminergic innervation. The present experiments were undertaken to examine the functional consequences of this enhanced sympathetic outflow to the ovary. The steroidal responses of the gland to beta-adrenergic receptor stimulation and hCG were examined in vitro 60 days after EV administration, i.e. at the time when follicular cysts are well established. EV-treated rats exhibited a remarkable increase in ovarian progesterone and androgen responses to isoproterenol, a beta-adrenergic receptor agonist, with no changes in estradiol responsiveness. Basal estradiol release was, however, 50-fold higher than the highest levels released from normal ovaries at any phase of the estrous cycle. The ovarian progesterone and androgen responses to hCG were enhanced in EV-treated rats, as were the responses to a combination of isoproterenol and hCG. Transection of the superior ovarian nerve (SON), which carries most of the catecholaminergic fibers innervating endocrine ovarian cells, dramatically reduced the exaggerated responses of all three steroids to both beta-adrenergic and gonadotropin stimulation. SON transection also reduced the elevated levels of ovarian NE resulting from EV treatment and caused up-regulation of beta-adrenoreceptors. Most importantly, SON transection restored estrous cyclicity and ovulatory capacity. The results indicate that the increased output of ovarian steroids in PCOS is at least in part due to an enhanced responsiveness of the gland to both catecholaminergic and gonadotropin stimulation. The ability of SON transection to restore a normal response indicates that the alteration in steroid output results from a deranged activation of selective components of the noradrenergic innervation to the ovary. These findings support the concept that an alteration in the neurogenic control of the ovary contributes to the etiology of PCOS.

Guanethidine-mediated destruction of ovarian sympathetic nerves disrupts ovarian development and function in rats.

Immunosympathectomy produced by treatment of newborn rats with antibodies to nerve growth factor (NGF) delays ovarian development and disrupts estrous cyclicity. While these alterations have been ascribed to loss of sympathetic neurons innervating the ovary, the treatment also causes partial loss of ovarian sensory innervation. The present experiments were undertaken to determine if selective interference with ovarian noradrenergic/sympathetic action would result in alterations of ovarian development similar to those caused by NGF antibodies (NGF Ab). We have used two approaches to disrupt catecholamine action on ovarian cells: 1) inhibition of beta-adrenoreceptors by local delivery of receptor blockers to the ovaries of juvenile rats; and 2) elimination of the sympathetic innervation by long term postnatal treatment with guanethidine (GD), an adrenergic neuron blocking agent. When GD is administered chronically it produces an autoimmune-mediated destruction of peripheral sympathetic nerves, without affecting cholinergic or sensory neurons. Of the receptor blockers tested, FM-24, a nonreversible antagonist, resulted in a sustained 70% decrease in available receptors throughout the 10-day period studied. In spite of this, the timing of puberty, assessed by the age at vaginal opening and first ovulation, was not delayed, suggesting that activation of the remaining receptors by an intact innervation suffices to maintain a normal noradrenergic influence. GD treatment initiated at the end of the first week of postnatal life and maintained for three weeks slowed the juvenile-peripubertal rate of body growth, delayed the time of vaginal opening and first ovulation, and disrupted subsequent estrous cyclicity, but did not affect the animals' fertility. The ovaries of GD-treated rats exhibited a striking loss of sympathetic (norepinephrine and neuropeptide Y) nerves but a normal sensory innervation (represented by fibers containing calcitonin gene-related peptide). The concentration of beta-adrenoreceptors in granulosa cells was reduced, suggesting follicular immaturity. Direct assessment of this inference by morphometric analysis of the ovaries revealed that follicular development was retarded. The progesterone and estrogen response of juvenile ovaries to gonadotropins in vitro were also reduced. At this time, circulating LH levels were slightly decreased, but neither LHRH content in the median eminence nor the LHRH response to prostaglandin E2 in vitro were affected.(ABSTRACT TRUNCATED AT 400 WORDS)

Immature rat ovaries become revascularized rapidly after autotransplantation and show a gonadotropin-dependent increase in angiogenic factor gene expression.

When the ovaries of 23-day-old juvenile rats are transplanted to an ectopic site, they recover within 1 week the ability to control gonadotropin secretion via steroid negative feedback. Vascular corrosion casting followed by scanning electron microscopy revealed that the transplanted ovary becomes profusely revascularized within 48 h after transplantation. Vascular ingrowth was accompanied by a 40- to 60-fold increase in expression of the genes encoding two angiogenic factors, vascular endothelial growth factor (VEGF) and transforming growth factor-beta 1 (TGF beta 1), as assessed by RNA blot hybridization of the corresponding mRNAs. Although TGF beta 3 mRNA levels also increased, no changes in the levels of mRNAs encoding other putative angiogenic factors, such as TGF alpha, basic fibroblast growth factor, and TGF beta 2, were observed. Hybridization histochemistry demonstrated that in intact ovaries, VEGF mRNA is mainly expressed in granulosa cells of the cumulus oophorus and thecal cells of large antral follicles. Transplantation is followed by an increase in mRNA abundance and a dramatic shift in cellular localization, so that the mRNA becomes predominantly expressed in cells of the outer ovarian cortex. In intact ovaries, low levels of TGF beta 1 mRNA were detected in thecal-interstitial cells; after transplantation, its expression also became more predominant in the ovarian outer cortex, but this change was not as marked as in the case of VEGF. Because ovarian autotransplantation is followed by a rapid increase in serum gonadotropin levels, experiments were conducted to determine the importance of this rise in the activation of VEGF and TGF beta 1 gene expression. After transplantation, some animals were treated with the LHRH antagonist Nal-Glu LHRH (50 micrograms/rat, once a day for 2 days) to prevent the posttransplantation rise in serum gonadotropins. Quantitation of VEGF and TGF beta 1 mRNA by RNase protection assay 48 h later showed that suppression of gonadotropin secretion diminished the increase in both VEGF and TGF beta 1 gene expression. Concomitant treatment with PMSG (8 IU/rat, single injection), which mainly bypasses the suppression of endogenous FSH levels, restored the TGF beta 1 mRNA response, but had no effect on VEGF mRNA. The results suggest that the increase in gonadotropin secretion following ovarian transplantation contributes to revascularization of the graft by up-regulating the gene expression of two major angiogenic factors.

The gene encoding nerve growth factor is expressed in the immature rat ovary: effect of denervation and hormonal treatment.

The rat ovary is innervated by sympathetic nerve fibers. Since the development and survival of peripheral sympathetic neurons innervating nonreproductive organs have been shown to depend on the production of nerve growth factor (NGF) by the innervated tissues, the present experiments were undertaken to determine if the immature rat ovary has the capability of synthesizing NGF. Blot hybridization of ovarian polyadenylated RNA (A+-RNA) to a NGF cRNA probe revealed the presence of a 1.3- to 1.4-kilobase (kb) mRNA species similar to mature NGF mRNA detected in mouse submaxillary gland, a source rich in NGF. Quantitation of NGF protein by a sensitive and specific two-site enzyme immunoassay demonstrated the presence of NGF in juvenile ovaries at levels comparable to those found in other sympathetically innervated tissues. Neither denervation of the ovary nor treatment with gonadotropins (hCG and FSH) or somatomammotropins (PRL and GH) affected the levels of NGF mRNA. However, denervation significantly increased NGF levels, suggesting that, as in other target tissues, denervation prevents the retrograde transport of NGF by the sympathetic terminals and leads to accumulation of the protein at its site of production. It is concluded that 1) the developing ovary is able to both transcribe the NGF gene and translate its mRNA into NGF protein; and 2) the NGF content in the ovary is regulated by its innervation. The results provide the biochemical basis for the concept, elaborated in the companion paper, that NGF through its trophic actions on ovarian sympathetic neurons contributes to the regulation of ovarian development and, hence, to the acquisition of female reproductive capacity.

Activation of ovarian sympathetic nerves in polycystic ovary syndrome.

Polycystic ovarian syndrome (PCOS) is one of the most common human ovarian pathologies affecting women of reproductive age. Despite extensive investigation, the etiology of PCOS remains poorly understood. Experimentally, a PCO-like syndrome can be induced in rodents by a single dose of the long-acting estrogen, estradiol valerate (EV). We have used this model to examine the possibility that PCOS is associated with derangement of the sympathetic control of the ovary. The release of newly incorporated norepinephrine (NE) from ovarian nerve terminals in response to transmural stimulation of the gland increased significantly before the formation of cysts (30 days after EV injection) and remained elevated at the time when cysts form (60 days). The increase in evoked NE release was accompanied by an augmented NE content and enhanced incorporation of [3H]NE into ovarian tissue; both of these changes had been initiated by 30 days after EV treatment and became unambiguous at the time of cyst formation. The overall increase in ovarian sympathetic outflow suggested by these alterations in catecholamine homeostasis was accompanied by a thecal cell-interstitial tissue selective down-regulation of beta-adrenergic receptors; the beta-adrenergic receptor concentration in these sympathetically innervated ovarian compartments was significantly lower in PCO than during the estrous phase of the estrous cycle, a time at which the beta-adrenergic receptor concentration reaches its lowest levels in normal cycling ovaries. Tyrosine hydroxylase activity was found to increase only when expressed per mg ovary, but not in absolute terms (i.e. per total ovary), suggesting regulation of enzyme activity by the enhanced catecholamine content. The results demonstrate that an activation of the sympathetic neurons innervating the ovary precedes the development of cysts in EV-induced PCOS and raise the possibility that a derangement of sympathetic inputs to the ovary contributes to the etiology of PCOS.

A role for trkA nerve growth factor receptors in mammalian ovulation.

Several members of the neurotrophin (NT) family, including nerve growth factor (NGF), NT-3, and NT-4/5, are expressed in the mammalian ovary. As their respective receptor tyrosine kinases are also found in the gland, the possibility exists that NTs act directly on the gonads to exert effects unrelated to their support of the ovarian innervation. We now report that trkA, the NGF receptor tyrosine kinase, is involved in the acute activational process that leads to the first ovulation. The trkA gene becomes transiently expressed in periovulatory follicules at the time of the first preovulatory surge of gonadotropins at puberty; the increase in trkA messenger RNA (mRNA) content is dramatic ( > 100-fold), but transient (approximately 9 h). No such changes in trkB or trkC mRNA were observed; the abundance of these mRNAs, which encode the receptor tyrosine kinase for NT-4/5 and brain-derived neurotrophic factor, and NT-3, respectively, remained at very low levels throughout puberty. In vivo and in vitro experiments demonstrated that the activation of trkA gene expression is brought about by the proestrous discharge of LH. The increase in trkA mRNA levels is mainly localised to cells of the follicular wall and interstitial tissue of the ovary. NGF mRNA abundance also increases at proestrus, with peak values detected about 5 h before ovulation; as in the case of trkA mRNA, NGF mRNA was found in thecal-interstitial cells. Both trkA and NGF protein, detected by immunohistochemistry, were localized to this same ovarian compartment. Interleukin-1 beta (IL-1 beta), a putative mediator of LH action, enhances both trkA and NGF gene expression in ovarian cells, an effect prevented by IL-1ra, a natural IL-1 beta receptor antagonist. Il-1 beta also stimulates PGE2 release, and this effect was inhibited by both NGF antibodies and a trk receptor blocker, NGF antibodies administered in vivo attenuated the increase in ovarian PGE2 synthesis that antedates ovulation. Immunoneutralization of NGF action or pharmacological blockade of trk tyrosine kinase activity targeted to one ovary resulted in the ipsilateral inhibition of ovulation. The remarkably narrow time frame of trkA gene activation at the completion of follicular growth suggests that NGF acting as a neuroendocrinotrophic factor in a developmentally restricted manner contributes to the acute cytodifferentiation process that leads to the first ovulation in mammals.

Functional recovery of the developing rat ovary after transplantation: contribution of the extrinsic innervation.

These experiments were undertaken to define the neuroendocrine mechanisms underlying the recovery of ovarian function after transplantation to an ectopic site. Both ovaries from 23-day-old rats were transplanted to the region of the neck, next to the jugular vein. Serum gonadotropin and plasma immunoreactive inhibin-alpha levels were determined at several intervals thereafter. Serum estradiol (E2) was measured during the first week posttransplantation. Reinnervation of the ovary by sympathetic and sensory nerves was monitored by immunohistochemistry. Sympathetic nerves were identified as adrenergic by the presence of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis, and as peptidergic, by their neuropeptide-Y (NPY) or vasoactive intestinal peptide (VIP) immunoreactivity. Sensory nerves were identified by the presence of substance P (SP) and calcitonin-gene related peptide (CGRP) immunoreactivity. Serum LH and FSH increased, and plasma inhibin levels decreased, within 48 h after transplantation. Serum LH reached maximum levels on day 4, decreasing rapidly thereafter to basal values by day 6. These changes were functionally correlated with the posttransplantation fluctuations in serum E2, which decreased at 48 h, rebounded by day 4, and returned to basal values on day 7. Removal of the transplanted ovaries on day 3 resulted in the disappearance of serum E2 levels on day 4, thus confirming the ovarian graft as the source of E2. In contrast to LH, serum FSH remained significantly elevated for at least 3 weeks after transplantation, then decreased to basal levels after day 21, coinciding with the rise in inhibin secretion. Although a substantial loss of follicles was noted 48 h after transplantation, quantitative examination of the changes on day 4 revealed that approximately 40% of antral follicles were not necrotic. Ovulation and formation of corpora lutea were noted 21 days after transplantation. Reinnervation of the transplanted ovary by TH-, VIP-, NPY-, SP-, and CGRP-containing fibers was first detected 7 days after transplantation. Although VIP reinnervation was sparse and only transiently detected (days 7-21), the density of sympathetic (TH, NPY) and sensory (SP, CGRP) fibers increased 2- to 3-fold between days 7-28, remaining unchanged thereafter. Since apparent completion of this reinnervation coincided with reestablishment of normal levels of both LH and FSH, an additional experiment was performed to determine if the two events were causally related.(ABSTRACT TRUNCATED AT 400 WORDS)