Estrogen Receptors in the Spinal Cord, Sensory Ganglia, and Pelvic Autonomic Ganglia

Low-Intensity Extracorporeal Shock Wave Therapy Ameliorates Detrusor Hyperactivity with Impaired Contractility via Transient Potential Vanilloid Channels: A Rat Model for Ovarian Hormone Deficiency

This study explores low-intensity extracorporeal shock wave therapy (LiESWT)'s efficacy in alleviating detrusor hyperactivity with impaired contractility (DHIC) induced by ovarian hormone deficiency (OHD) in ovariectomized rats. The rats were categorized into the following four groups: sham group; OVX group, subjected to bilateral ovariectomy (OVX) for 12 months to induce OHD; OVX + SW4 group, underwent OHD for 12 months followed by 4 weeks of weekly LiESWT; and OVX + SW8 group, underwent OHD for 12 months followed by 8 weeks of weekly LiESWT. Cystometrogram studies and voiding behavior tracing were used to identify the symptoms of DHIC. Muscle strip contractility was evaluated through electrical-field, carbachol, ATP, and KCl stimulations. Western blot and immunofluorescence analyses were performed to assess the expressions of various markers related to bladder dysfunction. The OVX rats exhibited significant bladder deterioration and overactivity, alleviated by LiESWT. LiESWT modified transient receptor potential vanilloid (TRPV) channel expression, regulating calcium concentration and enhancing bladder capacity. It also elevated endoplasmic reticulum (ER) stress proteins, influencing ER-related Ca2+ channels and receptors to modulate detrusor muscle contractility. OHD after 12 months led to neuronal degeneration and reduced TRPV1 and TRPV4 channel activation. LiESWT demonstrated potential in enhancing angiogenic remodeling, neurogenesis, and receptor response, ameliorating DHIC via TRPV channels and cellular signaling in the OHD-induced DHIC rat model.

Sex hormone mediated change on flexion reflex

It has been shown that estrogen and progesterone receptors are expressed in the spinal cord; therefore, fluctuation in their concentrations may affect the spinal network and modulate the control of movement. Herein, we assessed the neuro-modulatory effect of sex hormones on the polysynaptic spinal network by using a flexion reflex network as a model system. Twenty-four healthy eumenorrheic women (age 21-37 years) were tested every other day for one menstrual cycle. Serum estradiol and progesterone were acquired at the time of testing. The flexion reflex of the tibialis anterior was elicited by sending an innocuous electrical stimulus directly to the posterior tibial nerve or plantar cutaneous afferent. Analyses were performed for each menstrual cycle phase: the follicular phase and the luteal phase. Increases in estradiol or progesterone concentrations were not associated with reflex duration or root mean squared (RMS) amplitude in either the follicular or luteal phases. In the luteal phase, an increase in the estradiol concentration was associated with a longer latency of the reflex (b = 0.23, p = 0.038). The estradiol × progesterone interaction was found towards significance (b = -0.017, p = 0.081). These results highlight the potential synergistic effect of estradiol and progesterone and may provide indirect confirmatory evidence of the observed modulatory effect.

The Interaction Between NF-κB and Estrogen in Alzheimer's Disease

Post-menopausal women are at a higher risk of developing Alzheimer's disease (AD) than males. The higher rates of AD in women are associated with the sharp decline in the estrogen levels after menopause. Estrogen has been shown to downregulate inflammatory cytokines in the central nervous system (CNS), which has a neuroprotective role against neurodegenerative diseases including AD. Sustained neuroinflammation is associated with neurodegeneration and contributes to AD. Nuclear factor kappa-B (NF-κB) is a transcription factor involved with the modulation of inflammation and interacts with estrogen to influence the progression of AD. Application of 17β-estradiol (E2) has been shown to inhibit NF-κB, thereby reducing transcription of NF-κB target genes. Despite accumulating evidence showing that estrogens have beneficial effects in pre-clinical AD studies, there are mixed results with hormone replacement therapy in clinical trials. Furthering our understanding of how NF-κB interacts with estrogen and alters the progression of neurodegenerative disorders including AD, should be beneficial and result in the development of novel therapeutics.

Evaluation of the sexual quality of life and sexual function of cervical cancer survivors after cancer treatment: a retrospective trial

OBJECTIVE

The purpose of this study was to explore the factors influencing the sexual quality of life of patients with cervical cancer who underwent radical hysterectomy.

METHODS

This multicenter retrospective cohort study was conducted from June 2013 to June 2018 at nine hospitals in China. In total, 204 women diagnosed with stage IA to stage IIB cervical cancer who underwent radical hysterectomy completed the questionnaire. Sexual function was measured with the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire (PISQ). All analyses were performed with R version 3.4.3 statistical software packages. A two-sided significance level of 0.05 was used to evaluate the statistical significance.

RESULTS

The mean sexual quality of life score was 37.21 ± 17.28, where a higher PISQ score indicates a better sexual quality of life, and we identified the factors associated with sexual dysfunction. The average follow-up time was 29.0 ± 16.0 months. In addition to radical hysterectomy, 182 (89.2%) patients underwent ovarian suspension, 93 (45.6%) underwent chemotherapy, and 74 (36.3%) underwent concurrent radiotherapy. The univariate analysis confirmed that age represents a protective factor for sexual function (odds ratio (OR) 6.0, 95% confidence interval (CI) 1.1-10.8, p = 0.017). The patients who underwent ovarian suspension were more likely to experience a good sexual quality of life (OR - 7.2, 95% CI [- 14.8, - 0.4], p = 0.035) compared to those who did not undergo ovarian suspension. A significant negative association was observed between radiotherapy and the behavioral-emotive, physical and partner-related domains of the PISQ (behavioral-emotive, OR - 1.5, 95% CI [- 2.6, - 0.4], p = 0.011; physical, OR - 0.9, 95% CI [- 1.5, - 0.3], p = 0.006; partner-related, OR - 0.7, 95% CI [- 1.3, 0.0], p = 0.043). Chemotherapy and radiotherapy were common risk factors for sexual dysfunction, and radiotherapy exerted a stronger effect than chemotherapy.

CONCLUSIONS

This study shows that the sexual function of cervical cancer patients tends to be related to age, radiotherapy, and chemotherapy. However, across these factors, patients with preserved ovaries tend to return to a satisfactory sexual quality of life after recovering from surgery.

Age and Sex-Related Changes to Gene Expression in the Mouse Spinal Cord

The spinal cord is essential for neuronal communication between the brain and rest of the body. To gain further insight into the molecular changes underpinning maturation of the mouse spinal cord, we analysed gene expression differences between 4 weeks of age (prior to puberty onset) and adulthood (8 weeks). We found 800 genes were significantly differentially expressed between juvenile and adult spinal cords. Gene ontology analysis revealed an overrepresentation of genes with roles in myelination and signal transduction among others. The expression of a further 19 genes was sexually dimorphic; these included both autosomal and sex-linked genes. Given the presence of steroid hormone receptors in the spinal cord, we also looked at the impact of two major steroid hormones, oestradiol and dihydrotestosterone (DHT) on spinal cord gene expression for selected genes. In gonadectomised male animals, implants with oestradiol and DHT produced significant changes to spinal cord gene expression. This study provides an overview of the global gene expression changes that occur as the spinal cord matures, over a key period of maturation. This confirms that both age and sex are important considerations in studies involving the spinal cord.

A Controlled Study on Vaginal Blood Flow During Sexual Arousal Among Early-Stage Cervical Cancer Survivors Treated With Conventional Radical or Nerve-Sparing Surgery With or Without Radiotherapy

OBJECTIVE

Sexual problems among cervical cancer survivors may in part be caused by reduced vaginal blood flow due to damaged hypogastric nerves during radical hysterectomy with pelvic lymphadenectomy and/or by radiation-induced vaginal changes after pelvic radiotherapy. A nerve-sparing modification of radical hysterectomy (NSRH) may preserve vaginal blood flow. Vaginal blood flow during sexual arousal was compared between different treatment modalities.

METHODS

We investigated premenopausal women treated for early-stage cervical cancer with radical hysterectomy (n = 29), NSRH (n = 28), NSRH with radiotherapy (n = 14), and controls (n = 31). Genital arousal and subjective sexual arousal in response to sexual stimuli were measured using vaginal photoplethysmography and a questionnaire. Results were compared by using a between-study (treatment groups) by within-study (stimulus) design.

RESULTS

Participants were aged 29 to 51 years (mean, 42 years) and at 1 to 14 years (mean, 5 years) after treatment. Measured vaginal blood flow in women treated with NSRH was similar to controls. Women treated with radical hysterectomy had a significantly lower vaginal blood flow compared with controls overall and lower compared with the NSRH group during sexual stimulation. Women treated with radiotherapy had a vaginal blood flow intermediate between the other groups without significant differences. The erotic films were equally effective in enhancing subjective sexual arousal among treatment groups.

CONCLUSIONS

Cervical cancer treatment with radical hysterectomy disrupts the vaginal blood flow response, and this may be prevented by conducting an NSRH. Treatment with radiotherapy did not significantly impact vaginal blood flow, but further investigation is needed with a larger sample.

Porcine dorsal root ganglia ovarian neurons are affected by long lasting testosterone treatment

We studied the effect of testosterone overdose on the number, distribution and chemical coding of ovarian neurons in the dorsal root ganglia (DRGs) in pigs. On day 3 of the estrous cycle, the ovaries of both the control and experimental gilts were injected with retrograde tracer Fast Blue. From day 4 of the estrous cycle to the expected day 20 of the second studied cycle, the experimental gilts were injected with testosterone, while the control gilts received oil. After the completion of the protocol the Th16-L5 DRGs were collected. Injections of testosterone increased the testosterone (~3.5 fold) and estradiol-17beta (~1.6 fold) levels in the peripheral blood, and reduced the following in the DRGs: the total number of the Fast Blue-positive perikarya, the population of perikarya in the L2-L4 ganglia, and the numbers of SP(+)/CGRP(+), SP(+)/PACAP(+), SP(+)/nNOS(+) and SP(-)/nNOS(+) perikarya. In the testosterone-injected gilts, the populations of SP(+)CGRP(-), small and large androgen receptors-expressing perikarya were increased. These results suggest that elevated androgen levels during pathological states may regulate the transmission of sensory modalities from the ovary to the spinal cord, and antidromic regulation of the ovarian functions.

Positive association of female overactive bladder symptoms and estrogen deprivation: A nationwide population-based cohort study in Taiwan

OBJECTIVE

Estrogen is considered to be a unique hormone in females that has an impact on voiding function. Animal models and clinical epidemiologic studies showed high correlation between estrogen deficiency and female overactive bladder (OAB) symptoms. We designed a population-based cohort study from a national health database to assess the association of estrogen deprivation therapy and female OAB.

MATERIALS AND METHODS

This study examined the records of 16,128 patients ranging in age from 18 to 40 that were included in the Taiwan National Health Insurance Research Database (NHIRD) in the years between 2001 and 2010. Of these, 1008 had breast cancer with hormone therapy only and the other 15,120 controls did not have breast cancer or hormone therapy. All patients with neurologic diseases and those with pre-existing OAB identified by information in the NHIRD database were excluded. OAB was defined by medications prescribed for at least 1 month. Risk of new onset OAB in the breast cancer and nonbreast cancer groups was estimated. Fourteen patients (1.4%) experienced OAB in the breast cancer group. Overall, breast cancer with estrogen deprivation therapy increased the risk of OAB by 14.37-fold (adjusted hazard ratio, 95% confidence interval 7.06-29.27). Subgroup analysis showed that in the older age breast cancer group (36-40), a lower Charlson comorbidity index (CCI) score and antidepressant medication use for at least 30 days had an impact on the increase of OAB risk. After adjustment of variables, the higher CCI and the use of antipsychotic drugs increased risk of OAB 3.45-fold and 7.45-fold, respectively. The Kaplan-Meier analysis of OAB-free survival in the breast cancer group showed a significant time-dependent increase in incidence of OAB.

CONCLUSION

Estrogen deprivation in young patients with breast cancer increased the risk of OAB. The OAB development rate was steady and fast in the beginning 3 years after estrogen deprivation. This result indicates a role of estrogen in the modulation of female voiding function.

The Role of Sensory Neurons in Cervical Ripening: Effects of Estrogen and Neuropeptides

Central nervous system nuclei and circuits, such as the medial preoptic, ventromedial and paraventricular nuclei of the hypothalamus, play important roles in reproduction and parturition, and are influenced by estrogen. Peripheral autonomic and sensory neurons also play important roles in pregnancy and parturition. Moreover, the steroid hormone estrogen acts directly, not only on the reproductive tract organs (uterus and cervix), but also on the central and peripheral nerves by regulating expression of various neuronal genes. The peripheral primary afferent neurons innervating the uterine cervix relay mechanical and biochemical sensory information induced by local cervical events and by passage of fetuses, to the spinal cord and supraspinal centers. Consequently, the birth process in mammals is influenced by the combined action of neurons and hormones. Peripheral sensory stimuli, induced physiologically by fetal expulsion or mechanically by vaginocervical stimulation, alter behavior, as well as autonomic and neuroendocrine systems. Recent evidence indicates that primary afferent neurons innervating the cervix, in addition to their sensory effects, likely exert local “efferent” actions on the ripening cervix near term. These efferent effects may involve estrogen-regulated production of such neuropeptides as substance P and calcitonin gene-related peptide in lumbosacral dorsal root ganglia, and their release in the cervix. Collectively, these findings suggest an interrelationship among estrogen, cervix-related sensory neurons, and local cervical events near term.

Conventional versus nerve-sparing radical surgery for cervical cancer: a meta-analysis

Objective

Although nerve-sparing radical surgery (NSRS) is an emerging technique for reducing surgery-related dysfunctions, its efficacy is controversial in patients with cervical cancer. Thus, we performed a meta-analysis to compare clinical outcomes, and urinary, anorectal, and sexual dysfunctions between conventional radical surgery (CRS) and NSRS.

Methods

After searching PubMed, Embase, and the Cochrane Library, two randomized controlled trials, seven prospective and eleven retrospective cohort studies were included with 2,253 patients from January 2000 to February 2014. We performed crude analyses and then conducted subgroup analyses according to study design, quality of study, surgical approach, radicality, and adjustment for potential confounding factors.

Results

Crude analyses showed decreases in blood loss, hospital stay, frequency of intraoperative complications, length of the resected vagina, duration of postoperative catheterization (DPC), urinary frequency, and abnormal sensation in NSRS, whereas there were no significant differences in other clinical parameters and dysfunctions between CRS and NSRS. In subgroup analyses, operative time was longer (standardized difference in means, 0.948; 95% confidence interval [CI], 0.642 to 1.253), while intraoperative complications were less common (odds ratio, 0.147; 95% CI, 0.035 to 0.621) in NSRS. Furthermore, subgroup analyses showed that DPC was shorter, urinary incontinence or frequency, and constipation were less frequent in NSRS without adverse effects on survival and sexual functions.

Conclusion

NSRS may not affect prognosis and sexual dysfunctions in patients with cervical cancer, whereas it may decrease intraoperative complications, and urinary and anorectal dysfunctions despite long operative time and short length of the resected vagina when compared with CRS.

Estrogen and female reproductive tract innervation: cellular and molecular mechanisms of autonomic neuroplasticity

The female reproductive tract undergoes remarkable functional and structural changes associated with cycling, conception and pregnancy, and it is likely advantageous to both individual and species to alter relationships between reproductive tissues and innervation. For several decades, it has been appreciated that the mammalian uterus undergoes massive sympathetic axon depletion in late pregnancy, possibly representing an adaptation to promote smooth muscle quiescence and sustained blood flow. Innervation to other structures such as cervix and vagina also undergo pregnancy-related changes in innervation that may facilitate parturition. These tissues provide highly tractable models for examining cellular and molecular mechanisms underlying peripheral nervous system plasticity. Studies show that estrogen elicits rapid degeneration of sympathetic terminal axons in myometrium, which regenerate under low-estrogen conditions. Degeneration is mediated by the target tissue: under estrogen's influence, the myometrium produces proteins repulsive to sympathetic axons including BDNF, neurotrimin, semaphorins, and pro-NGF, and extracellular matrix components are remodeled. Interestingly, nerve depletion does not involve diminished levels of classical sympathetic neurotrophins that promote axon growth. Estrogen also affects sympathetic neuron neurotrophin receptor expression in ways that appear to favor pro-degenerative effects of the target tissue. In contrast to the uterus, estrogen depletes vaginal autonomic and nociceptive axons, with the latter driven in part by estrogen-induced suppression of BMP4 synthesis. These findings illustrate that hormonally mediated physiological plasticity is a highly complex phenomenon involving multiple, predominantly repulsive target-derived factors acting in concert to achieve rapid and selective reductions in innervation.

Female reproductive tract pain: targets, challenges, and outcomes

Pain from the female reproductive tract (FRT) is a significant clinical problem for which there are few effective therapies. The complex neuroanatomy of pelvic organs not only makes diagnosis of pelvic pain disorders difficult but represents a challenge to development of targeted therapies. A number of potential therapeutic targets have been identified on sensory neurons supplying the FRT but our knowledge on the basic neurophysiology of these neurons is limited compared with other viscera. Until this is addressed we can only guess if the new experimental therapies proposed for somatic, gastrointestinal, or bladder pain will translate to the FRT. Once suitable therapeutic targets become clear, the next challenge is drug delivery. The FRT represents a promising system for topical drug delivery that could be tailored to act locally or systemically depending on formulation. Development of these therapies and their delivery systems will need to be done in concert with more robust in vivo and in vitro models of FRT pain.

Effects of agonists for estrogen receptor α and β on ovariectomy-induced lower urinary tract dysfunction in the rat

The postmenopausal hypoestrogen status induces various lower urinary tract dysfunctions. Ovariectomized (OVX) rats exhibit voiding abnormalities, including increased postvoiding residual urine (PVR), decreased voiding efficiency (VE), and altered coordination between the detrusor and external urethral sphincter (EUS). Estradiol replacement partially normalizes voiding function in OVX rats. We determined if selective agonists for estrogen receptor (ER)α and/or ERβ can reverse lower urinary tract dysfunction in OVX rats. Cystometry and EUS electromyograms (EMGs) were recorded 6 wk after bilateral OVX in urethane-anesthetized female Sprague-Dawley rats. Animals received daily subcutaneous injections of selective ERα [propylpyrazole triol (PPT)] or ERβ [diarylpropionitrile (DPN)] agonists or vehicle for 1 wk starting on the fifth week after OVX. PPT (1 mg·kg(-1)·day(-1)) decreased PVR, improved VE, and shortened the EUS EMG active period (AP) during voiding. DPN (2 or 5 mg·kg(-1)·day(-1)) did not alter cystometric parameters or EUS EMG activity. Combined PPT + DPN treatment elicited changes in PVR, VE, and AP, similar to those induced by PPT alone, but also increased the EUS EMG silent period and volume threshold for triggering micturition. PPT increased uterine weight fourfold and decreased body weight by 11%. DPN increased uterine weight 30-45% but decreased body weight by 3-5%. Reduced voiding efficiency in OVX rats can be reversed by 1-wk drug treatment that selectively targets ERα and reduces AP during EUS bursting. Combined pharmacological activation of ERα and ERβ further enhanced EUS bursting by increasing the EUS EMG silent period and also facilitated bladder storage mechanisms by increasing the volume threshold.

Interaction between P2X3 and oestrogen receptor (ER)α/ERβ in ATP-mediated calcium signalling in mice sensory neurones

Emerging evidence supports a role of purinergic P2X3 receptors in modulating nociceptive signalling in sensory neurones. Previously, we showed that dorsal root ganglion (DRG) neurones (L1-S1) express both oestrogen receptor (ER)α and ERβ receptors. In the present study, we investigated the expression of P2X3 receptors and the effect of 17β-oestradiol (E(2)) on the ATP-induced [Ca(2+)](i) increase in DRG neurones collected from C57Bl/6J, ERα knockout (KO) and ERβKO mice. Our data showed a significant decrease for P2X3 in ERαKO (all levels) and ERβKO (mostly observed in L1, L2, L4 and L6). Furthermore, E(2) (100 nm) significantly attenuated the ATP (10 μm)-induced [Ca(2+)](i) in C57Bl/6J mice. ER antagonist ICI 182,780 (1 μm) blocked this attenuation. Homomeric P2X3 receptors are plentifully expressed in DRG neurones and contribute to nociceptive signals. α,β-Methylene (α,β-me) ATP, which is a specific agonist of P2X2/3 receptors, showed similar responses to the ATP-induced calcium increase in KO mice. A membrane-impermeable E-6-bovine serum albumin (1 μm) had the same effect as E(2) , suggesting action on the membrane. In DRG neurones from ERβKO and wild-type mice, E(2) attenuated the ATP/α,β-me ATP-induced [Ca(2+)](i) fluxes but, in DRG neurones from ERαKO mice, this hormone had no effect, suggesting that this attenuation depends on membrane-associated ERα receptors. Together, our data indicate an interaction between P2X3 and membrane-associated ERα in primary sensory neurones that may represent a novel mechanism to explain sex differences observed in the clinical presentation of visceral nociceptive syndromes.

17β-estradiol and progesterone independently augment cutaneous thermal hyperemia but not reactive hyperemia

OBJECTIVE

We examined the impact of estradiol and progesterone on skin LH and RH in 25 healthy women.

METHODS

Subjects were studied three times over 10-12 days. Endogenous sex hormones were suppressed with a GnRHa. Subjects were studied on day 4 of suppression (study day 1), three to four days later following treatment with either 17β-estradiol or progesterone (study day 2), and another three to four days later, following treatment with both estradiol and progesterone (study day 3). Subjects underwent identical LH and RH protocols on all study days. LH is characterized by an initial peak in blood flow, followed by a prolonged plateau. A brief nadir is seen between the phases.

RESULTS

Blood flow values are expressed as percent maximum CVC. Estradiol alone increased initial peak CVC from 71 ± 2% to 79 ± 2% (p = 0.001). Progesterone alone increased initial peak CVC from 72 ± 2% to 78 ± 2% (p = 0.046). Neither estradiol nor progesterone increased plateau CVC. No significant changes were seen between study days 2 and 3 for either group. No differences were observed in RH.

CONCLUSIONS

Both estradiol and progesterone increased initial peak CVC during LH, without altering plateau CVC. There was no additive effect of estradiol and progesterone.

Spinal cord processing of cardiac nociception: are there sex differences between male and proestrous female rats?

Sex differences in the characteristics of cardiac pain have been reported from clinical studies. For example, women experience chest pain less frequently than men. Women describe their chest pain as sharp and stabbing, while men have chest pain that is felt as a pressure or heaviness. Pain is also referred to the back more often in women than men. The mechanisms underlying sex differences in cardiac pain are unknown. One possible mechanism for the observed differences could be related to plasma estradiol. This study investigated the actions of estradiol on the activity of T(3) spinal neurons that process cardiosomatic information in male and female rats. Extracellular potentials of T(3) spinal neurons were recorded in response to mechanical somatic stimulation and noxious chemical cardiac stimulation in pentobarbital-anesthetized male and proestrous female rats. Fifty one percent and fifty percent of neurons responded to intrapericardial algogenic chemicals (0.2 ml) in male and female rats, respectively. Somatic fields were located by applying brush, pressure, and pinch to the upper body. Of those neurons receiving cardiac input, 54% in female and 55% in male rats also received somatic input. In both male and female rats, 81% of neurons responding to somatic stimuli had somatic fields located on the side of the upper body, while 19% of neurons had somatic fields located on the chest. These results indicate there are no significant differences in the responses of T(3) spinal neurons to cardiosomatic stimulation between male and proestrous female rats, despite differences in estradiol levels.

Effect of ovariectomy on external urethral sphincter activity in anesthetized female rats

PURPOSE

The postmenopausal hypoestrogen condition is associated with various lower urinary tract dysfunctions, including frequency, urgency, stress urinary incontinence and recurrent urinary infection. We determined whether hypoestrogen induced lower urinary tract dysfunction after ovariectomy is also associated with an alteration in external urethral sphincter activity.

MATERIALS AND METHODS

Bilateral ovariectomy was performed in female Sprague-Dawley® rats and sham operated rats served as controls. Transvesical cystometry and external urethral sphincter electromyogram activity were monitored 4, 6 and 12 weeks after sham operation or bilateral ovariectomy and at 6 weeks in bilaterally ovariectomized rats treated with estrogen.

RESULTS

The micturition reflex was elicited in sham operated and bilaterally ovariectomized, urethane anesthetized animals. Post-void residual urine increased and voiding efficiency decreased in rats with 4 to 12 weeks of bilateral ovariectomy. The silent period of external urethral sphincter electromyogram activity was shortened significantly and progressively at increased times after bilateral ovariectomy. These effects were prevented by estradiol treatment.

CONCLUSIONS

As evidenced by shortening of the external urethral sphincter electromyogram silent period in ovariectomized rats, the disruption of coordination between the external urethral sphincter and the detrusor muscle could decrease urine outflow and in turn voiding efficiency. Estrogen replacement reverses these changes, suggesting that the central pathways responsible for detrusor-sphincter coordination are modulated by gonadal hormones.

Potentiation of excitatory transmission in substantia gelatinosa neurons of rat spinal cord by inhibition of estrogen receptor alpha

Background

It has been shown that estrogen is synthesized in the spinal dorsal horn and plays a role in modulating pain transmission. One of the estrogen receptor (ER) subtypes, estrogen receptor alpha (ERα), is expressed in the spinal laminae I-V, including substantia gelatinosa (SG, lamina II). However, it is unclear how ERs are involved in the modulation of nociceptive transmission.

Results

In the present study, a selective ERα antagonist, methyl-piperidino-pyrazole (MPP), was used to test the potential functional roles of spinal ERα in the nociceptive transmission. Using the whole-cell patch-clamp technique, we examined the effects of MPP on SG neurons in the dorsal root-attached spinal cord slice prepared from adult rats. We found that MPP increased glutamatergic excitatory postsynaptic currents (EPSCs) evoked by the stimulation of either Aδ- or C-afferent fibers. Further studies showed that MPP treatment dose-dependently increased spontaneous EPSCs frequency in SG neurons, while not affecting the amplitude. In addition, the PKC was involved in the MPP-induced enhancement of synaptic transmission.

Conclusions

These results suggest that the selective ERα antagonist MPP pre-synaptically facilitates the excitatory synaptic transmission to SG neurons. The nociceptive transmission evoked by Aδ- and C-fiber stimulation could be potentiated by blocking ERα in the spinal neurons. Thus, the spinal estrogen may negatively regulate the nociceptive transmission through the activation of ERα.

Effects of estrogens and bladder inflammation on mitogen-activated protein kinases in lumbosacral dorsal root ganglia from adult female rats

Background

Interstitial cystitis is a chronic condition associated with bladder inflammation and, like a number of other chronic pain states, symptoms associated with interstitial cystitis are more common in females and fluctuate during the menstrual cycle. The aim of this study was to determine if estrogens could directly modulate signalling pathways within bladder sensory neurons, such as extracellular signal-related kinase (ERK) and p38 mitogen-activated protein (MAP) kinases. These signalling pathways have been implicated in neuronal plasticity underlying development of inflammatory somatic pain but have not been as extensively investigated in visceral nociceptors. We have focused on lumbosacral dorsal root ganglion (DRG) neurons projecting to pelvic viscera (L1, L2, L6, S1) of adult female Sprague-Dawley rats and performed both in vitro and in vivo manipulations to compare the effects of short- and long-term changes in estrogen levels on MAPK expression and activation. We have also investigated if prolonged estrogen deprivation influences the effects of lower urinary tract inflammation on MAPK signalling.

Results

In studies of isolated DRG neurons in short-term (overnight) culture, we found that estradiol and estrogen receptor (ER) agonists rapidly stimulated ER-dependent p38 phosphorylation relative to total p38. Examination of DRGs following chronic estrogen deprivation in vivo (ovariectomy) showed a parallel increase in total and phosphorylated p38 (relative to β-tubulin). We also observed an increase in ERK1 phosphorylation (relative to total ERK1), but no change in ERK1 expression (relative to β-tubulin). We observed no change in ERK2 expression or phosphorylation. Although ovariectomy increased the level of phosphorylated ERK1 (vs. total ERK1), cyclophosphamide-induced lower urinary tract inflammation did not cause a net increase of either ERK1 or ERK2, or their phosphorylation. Inflammation did, however, cause an increase in p38 protein levels, relative to β-tubulin. Prior ovariectomy did not alter the response to inflammation.

Conclusions

These results provide new insights into the complex effects of estrogens on bladder nociceptor signalling. The diversity of estrogen actions in these ganglia raises the possibility of developing new ways to modulate their function in pelvic hyperactivity or pain states.

17Beta-estradiol restores excitability of a sexually dimorphic subset of myelinated vagal afferents in ovariectomized rats

We recently identified a myelinated vagal afferent subpopulation (Ah type) far more prevalent in female than male rats and showed that this difference extends to functionally specific visceral sensory afferents, baroreceptors of the aortic arch. Excitability of myelinated Ah-type afferents is markedly reduced after ovariectomy (OVX). Here we tested the hypothesis that 17beta-estradiol can selectively restore excitability of these sex-specific vagal afferents. Acutely isolated vagal afferent neurons (VGN) from intact and OVX adult female rats were used with patch-clamp technique and current-clamp protocols to assess the effect of acute application of 17beta-estradiol on neuronal excitability. At over physiologically relevant 17beta-estradiol concentrations for rat (1-10 nM) excitability of myelinated Ah-type vagal afferents is restored to discharge frequencies comparable to those in intact females, albeit with some interesting differences related to burst and sustained patterns of neuronal discharge. Restoration of excitability occurs within 3 min of hormone application and is stereo specific, because 1,000 nM 17alpha-estradiol fails to alter excitability. Furthermore, activation of G protein-coupled estrogen receptor GPR30 with highly selective agonist G-1 similarly restores excitability of Ah-type afferents. The effectiveness of 17beta-estradiol and G-1 is completely eliminated by application of high-affinity estrogen receptor ligand ICI-182,780. 17beta-Estradiol conjugated with BSA is approximately 70% as effective as 17beta-estradiol alone in restoring Ah-type VGN excitability. These data support our conclusions that the cellular mechanisms leading to rapid restoration of neuronal excitability of myelinated Ah-type VGN after OVX occur, at least in part, via membrane-bound estrogen receptors. We contend that recovery of high-frequency discharge at physiologically relevant 17beta-estradiol concentrations implies that this unique subtype of low-threshold myelinated vagal afferent may account for some of the sex-related differences in visceral organ system function. Sex differences in cardiovascular and gastrointestinal function and the potential role of GPR30 in modulation of sex-specific myelinated Ah-type vagal afferents are discussed.

The gad2 promoter is a transcriptional target of estrogen receptor (ER)alpha and ER beta: a unifying hypothesis to explain diverse effects of estradiol

Estradiol (E(2)) regulates a wide range of neural functions, many of which require activation of estrogen receptor alpha (ERalpha) and/or ERbeta, ligand-gated transcriptional regulators. Surprisingly, very few neural gene targets of ERs have been identified, and these cannot easily explain the myriad effects of E(2). GABA regulates most of the same neural functions as E(2), and GABAergic neurons throughout the brain contain ER. Therefore, we examined whether E(2) directly regulates expression of glutamic acid decarboxylase 2 (gad2), the enzyme primarily responsible for GABA synthesis for synaptic release. Using dual luciferase assays, we found that E(2), but not other gonadal steroids, stimulated the activity of a 2691 bp rat gad2 promoter reporter construct. Activation required either ERalpha or ERbeta, and ERbeta did not repress ERalpha-mediated transactivation. Site-directed mutagenesis studies identified three estrogen response elements (EREs) with cell-specific functions. An ERE at -711 upstream of the gad2 translational start site was essential for transactivation in both MCF-7 breast cancer cells and SN56.B5.G4 neural cells, but an ERE at -546 enhanced transcription only in neural cells. A third ERE at -1958 was inactive in neural cells but exerted potent transcriptional repression in E(2)-treated MCF-7 cells. Chromatin immunoprecipitation assays in mouse GABAergic N42 cells confirmed that E(2) induced ERalpha binding to a DNA fragment containing sequences corresponding to the -546 and -711 EREs of the rat promoter. Based on these data, we propose that direct transcriptional regulation of gad2 may explain, at least in part, the ability of E(2) to impact such a diverse array of neural functions.

Inflammation in the uterus induces phosphorylated extracellular signal-regulated kinase and substance P immunoreactivity in dorsal root ganglia neurons innervating both uterus and colon in rats

In women, clinical studies suggest that pain syndromes such as irritable bowel syndrome and interstitial cystitis, which are associated with visceral hyperalgesia, are often comorbid with endometriosis and chronic pelvic pain. One of the possible explanations for this phenomenon is viscerovisceral cross-sensitization, in which increased nociceptive input from an inflamed pelvic organ sensitizes neurons that receive convergent input to the same dorsal root ganglion (DRG) from an unaffected visceral organ. Nociception induces up-regulation of cellular mechanisms such as phosphorylated extracellular signal-regulated kinase (pERK) and substance P (SP), neurotransmitters associated with induced pain sensation. The purpose of this study was to determine, in a rodent model, whether uterine inflammation increased the number of pERK- and SP-positive neurons that received input from both the uterus and the colon. Cell bodies of colonic and uterine DRG were retrogradely labeled with fluorescent tracer dyes microinjected into the colon/rectum and into the uterus. Ganglia were harvested for fluorescent microscopy to identify positively stained neurons. Approximately 6% of neurons were colon specific and 10% uterus specific. Among these uterus- or colon-specific neurons, up to 3-5% of DRG neurons in the lumbosacral neurons (L1-S3 levels) received input from both visceral organs. Uterine inflammation increased the number of pERK- and SP-immunoreactive DRG neurons innervating specifically colon, or innervating specifically uterus, and those innervating both organs. These results suggest that a localized inflammation activates primary visceral afferents, regardless of whether they innervate the affected organ. This visceral sensory integration in the DRG may underlie the observed comorbidity of female pelvic pain syndromes.

Vaginal blood flow after radical hysterectomy with and without nerve sparing. A preliminary report

Radical hysterectomy with pelvic lymphadenectomy (RHL) for cervical cancer causes damage to the autonomic nerves, which are responsible for increased vaginal blood flow during sexual arousal. The aim of the study of which we now report preliminary data was to determine whether a nerve-sparing technique leads to an objectively less disturbed vaginal blood flow response during sexual stimulation. Photoplethysmographic assessment of vaginal pulse amplitude (VPA) during sexual stimulation by erotic films was performed. Subjective sexual arousal was assessed after each stimulus. Thirteen women after conventional RHL, 10 women after nerve-sparing RHL, and 14 healthy premenopausal women participated. Data were collected between January and August 2006. The main outcome measure was the logarithmically transformed mean VPA. To detect statistically significant differences in mean VPA levels between the three groups, a univariate analysis of variance was used. Mean VPA differed between the three groups (P= 0.014). The conventional group had a lower vaginal blood flow response than the control group (P= 0.016), which tended also to be lower than that of the nerve-sparing group (P= 0.097). These differences were critically dependent on baseline vaginal blood flow differences between the groups. The conventional group follows a vaginal blood flow pattern similar to postmenopausal women. Conventional RHL is associated with an overall disturbed vaginal blood flow response compared with healthy controls. Because it is not observed to the same extent after nerve-sparing RHL, it seems that the nerve-sparing technique leads to a better overall vaginal blood flow caused by less denervation of the vagina.

Anatomical and physiological properties of pelvic ganglion neurons in female mice

Most neurons that regulate motility and blood flow in female pelvic organs are located within pelvic (paracervical) ganglia. In this study we investigated the anatomical and physiological properties of neurons within mouse (C57/Bl/6) paracervical ganglia. Most neurons showed immunoreactivity for choline acetyl transferase (CHAT) and were presumably cholinergic. Few neurons (approximately 5%) were tyrosine hydroxylase (TH) positive. Immunohistochemical labelling for microtubule associated protein 2 showed most neurons had small somata (cross sectional area approximately 300 microm(2)) and lacked dendrites. Action potential (AP) discharge characteristics, determined by depolarising current step injection, revealed most neurons (70%) adapted rapidly to depolarising current injection and were classified as "phasic". The remaining neurons discharged APs throughout the current step and were classified as "tonic". Membrane properties and current-voltage relationships were similar in phasic and tonic neurons, however the afterhyperpolarisation was significantly smaller in tonic neurons. Stimulation of preganglionic axons usually evoked a single strong preganglionic input (21/27 and 9/10 for pelvic and hypogastric nerves, respectively). In 19 preparations where we tested for inputs from both nerves pelvic inputs predominated (23/45 neurons) and inputs via the hypogastric nerve were rarely observed (3/45 neurons). Together, our data indicate that most neurons within mouse paracervical ganglia are cholinergic and parasympathetic. As there is little anatomical or functional evidence for integration of preganglionic inputs we propose that the role of paracervical neurons is restricted to one of spatial amplification or filtering of preganglionic inputs.

Carpal tunnel syndrome in postmenopausal women

OBJECTIVE

Hormonal changes that accompany menopause have a significant impact on the nervous and other physiological systems. Our objective was to evaluate the relationship between carpal tunnel syndrome (CTS) and the clinical features of menopause in postmenopausal women, in comparison to age-matched healthy controls.

METHODS

Overall, 6230 women were seen during the study period. Of these, 5587 were not eligible because they were premenopausal or perimenopausal. 537 women did not meet the criteria used in the study for a diagnosis of idiopathic CTS and were excluded. Finally, one hundred and six patients with CTS and 115 controls were examined. The presence of CTS was confirmed both clinically and electrophysiologically. Socio-demographic variables and reproductive histories were evaluated via a structured interview.

RESULTS

In comparison to healthy controls, patients with CTS showed a significantly greater number of pregnancies and an earlier age at menopause. Regarding the type of menopause, patients and controls showed similar frequencies for natural versus surgical menopause. The frequency of natural menopause was significantly higher than that of surgical menopause in both groups.

CONCLUSION

Our results suggest that age at menopause may be a significant factor in the development of CTS. Pregnancy-related hormonal changes may have long-term effects that increase the incidence of CTS in postmenopausal women.

Return of chronic pelvic pain from endometriosis after raloxifene treatment: a randomized controlled trial

OBJECTIVE

To evaluate whether 6 months of raloxifene was effective in treatment of chronic pelvic pain in women with endometriosis.

METHODS

Women with chronic pelvic pain and no endometriosis treatment for 6 months underwent laparoscopy for excision of all lesions. Those with biopsy-proven endometriosis were randomly allocated to raloxifene (180 mg) or placebo daily. A second laparoscopy was performed at 2 years, or earlier, if pain returned. Return of pain was defined as 2 months of pain equal to or more severe than that at study entry. Menstrual cycles and adverse events were recorded. The log rank test was used to compare the time to return of pain by drug group. Analyses were done as intent-to-treat.

RESULTS

A total of 127 of 158 women underwent surgery. Of these, 93 had biopsy-confirmed endometriosis and were randomly assigned to study treatment. Menstrual cycle length, pelvic pain severity, quality of life, bone mineral density, and adverse events did not differ between treatment groups. The Data Safety Monitoring Committee terminated the study early when the raloxifene group experienced pain (P=.03) and had second surgery (P=.016) significantly sooner than the placebo group. Interestingly, biopsy-proven endometriosis was not associated with return of pain (P=.6).

CONCLUSION

Raloxifene significantly shortened the time to return of chronic pelvic pain. Because recurrence of endometriosis lesions did not correlate with return of pain, other factors are implicated in pelvic pain.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, www.cliicaltrials.gov, NCT00001848

LEVEL OF EVIDENCE

I.

Estrogen receptor beta is essential for sprouting of nociceptive primary afferents and for morphogenesis and maintenance of the dorsal horn interneurons

Estrogen is known to influence pain, but the specific roles of the two estrogen receptors (ERs) in the spinal cord are unknown. In the present study, we have examined the expression of ERalpha and ERbeta in the spinal cord and have looked for defects in pain pathways in ERbeta knockout (ERbeta(-/-)) mice. In the spinal cords of 10-month-old WT mice, ERbeta-positive cells were localized in lamina II, whereas ERalpha-positive cells were mainly localized in lamina I. In ERbeta(-/-) mice, there were higher levels of calcitonin gene-regulated peptide and substance P in spinal cord dorsal horn and isolectin B4 in the dorsal root ganglion. In the superficial layers of the spinal cord, there was a decrease in the number of calretinin (CR)-positive neurons, and in the outer layer II, there was a loss of calbindin-positive interneurons. During embryogenesis, ERbeta was first detectable in the spinal cord at embryonic day 13.5 (E13.5), and ERalpha was first detectable at E15.5. During middle and later embryonic stages, ERbeta was abundantly expressed in the superficial layers of the dorsal horn. ERalpha was also expressed in the dorsal horn but was limited to fewer neurons. Double staining for ERbeta and CR showed that, in the superficial dorsal horn of WT neonates [postnatal day 0 (P0)], most CR neurons also expressed ERbeta. At this stage, few CR-positive cells were detected in the dorsal horn of ERbeta(-/-) mice. Taken together, these findings suggest that, early in embryogenesis, ERbeta is involved in dorsal horn morphogenesis and in sensory afferent fiber projections to the dorsal horn and that ERbeta is essential for survival of dorsal horn interneurons throughout life.

Glutamate and metabotropic glutamate receptors associated with innervation of the uterine cervix during pregnancy: Receptor antagonism inhibits c-fos expression in rat lumbosacral spinal cord at parturition

Dorsal root ganglia (DRG) neurons connect the spinal cord and uterine cervix, and are activated at parturition with subsequent stimulation of secondary neurons in the spinal dorsal horn and autonomic areas. Neuropeptide neurotransmitters and receptors have been studied in these areas, but amino acid transmitters, e.g., glutamate, an excitatory neurotransmitter involved in sensory and nociceptive processing, have not been characterized. To determine if glutamate is involved in innervation of the cervix, rats were examined for markers of glutamatergic neurons in the L6-S1 spinal cord, DRG and cervix. Metabotropic glutamate receptors mGluR5 in the spinal dorsal horn and their expression over pregnancy were examined in pregnant rats and pregnant rats treated continuously with an antagonist of mGluR5, 2-methyl-6-(phenylethynyl) pyridine (MPEP). Rats were allowed to deliver pups to determine if the antagonist altered the expression of an early response gene protein, Fos, in the L6-S1 cord. Immunohistochemistry showed glutamate- and vesicular glutamate transporter1 (VGluT1)-positive fibers in the cervix, glutamate- and VGluT1-expressing neurons in the DRG, some of which also exhibited retrograde tracer from cervical injections, and VGluT1 and mGluR5 immunoreactivities in the L6-S1 spinal dorsal horns. Expression of mGluR5 receptors increased over pregnancy. Fos-positive neurons were present among mGluR5-immunoreactivity in the spinal dorsal horn. Parturition-induced Fos-positive neurons in the spinal cords were abundant in control rats, but were reduced by 70% in MPEP-treated animals. These results suggest that glutamate is likely involved in the transmission of sensory signals, possibly pain, from the cervix to the spinal cord at parturition.

The effects of ovariectomy and estrogen replacement on acetylcholine release from nerve fibres and passive stretch-induced acetylcholine release in female rat bladder

AIMS

The present study investigated the effects of ovariectomy and estrogen replacement on the release of acetylcholine (Ach) from cholinergic neurons as well as on the tetrodotoxin (TTX)-insensitive stretch-induced Ach release in isolated rat detrusor. In addition, the above effects on rat micturition characteristics were also studied.

METHODS

Thirty female rats randomly received a sham operation, ovariectomy, or ovariectomy plus estrogen replacement. Using metabolic cages, micturition parameters were recorded. Then, in vitro functional experiments that included the measurements of nerve-mediated detrusor muscle contraction, Ach release from nerve fibres, and stretch-induced TTX-insensitive Ach release were performed. Ach release was measured using microdialysis and high-performance liquid chromatography.

RESULTS

Ovariectomized rats showed a significant decrease in voided volume and significant increase in 24-hr frequency of voiding. Ovariectomy caused the significant increase in both TTX-insensitive basal Ach release and TTX-insensitive stretch-induced Ach release. On the other hand, ovariectomy caused a significant decrease in Ach release from nerve fibres, resulting in the decrease in the contractile responses of detrusor muscle to electrical nerve stimulation. Estrogen replacement restored these alterations induced by ovariectomy.

CONCLUSIONS

Our findings showed that as a results of estrogen deficiency, Ach release from nerve fibres decreased, suggesting that this reduction of Ach released from cholinergic nerves may cause the decrease in detrusor contractility. Furthermore, this study also demonstrated that stretch-induced TTX-insensitive Ach release was increased by ovariectomy. This may be a contributing factor to the development of overactive bladder in elderly women.

Cross-organ interactions between reproductive, gastrointestinal, and urinary tracts: modulation by estrous stage and involvement of the hypogastric nerve

Central nervous system neurons process information converging from the uterus, colon, and bladder, partly via the hypogastric nerve. This processing is influenced by the estrous cycle, suggesting the existence of an estrous-modifiable central nervous system substrate by which input from one pelvic organ can influence functioning of other pelvic organs. Here, we tested predictions from this hypothesis that acute inflammation of colon, uterine horn, or bladder would produce signs of inflammation in the other uninflamed organs (increase vascular permeability) and that cross-organ effects would vary with estrous and be eliminated by hypogastric neurectomy (HYPX). Under urethane anesthesia, the colon, uterine horn, or bladder of rats in proestrus or metestrus, with or without prior HYPX, was treated with mustard oil or saline. Two hours later, Evans Blue dye extravasation was measured to assess vascular permeability. Extravasation was increased in all inflamed organs, regardless of estrous stage. For rats in proestrus, but not metestrus, either colon or uterine horn inflammation significantly increased extravasation in the uninflamed bladder. Much smaller cross-organ effects were seen in colon and uterine horn. HYPX reduced extravasation in the inflamed colon and inflamed uterine horn, but not the inflamed bladder. HYPX eliminated the colon-to-bladder and uterine horn-to-bladder effects. These results demonstrate that inflaming one pelvic organ can produce estrous-modifiable signs of inflammation in other pelvic organs, particularly bladder, and suggest that the cross-organ effects involve the hypogastric nerve and are at least partly centrally mediated. Such effects could contribute to cooccurrence and cyclicity of distressing pelvic disorders in women.

Involvement of the coeliac ganglion in the luteotrophic effect of androstenedione in late pregnant rats

Using the ex vivo coeliac ganglion-superior ovarian nerve-ovary system at the end of pregnancy when luteal regression starts, we investigated whether, when administered systemically or when added directly to the ganglion compartment, androstenedione (A2) can reverse such regression, and whether the neural (noradrenaline (NA)) and endocrine (A2) joint action modifies the release of ovarian progesterone. The experimental groups were as follows: group 1 – A2 injected systemically 48 h before incubation of the system (A2)s; group 2 – A2 directly added to the ganglion compartment (A2)g; group 3 – A2 injected 48 h before incubation of the system with NA in the ganglion compartment (A2 + NA); group 4 – A2 plus NA added to the ganglion compartment (NA + A2)g. The controls were ex vivo systems without treatment (control), and with the addition of NA alone in the ganglion compartment (NA). The results were as follows. For (A2)s versus control, progesterone increased on days 19 and 21 of pregnancy at all the studied times and only at 180 min on day 20. For (A2 + NA) versus (A2)s, progesterone increased on days 19 and 21. For (A2 + NA) versus NA, progesterone increased at all the studied times on days 19 and 21 and at 180 min on day 20. For (A2)g versus control, progesterone significantly increased every pregnancy day. For (NA + A2)g versus (A2)g, progesterone decreased at 120 and 180 min on day 19. For (NA + A2)g versus NA, progesterone increased on days 20 and 21. We can conclude that A2 can reverse the functional regression of the corpus luteum either systemically or, what is more surprising, when directly added to the coeliac ganglion, whose action on the ovary is exerted via superior ovarian nerve.

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.

Estrogen receptor-alpha mediates estradiol attenuation of ATP-induced Ca2+ signaling in mouse dorsal root ganglion neurons

A mechanism underlying gender-related differences in pain perception may be estrogen modulation of nociceptive signaling in the peripheral nervous system. In rat, dorsal root ganglion (DRG) neurons express estrogen receptors (ERs) and estrogen rapidly attenuates ATP-induced Ca2+ signaling. To determine which estrogen receptor mediates rapid actions of estrogen, we showed ERalpha and ERbeta expression in DRG neurons from wild-type (WT) female mice by RT-PCR. To study whether ERalpha or ERbeta mediates this response, we compared estradiol action mediating Ca2+ signaling in DRG neurons from WT, ERalpha knockout (ERalphaKO), and ERbetaKO mice in vitro. ATP, an algesic agent, induced [Ca2+]i transients in 48% of small DRG neurons from WT mice. 17beta-Estradiol (E2) inhibited ATP-induced intracellular Ca2+ concentration ([Ca2+]i) with an IC50 of 27 nM. The effect of E2 was rapid (5-min exposure) and stereo specific; 17alpha-estradiol had no effect. E2 action was blocked by the ER antagonist ICI 182,780 (1 microM) in WT mouse. Estradiol coupled to bovine serum albumin (E-6-BSA), which does not penetrate the plasma membrane, had the same effect as E2 did, suggesting that a membrane-associated ER mediated the response. In DRG neurons from ERbetaKO mice, E2 attenuated the ATP-induced [Ca2+]i flux as it did in WT mice, but in DRG neurons from ERalphaKO mice, E2 failed to inhibit the ATP-induced [Ca2+]i increase. These results show that mouse DRG neurons express ERs and the rapid attenuation of ATP-induced [Ca2+]i signaling is mediated by membrane-associated ERalpha.

The pains of endometriosis

Endometriosis is a disease defined by the presence of endometrial tissue outside of the uterus. Severe pelvic pain is often associated with endometriosis, and this pain can be diminished with therapies that suppress estrogen production. Many women with endometriosis also suffer from other chronic pain conditions. Recent studies suggest that mechanisms underlying these pains and sensitivity to estrogen involve the growth into the ectopic endometrial tissue of a nerve supply, which could have a varied and widespread influence on the activity of neurons throughout the central nervous system.

P2X receptors in the rat uterine cervix, lumbosacral dorsal root ganglia, and spinal cord during pregnancy

ATP, an intracellular energy source, is released from cells during tissue stress, damage, or inflammation. The P2X subtype of the ATP receptor is expressed in rat dorsal root ganglion (DRG) cells, spinal cord dorsal horn, and axons in peripheral tissues. ATP binding to P2X receptors on nociceptors generates signals that can be interpreted as pain from damaged tissue. We have hypothesized that tissue stress or damage in the uterine cervix during late pregnancy and parturition can lead to ATP release and sensory signaling via P2X receptors. Consequently, we have examined sensory pathways from the cervix in nonpregnant and pregnant rats for the presence of purinoceptors. Antiserum against the P2X3-receptor subtype showed P2X3- receptor immunoreactivity in axon-like structures of the cervix, in small and medium-sized neurons in the L6/S1 DRG, and in lamina II of the L6/S1 spinal cord segments. Retrograde tracing confirmed the projections of axons of P2X3-receptor-immunoreactive DRG neurons to the cervix. Some P2X3-receptor-positive DRG neurons also expressed estrogen receptor-alpha immunoreactivity and expressed the phosphorylated form of cyclic AMP response-element-binding protein at parturition. Western blots showed a trend toward increases of P2X3-receptor protein between pregnancy (day 10) and parturition (day 22-23) in the cervix, but no significant changes in the DRG or spinal cord. Since serum estrogen rises over pregnancy, estrogen may influence purinoceptors in these DRG neurons. We suggest that receptors responsive to ATP are expressed in uterine cervical afferent nerves that transmit sensory information to the spinal cord at parturition.

Spinal effects of oxytocin on uterine motility in anesthetized rats

The rat uterus receives an innervation from the lumbosacral and thoracolumbar segments of the spinal cord. These segments receive descending oxytocinergic projections from the paraventricular nucleus of the hypothalamus. We tested the hypothesis that oxytocin regulates uterine motility through a spinal site of action. Oxytocin was administered in anesthetized female rats either intrathecally at the lumbosacral or thoracolumbar spinal cord levels or intravenously. Uterine activity was revealed by measuring changes of intrauterine pressure using an indwelling balloon placed in one caudal uterine horn. The uterus displayed a spontaneous activity characterized by intrauterine pressure rises, the frequency, amplitude, and duration of which were dependent on the stage of the estrous cycle. Oxytocin delivered at the lumbosacral level affected the frequency (during proestrus, estrus, and diestrus) and amplitude (during proestrus and estrus) of uterine activity. During estrus, oxytocin delivered at the thoracolumbar level affected the frequency, amplitude, and duration of the intrauterine pressure rises. Intravenous oxytocin not only affected intrauterine pressure rises (namely amplitude during proestrus and estrus and frequency and duration during estrus) but also increased the basal tone during estrus. The effects of lumbosacral oxytocin were partly mimicked by the oxytocin agonist [Thr4,Gly7]-oxytocin blocked by the oxytocin receptor antagonist atosiban and by hexamethonium. Arginine vasopressin delivered at the lumbosacral level had no effect. These results support our hypothesis that oxytocin released by descending paraventriculo-spinal pathways and acting on spinal oxytocin receptors modulates the activity of the uterus. This regulation is cycle dependent.