Vaginal Blood Flow Research Articles

Endothelin-1 Induces Contraction of Female Rat Internal Pudendal and Clitoral Arteries through ETA Receptor and Rho-Kinase Activation

Endothelin-1 (ET-1), a potent vasoconstrictor peptide, acts mainly through the Gprotein-coupled ET(A) receptor (ET(A)R). Increased vascular ET-1 production and constrictor sensitivity have been observed in various cardiovascular diseases, including hypertension, as well as erectile dysfunction. The internal pudendal artery (IPA) supplies blood to the vagina and clitoris. Inadequate blood flow through the IPA may lead to insufficient vaginal engorgement and clitoral tumescence. Characterize the effects of ET-1 on the IPA and clitoral artery (CA). IPA and CA from female Sprague Dawley rats (225-250 g) were mounted in myograph chambers. Arterial segments were submitted to increasing concentrations of ET-1 (10-10-10-6 M). Segments were incubated with the ET(A)R antagonist, atrasentan (10-8 M) or the Rho-kinase inhibitor, Y-27632 (10-6 M) 30 minutes prior to agonist exposure. All E(max) values are expressed as % KCl-induced maximal contraction. ET(A)R, RhoA, and Rho-kinase expression from IPA was evaluated by Western blot. mRNA of preproET-1, ET(A)R, ET(B)R, RhoA, and Rho-kinase were measured by real time PCR. ET-1 constrictor sensitivity in IPA and CA, protein expression and messenger RNA levels of ET-1-mediated constriction components. ET-1 concentration-dependently contracted IPA (% Contraction and pD2, respectively: 156 ± 18, 8.2 ± 0.1) and CA (163 ± 12, 8.8 ± 0.08), while ET(A)R antagonism reduced ET-1-mediated contraction (IPA: 104 ± 23, 6.4 ± 0.2; CA: 112 ± 17, 6.6 ± 0.08). Pretreatment with Y-27632 significantly shifted ET-1 pD2 in IPA (108 ± 24, 7.9 ± 0.1) and CA (147 ± 58 and 8.0 ± 0.25). Protein expression of ET(A)R, ET(B)R, RhoA, and Rho-kinase were detected in IPA. IPA and CA contained preproET-1, ET(A)R, ET(B)R, RhoA, and Rho-kinase message. We observed that the IPA and CA are sensitive to ET-1, signaling through the ET(A)R and Rho-kinase pathway. These data indicate that ET-1 may play a role in vaginal and clitoral blood flow and may be important in pathologies where ET-1 levels are elevated.

Post-translational Regulation of Endothelial Nitric Oxide Synthase (eNOS) by Estrogens in the Rat Vagina

Estrogens control vaginal blood flow during female sexual arousal mostly through nitric oxide (NO). Although vascular effects of estrogens are attributed to an increase in endothelial NO production, the mechanisms of endothelial NO synthase (eNOS) regulation by estrogens in the vagina are largely unknown. Our hypothesis was that estrogens regulate eNOS post-translationally in the vagina, providing a mechanism to affect NO bioavailability without changes in eNOS protein expression. We measured eNOS phosphorylation and eNOS interaction with caveolin-1 and heat shock protein 90 (HSP90) in the distal and proximal vagina of female rats at diestrus, 7 days after ovariectomy and 2 days after replacement of ovariectomized rats with estradiol-17beta (15 microg). Molecular mechanisms of eNOS regulation by estrogen in the rat vagina. We localized phospho-eNOS (Ser-1177) immunohistochemically to the endothelium lining blood vessels and vaginal sinusoids. Estrogen withdrawal decreased phosphorylation of eNOS on its positive regulatory site (Ser-1177) and increased eNOS binding to its negative regulator caveolin-1 (without affecting eNOS/HSP90 interaction), and they were both normalized by estradiol replacement. Protein expressions of phosphorylated Akt (protein kinase B) and extracellular signal-regulated protein kinase 1/2 (ERK1/2) were not affected by estrogen status, suggesting that the effect of estrogens on eNOS (Ser-1177) phosphorylation was not mediated by activated AKT or ERK1/2. eNOS phosphorylation on its negative regulatory site (Ser-114) was increased in the vagina by estrogen withdrawal and normalized by estradiol replacement, implying that the maintenance of low phosphorylation of eNOS on this site by estradiol may limit eNOS interaction with caveolin-1 and preserve the enzyme's activity. Total eNOS, inducible NOS, caveolin-1, and HSP90 protein expressions were not affected by ovariectomy or estradiol replacement in the distal or proximal vagina. These results define novel estrogen signaling mechanisms in the vagina which involve eNOS phosphorylation and eNOS-caveolin-1 interaction.

UK‐414,495, a selective inhibitor of neutral endopeptidase, potentiates pelvic nerve‐stimulated increases in female genital blood flow in the anaesthetized rabbit

Female sexual arousal consists of a number of physiological responses resulting from increased genital blood. Vasoactive intestinal peptide (VIP), neuropeptide Y and to a lesser extent nitric oxide are neurotransmitters found in the vasculature of the genitalia. Neutral endopeptidase (NEP) modulates the activity of neuropeptides including VIP. The aim of this study was to investigate the control of genital blood flow by VIP and endogenous neuropeptides using a selective NEP inhibitor [UK-414,495, ((R)-2-({1-[(5-ethyl-1,3,4-thiadiazol-2-yl) carbamoyl]cyclopentyl}methyl) valeric acid)]. Vaginal and clitoral blood flow (VBF and CBF) were monitored using laser Doppler in terminally anaesthetized New Zealand rabbits. Increases in VBF and CBF were induced by either electrical stimulation of the pelvic nerve or by i.v. infusion of VIP. Stimulation of the pelvic nerve increased VBF and CBF, compared with basal flow. Increases were mimicked by infusion of exogenous VIP. UK-414,495 dose-dependently potentiated pelvic nerve-stimulated increases in VBF (EC(50)= 37 +/- 9 nM; 3.6 x IC(50) rabbit NEP). Nerve-stimulated increases in VBF and CBF were both enhanced after UK-414,495. UK-414,495 increased the amplitude and duration of VIP-induced increases in VBF. UK-414,495 had no effect on basal VBF or cardiovascular parameters. Inhibition of NEP potentiates pelvic nerve-stimulated increases in genital blood flow. This suggests that the endogenous neurotransmitter mediating genital blood flow is a substrate for NEP (most likely VIP). NEP inhibitors may restore sexual arousal in women adversely affected by female sexual arousal disorder.

ORIGINAL RESEARCH—BASIC SCIENCE: I. Slow Oscillations in Vaginal Blood Flow: Alterations during Sexual Arousal in Rodents and Humans

This study investigated slow oscillatory rhythms in vaginal blood flow as a physiological marker of female sexual arousal in rodents, human healthy volunteers, and women with female sexual arousal disorder (FSAD). Vaginal blood flow was measured in urethane-anesthetized rodents using laser Doppler flowmetry, while in humans, vaginal photoplethysmography was used. Acquired data were filtered for frequency analysis in the range of 0.013-2.5 Hz in rodents and 0.01-0.5 Hz in humans. Rodents were assessed for changes in a high frequency range (HF = 0.6-2.5 Hz), and a low frequency range (LF = 0.013-0.6 Hz). Human data were assessed for total spectral power in the entire frequency range. During naturally induced arousal (exposure to male), oscillatory rhythms in vaginal blood flow from rodents demonstrated an increase in the ratio of LF oscillations to HF oscillations (LF/HF ratio). Drugs known to induce sexual arousal (apomorphine and melanotan II) were tested in anesthetized rodents. Both compounds induced an increase in the LF/HF ratio. In humans, visual sexual stimulation induced an increase in the total power of slow oscillatory activity in vaginal blood flow in healthy human volunteers. No such increase was observed in women with FSAD. This study demonstrated that slow oscillations in vaginal blood flow are correlated with subjective physiological arousal and display diminished responsiveness in women with FSAD. Slow oscillations in vaginal blood flow are entirely independent of vaginal vasocongestion as women with FSAD demonstrated a normal vasocongestion response to visual sexual stimulation. In conditions where rodents would be expected to be sexually aroused, slow oscillations in vaginal blood flow showed a shift from HFs to LFs. This technique will greatly enhance the investigation of female sexual function both clinically and preclinically.

II. Slow Oscillations in Vaginal Blood Flow: Regulation of Vaginal Blood Flow Patterns in Rat by Central and Autonomic Mechanisms

A new method for assessing female sexual arousal through changes in slow oscillatory patterns in vaginal blood flow was first described in the previous manuscript [1]. This method was translational and discriminated between normal healthy volunteers and women with female sexual arousal disorder. These studies addressed the influence of autonomic and central nervous systems on slow vaginal blood flow oscillations in rats. Vaginal blood flow oscillations were measured in urethane-anesthetized rodents using laser Doppler flowmetry. Acquired data were filtered for frequency analysis range of 0.013-2.5 Hz. Data were assessed for changes in a high frequency range (HF = 0.6-2.5 Hz), and low frequency range (LF = 0.013-0.6 Hz). The basal HF oscillatory component of vaginal blood flow was primarily vagally mediated, although could be modulated pharmacologically with p-chloroamphetamine in the absence of vagal innervation. The LF component could be modulated by antagonists of noradrenergic receptors but did not appear to be dependent upon tonic activation of sympathetic circuitry. The non-selective dopamine receptor agonist apomorphine induced changes in vaginal blood flow oscillations consistent with sexual arousal during metestrus in the presence of the peripheral antagonist domperidone but not in the presence of the centrally acting antagonist haloperidol. Electrical stimulation of the paraventricular nucleus (PVN) of the hypothalamus induced an anti-arousal response in vaginal blood flow oscillations. These data demonstrated that manipulation of the central nervous system alone (via centrally acting apomorphine or electrical stimulation of the PVN) could produce either a pro-arousal or an anti-arousal response in vaginal blood flow oscillations. Alterations in the LF/HF ratio measured from vaginal laser Doppler flowmetry were independently regulated from vasculature in the trunk, the tongue, and electrocardiogram-derived heart rate variability, and were independent of overall vasocongestion of the vagina as measured by mean blood flow. These data indicated that slow oscillations in vaginal blood flow from rodents may be utilized as an animal model of female sexual arousal. Changes in these oscillations are driven by the central nervous system and modulated by the autonomic nervous system.

Female Sexual Responses Using Signal Processing Techniques

An automatic algorithm for processing vaginal photoplethysmograph signals could benefit researchers investigating sexual behaviors by standardizing interlaboratory methods. Female sexual response does not co-vary consistently in the self-report and physiological domains, making the advancement of measurements difficult. Automatic processing algorithms would increase analysis efficiency. Vaginal pulse amplitude (VPA) is a method used to measure female sexual responses. However, VPA are problematic because of the movement artifacts that impinge on the signal. This article suggests a real-time approach for automatic artifact detection of VPA signals. The stochastic changes (artifacts) of VPA are characterized mathematically in this research, and a method is presented to automatically extract the frequency of interest from VPA based on the autocorrelation function and wavelet analysis. Additionally, a calculation is presented for the vaginal blood flow change rate (VBFCR) during female sexual arousal using VPA signals. The primary aim is to investigate the experimental VPA measures based on theoretical techniques. Particularly, the goal is to introduce an automatic monitoring system for female sexual behaviors, which may be helpful for experts of female sexuality. The methods in the research are divided into experimental and theoretical parts. The VPA in twenty women was measured by a common vaginal photoplethysmography system in two conditions. Each subject was tested watching a neutral video followed by an erotic video. For theoretical analysis, an approach was applied based on wavelet transform to process the VPA. Introduction of an automatic and real-time monitoring system for female sexual behaviors, automatic movement artifact detection, VBFCR, first application of wavelet transform, and correlogram in VPA analysis. The natural and significant frequency information of VPA signals was extracted to automatically detect movement artifacts and to investigate the effects of erotic videos on female sexual responses. The computerized automatic systems based on advanced math and statistics have several advantages for human sexuality research such as: savings in time and budget; increase in the accuracy of results; and reduction in human errors for data analysis.

Pharmacological activity and protein phosphorylation caused by nitric oxide-releasing microparticles

Nitric oxide (NO)-releasing microparticles were developed as a potential treatment option against various blood flow irregulations including sexual dysfunction, atherosclerosis and metal stent-induced restenosis. Polymeric microparticles containing diethylenetriamine diazeniumdiolate (DETA NONOate), a NO donor, were prepared using modified double-emulsion solvent evaporation method to maximize the loading efficacy and stability of DETA NONOate. The pharmacological effects of the NO-releasing microparticles were evaluated by examining the changes in the vaginal blood flow in rats. The effects of NO on the phosphorylation of protein kinase C (PKC) and mitogen activated protein (MAP) kinases in excised vaginal mucosa, such as extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK) and p38, were examined using immunoblotting technique to determine whether NO activates PKC, which subsequently plays an integral role in the formation of PKC-MAP kinase modules. The viability of vagina cells (VK2E6E7) upon exposure to NO-releasing microparticles was examined for cytotoxicity assessment. In contrast to rapid and short-term effects of non-formulated DETA NONOate, microparticles containing DETA NONOate exerted beneficial effects on the blood flow (148 ± 13%) for an extended period of time, inducing a significant change at 5 min after its application and the maximum blood flow of 172 ± 23% at 120 min. The enhanced vaginal blood flow was maintained for up to 210 min and gradually returned to the baseline afterward. The results of Western immunoblotting study displayed differential expression of MAP kinases (ERK1/2 and JNK) upon NO treatment, clearly demonstrating that PKC is involved in the blood flow regulation process. There were no significant changes in cell viability in vaginal cells upon exposure to NO-releasing microparticles as compared with the control. The results of this work supported that NO-releasing microparticles could improve the vaginal blood flow without causing cytotoxic effects and PKC-MAP kinase modules are involved in the NO-induced blood flow regulation process.

VIP, Vagina, Clitoral and Periurethral Glans — an Update on Human Female Genital Arousal

The sexually quiescent human vagina is a just moist, potential space with a minimal blood flow and very low luminal oxygen tension. The first measurable sign of sexual arousal is an increase in the blood flow. This creates the engorged condition, elevates the luminal oxygen tension and stimulates the production of surface vaginal fluid by an increased plasma transudation that saturates the fluid reabsorptive capacity of the epithelium. The vaginal lubrication created allows painless penile penetration and coital movements. The mechanisms underlying the changes appear to be mediated by Vasoactive Intestinal Peptide (VIP). VIP is present in nerves closely applied to blood vessels in the vaginal wall. Administration of VIP either intravenously, or by subepithelial injection in the vaginal wall, increases vaginal blood flow and induces vaginal fluid production. Increases in vaginal blood flow by sexual arousal are not blocked by atropine injection indicating that cholinergic mechanisms are unimportant. All the present evidence suggests that the local vaginal release of VIP induces the vaginal changes of arousal. Discourse on vaginal and pudendal anatomy (Sevely, 1987) has proposed that the female glans of the clitoris is not the true homologue of the penile glans because it has no urethral opening. The speculative suggestion is that the true female glans is the area surrounding the urethral opening (which has no specific anatomical name). Preliminary studies indicate that the area of this tissue (periurethral glans) decreases on vaginal penile insertion and reappears on withdrawal indicating that it is moved during coitus. How important such movement is to stimulate erotic sensation and how sensitive this area is to erotic stimulation are unanswered questions.

Endothelial Nitric Oxide Synthase Regulation in Female Genital Tract Structures

Female sexual arousal disorder (FSAD) is a major component of female sexual dysfunctions, affecting 25-70% of women. The mechanisms of FSAD are poorly understood. Estrogen contributes to the control of genital blood flow during the sexual response. Vascular effects of estrogen are mostly attributed to its regulation of endothelial nitric oxide (NO) production. However, the role of endothelial NO synthase (eNOS) and the mechanisms that regulate eNOS in female genital tract structures are largely unknown. To review available evidence of the mechanisms of eNOS regulation in female genital tract structures. This article reviews the literature that relates to the role of NO and eNOS in female sexual arousal and its modulation by estrogen. Association between female sexual arousal, NO, and eNOS. The NO/cyclic guanosine monophosphate pathway is believed to have a primary role in the regulation of clitoral and vaginal blood flow, and smooth muscle relaxation during sexual arousal. Estrogen is critical for maintaining vaginal and clitoral blood flow and vaginal transudate production. Estrogen regulates eNOS by genomic mechanisms, involving augmented mRNA transcription and protein synthesis, and by non-genomic mechanisms, which occur without alterations in gene expression. However, limited studies have evaluated the physiological role of endothelial NO and the molecular mechanisms of eNOS regulation in the female genital tract. The effects of estrogen on increasing genital blood flow and smooth muscle relaxation have been attributed mostly to regulation of eNOS. However, the exact mechanisms of eNOS regulation in female genital tract structures and the molecular basis for the eNOS defect with aging and vascular diseases warrant further investigation.

Efficacy of red clover isoflavones in the menopausal rabbit model

To evaluate the effectiveness of phytoestrogens as alternatives for selective dysfunctional changes in the menopausal rabbit model. Prospective, vehicle-controlled experimental study. Reproductive pharmacology laboratory in a university department. Twenty-four rabbits with experimentally induced menopause and six intact controls. Surgical menopause was induced in 24 rabbits by ovariectomy. After 4 weeks of convalescence, three groups (n = 6) were given 100 microg/kg E(2) valerate, 100 microg/kg daidzein, or 6.68 mg/kg red clover extract daily for 12 weeks. The remaining six rabbits served as the operated control group. Vaginal blood flow using Doppler flowmetry, before, during, and after pelvic nerve stimulation; and measured parameters of uterine weight, femoral bone density, clitoral cavernosal histology, and hormone levels. After pelvic nerve stimulation, blood flow increased remarkably in the daidzein-treated group. Serum E(2) and uterine weight increased significantly in the estrogen group. Cavernosal structure was well preserved in all three treatment groups, and bone mineral density was lowest in ovariectomized controls (0.3467 g/cm(2)) and highest in the red clover (0.4012 g/cm(2)) groups. Supplementing isoflavones for menopause leads to significant improvements in bone density, tissue integrity, and vaginal blood flow with minimal effect on uterine weight and may therefore be a viable alternative to conventional regimens using synthetic estrogens.

Zaprinast, a phosphodiesterase type-5 inhibitor, alters paced mating behavior in female rats

Nitric oxide (NO) is the primary mediator of blood flow in female genital tissues and drugs that enhance the activity of nitric oxide, such as phosphodiesterase type-5 (PDE-5) inhibitors, increase vaginal blood flow in anesthetized rats. The goal of the present study was to test the effects of one PDE-5 inhibitor, zaprinast, on the display of sexual behaviors in gonadectomized, estrogen- and progesterone-treated female rats. Experiment 1 demonstrates that zaprinast alters paced mating behavior by lengthening the contact-return latency to ejaculation; there is a significant relationship between dose of zaprinast (range 1.5–6 mg/kg) and contact-return latency to ejaculation. Experiment 2 illustrates that zaprinast has no effect on preference for an intact male as measured in a No Contact partner preference test. Rats receiving zaprinast tend to exhibit reduced locomotor activity in both experiments. Collectively, these findings demonstrate that modulation of the NO–cGMP pathway using a PDE-5 inhibitor alters the display of paced mating behaviors in rats.

Activation of Somatosensory Afferents Elicit Changes in Vaginal Blood Flow and the Urethrogenital Reflex Via Autonomic Efferents

We examined the effects of pudendal sensory nerve stimulation and urethral distention on vaginal blood flow and the urethrogenital reflex, and the relationship between somatic and autonomic pathways regulating sexual responses. Distention of the urethra and stimulation of the pudendal sensory nerve were used to evoke changes in vaginal blood flow (laser Doppler perfusion monitoring) and pudendal motor nerve activity in anesthetized, spinally transected female rats. Bilateral cuts of either the pelvic or hypogastric nerve or both autonomic nerves were made, and blood flow and pudendal nerve responses were reexamined. Stimulation of the pudendal sensory nerve or urethral distention elicited consistent increases in vaginal blood flow and rhythmic firing of the pudendal motor nerve. Bilateral cuts of the pelvic plus hypogastric nerves significantly reduced vaginal blood flow responses without altering pudendal motor nerve responses. Pelvic nerve cuts also significantly reduced vaginal blood flow responses. In contrast, hypogastric nerve cuts did not significantly change vaginal blood flow. Bilateral cuts of the pudendal sensory nerve blocked pudendal motor nerve responses but stimulation of the central end evoked vaginal blood flow and pudendal motor nerve responses. Stimulation of the sensory branch of the pudendal nerve elicits vasodilatation of the vagina. The likely mechanism is via activation of spinal pathways that in turn activate pelvic nerve efferents to produced changes in vaginal blood flow. Climatic-like responses (firing of the pudendal motor nerve) occur in response to stimulation of the pudendal sensory nerve and do not require intact pelvic or hypogastric nerves.

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.

Testosterone Increases Blood Flow and Expression of Androgen and Estrogen Receptors in the Rat Vagina

The mechanisms by which testosterone modulates female genital sexual arousal responses are poorly understood. To investigate the effects of testosterone on vaginal blood flow and the expression of estrogen and androgen receptor proteins in the rat vagina. Mature female Sprague-Dawley rats were sham-operated (intact) or ovariectomized. Fourteen days after ovariectomy, animals were continuously infused with vehicle or varying doses of testosterone (5.5-55 microg/day). After 2 weeks of treatment, vaginal blood flow in response to pelvic nerve stimulation was measured by laser Doppler flowmetry. Plasma levels of testosterone and estradiol were determined by radioimmunoassay and epithelial thickness was examined in fixed vaginal tissue sections. Androgen and estrogen receptor levels were assessed by equilibrium radioligand binding and by Western blot analyses. Vaginal blood flow responses were significantly reduced in ovariectomized rats and normalized in animals infused with testosterone. Ovariectomy increased the expression of estrogen receptors and reduced the expression of androgen receptors with no change in receptor-ligand affinity. Testosterone increased the expression of both androgen and estrogen receptors in the vagina. While physiological (11 microg/day) and supraphysiological (55 microg/day) concentrations of testosterone normalized vaginal tissue weight, uterine tissue and whole body weights were not significantly different from ovariectomized rats infused with vehicle. Testosterone infusion, even at supraphysiological concentrations, did not change plasma estradiol levels when compared to vehicle-infused, ovariectomized rats. Likewise, the vaginal epithelium of testosterone-infused rats remained atrophic, similar to vehicle-infused, ovariectomized rats, indicating that testosterone is not aromatized to estrogens at significant levels in the vagina. Our data suggest that testosterone regulates androgen and estrogen receptor protein expression in the vagina and enhances vaginal perfusion by an androgen-dependent mechanism. We conclude that testosterone plays an important role in modulating the physiology of the vagina and contributes to improvement of genital sexual arousal responses.

Effects of tamoxifen on vaginal blood flow and epithelial morphology in the rat

BackgroundTamoxifen, a selective estrogen receptor modulator with both estrogenic and anti-estrogenic activity, is widely used as adjuvant therapy in breast cancer patients. Treatment with tamoxifen is associated with sexual side effects, such as increased vaginal dryness and pain/discomfort during sexual activity. There have been limited investigations of the effect of tamoxifen on estrogen-dependent peripheral genital arousal responses. The objective of this study was to investigate the effects of tamoxifen on vaginal physiology in the rat.MethodsFemale Sprague-Dawley rats were subjected to sham surgery or bilateral ovariectomy. After 2 weeks, sham-operated rats were implanted with subcutaneous osmotic infusion pumps containing vehicle (control) or tamoxifen (150 μg/day). Ovariectomized rats were similarly infused with vehicle. After an additional 2 weeks, vaginal blood flow responses to pelvic nerve stimulation were measured by laser Doppler flowmetry and vaginal tissue was collected for histological and biochemical assay.ResultsTamoxifen treatment did not change plasma estradiol concentrations relative to control animals, while ovariectomized rats exhibited a 60% decrease in plasma estradiol. Tamoxifen treatment caused a significant decrease in mean uterine weight, but did not alter mean vaginal weight. Vaginal blood flow was significantly decreased in tamoxifen-infused rats compared to controls. Similar to ovariectomized animals, estrogen receptor binding was increased and arginase enzyme activity was decreased in tamoxifen-infused rats. However, different from control and ovariectomized animals, the vaginal epithelium in tamoxifen-infused rats appeared highly mucified. Periodic acid-Schiff staining confirmed a greater production of carbohydrate-rich compounds (e.g. mucin, glycogen) by the vaginal epithelium of tamoxifen-infused rats.ConclusionThe observations suggest that tamoxifen exerts both anti-estrogenic and pro-estrogenic effects in the vagina. These physiological alterations may eventually lead to vaginal atrophy and compromise sexual function.

A randomized comparative study of the effects of oral and topical estrogen therapy on the vaginal vascularization and sexual function in hysterectomized postmenopausal women

To compare the effects of oral and vaginal estrogen therapy (ET) on the vaginal blood flow and sexual function in postmenopausal women with previous hysterectomy. Fifty-seven women were randomized to receive either oral (0.625 mg of conjugated equine estrogens per tablet; n = 27) or topical (0.625 mg conjugated equine estrogens per 1 g vaginal cream; n = 30) estrogen administered once daily. All women underwent estradiol measurements, urinalysis, pelvic examination, introital color Doppler ultrasonographies, and personal interviews for sexual symptoms using a validated questionnaire before and 3 months after ET. A higher serum level of estradiol was noted in the oral group compared with the topical group after 3 months of ET. There were significant increases in the number of vaginal vessels and the minimum diastole (P < 0.01), and marked decreases of pulsatility index values (P < 0.01) in both groups after ET. Regarding the systolic peak, we found a significant decrease only in the topical group (P < 0.05). Although the post-ET prevalence of anorgasmia decreased significantly in both groups (P < 0.05), changes in other domains, including the rates of low libido and coital frequency, were not statistically significant (P > 0.05). In the topical group, ET improved sexual function on the vaginal dryness and dyspareunia domains in a statistically significant manner (P < 0.05), but this was not the case in the oral group (P > 0.05). However, the efficacy of oral ET for vaginal dryness and dyspareunia reached 80% and 70.6%, respectively. The corresponding figures of the topical ET were 79.2% and 75%. The results of our study suggest that ET alone in hysterectomized postmenopausal women increases the vaginal blood flow and improves some domains of sexual function, but it may not have an impact on diminished sexual desire or activity. Compared with systemic therapy, topical vaginal preparations are found to correlate with better symptom relief despite the lower serum level of estradiol.

Sleep Exacerbation of Persistent Sexual Arousal Syndrome in a Postmenopausal Woman

To investigate possible causes and treatment of persistent sexual arousal syndrome, which was exacerbated by sleep onset, in a postmenopausal subject. A clinical examination and interviews with the patient to obtain her case history and follow-up of the effects of drug treatments. Pretreatment laboratory investigations monitored vaginal blood flow by photoplethysmography and heated electrode. Routine blood chemistry and endocrine assessments were undertaken. Magnetic resonance imaging (MRI) scans of brain, pelvis, and spinal cord and genito-sensory neural analysis of clitoral and vaginal areas were performed. A selective internal iliac artery arteriogram was utilized to check the normality of the pelvic blood supply. Genitalia appeared normal and uncongested. No structural abnormalities were observed in the MRI scans. Hormonal levels and blood chemistry were commensurate with the subject's postmenopausal status. Basal vaginal blood flow (heat electrode) was within the range of normal premenopausal women and showed (photoplethysmography) normal vasomotion. On becoming drowsy and falling lightly asleep in the laboratory the vaginal pulse amplitude (VPA) increased by 95% of the basal value and the low-amplitude VPAs were replaced by high-amplitude VPAs--all evidence of increased vaginal blood flow and congestion and confirming the subject's complaint of persistent sexual arousal during sleep. A simple cognitive task of repeatedly subtracting 7 from 500 out aloud did not hasten the reversion to the basal level. There was no evidence of malfunction of the brain, spinal cord, or pelvic area by MRI but genito-sensory analysis of the clitoral and vaginal area showed evidence of reduced sensory function. Of the treatments tried only risperidone has been effective allowing the subject to sleep throughout the night without disturbance and according to the subject has significantly reduced the aggravation of the arousal during the day.

Effects of Korean Red Ginseng on the Vaginal Blood Flow and Structure in Female Castrated Rats

Purpose: Ginseng is a traditional Asian remedy for sexual dysfunction. The purposes of this study were to investigate the effects of Korean red ginseng (KRG) on the vaginal blood flow and tissue structure in female castrated rats. Materials and Methods: Female Spague-Dawley rats (200-210gm) were divided into 4 groups: the control (n=20), castration (n=30), and castration plus oral administration of KRG extracts (50 and 100mg/kg/day, n=15 and n=15, respectively). After 1 month of treatment, the serum estrogen and total cholesterol levels were measured. The vaginal blood flow was measured using laser Doppler flowmeter before and after pelvic nerve stimulation (PNS). The vaginal tissue was processed for Masson's trichrome stain, immunohistochemistry and Western blotting. Results: The serum estrogen level was significantly decreased in the castration group (0.8±1.9ng/ml); however, it increased up to the control level (2.2±1.3ng/ml) in both the KRG administration groups (p<0.05). The PNS-induced vaginal blood flow tended to improve in the KRG treatment groups. On the histology, the vaginal epithelial layer and submucosal microvasculature showed improvement in the KRG treatment groups. The expression of estrogen receptor increased in the KRG treatment groups compared to the castration group. Conclusions: These results suggested that KRG extracts seem to have an estrogenic effect on castrated female rats. This implies that the KRG extracts may have an ameliorating effect on sexual function in menopausal woman. (Korean J Urol 2006;47:888-894) ꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏ

Streptozotocin-induced diabetes in the rat is associated with changes in vaginal hemodynamics, morphology and biochemical markers

BackgroundDiabetes is associated with declining sexual function in women. However, the effects of diabetes on genital tissue structure, innervation and function remains poorly characterized. In control and streptozotocin-treated female rats, we investigated the effects of diabetes on vaginal blood flow, tissue morphology, and expression of arginase I, endothelial nitric oxide synthase (eNOS) and cGMP-dependent protein kinase (PKG), key enzymes that regulate smooth muscle relaxation. We further related these changes with estrogen receptor alpha (ERα) and androgen receptor (AR) expression.ResultsIn addition to significantly elevated blood glucose levels, diabetic rats had decreased mean body weight, lower levels of plasma estradiol, and higher plasma testosterone concentration, compared to age-matched controls. Eight weeks after administration of buffer (control) or 65 mg/kg of streptozotocin (diabetic), the vaginal blood flow response to pelvic nerve stimulation was significantly reduced in diabetic rats. Histological examination of vaginal tissue from diabetic animals showed reduced epithelial thickness and atrophy of the muscularis layer. Diabetic animals also had reduced vaginal levels of eNOS and arginase I, but elevated levels of PKG, as assessed by Western blot analyses. These alterations were accompanied by a reduction in both ERα and AR in nuclear extracts of vaginal tissue from diabetic animals.ConclusionIn ovariectomized (estrogen deficient) animals, previous reports from our lab and others have documented changes in blood flow, tissue structure, ERα, arginase I and eNOS that parallel those observed in diabetic rats. We hypothesize that diabetes may lead to multiple disruptions in sex steroid hormone synthesis, metabolism and action. These pathological events may cause dramatic changes in tissue structure and key enzymes that regulate cell growth and smooth muscle contractility, ultimately affecting the genital response during sexual arousal.

MODULATION OF RAT VAGINAL BLOOD FLOW AND ESTROGEN RECEPTOR BY ESTRADIOL

The effects of subphysiological and physiological levels of estradiol on vaginal blood flow and estrogen receptor were investigated. Intact or ovariectomized female Sprague-Dawley rats were used. Two weeks after surgery rats were infused with vehicle (polyethyleneglycol), or estradiol at subphysiological (5 microg daily) or physiological (15 microg daily) concentrations for 14 days using osmotic pumps. Changes in vaginal blood flow elicited by pelvic nerve stimulation were assessed by laser Doppler flowmetry. Total levels of functional estrogen receptor were determined by radioligand binding and Western blot analyses were used to assess estrogen receptor (ER) alpha protein. Mean plasma estradiol concentration +/- SEM decreased by 63% in the vehicle group (intact 36.5 +/- 10.3 pg/ml). The subphysiological and physiological estradiol groups had plasma levels that were 55% and 83% of the intact group, respectively. Uterine and vaginal wet weight, and vaginal blood flow were significantly decreased in the vehicle group and normalized by physiological levels of estradiol. However, vaginal blood flow was significantly greater in the subphysiological estradiol group compared to intact animals. Specific binding of [H]estradiol in vaginal tissue extracts from intact rats was 0.51 fmol/mg protein and it was increased 30-fold in the vehicle group. ER binding in vaginal tissue in the physiological estradiol group decreased to levels that were comparable to those in intact animals, whereas estrogen receptor binding remained elevated in the subphysiological estradiol group. These changes were paralleled by ERalpha protein levels. Estradiol is crucial for maintaining optimal vaginal blood flow in the rat. Lower levels of plasma estradiol trigger compensatory ERalpha up-regulation.