The sympathetic innervation of the mammalian ovary. A review of pharmacological and histological studies

Increased Vasoactive Intestinal Peptide (VIP) in polycystic ovary syndrome patients undergoing IVF

Introduction

Polycystic ovary syndrome (PCOS) is a common multifactorial and polygenic disorder of the endocrine system, affecting up to 20% of women in reproductive age with a still unknown etiology. Follicular fluid (FF) represents an environment for the normal development of follicles rich in metabolites, hormones and neurotransmitters, but in some instances of PCOS the composition can be different. Vasoactive intestinal peptide (VIP) is an endogenous autonomic neuropeptide involved in follicular atresia, granulosa cell physiology and steroidogenesis.

Methods

ELISA assays were performed to measure VIP and estradiol levels in human follicular fluids, while AMH, FSH, LH, estradiol and progesterone in the plasma were quantified by chemiluminescence. UHPLC/QTOF was used to perform the untargeted metabolomic analysis.

Results

Our ELISA and metabolomic results show: i) an increased concentration of VIP in follicular fluid of PCOS patients (n=9) of about 30% with respect to control group (n=10) (132 ± 28 pg/ml versus 103 ± 26 pg/ml, p=0,03) in women undergoing in vitro fertilization (IVF), ii) a linear positive correlation (p=0.05, r=0.45) between VIP concentration and serum Anti-Müllerian Hormone (AMH) concentration and iii) a linear negative correlation between VIP and noradrenaline metabolism. No correlation between VIP and estradiol (E2) concentration in follicular fluid was found. A negative correlation was found between VIP and noradrenaline metabolite 3,4-dihydroxyphenylglycolaldehyde (DOPGAL) in follicular fluids.

Conclusion

VIP concentration in follicular fluids was increased in PCOS patients and a correlation was found with noradrenaline metabolism indicating a possible dysregulation of the sympathetic reflex in the ovarian follicles. The functional role of VIP as noradrenergic modulator in ovarian physiology and PCOS pathophysiology was discussed.

Regulation of synaptic connections in the rabbit ciliary ganglion

One of the intriguing questions about the establishment of synaptic connections is how appropriate numbers of different axons come to innervate each target neuron. A reorganization of connections in early postnatal life appears to be an important aspect of this process, since many of the axons terminals that initially innervate target cells are subsequently lost. The rabbit ciliary ganglion is a remarkably simple neural ensemble in which to examine this rearrangement of developing synaptic connections. Using this system we have found that a reduction in the number of axons innervating each cell occurs without any change in the number of ciliary ganglion cells or preganglionic neurons; therefore the rearrangement is not based on cell death. The number of different axons that ultimately innervate each cell is, however, influenced in some way by the geometry of individual target neurons. Thus, mature ganglion cells that lack dendrites are generally innervated by a single axon, while neurons with increasingly complex dendritic arbors receive innervation from a commensurate number of different axons. At birth, on the other hand, neurons with or without dendritic processes receive about the same number of preganglionic inputs. These results suggest that the geometry of the target cell influences the competitive interaction between different axons innervating the same neuron. Indeed, an important function of dendrites may be to regulate the number of axons that innervate each nerve cell.

Plasticity of pelvic autonomic ganglia and urogenital innervation

Pelvic ganglia contain a mixture of sympathetic and parasympathetic neurons and provide most of the motor innervation of the urogenital organs. They show a remarkable sensitivity to androgens and estrogens, which impacts on their development into sexually dimorphic structures and provide an array of mechanisms by which plasticity of these neurons can occur during puberty and adulthood. The structure of pelvic ganglia varies widely among species, ranging from rodents, which have a pair of large ganglia, to humans, in whom pelvic ganglion neurons are distributed in a large, complex plexus. This plexus is frequently injured during pelvic surgical procedures, yet strategies for its repair have yet to be developed. Advances in this area will come from a better understanding of the effects of injury on the cellular signaling process in pelvic neurons and also the role of neurotrophic factors during development, maintenance, and repair of these axons.

Morphodynamics of the follicular-luteal complex during early ovarian development and reproductive life

Female reproductive activity depends upon cyclic morphofunctional changes of the ovarian tissue during the female's fertile period, but the primum movens of an active gonadal rearrangement can be found from early phases of embryo development. To offer a basic account of the main steps of ovarian dynamics, we review the morphofunctional behavior of the follicular-luteal complex in an integrated study using light microscopy and transmission and scanning electron microscopy as well as through the use of numerous drawings. Particular emphasis is given to some reproductive aspects including (1) germ-somatic cell relationships and onset of folliculogenesis during early gonadal development; (2) follicular development and oocyte-follicle cell associations through adult folliculogenesis, finally leading to ovulation; (3) morphodynamics of corpus luteum formation, development, and regression, and (4) degenerative processes involving germ and somatic cells. The results reported, many of which originated in our laboratory, arise from some experiments on laboratory mammals but mostly from a large selection of human specimens. The data obtained are integrated and correlated with classic reports as well as with current views. Crucial biochemical, histophysiological, and clinical aspects are also emphasized.

Release of norepinephrine from human ovary: coupling to steroidogenic response

We investigated the possibility that norepinephrine from the human ovary is released after nerve stimulation and that this neurotransmitter is coupled to a steroidogenic response. Biologically significant levels of both norepinephrine and dopamine were found in human ovarian biopsies. [3H]norepinephrine incorporated in vitro was readily released by electrical stimulation in a Ca2+-dependent process. Ovarian membrane preparations exhibited specific binding sites for the beta-adrenergic antagonist [3H]dihydroalprenolol. Displacement of [3H]dihydroalprenolol with zinterol (a specific beta2-agonist) indicated that 72% of these sites were type beta2-receptors. beta-receptors were also present on granulosa cells. Stimulation of granulosa cells with luteinizing hormone or the beta-agonist isoproterenol increased the release of progesterone after 4 d in culture. These results suggest that the sympathetic nerves present in human ovary are coupled to beta-adrenergic receptors present in endocrine cells and, as in nonprimate mammals, appear to participate in the regulation of ovarian function.

Expression and regulation of P2U-purinergic receptor in human granulosa-luteal cells

The P2U purinoceptor (P2UR) has been identified pharmacologically in the ovary. However, the expression and regulation of the P2UR messenger RNA (mRNA) in human ovarian cells are still poorly characterized. The present study was designed to examine the expression and regulation of the P2UR in human granulosa-luteal cells (hGLCs) by RT-PCR and Northern blot analysis. A PCR product corresponding to the expected 599-bp P2UR complementary DNA was obtained from hGLCs. Molecular cloning and sequencing of the PCR product revealed an identical sequence to the reported P2UR complementary DNA. Two mRNA transcripts of 2.0 kb and 4.6 kb were identified in hGLCs using Northern blot analysis. The expression of the P2UR mRNA was down-regulated by human CG in a dose- and time-dependent manner. Treatment with 8-bromo-cAMP and forskolin also attenuated P2UR mRNA levels. Calcium signaling following the activation of the P2UR in single hGLCs was studied using microspectrofluorimetry. It revealed that, like ATP, uridine triphosphate (UTP) also induced cytosolic calcium mobilization in a dose-dependent manner. These results demonstrate for the first time that the P2UR mRNA is expressed in hGLCs and that P2UR mRNA is regulated by human CG, cAMP, and forskolin. The P2UR expressed in hGLCs functional because activation of the P2UR by ATP or UTP resulted in rapid and transient mobilization of cytosolic calcium at the single cell level. These findings further support a potential role of this neurotransmitter receptor in the human ovary.

Oocytes are a source of catecholamines in the primate ovary: evidence for a cell-cell regulatory loop

Catecholamines, thought to derive from the extrinsic innervation of the ovary, participate in the regulation of ovarian development and mature gonadal function. Recently, intraovarian neurons containing tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis, were described in the ovary of nonhuman primates. We now show that the primate ovary expresses both the genes encoding TH and dopamine beta-hydroxylase (DBH), the key enzymes in norepinephrine (NE) biosynthesis. Ovarian neurons were identified as a site of TH and DBH gene expression, and surprisingly, oocytes were identified as an exclusive site of DBH synthesis. Oocytes contain neither TH mRNA nor protein, indicating that they are unable to synthesize dopamine (DA). They did, however, express a DA transporter gene identical to that found in human brain. The physiological relevance of this transporter system and DBH in oocytes was indicated by the ability of isolated oocytes to metabolize exogenous DA into NE. Isolated follicles containing oocytes-but not those from which the oocytes had been removed-responded to DA with an elevation in cAMP levels; this elevation was prevented by propranolol, a beta-adrenoreceptor antagonist. The results suggest that oocytes and somatic cells are linked by a neuroendocrine loop consisting of NE synthesized in oocytes from actively transported DA and cAMP produced by somatic follicular cells in response to NE-induced beta-adrenoreceptor activation.

Alterations in 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) mRNA accumulation induced by beta-adrenergic stimulation in cultured porcine granulosa cells

1. In primary cultures of porcine granulosa cells incubation with isoproterenol (10(-7)-10(-5) M) produced a dose-dependent increase in 3 beta-HSD mRNA, 3 beta-HSD content and progesterone production which ranged from 1.5- to 5-fold. 2. These effects were completely blocked by alprenolol. Terbutaline (10(-6) M) increased 3 beta-HSD mRNA, 3 beta-HSD content and progesterone production (1.5- to 3-fold), an effect which could be prevented by alprenolol. 3. Treatment with dobutamine (10(-6) M) produced no significant change in 3 beta-HSD mRNA accumulation. 4. The results suggest that beta-adrenergic agonists have the capacity to regulate transcription and translation of 3 beta-HSD mRNA in granulosa cells and this effect is mediated by the beta 2 adrenergic receptor.

Ovarian innervation develops before initiation of folliculogenesis in the rat

Sympathetic neurotransmitters have been shown to be present in the ovary of the rat during early postnatal development and to affect steroidogenesis before the ovary becomes responsive to gonadotropins, and before the first primordial follicles are formed. This study was undertaken to determine if development of the ovarian innervation is an event that antedates the initiation of folliculogenesis in the rat, Rattus norvegicus. Serial sections of postnatal ovaries revealed a negligible frequency of follicles 24 h after birth (about 1 primordial follicle per ovary). Twelve hours later there were about 500 follicles per ovary, a number that more than doubled to about 1300 during the subsequent 12 h, indicating that an explosive period of follicular differentiation occurs between the end of postnatal days 1 and 2. Electron microscopy demonstrated that before birth the ovaries are already innervated by fibers containing clear and dense-core vesicles. Immunohistochemistry performed on either fetal (day 19) or newborn (less than 15h after birth) ovaries showed the presence of catecholaminergic nerves, identified by their content of immunoreactive tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis. While some of these fibers innervate blood vessels, others are associated with primordial ovarian cells, thereby suggesting their participation in non-vascular functions. Since prefollicular ovaries are insensitive to gonadotropins, the results suggest that the developing ovary becomes subjected to direct neurogenic influences before it acquires responsiveness to gonadotropins.

Adrenergic influence on progesterone metabolism and cyclicity in the rat ovary: autotransplantation and chemical sympathectomy

Elimination of adrenergic nerve endings by chemical sympathectomy with 6-hydroxydopamine of normally cycling rats produced no differences in the weights of body, uterus, ovaries or adrenals, but suppressed significantly proestrus/estrus stages. Unilateral fully denervated (autotransplanted) ovaries showed the following changes in [¹⁴C]progesterone metabolism: the formation of 20α-hydroxy-4-pregnen-3-one increased, whereas 5α-pregnane-3α,20α- and 3ß,20α-diol, 3α- and 3ß-hydroxy-5α-pregnan-20-one, 20α-hydroxy-5α-pregnan-3-one, an unidentified metabolite Y and a group of hydrophobic metabolites decreased dramatically. Enzyme activities could not be restored with epinephrine. Sympathectomy changed the spectrum of [¹⁴C] progesterone metabolites in the same direction, but only at diestrus and metestrus. Autotransplantation suppressed 5α-reductase, 3α- and 3ß-hydroxysteroid dehydrogenase activities (-HSD) measured by the sum of all 5α-, 3α, and 3ß-metabolites, respectively. Sympathectomy suppressed significantly 5α-reductase and 3α-HSD at metestrus. 20α-HSD was not changed in any experiment. These studies provide evidence that 5α-reductase depends on adrenergic input in ovaries of rats at metestrus, a stage of nadir of gonadotropins. During the estrous cycle 5α-reductase may be a regulatory enzyme for progesterone metabolism and also influence estradiol biosynthesis.

Smooth muscle cells in the walls of ovarian follicles in the Japanese quail

The walls of pre-ovulatory follicles of the Japanese quail were examined at the ultrastructural level for the presence of cells displaying the typical morphological features of smooth muscle cells. These characteristics were found in the cells of the chordae, the tunica albuginea, and the theca externa. Small, elongated cells, containing microfilaments, were observed in the theca of prelampbrush follicles localized in the ovarian cortex. These thecal cells were considered as the putative precursors of the thecal smooth muscle cells of the pre-ovulatory follicle. The difference between the smooth muscle cells of the pre-ovulatory follicle and those in the wall of the most recent post-ovulatory follicle is the contracted state of the latter, which is most evident in the cells of the theca externa. It can be concluded that the cells of the theca externa are smooth muscle cells which are mainly contracted during the ovulatory process. A comparison was made with other vertebrate species.

The noradrenergic innervation of the ovary in old rats

The influence of ageing on the noradrenergic innervation of the ovary was studied in female Wistar rats using high pressure liquid chromatography (HPLC) with electrochemical detection and catecholamine histofluorescence techniques. Old age was accompanied by a significant decrease in ovarian noradrenaline levels. In young animals (3-month-old) noradrenergic nerve fibres were distributed primarily to blood vessels and in lesser amounts to the interstitial glands. In aged animals (24-month-old) perivascular noradrenergic fibres were reduced by more than 40%; interstitial gland nerve fibres were reduced by approximately 20%. The possibility that impaired noradrenergic ovarian innervation occurring in old age may be in some way related with age-dependent failure in reproductive activity is discussed.

Catecholaminergic regulation of ovarian function in mammals: current concepts

A review of the rapidly accumulating data in the literature continues to support the notion that catecholamines regulate ovarian function, and extends the complexity of catecholaminergic effects on the ovary via interactions with pituitary and adrenal hormones. It is clear that catecholamines affect growth and differentiation of ovarian follicles, but their role in follicular rupture during ovulation and in corpus luteum function remains unclear. The effects of catecholamines (mediated by membrane receptors) on ovarian function probably should be considered paracrine but classic endocrine regulation of ovarian function cannot be ruled out. Myogenic tonus of ovarian vasculature appears to be regulated by catecholamines, and estrogens may enhance adrenergic receptors in ovarian smooth muscle cells.

Evidence for prejunctional GABAB receptors mediating inhibition of ovarian follicle contraction induced by nerve stimulation

The motor effects of gamma-aminobutyric acid (GABA) on the bovine ovarian follicle were studied in vitro using strips from follicle walls. Electrical field stimulation of nerves in the preparation, secured by tetrodotoxin blockade, caused a contraction that was almost totally abolished by phentolamine and only slightly affected by atropine. This mainly adrenergic neurogenic response was inhibited by GABA in a dose-dependent way. The GABAA-receptor antagonists, bicuculline and picrotoxin, did not affect the GABA action whereas the GABAB-receptor antagonist, homotaurine, significantly inhibited the GABA effect. The GABAA-receptor agonist, muscimol, did not affect the contractile response while the GABAB-receptor agonist, baclofen, imitated the action of GABA. On the other hand, GABA had no direct contractile or relaxing effect on the follicle strips nor did it interfere with the contractile response induced by noradrenaline or acetylcholine. The findings suggest that activation of prejunctional GABAB receptors inhibits transmitter release from mainly adrenergic nerves associated with the follicle, thereby affecting nerve-mediated tension in the follicle wall.

The rat costo-uterine muscle: a preparation of smooth muscle containing a homogeneous population of beta-adrenoreceptors

This paper describes some histological features of the costo-uterine muscle of the rat together with the effects of some sympathomimetic amines upon contractions evoked by field electrical stimulation of isolated preparations. Light and electron microscopy confirmed that the costo-uterine muscle of the rat consists of smooth muscle bundles, arranged longitudinally and interspersed with collagen. There were close contacts between individual cells within bundles. No axon profiles were observed. Histochemical techniques revealed only sparse catecholamine fluorescence at the border of the tissue in association with blood vessels. Isoprenaline, fenoterol, adrenaline, noradrenaline, salbutamol and phenylephrine consistently inhibited contractions evoked by field stimulation (40V, 30Hz, 2 ms for 5 sec every 200 sec). In contrast, tyramine was without effect upon electrically evoked contractions in concentrations of up to 200 mumol/l. The slopes of the log concentration-response curves of effective amines were similar, and all of these were capable of producing 100% inhibition of contraction. The potencies of the amines relative to isoprenaline = 100 were: fenoterol 135; salbutamol 16; adrenaline 16; noradrenaline 0.7; phenylephrine 0.1; tyramine less than 0.001. Propranolol, added to preparations in the absence of inhibitors of amine uptake and alpha-adrenoreceptors, competitively antagonised the effects of the amines. Schild plots had slopes which did not differ significantly from minus one, and the mean pA2 values fell within a narrow range, e.g. 8.65 with salbutamol; 9.20 with fenoterol. Mean pA2 values for propranolol with noradrenaline and isoprenaline were unaffected by the combined presence of phentolamine (10 mumol/l), cocaine (10 mumol/l), and corticosterone (10 mumol/l). The potencies of the agonists were also unaffected by the presence of these drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of adrenergic and cholinergic agents on progesterone production by human corpus luteum in vitro

We investigated the effects of adrenergic and cholinergic agents on human corpus luteum production of progesterone in vitro. Luteinizing hormone (LH) (50 ng/ml), dibutyryl cyclic adenosine monophosphate (Bu2cAMP) (10(-3)M), and prostaglandin E2 (PGE2) (1 microgram/ml) significantly stimulated the production of progesterone in short-term (4-hour) cell suspensions of five early and middle luteal phase corpora lutea. The adrenergic agents isoproterenol, norepinephrine, and epinephrine, and the cholinergic agents acetylcholine and carbachol at concentrations up to 10(-4)M did not alter basal or stimulated production of progesterone. Similarly, in long-term (10-day) monolayer cultures of cells from four corpora lutea, human chorionic gonadotropin (hCG) (50 ng/ml) and PGE2 stimulated, but none of the adrenergic or cholinergic agents altered, the production of progesterone significantly, except for an inhibitory effect of norepinephrine and carbachol in the presence of 17 beta-estradiol (10(-7)M) added to the culture medium. These results differ strikingly from the consistent stimulatory effect of beta-adrenergic agents on the luteal production of progesterone in several animal species.

Effects of ovarian steroids upon responses mediated by adrenoceptors in separated layers of the myometrium and in the costo-uterine muscle of the guinea-pig

1 This study describes the effects of ovarian steroid hormones upon the responses to adrenoceptor agonists of isolated myometrium, separated into its longitudinal and circular layers, and of costo-uterine muscle from guinea-pigs. The preparations were field-stimulated at 100 s intervals, and the adrenoceptor agonists phenylephrine and isoprenaline produced enhancement or inhibition of the evoked contractions.2 Isoprenaline produced propranolol-sensitive inhibitory effects in longitudinal and circular myometrium and costo-uterine muscle preparations from animals from all experimental groups: i.e. from nonsteroid-treated animals (ovariectomized and intact); intact animals treated with either oestrogen or progesterone alone; ovariectomized animals treated with oestrogen; ovariectomized and intact animals treated with progesterone following oestrogen priming; and from animals 1-4 days post-partum. Longitudinal myometrial preparations from progesterone-treated oestrogen-primed and from post-partum animals were most sensitive to this agonist.3 Phenylephrine produced phentolamine-sensitive excitatory effects in circular myometrial and costo-uterine muscle preparations from animals from all the experimental groups. In contrast, propranolol-sensitive inhibitory responses to phenylephrine occurred in longitudinal myometrial preparations taken from animals treated with progesterone following oestrogen priming, and from post-partum animals. Longitudinal myometrium from animals from the remaining experimental groups exhibited phentolamine-sensitive excitatory responses to phenylephrine.4 The basis for the selective effect upon the longitudinal myometrium of exposure to progesterone following a period of oestrogen priming, is discussed. The results described are consistent with the possibility that in the longitudinal layer of guinea-pig uterus exposed to progesterone following oestrogen priming there is an increase in the proportion of beta-adrenoceptors in this layer. This increase may reduce the likelihood of contractions arising via direct stimulation of alpha-adrenoceptors in this layer in response to sympathetic activation during pregnancy.