Oxytocin and male reproductive function

Validity of mental and physical stress models

Different stress models are employed to enhance our understanding of the underlying mechanisms and explore potential interventions. However, the utility of these models remains a critical concern, as their validities may be limited by the complexity of stress processes. Literature review revealed that both mental and physical stress models possess reasonable construct and criterion validities, respectively reflected in psychometrically assessed stress ratings and in activation of the sympathoadrenal system and the hypothalamic-pituitary-adrenal axis. The findings are less robust, though, in the pharmacological perturbations' domain, including such agents as adenosine or dobutamine. Likewise, stress models' convergent- and discriminant validity vary depending on the stressors' nature. Stress models share similarities, but also have important differences regarding their validities. Specific traits defined by the nature of the stressor stimulus should be taken into consideration when selecting stress models. Doing so can personalize prevention and treatment of stress-related antecedents, its acute processing, and chronic sequelae. Further work is warranted to refine stress models' validity and customize them so they commensurate diverse populations and circumstances.

The Effects of Age on Prostatic Responses to Oxytocin and the Effects of Antagonists

Benign prostatic hyperplasia (BPH) is an age-related enlargement of the prostate with urethral obstruction that predominantly affects the middle-aged and older male population, resulting in disruptive lower urinary tract symptoms (LUTS), thus creating a profound impact on an individual's quality of life. The development of LUTS may be linked to overexpression of oxytocin receptors (OXTR), resulting in increased baseline myogenic tone within the prostate. Thus, it is hypothesised that targeting OXTR using oxytocin receptor antagonists (atosiban, cligosiban, and β-Mercapto-β,β-cyclopentamethylenepropionyl1, O-Me-Tyr2, Orn8]-Oxytocin (ßMßßC)), may attenuate myogenic tone within the prostate. Organ bath and immunohistochemistry techniques were conducted on prostate tissue from young and older rats. Our contractility studies demonstrated that atosiban significantly decreased the frequency of spontaneous contractions within the prostate of young rats (**** p < 0.0001), and cligosiban (* p < 0.05), and ßMßßC (**** p < 0.0001) in older rats. Additionally, immunohistochemistry findings revealed that nuclear-specific OXTR was predominantly expressed within the epithelium of the prostate of both young (*** p < 0.001) and older rats (**** p < 0.0001). In conclusion, our findings indicate that oxytocin is a key modulator of prostate contractility, and targeting OXTR is a promising avenue in the development of novel BPH drugs.

Oxytocin preprotein and oxytocin receptor mRNA expression is altered in semen samples with abnormal semen parameters

RESEARCH QUESTION

Are oxytocin preprotein and the oxytocin receptor expressed in human spermatozoa and is their mRNA expression different between normal semen samples and samples with at least one abnormal parameter?

DESIGN

An in-vitro prospective study of 175 semen samples from Greek men, according to World Health Organization criteria, 2010. mRNA expression levels were compared between different categories of semen samples, classified according to their concentration, total number, motility and morphology. Immunohistochemistry was used to detect oxytocin preprotein and its receptor on spermatozoa smears.

RESULTS

Compared with normal samples (normal motility and normal concentration), samples with at least one abnormal sperm parameter had statistically significantly lower oxytocin preprotein mRNA expression (P = 0.019) and higher oxytocin receptor mRNA expression levels (P < 0.001). Oligozoospermic samples had statistically significantly higher oxytocin preprotein mRNA expression levels (P = 0.002) and lower oxytocin receptor mRNA expression levels (P = 0.047). Asthenozoospermic samples had statistically significantly lower oxytocin preprotein mRNA expression levels (P < 0.001). Teratozoospermic samples had statistically significantly lower oxytocin preprotein mRNA expression levels (P = 0.049) and higher oxytocin receptor mRNA expression levels (P < 0.001). Oxytocin preprotein mRNA expression was positively associated with total progressive motility (P < 0.001) and negatively associated with the percentage of immotile spermatozoa (P = 0.001). Oxytocin receptor mRNA expression was negatively associated with the percentage of normal forms (P < 0.001).

CONCLUSION

Oxytocin preprotein and oxytocin receptor mRNA expression in spermatozoa could be used as a novel and unbiased diagnostic tool for male infertility.

Neuropeptides as regulators of the hypothalamus-pituitary-gonadal (HPG) axis activity and their putative roles in stress-induced fertility disorders

Neuropeptides being regulators of the hypothalamus-pituitary-adrenal (HPA) axis activity, also affect the function of the hypothalamus-pituitary-gonadal (HPG) axis by regulating gonadotrophin-releasing hormone (GnRH) secretion from hypothalamic neurons. Here, we review the available data on how neuropeptides affect HPG axis activity directly or indirectly via their influence on the HPA axis. The putative role of neuropeptides in stress-induced infertility, such as polycystic ovary syndrome, is also described. This review discusses both well-known neuropeptides (i.e., kisspeptin, Kp; oxytocin, OT; arginine-vasopressin, AVP) and more recently discovered peptides (i.e., relaxin-3, RLN-3; nesfatin-1, NEFA; phoenixin, PNX; spexin, SPX). For the first time, we present an up-to-date review of all published data regarding interactions between the aforementioned neuropeptide systems. The reviewed literature suggest new pathophysiological mechanisms leading to fertility disturbances that are induced by stress.

Expression of oxytocin receptors and oxytocin assisted electroejaculation in the domestic cat (Felis catus)

Oxytocin is a peptide hormone that mainly functions to control the contractility of smooth muscles and sex related steroidogenesis in male reproductive tracts. However, specific information concerning this hormone in controlling the reproductive organs of cats is limited. This study aimed to investigate the expression of oxytocin receptors (OTRs) and their signal mediator via prostacyclin synthase (PTGIS) in reproductive structures following oxytocin assisted electroejaculation. In Experiment 1, the testis, cauda epididymis and vas deferens from five cats were examined by immunohistochemistry and quantitative polymerase chain reaction in order to study the responses of OTR and PTGIS mRNA to oxytocin injection. Experiment 2 examined the effect of oxytocin administration prior to electroejaculation on ejaculate characteristics and sperm quality in terms of motility, viability and fertilising ability. Immunohistochemistry revealed the expression of OTRs in Leydig's, peritubular myoid cells and some spermatogenic cells. The expression was found in the epithelium and smooth muscle of the epididymis and vas deferens. After oxytocin administration, the OTR mRNA was upregulated in the epididymis (p > 0.05) and vas deferens (p = 0.01). The expression level of PTGIS mRNA increased in the response to oxytocin treatment only for the vas deferens (p > 0.05). Oxytocin treatment before electroejaculation resulted in an approximately two-fold increase in sperm concentration and total sperm output/ejaculate, while this intervention did not significantly affect ejaculate volume, sperm quality or fertilising ability. This study concluded that the oxytocin cascade is locally present in the reproductive structures and plays a role in promoting sperm delivery during electroejaculation in cats.

Exogenous oxytocin administration improves the testicular blood flow in rams

The current research aimed to examine the effects of single-dose oxytocin administration on testicular blood flow measurements peak systolic velocity (PSV), end-diastolic velocity (EDV), resistive index (RI) and pulsatility index (PI) and plasma steroid (testosterone and oestradiol-17β) concentrations in rams. In the treated group, eight mature Ossimi rams during the breeding season were injected intravenously (iv) with 20 IU oxytocin, while the other eight male rams were administered normal saline (2 ml) iv as a control group. Venous blood samples and testicular blood flow in the left and right testes were examined immediately before (0) and 5, 30, 60 and 120 min after injections. The control group did not show significant changes in the variables examined (p > .05), except for the EDV (p < .05). In the treated group, the administration of oxytocin led to a significant decrease in RI and PI values starting 5 min after oxytocin administration until 60 min after its application (p < .05). The plasma concentrations of testosterone and oestradiol-17β raised from 5 to 30 min after oxytocin injection (p > .05) and then declined significantly until 120 min (p < .05). In conclusion, oxytocin is a potent testicular vasodilator affecting the testicular vascular tone and steroid concentrations in rams.

Identification of peripheral oxytocin-expressing cells using systemically applied cell-type specific adeno-associated viral vector

Oxytocin is primarily synthesised in the brain and is widely known for its role in lactation and parturition after being released into the blood from the posterior pituitary gland. Nevertheless, peripheral tissues have also been reported to express oxytocin. Using systemic injection of a recombinant adeno-associated virus vector, we investigated the expression of the green fluorescent protein Venus under the control of the oxytocin promoter in the gastrointestinal tract, pancreas and testes of adult rats. Here, we confirm that the vector infects oxytocin neurones of the enteric nervous system in ganglia of the myenteric and submucosal plexuses. Venus was detected in 25%-60% of the ganglia in the myenteric and submucosal plexuses identified by co-staining with the neuronal marker PGP9.5. Oxytocin expression was also detected in the islets of Langerhans in the pancreas and the Leydig cells of the testes. Our data illustrate that peripheral administration of the viral vector represents a powerful method for selectively labelling oxytocin-producing cells outside the brain.

In vitro contractile responses of human detrusor smooth muscle to oxytocin: does it really have effect?

BACKGROUND AND OBJECTIVES

The aim of this study was to investigate the contractile effects of oxytocin (OT) in human detrusor muscle in in vitro conditions.

MATERIAL AND METHODS

Human detrusor muscle samples were obtained from seven patients that undergone radical cystectomy. Four female Wistar rats' uterine samples were used as control. Contractile responses were tested of carbachol in organ bath. Cumulative concentration response curves were constructed to OT and then the strips were incubated with atosiban (OT antagonist) and a second concentration response curve to OT were constructed.

RESULTS

Carbachol, contracted all human strips for the functionality test whereas OT in any concentrations did not produce significant contraction on all human strips. In only one bladder strip and in a very high concentration slight contraction was recorded. Moreover no contractile response was recorded in any OT concentrations in the presence of atosiban. The rat uterine strips responded to OT in a dose dependent manner. Atosiban, the OT receptor antagonist diminished totally those contractile responses.

CONCLUSION

It is been demonstrated here that there is no contractile response to OT in human detrusor muscle. These findings should be supported by further investigations determining the presence of the OT receptor in human detrusor.

Are We missing out the role of oxytocin in overactive bladder syndrome?

Overactive bladder (OAB) is characterized by the storage symptoms of urgency with or without urgency incontinence. Although there is no clear cause of this idiopathic disease, overall prevalence of OAB symptoms in individuals aged 40 years old is more than 15%. Oxytocin, which is one of the most powerful contracting neuropeptide, was also shown to exhibit high intrinsic contractile activity on detrusor muscle. Oxytocin receptor antagonists that inhibit of bladder activity might offer new insights into the treatment of OAB.

Oxytocin Blocks Opioid Withdrawal Symptoms Only When Combined with Group Therapy: A Double-Blind, Randomized Controlled Clinical Trial

Background: Oxytocin is a well-known central nervous system mediator in social-related behaviors and stress management. Oxytocin has also been shown to prevent withdrawal symptoms of opioids in animal studies. Group interactions with emotion sharing have been shown to result in an increase in endogenous oxytocin. Although abrupt discontinuation of methadone in opioid substitution therapy is not routinely recommended, it might result in severe withdrawal symptoms and relapse in cases that there is a clinical justification for quitting methadone. Objectives: To evaluate and compare the role of oxytocin and group interactions, combined or independently, in abrupt discontinuation of methadone in methadone maintenance treatment (MMT) cases, where there had been a reasonable clinical judgment to cease medication. Methods: In a double-blind randomized clinical trial, four groups of participants who were on methadone treatment for more than six months received either oxytocin or placebo and marathon group therapy or routine group therapy upon abrupt discontinuation of methadone. The participants were monitored for opioid withdrawal symptoms, depression, and anxiety during a four-month follow-up program. The participants were also screened by urine tests for lapses. Results: Administration of oxytocin combined with marathon group activity, with highly emotional content, resulted in less craving (P < 0.000) and withdrawal symptoms (P < 0.000) compared to placebo and non-marathon group intervention in different combinations, irrespective of methadone dose and age. The same combination also resulted in continued participation in group therapy for a longer period (P < 0.000). Additionally, the same combination was effective in improving mental health, as measured by the Beck Anxiety (P < 0.002) and Beck depression (P < 0.014) inventories. Conclusions: In order to prevent methadone craving and withdrawal symptoms and sustained abstinence, group therapy with a highly emotional theme appears to be an essential factor for the manifestation of oxytocin effects in the brain.

Cellular mechanism underlying oxytocin-stimulated Cl- secretion in rat cauda epididymal epithelium

The neurohypophyseal hormone oxytocin (OT) plays critical roles in lactation and parturition, while its function in male reproduction system is largely unknown. This study aims to investigate the effect of OT on regulating transepithelial ion transport in rat cauda epididymal epithelium. With the use of RT-PCR, Western blot, and immunohistochemical analysis, we found that OT receptor (OTR) was expressed and localized at the basal membrane of rat cauda epididymal epithelium. The short-circuit current (I_sc) measurement showed that basolateral application of OT to the primary cultured rat cauda epididymal epithelial cells elicited an increase in I_sc, which was abrogated by pretreating the epithelial cells with CFTR_inh-172, a blocker of cystic fibrosis transmembrane conductance regulator (CFTR). Pretreatment with the prostaglandin H synthase inhibitors indomethacin and piroxicam, or the nonselective antagonists of prostaglandin E2 (PGE₂) receptor EP2 or EP4, AH-6809, and AH-23848, significantly attenuated OT-stimulated I_sc response. Furthermore, the generation of PGE₂ was measured using enzyme-linked immunosorbent assay, demonstrating that OT induced a substantial increase in PGE₂ release from primary cultured rat cauda epididymal epithelial cells. In conclusion, activation of OTR by OT triggered PGE₂ release, resulting in CFTR-dependent Cl^- secretion through paracrine/autocrine pathways in rat cauda epididymal epithelium.

Ejaculate Collection Influences the Salivary Oxytocin Concentrations in Breeding Male Pigs

Simple Summary

This study aimed to evaluate how the process of ejaculate collection affects oxytocin concentrations in saliva of boars used in artificial insemination. Saliva samples of 33 boars were collected the day before ejaculate collection, during the ejaculation time, and two hours after ejaculate collection. Free oxytocin and oxytocin linked to proteins were quantified in these saliva samples. Oxytocin concentrations during the ejaculation time were higher than the day before with oxytocin linked to proteins showing higher differences. In addition, younger boars, boars with higher libido intensity and boars of the Pietrain breed showed higher values of oxytocin in saliva during ejaculation than the day before. This study demonstrated that ejaculation influences the salivary oxytocin concentrations boars.

Abstract

The objective of the present study was to evaluate the possible changes of oxytocin concentrations in saliva during and after ejaculate collection in breeding boars usually used in artificial insemination programs. Saliva samples of 33 boars were collected the day before ejaculate collection (DB), during the ejaculation time (T0) and two hours after ejaculate collection (T2). Free oxytocin and oxytocin linked to proteins concentrations were measured by two methods previously developed and validated for saliva of pigs. Younger boars, boars with higher libido intensity and boars of the Pietrain breed showed higher values of oxytocin in saliva during ejaculation than the day before. In addition, boars with higher libido showed higher concentrations two hours after ejaculate collection than during the day before. These changes were of higher magnitude and significance when oxytocin linked to proteins was measured. In conclusion, this study demonstrated for the first time that ejaculation influences the salivary oxytocin concentrations in breeding boars, although this influence varies according to age, libido and breed.

Greater family size is associated with less cancer risk: an ecological analysis of 178 countries

BACKGROUND

Greater family size measured with total fertility rate (TFR) and with household size, may offer more life satisfaction to the family members. Positive psychological well-being has been postulated to decrease cancer initiation risk. This ecological study aims to examine the worldwide correlation between family size, used as the measure of positive psychological well-being, and total cancer incidence rates.

METHODS

Country specific estimates obtained from United Nations agencies on total cancer incidence rates (total, female and male rates in age range 0-49 years and all ages respectively), all ages site cancer incidence (bladder, breast, cervix uteri, colorectum, corpus uteri, lung, ovary and stomach), TFR, household size, life expectancy, urbanization, per capita GDP PPP and self-calculated Biological State Index (Ibs) were matched for data analysis. Pearson's, non-parametric Spearman's, partial correlations, independent T-test and multivariate regressions were conducted in SPSS.

RESULTS

Worldwide, TFR and household size were significantly and negatively correlated to all the cancer incidence variables. These correlations remained significant in partial correlation analysis when GDP, life expectancy, Ibs and urbanization were controlled for. TFR correlated to male cancer incidence rate (all ages) significantly stronger than it did to female cancer incidence rate (all ages) in both Pearson's and partial correlations. Multivariate stepwise regression analysis indicated that TFR and household size were consistently significant predictors of all cancer incidence variables.

CONCLUSIONS

Countries with greater family size have lower cancer risk in both females, and especially males. Our results seem to suggest that it may be worthwhile further examining correlations between family size and cancer risk in males and females through the cohort and case-control studies based on large samples.

De-masking oxytocin-deficiency in craniopharyngioma and assessing its link with affective function

Despite the high prevalence of panhypopituitarism and diabetes insipidus in patients with craniopharyngioma (CP), little is known about the functioning of the neuropeptide oxytocin in these patients. This is of special interest as tumor-associated lesions often impair sites critical for oxytocin production and release, and affective dysfunction in CP links with elsewhere reported prosocial, antidepressant and anxiolytic oxytocin effects. Using a prospective study-design, we tested whether oxytocin is reduced in CP-patients, and whether altered oxytocin levels account for affective and emotional dysfunction. 26 adult CP-patients and 26 healthy controls matched in sex and age underwent physical exercise, a stimulus previously shown to induce oxytocin release. Baseline and stimulated salivary oxytocin levels, as well as empathy, depression and anxiety scores were measured. Results showed that patients overall did not present with lower baseline oxytocin levels than controls (F[1,30]=0.21, p=0.649), but baseline oxytocin levels were indeed reduced in patients with hypothalamic damage, as assessed by MRI-based grading (F[2,9.79]=4.54, p=0.040). In response to exercise-induced stimulation, all CP-patients showed a blunted oxytocin-release compared to controls (F[1,30]=9.36, p=0.005). DI was not associated with oxytocin levels. Regarding affective function, unexpectedly, higher baseline oxytocin was related to higher trait anxiety (b=2.885, t(43)=2.421, p=0.020, CI[.478; 5.292]); the positive link with higher depression failed to reach statistical significance (b=1.928, t(43)=1.949, p=0.058, CI[-0.070; 3.927]). A blunted oxytocin-release was linked with higher state anxiety (b=-0.133, t(43)=-2.797, p=0.008, CI[-0.230; -0.037]). Empathy was not associated with oxytocin measures. In conclusion, we observed reduced baseline oxytocin levels only in CP-patients with hypothalamic damage. Exercise-induced stimulation de-masked an oxytocin-deficiency in all CP-patients. Baseline oxytocin levels and stimulated OT-responses might have different effects on affective function, which should be considered in future substitution paradigms.

Premature ejaculation: challenging new and the old concepts

Premature ejaculation remains a difficult condition to manage for patients, their partners, and the clinician. Whilst prevalence rates are estimated to be 20-40%, determining a diagnosis of premature ejaculation is difficult, as the definition remains both subjective and ill-defined in the clinical context. As our understanding of the ejaculatory pathway has improved, new opportunities to treat the condition have evolved with mixed results. In this review, we explore some of these controversies surrounding the aetiology, diagnosis, and treatment of this condition and discuss potential novel therapeutic options.

Fluorescent visualization of oxytocin in the hypothalamo-neurohypophysial system

Oxytocin (OXT) is well known for its ability to the milk ejection reflex and uterine contraction. It is also involved in several other behaviors, such as anti-nociception, anxiety, feeding, social recognition, and stress responses. OXT is synthesized in the magnocellular neurosecretory cells (MNCs) in the hypothalamic paraventricular (PVN) and the supraoptic nuclei (SON) that terminate their axons in the posterior pituitary (PP). We generated transgenic rats that express the OXT and fluorescent protein fusion gene in order to visualize OXT in the hypothalamo-neurohypophysial system (HNS). In these transgenic rats, fluorescent proteins were observed in the MNCs and axon terminals in the PP. This transgenic rat is a new tool to study the physiological role of OXT in the HNS.

Seminal plasma oxytocin and oxidative stress levels in infertile men with varicocele

This study aimed to assess seminal plasma oxytocin (OT) and oxidative stress (OS) levels in infertile men with varicocele (Vx). A total of 131 men were divided into fertile men (n = 20), fertile men with Vx (n = 17), infertile men without Vx (n = 40) and infertile men with Vx (n = 54). OT, malondialdehyde (MDA) and glutathione peroxidase (GPx) were estimated in seminal plasma. Mean levels of seminal OT, MDA were significantly decreased, and the mean level of GPx was significantly increased in fertile men with/without Vx compared with infertile men with/without Vx. Mean levels of OT, MDA were increased, and mean level of GPx was significantly decreased in Vx grade III cases compared with Vx grades I, II cases and in bilateral Vx cases compared with unilateral Vx. There was significant negative correlation between seminal OT with sperm count, sperm motility, seminal GPx and significant positive correlation with sperm abnormal forms, seminal MDA. It is concluded that seminal OT is significantly decreased in fertile men with/without Vx compared with infertile men with/without Vx. Seminal OT demonstrated significant negative correlation with sperm count, sperm motility, seminal GPx and significant positive correlation with sperm abnormal forms, seminal MDA. Seminal OT is associated with Vx grade and its bilaterality.

The ERβ ligand 5α-androstane, 3β,17β-diol (3β-diol) regulates hypothalamic oxytocin (Oxt) gene expression

The endocrine component of the stress response is regulated by glucocorticoids and sex steroids. Testosterone down-regulates hypothalamic-pituitary-adrenal (HPA) axis activity; however, the mechanisms by which it does so are poorly understood. A candidate testosterone target is the oxytocin gene (Oxt), given that it too inhibits HPA activity. Within the paraventricular nucleus of the hypothalamus, oxytocinergic neurons involved in regulating the stress response do not express androgen receptors but do express estrogen receptor-β (ERβ), which binds the dihydrotestosterone metabolite 3β,17β-diol (3β-diol). Testosterone regulation of the HPA axis thus appears to involve the conversion to the ERβ-selective ligand 5α-androstane, 3β-diol. To study mechanisms by which 3β-diol could regulate Oxt expression, we used a hypothalamic neuronal cell line derived from embryonic mice that expresses Oxt constitutively and compared 3β-diol with estradiol (E2) effects. E2 and 3β-diol elicited a phasic response in Oxt mRNA levels. In the presence of either ligand, Oxt mRNA levels were increased for at least 60 min and returned to baseline by 2 h. ERβ occupancy preceded an increase in Oxt mRNA levels in the presence of 3β-diol but not E2. In tandem with ERβ occupancy, 3β-diol increased occupancy of the Oxt promoter by cAMP response element-binding protein and steroid receptor coactivator-1 at 30 min. At the same time, 3β-diol led to the increased acetylation of histone H4 but not H3. Taken together, the data suggest that in the presence of 3β-diol, ERβ associates with cAMP response element-binding protein and steroid receptor coactivator-1 to form a functional complex that drives Oxt gene expression.

Oxytocin and social motivation

Humans are fundamentally social creatures who are ‘motivated’ to be with others. In this review we examine the role of oxytocin (OT) as it relates to social motivation. OT is synthesized in the brain and throughout the body, including in the heart, thymus, gastrointestinal tract, as well as reproductive organs. The distribution of the OT receptor (OTR) system in both the brain and periphery is even more far-reaching and its expression is subject to changes over the course of development. OTR expression is also sensitive to changes in the external environment and the internal somatic world. The OT system functions as an important element within a complex, developmentally sensitive biobehavioral system. Other elements include sensory inputs, the salience, reward, and threat detection pathways, the hypothalamic-pituitary-gonadal axis, and the hypothalamic-pituitary-adrenal stress response axis. Despite an ever expanding scientific literature, key unresolved questions remain concerning the interplay of the central and peripheral components of this complex biobehavioral system that dynamically engages the brain and the body as humans interact with social partners over the course of development.

Oxytocin immunoreactivity in the corpus cavernosum of patients with erectile dysfunction

OBJECTIVES

Oxytocin is released by the posterior pituitary gland during male orgasm. Additionally, the presence of an oxytocin receptor gene and protein expression in human corpus cavernosum is demonstrated, and it has contractile activity on the smooth muscle of the animal and human corpus cavernosum in vitro. The aim of this study was to investigate the immunoreactivity of oxytocin in corpus cavernosum of patients with organic erectile dysfunction and to compare it with healthy controls.

METHODS

Cavernous biopsies were obtained from 31 patients with erectile dysfunction and 11 patients without erectile dysfunction. Oxytocin immunohistochemistry was performed using the streptavidin-biotin immunoperoxidase staining on all cases. Intensity and proportion of stained cells were added for the immunoreactivity score.

RESULTS

The mean ages of patients with erectile dysfunction and controls were 41.47 ± 2.08 and 36.50 ± 3.35 years, respectively (p > 0.05). Oxytocin expression was detected in smooth muscle as well as in endothelial cells in both groups. The mean oxytocin immunoreactivity score values of patients with erectile dysfunction and controls were also 2.16 ± 0.12 and 2.30 ± 0.21, respectively (p > 0.05). There was no significant difference in immunoreactivity scores both in arterial and cavernosal failure and also in smoker and nonsmoker groups (p > 0.05). Immunoreactivity scores were not statistically significantly different between patients with concomitant medical disorders and patients with no other medical disorder (p > 0.05).

CONCLUSION

We detected oxytocin immunoreactivity in male corpus cavernosum, but staining was not different between patients with erectile dysfunction and controls. However, further studies are necessary to reach a final conclusion regarding the effects of oxytocin on corpus cavernosum.

Oxytocin increases invasive properties of endometrial cancer cells through phosphatidylinositol 3-kinase/AKT-dependent up-regulation of cyclooxygenase-1, -2, and X-linked inhibitor of apoptosis protein

Traditionally, oxytocin (OT) is well known to play a crucial role in the regulation of cyclic changes in the uterus, implantation of the embryo, and parturition. Recently, an additional role for OT has been identified in several types of cancer cells in which OT acts as a growth regulator. In endometrial cancer cells, OT is known to efficiently inhibit cellular proliferation. In the present study, we show that OT increases invasiveness of human endometrial carcinoma (HEC) cells, which are otherwise resistant to the growth-inhibiting effects of OT. Using pharmacological inhibitors, invasion assay, RNA interference, and immunofluorescence, we found that OT enhances the invasive properties of HEC cells through up-regulation of X-linked inhibitor of apoptosis protein (XIAP), matrix-metalloproteinase 2 (MMP2), and matrix-metalloproteinase 14 (MMP14). In addition, we show that OT-mediated invasion is both cyclooxygenase 1 (PTGS1) and cyclooxygenase-2 (PTGS2) dependent via the phosphatidylinositol 3-kinase/AKT (PIK3/AKT) pathway. PTGS2 knockdown by shRNA resulted in XIAP down-regulation. We also show that OT receptor is overexpressed in grade I to III endometrial cancer. Taken together, our results describe for the first time a novel role for OT in endometrial cancer cell invasion.

Somatic genital reflexes in rats with a nod to humans: anatomy, physiology, and the role of the social neuropeptides

Somatic genital reflexes such as ejaculation and vaginocervical contractions are produced through the striated muscles associated with the genitalia. The coordination of these reflexes is surprisingly complex and involves a number of lumbosacral spinal and supraspinal systems. The rat model has been proven to be an excellent source of information regarding these mechanisms, and many parallels to research in humans can be drawn. An understanding of the spinal systems involving the lumbosacral spinal cord, both efferent and afferent, has been generated through decades of research. Spinal and supraspinal mechanisms of descending excitation, through a spinal ejaculation generator in the lumbar spinal cord and thalamus, and descending inhibition, through the ventrolateral medulla, have been identified and characterized both anatomically and physiologically. In addition, delineation of the neural circuits whereby ascending genitosensory information regarding the regulation of somatic genital reflexes is relayed supraspinally has also been the topic of recent investigation. Lastly, the importance of the "social neuropeptides" oxytocin and vasopressin in the regulation of somatic genital reflexes, and associated sociosexual behaviors, is emerging. This work not only has implications for understanding how nervous systems generate sexual behavior but also provides treatment targets for sexual dysfunction in people.

Oxytocin immunoreactivity in the human urethral (Littrè's) glands

Oxytocin is a cyclic nonapeptide whose best known effects are stimulation of uterine smooth muscle cells during labor and of milk ejection during lactation. Circulating oxytocin originates from the hypothalamus, but its production has also been documented in peripheral tissues. Furthermore, seminal plasma also contains oxytocin, but its functional role is still unknown, although its secretion is generally ascribed to the prostate. In this study, we investigated the possibility that seminal oxytocin is also secreted by other exocrine glands of the human male genital tract. Intramural (Littrè's) glands isolated from bioptic specimens of normal urethrae were processed for immunogold localization of oxytocin. Immunostaining was detected in principal cells, with gold particles specifically found on secretory granules. Basal and endocrine cells were unstained. The present findings suggest that urethral glands not only produce the mucinous layer that protects and lubricates the urethral wall, but also are potential sources of other seminal components, such as oxytocin, which probably play still unclear roles in reproductive physiology.

Neurosteroid biosynthesis: enzymatic pathways and neuroendocrine regulation by neurotransmitters and neuropeptides

Neuroactive steroids synthesized in neuronal tissue, referred to as neurosteroids, are implicated in proliferation, differentiation, activity and survival of nerve cells. Neurosteroids are also involved in the control of a number of behavioral, neuroendocrine and metabolic processes such as regulation of food intake, locomotor activity, sexual activity, aggressiveness, anxiety, depression, body temperature and blood pressure. In this article, we summarize the current knowledge regarding the existence, neuroanatomical distribution and biological activity of the enzymes responsible for the biosynthesis of neurosteroids in the brain of vertebrates, and we review the neuronal mechanisms that control the activity of these enzymes. The observation that the activity of key steroidogenic enzymes is finely tuned by various neurotransmitters and neuropeptides strongly suggests that some of the central effects of these neuromodulators may be mediated via the regulation of neurosteroid production.

Oxytocin increases 5alpha-reductase activity of human prostate epithelial cells, but not stromal cells

BACKGROUND

Oxytocin is known to modulate 5-alpha-reductase expression and has, therefore, been implicated in the etiology and novel pharmacological treatments of benign prostatic hyperplasia (BPH). These suggestions have been made in the absence of any direct evidence that oxytocin regulates expression or activity of 5-alpha-reductase isoenzymes in the human prostate. This study evaluated the effects of oxytocin on the activity and expression of 5-alpha-reductase isoenzymes I and II of human prostate stromal (PrSC; primary site of BPH development) and epithelial (PrEC) cells.

METHODS

Cell cultures were incubated with oxytocin, or oxytocin plus a specific oxytocin antagonist for 24 hr, and conversion of (3)H-Testosterone to dihydrotestosterone used to estimate total 5-alpha-reductase activity and to determine activity of both type I and type II isoenzymes. Fully quantitative real-time RT-PCR determined levels of expression of both isoenzymes following treatments.

RESULTS

Oxytocin significantly increased the total 5-alpha-reductase activity of PrEC but not of PrSC. 5-alpha-Reductase I gene expression and enzyme activity were also increased (P<0.05) in PrEC by oxytocin. Oxytocin significantly increased type II activity, but not expression, in PrEC. Oxytocin did not significantly affect 5-alpha-reductase activity or expression in PrSC.

CONCLUSION

Both 5-alpha-reductase I and II are expressed in normal human prostate stromal and epithelial cells. Only 5-alpha-reductase isoenzymes of prostate epithelium are modulated by oxytocin.

Differential modulation of bovine epididymal activity by oxytocin and noradrenaline

Passage of spermatozoa through the epididymis and emission of sperm during ejaculation are based on spontaneous and induced contractions of epididymal peritubular muscle layers. This study deals with the ejaculation-relevant factors noradrenaline (NA) and oxytocin (OT) and their contractile effects in the course of the bovine epididymal duct. Muscle tension recording revealed excitatory effects of NA in all duct regions. A peculiarity was found in a duct section between the mid-cauda and ductus deferens, where the responsiveness to NA was particularly faint in comparison with the adjacent regions. NA-induced contraction was primarily mediated by postjunctional alpha(2)-adrenoceptors (ADRA) in the caput and corpus regions, and by alpha(1)-ADRA in the cauda region. Contrary to NA, OT exerted regionally varying effects. The peptide induced contraction in intact and epithelium-denuded caput as well as in epithelium-denuded corpus segments but had a relaxant net effect in intact corpus and proximal cauda segments. Within the mid-cauda, OT evoked strong contraction, which progressively decreased distally. Receptor specificity of the epididymal OT effects was verified using the selective OT receptor (OTR) agonist [Thr(4),Gly(7)]OT and vasopressin. OTR immunoreactivity was detected in the epididymal peritubular muscle wall and epithelial principal cells. RT-PCR analysis confirmed the presence of OTR in all duct regions. In summary, different contractile responses to OT and NA occur in the course of the epididymal duct, possibly preventing excessive sperm transport through the corpus and serving orthograde emission of sperm during ejaculation.

The effect of oxytocin on cell proliferation in the human prostate is modulated by gonadal steroids: implications for benign prostatic hyperplasia and carcinoma of the prostate

BACKGROUND

Oxytocin (OT) is implicated in regulating prostate growth. OT concentrations are increased in benign, and decreased in malignant prostate disease. This study investigated whether the altered concentrations of OT present in prostate disease affect the proliferation of malignant and non-malignant human prostate cells.

METHODS

The effects of varying concentrations of OT and gonadal steroids on cell proliferation of non-malignant prostatic epithelial (PrEC) and stromal (PrSC) cells and androgen dependent (LNCaP) and independent (PC-3) malignant cell lines were assessed.

RESULTS

OT (>0.5 nmol . L(-1)) had no effect on PrEC proliferation when cells were cultured alone. When co-cultured with PrSC and gonadal steroids, OT inhibited epithelial cell proliferation. OT inhibited PrSC proliferation, when cells were cultured alone. When PrSC were co-cultured in the presence of estrogen physiological concentrations of OT were inhibitory. No effect on cell proliferation was observed with higher concentrations of OT. OT did not affect the proliferation of malignant cell lines in the absence of androgens but, in the presence of testosterone, low concentrations of OT (<1 nmol . L(-1)) stimulated proliferation of PC-3 cells. Disruption of caveolae in the plasma membrane removed the inhibitory effect of OT on PrSC proliferation but did not affect the stimulatory effect of OT on PC-3 cells cultured in the presence of androgens.

CONCLUSIONS

Changes in prostatic concentrations of OT that occur with aging and malignant disease may act to facilitate cell proliferation. The localization of the OT receptor within the plasma membrane modulates OT's proliferative response in the prostate.

Social and sexual incentive properties of estrogen receptor alpha, estrogen receptor beta, or oxytocin knockout mice

Social and sexual incentive motivation, defined as the intensity of approach to a social and a sexual incentive, respectively, were studied in female Swiss Webster mice. In the first experiment, the social incentive was a castrated mouse of the same strain as the females, whereas the sexual incentive was an intact male mouse of the same strain. Ovariectomized females were first tested after oil treatment and then after administration of estradiol benzoate + progesterone in doses sufficient to induce full receptivity. The hormones increased sexual incentive motivation while leaving social incentive motivation unaffected. This suggests that sexual incentive motivation in the female mouse is dependent on ovarian hormones. In the next experiment, ovariectomized females were tested with an intact, male estrogen receptor alpha knockout and its wild type as incentives, first without hormones and then when fully receptive. There were no differences in incentive properties between the wild type and the knockout. In a similar experiment, we used an intact male estrogen receptor beta knockout and its corresponding wild type as incentives. The wild type turned out to be a more attractive social incentive than the knockout, while they were equivalent as sexual incentives. Finally, an intact male oxytocin knockout and its wild type were used as incentives. The knockout turned out to be a superior incentive, particularly a superior sexual incentive. The fact that the estrogen receptor beta and oxytocin knockouts have incentive properties different from their wild types may be important to consider in studies of these knockouts' sociosexual behaviors.

Oxytocin and vasopressin stimulate anion secretion by human and porcine vas deferens epithelia

Experiments were conducted to characterize the effects of oxytocin (OT) and vasopressin (VP) on epithelial cells isolated from human (1 degree HVD) and porcine (1 degree PVD) vas deferens and an immortalized epithelial cell line derived from porcine vas deferens (PVD9902 cells). Cultured monolayers were assessed in modified Ussing flux chambers and the OT- or VP-induced change in short circuit current (I(SC)) was recorded. All cell types responded to basolateral OT or VP with a transient increase in I(SC) that reached a peak of 3-5 microA cm(-2). Concentration-response curves constructed with 1 degree PVD and PVD9902 cells revealed that the apparent K(D) (k(app)) for OT was approximately 100-fold less than the k(app) for VP. Amplicons for the OT receptor (OXTR) and vasopressin type 2 and type 1a receptors (AVPR2 and AVPR1A) were generated with RT-PCR and the identification of each amplicon confirmed by sequence analysis. A selective antagonist for OXTR and AVPR1A fully blocked the effects of OT and partially blocked the effects of VP when assessed in both 1 degree PVD and PVD9902 monolayers. APVR2 antagonists blocked the effects of low (< or =30 nM) but not high concentrations of VP, indicating that VP was affecting both AVPR2 and a second receptor subtype, likely OXTR or AVPR1A. Experiments employing chelerythrine demonstrated that OT stimulation of vas deferens monolayers requires PKC activity. Alternatively, VP (but not OT) increased the accumulation of cytosolic cAMP in vas deferens epithelial cells. Results from this study demonstrate that OT and VP can modulate ion transport across vas deferens epithelia by independent mechanisms. OT and VP have the potential to acutely change the environment to which sperm are exposed and thus, have the potential to affect male fertility.

Oxytocin and the human prostate in health and disease

Oxytocin is a peptide hormone produced by the neurohypophysis. The discovery that the peptide is produced locally within the male and female reproductive tracts has raised the possibility that oxytocin may have paracrine and autocrine actions outside of the nervous system. Oxytocin and its receptor have been identified in the human prostate. The prostate is an androgen-dependent organ whose function is to secrete components of the seminal fluid. Oxytocin has been shown to modulate contractility of prostate tissue and also to regulate local concentrations of the biologically active androgens. Oxytocin has also been shown to regulate cell growth. Prostate disease is common and results from abnormal growth of the gland. Oxytocin concentrations are altered in both benign and malignant prostate diseases and in vitro studies suggest that the peptide may be involved in the pathophysiology of these diseases.

Oxytocin Involvement in SSRI-Induced Delayed Ejaculation: A Review of Animal Studies

INTRODUCTION

Selective serotonin reuptake inhibitors (SSRIs) differ in the severity of induced ejaculation delay. Various studies indicate that oxytocin is involved in sexual behavior.

AIM

To review and evaluate the involvement of oxytocin in SSRI-induced ejaculation delay.

MAIN OUTCOME MEASURES

Oxytocine release, 5-hydroxytryptamine (5-HT) neurotransmission, and desensitization of 5-HT(1A) receptors.

METHODS

A review and critical analysis of animal studies investigating the interaction of serotonergic and oxytocinergic neurotransmission in relation to the ejaculation process.

RESULTS

Although acute treatment with the SSRIs fluoxetine and paroxetine immediately causes increased serotonin levels, delayed ejaculation does not occur. The increased serotonin levels induce oxytocin release via activation of 5-HT(1A) receptors, and this might compensate for the inhibitory actions of serotonin on sexual behavior. Chronic treatment with fluoxetine and paroxetine desensitizes 5-HT(1A) receptors on oxytocin neurons, and that might in part determine the onset of delayed ejaculation. Desensitization of 5-HT(1A) receptors is less strong following chronic treatment with the SSRIs fluvoxamine or citalopram, which may attenuate the degree of delayed ejaculation.

CONCLUSIONS

Preliminary data suggest that the severity of chronic SSRI treatment-induced delayed ejaculation and the differences between the various SSRIs in inducing ejaculation delay is related to gradual desensitization of 5-HT(1A) receptors on oxytocin neurons.

alpha-Melanocyte-stimulating hormone and oxytocin: a peptide signalling cascade in the hypothalamus

alpha-Melanocyte-stimulating hormone (alpha-MSH) and oxytocin share remarkable similarities of effects on behaviour in rats; in particular, they both inhibit feeding behaviour and stimulate sexual behaviour. Recently, we showed that alpha-MSH interacts with the magnocellular oxytocin system in the supraoptic nucleus; alpha-MSH induces the release of oxytocin from the dendrites of magnocellular neurones but it inhibits the secretion of oxytocin from their nerve terminals in the posterior pituitary. This effect of alpha-MSH on supraoptic nucleus oxytocin neurones is remarkable for two reasons. First, it illustrates the capacity of magnocellular neurones to differentially regulate peptide release from dendrites and axons and, second, it emphasises the putative role of magnocellular neurones as a major source of central oxytocin release, and as a likely substrate of some oxytocin-mediated behaviours. The ability of peptides to differentially control secretion from different compartments of their targets indicates one way by which peptide signals might have a particularly significant effect on neuronal circuitry. This suggests a possible explanation for the striking way in which some peptides can influence specific, complex behaviours.

Presynaptic actions of endocannabinoids mediate α-MSH-induced inhibition of oxytocin cells

We recently showed that central injections of α-melanocyte-stimulating hormone (α-MSH) inhibits oxytocin cells and reduces peripheral release of oxytocin, but induces oxytocin release from dendrites. Dendritic oxytocin release can be triggered by agents that mobilize intracellular calcium. Oxytocin, like α-MSH, mobilizes intracellular calcium stores in oxytocin cells and triggers presynaptic inhibition of afferent inputs that is mediated by cannabinoids. We hypothesized that this mechanism might underlie the inhibitory effects of α-MSH. To test this, we recorded extracellularly from identified oxytocin and vasopressin cells in the anesthetized rat supraoptic nucleus (SON). Retrodialysis of a CB1 cannabinoid receptor antagonist to the SON blocked the inhibitory effects of intracerebroventricular injections of α-MSH on the spontaneous activity of oxytocin cells. We then monitored synaptically mediated responses of SON cells to stimulation of the organum vasculosum of the lamina terminalis (OVLT); this evoked a mixed response comprising an inhibitory component mediated by GABA and an excitatory component mediated by glutamate, as identified by the effects of bicuculline and 6-cyano-7-nitroquinoxaline-2,3-dione applied to the SON by retrodialysis. Application of CB1 receptor agonists to the SON attenuated the excitatory effects of OVLT stimulation in both oxytocin and vasopressin cells, whereas α-MSH attenuated the responses of oxytocin cells only. Thus α-MSH can act as a “switch”; it triggers oxytocin release centrally, but at the same time through initiating endocannabinoid production in oxytocin cells inhibits their electrical activity and hence, peripheral secretion.

Oxytocin--its role in male reproduction and new potential therapeutic uses

Oxytocin (OT) is traditionally thought of as a "female" neurohypophysis hormone due to its role in parturition and milk ejection. However, OT is recognized as having endocrine and paracrine roles in male reproduction. At ejaculation, a burst of OT is released from the neurohypophysis into the systemic circulation and stimulates contractions of the reproductive tract aiding sperm release. There is conclusive evidence that OT is synthesized within the mammalian testis, epididymis and prostate and the presence of OT receptors (OTRs) through the reproductive tract supports a local action for this peptide. OT has a paracrine role in stimulating contractility of the seminiferous tubules, epididymis and the prostate gland. Interestingly, OT has also been shown to modulate androgen levels in these tissues via stimulation of the conversion of testosterone to dihydrotestostone (DHT) by 5alpha-reductase. The elucidation of OT's role in male reproduction has suggested a number of potential therapeutic uses for this hormone. Exogenous administration of OT has, in some cases, been shown to increase the numbers of ejaculated sperm, possibly by stimulating contractions of the reproductive tract and thus aiding sperm passage. Within the prostate, OT has been shown to affect gland growth both directly and via its interaction with androgen metabolism. Prostate pathologies due to unregulated cell proliferation/growth, such as benign prostatic hyperplasia and cancer, are unfortunately very common and few effective treatments are available. Greater understanding of paracrine growth mediators, such as OT, is likely to provide new mechanisms for treating such pathologies.

Androgen-binding protein is co-expressed with oxytocin in the male reproductive tract

Androgen-binding protein (ABP) and the posterior lobe hormone oxytocin (OT) were co-localized in male rat reproductive organs. Immunostaining of serial semi-thin sections revealed a high rate of coexistence of both antigens in Sertoli cells and in the epithelial cells of the prostate. There was a considerably less co-localization of OT and ABP in epithelial cells of the epididymis, and in the different tissues of the ductus deferens. In situ hybridization with synthetic oligonucleotides complementary to a fragment of ABP mRNA showed specific staining in the same sites that were immunostained for ABP. ABP was isolated by affinity chromatography from homogenates of testis, epididymis, prostate and the content of the prostate lumen. Identical protein patterns could be shown with surface-enhanced laser desorption/ionization time-of-flight mass spectrometry in all samples except for the epididymis indicating that ABP structure is similar in all these tissues. ABP seems to be expressed in specified cells throughout the male rat reproductive tract. Most of these cells appear to be oxytocinergic. ABP and OT have previously been detected in the ejaculate. The observed epithelial cells are likely to be their source.

Seasonal Changes in Mesotocin and Localization of Its Receptor in the Prostate of the Brushtail Possum (Trichosurus vulpecula)

The prostate gland in the brushtail possum grows and regresses seasonally. It has similarities to the human prostate and may therefore provide a unique model for investigating prostatic hyperplasia. Oxytocin has been implicated in the regulation of prostate growth in eutherian mammals, and the initial aim of this study was to identify and localize the marsupial equivalent, mesotocin, and its receptor in the prostate of the brushtail possum. Seasonal changes in prostatic mesotocin concentrations and receptor localization were then assessed and related to prostate growth. Mesotocin and mesotocin receptor gene transcripts with high sequence homology to eutherian oxytocin/oxytocin receptors were demonstrated, and mesotocin, neurophysin, and the receptor were all localized predominantly in the epithelial cells of the glandular acini. Western blot analysis confirmed the presence of a single immunoreactive receptor protein of approximately 60 Mr-3. Prostatic mesotocin concentrations were highest immediately before the increases in prostate weight associated with the autumn and spring breeding periods. At this time, mesotocin receptors were also present in the prostatic capsule in addition to those present in the glandular tissue. Mesotocin concentrations proceeded to decrease in association with the regression of prostate size toward the end of the breeding periods. No significant differences were present in serum testosterone or dihydrotestosterone throughout the year. The identification of mesotocin and its receptor in the possum prostate and the demonstration of seasonal changes in local mesotocin concentrations preceding changes in prostate size suggests that mesotocin may play a physiological role in regulating prostate growth and regression.

Regulation of Oxytocin Secretion

A baby sucks at a mother's breast for comfort and, of course, for milk. Milk is made in specialized cells of the mammary gland, and for a baby to feed, the milk must be released into a collecting chamber from where it can be extracted by sucking. Milk "let-down" is a reflex response to the suckling and kneading of the nipple--and sometimes in response to the sight, smell, and sound of the baby--and is ultimately affected by the secretion of oxytocin. Oxytocin has many physiological roles, but its only irreplaceable role is to mediate milk let-down: oxytocin-deficient mice cannot feed their young; the pups suckle but no milk is let down, and they will die unless cross-fostered. Most other physiological roles of oxytocin, including its role in parturition, are redundant in the sense that the roles can be assumed by other mechanisms in the absence of oxytocin throughout development and adult life. Nevertheless, physiological function in these roles can be altered or impaired by acute interventions that alter oxytocin secretion or change the actions of oxytocin. Here we focus on the diverse stimuli that regulate oxytocin secretion and on the apparent diversity of the roles for oxytocin.

Regulation of 5alpha-reductase isoforms by oxytocin in the rat ventral prostate

Oxytocin (OT) is present in the male reproductive tract, where it is known to modulate contractility, cell growth, and steroidogenesis. Little is known about how OT regulates these processes. This study describes the localization of OT receptor in the rat ventral prostate and investigates if OT regulates gene expression and/or activity of 5alpha-reductase isoforms I and II. The ventral prostates of adult male Wistar rats were collected following daily sc administration of saline (control), OT, a specific OT antagonist or both OT plus antagonist for 3 d. Expression of the OT receptor was identified in the ventral prostate by RT-PCR and Western blot, and confirmed to be a single active binding site by radioreceptor assay. Immunohistochemistry localized the receptor to the epithelium of prostatic acini and to the stromal tissue. Real-time RT-PCR determined that OT treatment significantly reduced expression of 5alpha-reductase I but significantly increased 5alpha-reductase II expression in the ventral prostate. Activity of both isoforms of 5alpha-reductase was significantly increased by OT, resulting in increased concentration of prostatic dihydrotestosterone. In conclusion, OT is involved in regulating conversion of testosterone to the biologically active dihydrotestosterone in the rat ventral prostate. It does so by differential regulation of 5alpha-reductase isoforms I and II.

Oxytocin, oxytocin-associated neurophysin and the oxytocin receptor in the human prostate

Oxytocin has been implicated in the regulation of prostate growth. However, the cellular localisation of oxytocin in the normal and diseased human prostate is not known. Oxytocin, oxytocin-associated neurophysin and oxytocin receptor were detected by immunohistochemistry in tissues from patients undergoing routine prostatectomy and in normal human prostate epithelial and stromal cell lines. Western blot analysis detected a single band at 14 kDa with neurophysin antiserum and a 66-kDa band with oxytocin receptor antiserum in epithelial and stromal cell lines. Similar sized bands were also detected in extracts of hyperplastic and adenocarcinomic prostate tissues. Oxytocin, oxytocin-associated neurophysin and oxytocin receptor were present in stromal and epithelial cell lines and in tissue from patients with benign prostatic hyperplasia. The peptides were localised predominantly to the epithelial cells, although discrete areas of stromal staining were also observed. There was a significant difference in the intensity of oxytocin-staining between tissue displaying benign prostatic hyperplasia and invasive carcinoma, with less immunoreactivity being present in the malignant epithelial cells. Thus, oxytocin and its neurophysin and receptor are present in epithelial and stromal cells of the human prostate. Oxytocin expression is reduced with tumour progression and may provide a marker for invasive disease.

Aphrodisiac properties of Montanoa tomentosa aqueous crude extract in male rats

Cihuapatli, the Mexican zoapatle (Montanoa tomentosa) has an extensive ethnomedical history of use as a traditional remedy for reproductive impairments. During the study of the ejaculatory function in rats and by testing a set of Mexican plants with medicinal properties, we observed that crude extracts of M. tomentosa facilitated ejaculation. Thus, we decided to analyze the possibility that this plant possessed sexual stimulant properties. To that aim, copulatory behavior of sexually active male rats receiving doses of 38, 75 and 150 mg/kg of the aqueous crude extract of M. tomentosa, as it is prepared in traditional medicine, was assessed. In addition, we evaluated the effect of the 75-mg/kg dose of the extract on males with anesthetization of the genital area and on sexual behavior of sexually inactive male rats (noncopulators). Results showed that acute oral administration of crude extracts of M. tomentosa facilitates expression of sexual behavior in sexually active male rats, significantly increases mounting behavior in genitally anesthetized animals and induces the expression of sexual behavior in noncopulating males. Altogether, these data reveal a facilitatory action of this extract on sexual activity and particularly on sexual arousal. Present findings provide experimental evidence that the crude extract preparation of M. tomentosa, used as a traditional remedy, possesses aphrodisiac properties.

Effects of steroids on oxytocin secretion by the human prostate in vitro

Oxytocin (OT) concentrations are elevated in prostate tissue of patients with benign prostatic hyperplasia (BPH). Oxytocin specifically increases growth, 5 alpha-reductase activity and contractility in the prostate. In the rat prostatic OT concentrations are regulated by gonadal steroids, with androgens reducing but oestrogens increasing OT concentrations. The regulation of prostatic oxytocin in man is not understood. This study investigates the effects of gonadal steroids on oxytocin production by the human prostate. Primary explants (approx. 1 mm3) of prostate tissue from patients with BPH were incubated in Dulbecco's modified Eagle's media in the absence or presence of 10 nmol/L testosterone (T), 10 nmol/L dihydrotestosterone (DHT), T or DHT plus 100 nmol/L of the anti-androgen cyproterone acetate (CPA), 55 pmol/L diethylstilbestrol (DES), or DES plus DHT. The amount of oxytocin secreted into the media after 3 days was measured by radioimmunoassay. Testosterone and DHT significantly increased oxytocin concentrations secreted into the media from 0.86 +/- 0.11 ng/g of tissue (control) to 1.51 +/- 0.14 ng/g (p < 0.01) and 1.54 +/- 0.13 ng/g (p < 0.05), respectively. Incubation of tissue samples with CPA resulted in oxytocin concentrations similar to control levels. Treatment with DES caused a significant increase from 1.99 +/- 0.71 to 3.98 +/- 1.36 ng/g (p < 0.05). A similar increase was measured in media of tissue incubated in DES plus DHT (p < 0.001). The results demonstrate that, unlike the rat where androgens decrease oxytocin, in hyperplastic human prostate tissue both androgens and oestrogens increase oxytocin. This imbalance in the regulation of oxytocin may result in promoting prostatic overgrowth in the pathogenesis of BPH.

Somatodendritic secretion in oxytocin neurons is upregulated during the female reproductive cycle

During the female reproductive cycle, hypothalamic oxytocin (OT) neurons undergo sharp changes in excitability. In lactating mammals, bursts of electrical activity of OT neurons result in the release of large amounts of OT in the bloodstream, which causes milk ejection. One hypothesis is that OT neurons regulate their own firing activity and that of nearby OT neurons by somatodendritic release of OT. In this study, we show that OT neuron activity strongly reduces inhibitory synaptic transmission to these neurons. This effect is blocked by antagonists of both adenosine and OT receptors and is mimicked by OT application. Inhibition of soluble N-ethylmaleimide-sensitive factor attachment protein receptor complex formation by tetanus toxin completely blocked the stimulation-induced reduction in inhibitory input, as did the calcium chelator BAPTA. During lactation, the readily releasable pool of secretory vesicles in OT cell bodies was doubled, and calcium currents were upregulated. This resulted in an increased inhibition of GABAergic synaptic transmission by somatodendritic release during lactation compared with the adult virgin stage. These results demonstrate that somatodendritic release is augmented during lactation, which is a novel form of plasticity to change the strength of synaptic transmission.

Projections of the posterodorsal preoptic nucleus and the lateral part of the posterodorsal medial amygdala in male gerbils, with emphasis on cells activated with ejaculation

The posterodorsal preoptic nucleus (PdPN) and the lateral part of the posterodorsal medial amygdala (MeApd) express Fos with ejaculation in male gerbils. Ejaculation-activated cells participate in the PdPN and MeApd projections to each other and to the sexually dimorphic preoptic area (SDA), but those projections involve less than 20% of the activated PdPN cells and less than 50% of the activated MeApd cells. To identify other potential targets of ejaculation-activated cells, we traced PdPN and lateral MeApd outputs using biotinylated dextran amine. The principal part of the bed nucleus of the stria terminalis (BSTpr) and the anteroventral periventricular nucleus (AVPv) were labeled from both sites and were injected with Fluoro-Gold to determine whether PdPN and lateral MeApd cells that express Fos with ejaculation would be retrogradely labeled. Fluoro-Gold was also applied to the dorsomedial hypothalamus (DMH) and retrorubral field (RRF) because such injections label PdPN cells in rats. The PdPN-DMH projection is minimal in gerbils, involving few, if any, ejaculation-related cells. Ejaculation-activated PdPN cells project to the AVPv (43%), dorsal BSTpr (30%), and RRF (12%). Those in the lateral MeApd project to the dorsal BSTpr (43%) and AVPv (18%). When these percentages are combined with those for ejaculation-activated cells involved in the PdPN and lateral MeApd projections to each other and to the medial SDA, the totals reach 100%. Thus, every PdPN and MeApd cell activated with ejaculation may participate in one of these projections. Similar projections may contribute to the similar behavioral effects of the PdPN and MeApd.

The effect of single-dose oxytocin application on time to ejaculation and seminal parameters in men

PURPOSE

To report the effect of a single dose of oxytocin on ejaculation time and seminal parameters.

METHODS

The prospective randomized clinical study was performed at a private assisted reproduction technology center and included 103 consecutive healthy men (semen donors or husbands of IVF patients). Oxytocin (16 IU) were administered intranasally to 49 subjects, randomly assigned to the study group just before masturbation to ejaculation. The time needed for ejaculation as well as the semen parameters was recorded according to the WHO standards, and compared to the control group of 54 subjects with no prior oxytocin treatment.

RESULTS

No significant difference was noted between the two groups concerning ejaculation time and semen parameters.

CONCLUSIONS

Although the administration of oxytocin stimulates sexual behavior and performance in mammalian species, our data indicate that oxytocin has no detectable effect on ejaculation time and seminal parameters after intranasal application in normal, healthy men.

The oxytocin receptor system: structure, function, and regulation

The neurohypophysial peptide oxytocin (OT) and OT-like hormones facilitate reproduction in all vertebrates at several levels. The major site of OT gene expression is the magnocellular neurons of the hypothalamic paraventricular and supraoptic nuclei. In response to a variety of stimuli such as suckling, parturition, or certain kinds of stress, the processed OT peptide is released from the posterior pituitary into the systemic circulation. Such stimuli also lead to an intranuclear release of OT. Moreover, oxytocinergic neurons display widespread projections throughout the central nervous system. However, OT is also synthesized in peripheral tissues, e.g., uterus, placenta, amnion, corpus luteum, testis, and heart. The OT receptor is a typical class I G protein-coupled receptor that is primarily coupled via G(q) proteins to phospholipase C-beta. The high-affinity receptor state requires both Mg(2+) and cholesterol, which probably function as allosteric modulators. The agonist-binding region of the receptor has been characterized by mutagenesis and molecular modeling and is different from the antagonist binding site. The function and physiological regulation of the OT system is strongly steroid dependent. However, this is, unexpectedly, only partially reflected by the promoter sequences in the OT receptor gene. The classical actions of OT are stimulation of uterine smooth muscle contraction during labor and milk ejection during lactation. While the essential role of OT for the milk let-down reflex has been confirmed in OT-deficient mice, OT's role in parturition is obviously more complex. Before the onset of labor, uterine sensitivity to OT markedly increases concomitant with a strong upregulation of OT receptors in the myometrium and, to a lesser extent, in the decidua where OT stimulates the release of PGF(2 alpha). Experiments with transgenic mice suggest that OT acts as a luteotrophic hormone opposing the luteolytic action of PGF(2 alpha). Thus, to initiate labor, it might be essential to generate sufficient PGF(2 alpha) to overcome the luteotrophic action of OT in late gestation. OT also plays an important role in many other reproduction-related functions, such as control of the estrous cycle length, follicle luteinization in the ovary, and ovarian steroidogenesis. In the male, OT is a potent stimulator of spontaneous erections in rats and is involved in ejaculation. OT receptors have also been identified in other tissues, including the kidney, heart, thymus, pancreas, and adipocytes. For example, in the rat, OT is a cardiovascular hormone acting in concert with atrial natriuretic peptide to induce natriuresis and kaliuresis. The central actions of OT range from the modulation of the neuroendocrine reflexes to the establishment of complex social and bonding behaviors related to the reproduction and care of the offspring. OT exerts potent antistress effects that may facilitate pair bonds. Overall, the regulation by gonadal and adrenal steroids is one of the most remarkable features of the OT system and is, unfortunately, the least understood. One has to conclude that the physiological regulation of the OT system will remain puzzling as long as the molecular mechanisms of genomic and nongenomic actions of steroids have not been clarified.