Male Erectile Function Research Articles

The impact of minimally invasive surgeries for the treatment of symptomatic benign prostatic hyperplasia on male sexual function: a systematic review

A systematic review of randomized controlled trials and cohort studies was conducted to evaluate data for the effects of minimally invasive procedures for treatment of symptomatic benign prostatic hyperplasia (BPH) on male sexual function. The studies searched were trials that enrolled men with symptomatic BPH who were treated with laser surgeries, transurethral microwave therapy (TUMT), transurethral needle ablation of the prostate (TUNA), transurethral ethanol ablation of the prostate (TEAP) and high-intensity frequency ultrasound (HIFU), in comparison with traditional transurethral resection of the prostate (TURP) or sham operations. A total of 72 studies were identified, of which 33 met the inclusion criteria. Of the 33 studies, 21 were concerned with laser surgeries, six with TUMT, four with TUNA and two with TEAP containing information regarding male sexual function. No study is available regarding the effect of HIFU for BPH on male sexual function. Our analysis shows that minimally invasive surgeries for BPH have comparable effects to those of TURP on male erectile function. Collectively, less than 15.4% or 15.2% of patients will have either decrease or increase, respectively, of erectile function after laser procedures, TUMT and TUNA. As observed with TURP, a high incidence of ejaculatory dysfunction (EjD) is common after treatment of BPH with holmium, potassium-titanyl-phosphate and thulium laser therapies (> 33.6%). TUMT, TUNA and neodymium:yttrium aluminum garnet visual laser ablation or interstitial laser coagulation for BPH has less incidence of EjD, but these procedures are considered less effective for BPH treatment when compared with TURP.

An Initial Evaluation of the Safety, Efficacy and Purity of VigRX, an Herbal Combination Formula, for the Enhancement of Male Sexual Health~!2009-12-10~!2010-03-04~!2010-03-31~!

A patented herbal combination formula, known as VigRX, has been studied for purity, and for safety and effi- cacy in a Sprague-Dawley rat model. Two separate assays determined that VigRX was free from pharmaceutical adulter- ants, including phosphodiesterase type 5 (PDE-5) inhibitors and related analogues. An in vitro assay determined that VigRX is able to inhibit the enzyme Rho-kinase, suggesting a potential mechanism of action for this product. A 2-week (14-day) study in rats demonstrated a marked enhancement in sexual behavior, including decreased intromission and ejaculation latencies, and increased intromission, ejaculation and mounting frequencies, upon oral administration of 30 mg/kg/day. A longer 12-week study using 15 mg/kg/day showed only a decrease in ejaculation latency with respect to sexual behavior. In both studies, the treatment led to increased intracavernosal pressure, increased sperm concentration, and increased width of erect penis (and an increase in erect penile length in the 14-day study only). There was a statisti- cally significant increase in blood testosterone levels in rats at the end of the 12-week study, which did not occur in the 14-day study. A non-dose dependent decrease in kidney and liver weights was found in the 14-day study that was not seen in the 12-week study, and neither study found any notable histopathological changes in any tissues studied. In conclusion, these preliminary results demonstrate safety and efficacy of VigRx for use in supporting male erectile function, and justify further investigation in these areas.

Chronic partial bladder outlet obstruction does not impair erectile function in male rats

To evaluate, in a well-controlled study, the effect of surgically induced partial bladder outlet obstruction (PBOO) on male erectile function in a rat model. PBOO was created in 17 adult male Sprague-Dawley rats by partial ligation of the proximal urethra. Sham-operated and PBOO rats were evaluated for urodynamic and erectile function at 4-8 weeks after surgery. Erectile responses to electrical field stimulation (EFS) to the major pelvic ganglion, and to erectogenic agents (1,1-diethyl-2-hydroxy-2-nitroso-hydrazine, DEA-NO, and Y-27632) were evaluated and the area under the curve (AUC, a product of the intracavernous pressure and duration) was used to denote the erectile response. Experimental PBOO in rats significantly increased the mean (sem) bladder weight, to 256 (25) mg in PBOO rats vs 123 (24) mg in sham controls, and the voiding frequency to 1.01 (0.1) voids/min vs 0.72 (0.14) voids/min in sham controls (P < 0.05). There was no significant difference between the erectile response to EFS, with a mean AUC in sham control rats at 1.5, 3.0 and 4.5 V of 2603 (372), 3200 (332) and 3357 (166), respectively, vs 2273 (183), 3794 (211) and 4177 (306) in PBOO rats (P > 0.05); or to the erectogenic agents, the AUC for DEA-NO being 9000 (975) in PBOO rats vs 13 201 (2756) in sham controls, and the AUC for Y-27 632 being 44 915 (2462) and 45 907 (7408), respectively (P > 0.05). There was greater immunoreactivity to RhoA in bladder and penile tissues of PBOO than control rats. PBOO does not affect erectile function in rats. Additional mechanisms or pathways might be involved in lower urinary tract symptom-related erectile dysfunction in humans.

Simple and Reliable Measurement of Nitric Oxide Metabolites in Plasma

Featured article: Moshage H, Kok B, Huizenga JR, Jansen PLM. Nitrite and nitrate determinations in plasma: a critical evaluation. Clin Chem 1995;41: 892–6.1 The history of nitric oxide (NO•) is a remarkable one. In the early 1980s it was established that nitric oxide was produced in the human body. Shortly afterward it became clear that nitric oxide had important functions in the regulation of vascular tone, and it was demonstrated that nitric oxide was identical to endothelium-derived relaxing factor, a factor derived from endothelial cells that induced relaxation of smooth muscle cells. Nitric oxide was selected as the 1992 Molecule of the Year by the journal Science , and the 1998 Nobel Prize for Medicine or Physiology was awarded to Louis Ignarro, Ferid Murad, and Robert Furchgott, the founders of nitric oxide research. Since its discovery, the gaseous radical nitric oxide has elicited much attention from the scientific community, and nitric oxide has been implicated in many diverse processes ranging from the regulation of vascular tone and male erectile function to neurotransmission and microbiocidal activity. Soon …

Potential Mechanism of Action of Human Growth Hormone on Isolated Human Penile Erectile Tissue

To evaluate the mechanisms of growth hormone (GH) action on isolated human penile erectile tissue. Human GH (hGH) has been suggested to play a role in male reproductive function, including penile erection. Nevertheless, it still remains unclear which intracellular pathways mediate the physiological effects of GH on the human corpus cavernosum (HCC). Using the organ bath technique, the effects of GH were investigated on electrical field stimulation (EFS)-induced relaxation of isolated HCC in the absence and presence of the guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and nitric oxide synthase (NOS) inhibitor N(G)-nitro-l-arginine (l-NOARG, 10 microm). Effects of GH on the production of tissue cyclic guanosine monophosphate (cGMP) in the absence and presence of ODQ and l-NOARG were also elucidated using radioimmunoassay. ODQ and l-NOARG abolished the relaxation of the tissue induced by EFS, whereas amplitudes were increased by physiological concentrations of GH (1-100 nm). The attenuation of EFS-induced amplitudes by l-NOARG but not ODQ was, in part, reversed by GH. The production of cGMP (pmol cGMP/mg protein) induced by 10 nm GH was abolished in the presence of 10 microm ODQ. In contrast, the combination of GH (10 nm) and l-NOARG (10 microm) maintained cGMP production significantly greater than baseline (0.68 +/- 0.36 vs 1.07 +/- 0.48 pmol cGMP/mg protein). Our data provide evidence that GH may act on human HCC by an NO-independent effect on guanylyl cyclase activity and may thus explain how growth factors, such as hGH, regulate male erectile function.

Effects of arginase inhibitors on the contractile and relaxant responses of isolated human penile erectile tissue

An impairment in the local availability of nitric oxide (NO) may impair male erectile function. The activity of l-arginine-degrading arginase enzymes may attenuate the relaxation of cavernous smooth muscle by reducing local NO production. Arginase enzymes compete with the nitric oxide synthases for the common substrate, the amino acid l-arginine. Very little data are available regarding the significance of arginase enzymes in the control of human penile erectile tissue. The aim of the present study was to elucidate the effects of drugs known to inhibit arginase activity on the relaxation of isolated human corpus cavernosum (HCC) and the production of cyclic GMP. Using the organ bath technique, the effects of the arginase inhibitors DFMO, H-Orn-OH·HCl, H-lle-OH and nor-NOHA (10 nM–10 μM) on the tension induced by NE (1 μM) and the relaxation induced by electrical field stimulation (EFS) of HCC were investigated. HCC strips were also exposed to increasing concentrations of the compounds, and the production of cGMP was determined by means of a radioimmunoassay. Only marginal effects of the arginase inhibitors were registered on the tension induced by NE and the relaxation exerted by EFS. Mean reversion of tension ranged from 18 to 8%. Only DFMO and nor-NOHA amplified the EFS-induced relaxation by 11 and 29%, respectively. These effects were not paralleled by an increase in tissue levels of cGMP. Arginase inhibitors appeared to be ineffective in reversing the adrenergic tension and increasing the electrically induced relaxation of isolated HCC.

The Effects of Citalopram and Fluoxetine on Sexual Behavior in Healthy Men: Evidence of Delayed Ejaculation and Unaffected Sexual Desire. A Randomized, Placebo‐Controlled, Double‐Blind, Double‐Dummy, Parallel Group Study

Selective serotonin reuptake inhibitors (SSRIs) are known to induce delayed orgasm and delayed ejaculation, while their effect on other aspects of sexual function, such as sexual motivation, arousal, and erectile function are unclear. In order to evaluate the effect of chronic administration of two SSRIs, citalopram and fluoxetine, on normal sexual function, we studied the parameters of male sexual behavior, erectile function, and ejaculation on 48 healthy male volunteers, aged 29.5 +/- 4.9, in a randomized, placebo-controlled, double-blind, double-dummy study. Methods. The subjects were randomized to receive placebo (16 subjects), or fluoxetine (20 mg/day) (16 subjects) or citalopram (20 mg/day) for the first week, and 40 mg/day in the following 3 weeks (16 subjects). Sexual function was investigated at the screening and at the end of the study by means of test of penile erection (TPE) and masturbation ejaculation latency time (MELT) performed during visual erotic stimulation, and at each visit by self-filled questionnaires (International Index Erectile Function [IIEF-15] and Golombock Rust Inventory of Sexual Satisfaction [GRISS]). All the erectile parameters, evaluated by means of RigiScan Plus during TPE, were not significantly different when both fluoxetine and citalopram were compared with placebo. A delay in the ejaculation time was observed both during citalopram and during fluoxetine treatment when compared with placebo, reaching a statistical significance only with citalopram. During the treatment with citalopram and fluoxetine, the IIEF-15 score of all items decreased except for those items related to sexual desire; however, the scores were significantly lower only for the citalopram treatment. The treatment with citalopram or with fluoxetine was confirmed to delay ejaculation, but was significant only for citalopram. Citalopram and fluoxetine did not affect sexual desire. Citalopram and fluoxetine did not directly affect penile erection as objectively assessed by RigiScan, although an impairment in the subjective assessment of erectile function was observed, but was significant only for citalopram, and it was thought to be a possible consequence of the delayed ejaculation perceived as a trouble.

Laboratory Forum: Rat as an Animal Model for Male Erectile Function Evaluation in Sexual Medicine Research

Animal models have contributed, to a great extent, to our understanding and advancement in the field of sexual medicine. Many current medical and surgical therapies in sexual medicine are the direct result of the development of such animal models. Over the past 15-20 years, rodents have become the premier models for such studies. In particular, the rat model provided the most valuable and reproducible investigations that significantly contributed to our knowledge of male sexual dysfunction as well as in the development of various treatment modalities. In addition, such in vivo animal models helped us develop the latest biotechnological tools that allowed numerous investigations at the cellular and molecular levels. Review the most common laboratory techniques that employ rat model for the evaluation of male erectile function and erectile tissue end-organ analyses. Review of peer-reviewed literature. Pathophysiology and laboratory research outcome correlation. The review suggests that rat is a versatile model in sexual medicine research. This versatile model should help in the further development of research tools, characterize additional signaling target molecules and pathways, and help in our understanding of male sexual dysfunction.

A Prospective Evaluation of Sexual Function and Quality of Life After Ileal Pouch-Anal Anastomosis

This study was designed to assess the effect of ileal pouch-anal anastomosis on sexual function and quality of life in men and women. Sexual function of patients undergoing ileal pouch-anal anastomosis from February 2005 to June 2006 was prospectively evaluated using the International Index of Erectile Function in men and Female Sexual Function Index in women. Quality of life was assessed using the Short Inflammatory Bowel Disease Questionnaire. Preoperative scores were compared with scores at 6 and 12 months postoperatively. Of 110 patients eligible for inclusion, 59 (53.6 percent) agreed to participate. Male sexual function and erectile function scores remained high 12 months after surgery (mean International Index of Erectile Function score 51.7 preoperative vs. 58.3 at 12 months postoperative; P = not significant (NS)). Abnormal sexual function decreased from 33.3 percent before surgery to 22.7 percent 12 months after surgery (P = NS). Female sexual function improved 12 months after surgery (mean Female Sexual Function Index score 19.2 preoperative vs. 27 at 12 months postoperative; P = 0.031). Abnormal sexual function decreased from 73.1 percent before surgery to 25 percent 12 months after surgery (P = 0.001). Quality of life significantly improved after ileal pouch-anal anastomosis in both sexes. In men, ileal pouch-anal anastomosis does not have an adverse effect on sexual function, whereas sexual function in women seems to improve 12 months after surgery.

Long-term effects of spinal cord injury on sexual function in men: implications for neuroplasticity

Secure, web-based survey. Elicit specific information about sexual function from men with spinal cord injuries (SCI). World-wide web. Individuals 18 years or older living with SCI obtained a pass-code to enter a secure website and then answered survey questions. The presence of genital sensation was positively correlated with the ability to feel a build up of sexual tension in the body during sexual stimulation and in the feeling that mental arousal translates to the genitals as physical sensation. There was an inverse relationship between developing new areas of arousal above the level of lesion and not having sensation or movement below the lesion. A positive relationship existed between the occurrence of spasticity during sexual activity and erectile ability. Roughly 60% of the subjects had tried some type of erection enhancing method. Only 48% had successfully achieved ejaculation postinjury and the most commonly used methods were hand stimulation, sexual intercourse, and vibrostimulation. The most commonly cited reasons for trying to ejaculate were for pleasure and for sexual intimacy. Less than half reported having experienced orgasm postinjury and this was influenced by the length of time postinjury and sacral sparing. SCI not only impairs male erectile function and ejaculatory ability, but also alters sexual arousal in a manner suggestive of neuroplasticity. More research needs to be pursued in a manner encompassing all aspects of sexual function.

Sexual Dysfunction in Female Partners of Men Who Have Undergone Radical Prostatectomy Correlates with Sexual Dysfunction of the Male Partner

IntroductionPreservation and restoration of erectile function after radical prostatectomy (RP) for prostate cancer has been extensively studied. However, the influence of RP on the sexual function of female partners is poorly understood. AimThe purpose of this retrospective study is to assess sexuality in men who have undergone RP for prostate cancer and their female partners. MethodsMen who underwent RP for localized prostate cancer at our institution from 1996 to 2000 were identified and invited to participate in this study with their female partners. Both partners completed a demographic survey. Men completed the International Index of Erectile Function (IIEF) and female partners completed the Female Sexual Function Index (FSFI) and supplemental questions. Main Outcome MeasuresCorrelation between IIEF and FSFI domain scores was determined in matched couples using Pearson correlation coefficient. Kappa statistics and Spearman correlation coefficient were calculated for supplemental questions and IIEF domain scores. ResultsOf 1,134 men contacted by letter, 90 (8%) couples completed demographic surveys and both the IIEF/FSFI. Pearson correlation coefficients of IIEF and FSFI domain scores in matched couples demonstrated significant correlation (P < 0.05) of all IIEF domains with all FSFI domains with the exception of male erectile function and overall sexual function with female sexual desire. There was moderate agreement between partner supplemental questions and IIEF domain scores. ConclusionsResponse rate was very low. FSFI domain scores correlate with IIEF domain scores, indicating an interrelationship between male and female sexual dysfunction in these couples. Evaluation and treatment of sexual dysfunction after RP should involve both partners. Shindel A, Quayle S, Yan Y, Husain A, and Naughton C. Sexual dysfunction in female partners of men who have undergone radical prostatectomy correlates with sexual dysfunction of the male partner. J Sex Med 2005;2:833–841.

Rho‐kinase Inhibition Improves Erectile Function in Aging Male Brown‐Norway Rats

Physiological aging is a significant risk factor in the on-set of male erectile dysfunction (ED) and an imbalance in factors that modulate cavernosal smooth-muscle tone may play a role in these altered penile hemodynamic mechanisms. To evaluate the association between aging and male erectile function, we monitored neurogenic erectile response and its correlation to systemic arterial pressure changes in old (21-23 months of age) vs young (6-9 months of age) Brown-Norway (BN) rats. We tested the hypothesis that age-associated ED is due to unregulated vasoconstrictive tone, contributed in part by an increased Rho-kinase activity, and that antagonism of Rho-kinase activity attenuates the age-related decline in male erectile function. We also examined the hypothesis that a combination of Rho-kinase antagonism and phosphodiesterase-5 (PDE-5) inhibition has a synergistic effect in improving the erectile response in these aging animals. Erectile function in old BN rats was evaluated before and after intracavernosal injection of a specific inhibitor of Rho-kinase (Y-27632) alone or in combination with zaprinast, a PDE-5 inhibitor. Erectile capabilities of the young and old BN rat groups were significantly different in corpus cavernosum pressure response after electrical-field stimulation of the major pelvic ganglion. Y-27632 administration attenuated the aging-related changes in male erectile function seen in BN rats. Rho-kinase antagonism and PDE-5 inhibition had a synergistic effect in improving erectile function in old rats. Our data indicate that aging leads to impairment in the neurogenic erectile response in BN rats involving a possible derangement in penile hemodynamic mechanisms of the erectile tissue. Rho-kinase inhibition may be of value in treating age-related ED.

Round Table: Ejaculatory Disorders: L16: Measuring and Quantifying Ejaculation in the Laboratory

There are limited data concerning the relationship between the sexual functioning of each partner in a heterosexual couple.This cross‐sectional study was to investigate the association between female sexual function and the male partners' erectile function.Two self‐administered questionnaires were used, one distributed to 2,159 female employees of two hospitals in Southern Taiwan and the other to their male partners, if available, to assess sexual function in each partner of the couple.Female sexual function and male erectile function were assessed by the Female Sexual Function Index (FSFI) and by the International Index of Erectile Function (IIEF), respectively.Among the 1,580 female and 779 male respondents, 632 sexually active couples were eligible for the analysis with mean ages of 36.9 years (range 21–67) and 39.5 years (range 18–80) for the women and men, respectively. After adjustment for female age group, nearly all the FSFI and IIEF domain scores correlated significantly to a slight to moderate degree. On the basis of the FSFI and IIEF scores, 42.9% (255/594) of the women reported sexual difficulty, and 15.0% (96/632) of the men reported mild to moderate erectile dysfunction (ED). After adjustment for female age group, the female partners of men with ED had significantly lower total and domain scores of the FSFI than those of men without ED, with effect sizes of ηp2 = 0.02–0.08. After further adjustment for other risk factors, ED of the male partner was still a significant risk factor for female sexual difficulty as well as for sexual difficulty in the aspects of arousal, orgasm, sexual satisfaction, and sexual pain (odds ratio = 2.5–3.3).Significant correlations between female sexual functioning and male erectile function were identified. Jiann B‐P, Su C‐C, and Tsai J‐Y. Is female sexual function related to the male partners' erectile function? J Sex Med 2013;10:420-429.

The effects of androgen depletion on human erectile function: a prospective study in male-to-female transsexuals

The objective of the study was to determine the effects of androgen depletion on erectile function in a population of male-to-female transsexuals. The erectile function of 25 consecutive male-to-female transsexuals on androgen depletion treatment and scheduled for surgical gender reassignment was prospectively evaluated using medical and sexual history, physical examination, total serum testosterone, International Index of Erectile Function (IIEF-15) questionnaire, penile colour-coded Doppler ultrasonography (CDU) after pharmacological stimulation and nocturnal penile tumescence (NPT) test. All but one had undetectable or low testosterone. Subjective erectile function, according to IIEF-15 scores, and penile CDU findings did not correlate with testosterone levels, whereas NPT test findings correlated well with testosterone levels. These findings would suggest that nocturnal erections are androgen-dependent whereas sexually induced erections are androgen-independent. It can also be assumed that testosterone is important but not essential for male erectile function and that other androgen-independent pathways can be responsible for sexually induced erections.

Testosterone, sexuality, and erectile function in aging men.

Human aging is associated with many changes, which resemble those seen with deficiencies of sex steroids or growth hormone and with cortisol excess. Among these are decreases in lean body mass (LBM) and muscle strength, loss of bone mineral, increase in body fat, and, in men, reduced libido and erectile function. Circulating total and free testosterone (T) decrease progressively with age in men, and these decreases correlate with observed changes in body composition and function. T is implicated in maintaining both male libido and erectile function, the latter effect possibly mediated by local increases in nerve nitric oxide (NO) synthase in the corpora cavernosa. Preliminary studies of T replacement in older men suggest improvements in LBM, fat, bone, libido, and erections, but more research needs to be done to better delineate benefits and potential risks before definitive recommendations can be made regarding T replacement in older men.

Severity of female sexual dysfunction in partners of men after radical prostatectomy correlates with erectile function of the male partner

Objective: Preservation and restoration of male erectile function after radical retropubic prostatectomy for prostate cancer patients is extensively studied. Female sexual dysfunction (FSD) in female partners of these men was recently accessed. The objective of this study is to determine the impact of the patient’s erectile function following radical prostatectomy on his partner’s sexual function.

4-Aryl-3-(hydroxyalkyl)quinolin-2-ones: novel maxi-K channel opening relaxants of corporal smooth muscle targeted for erectile dysfunction.

Novel 4-aryl-3-(hydroxyalkyl)quinoline-2-one derivatives were prepared and evaluated as openers of the cloned maxi-K channel hSlo expressed in Xenopus laevis oocytes by utilizing electrophysiological methods. The effect of these maxi-K openers on corporal smooth muscle was studied in vitro using isolated rabbit corpus cavernosum. From this study, a potent maxi-K opener was identified as an effective relaxant of rabbit corporal smooth muscle and shown to be active in an in vivo animal model of male erectile function.

Issues and Controversies in Botanical Medicine: A growing number of scientific studies are being conducted on natural products, allowing more objective examination of their safety and efficacy.

There are limited data concerning the relationship between the sexual functioning of each partner in a heterosexual couple.This cross‐sectional study was to investigate the association between female sexual function and the male partners' erectile function.Two self‐administered questionnaires were used, one distributed to 2,159 female employees of two hospitals in Southern Taiwan and the other to their male partners, if available, to assess sexual function in each partner of the couple.Female sexual function and male erectile function were assessed by the Female Sexual Function Index (FSFI) and by the International Index of Erectile Function (IIEF), respectively.Among the 1,580 female and 779 male respondents, 632 sexually active couples were eligible for the analysis with mean ages of 36.9 years (range 21–67) and 39.5 years (range 18–80) for the women and men, respectively. After adjustment for female age group, nearly all the FSFI and IIEF domain scores correlated significantly to a slight to moderate degree. On the basis of the FSFI and IIEF scores, 42.9% (255/594) of the women reported sexual difficulty, and 15.0% (96/632) of the men reported mild to moderate erectile dysfunction (ED). After adjustment for female age group, the female partners of men with ED had significantly lower total and domain scores of the FSFI than those of men without ED, with effect sizes of ηp2 = 0.02–0.08. After further adjustment for other risk factors, ED of the male partner was still a significant risk factor for female sexual difficulty as well as for sexual difficulty in the aspects of arousal, orgasm, sexual satisfaction, and sexual pain (odds ratio = 2.5–3.3).Significant correlations between female sexual functioning and male erectile function were identified. Jiann B‐P, Su C‐C, and Tsai J‐Y. Is female sexual function related to the male partners' erectile function? J Sex Med 2013;10:420-429.

Ejaculatory Abnormalities in Mice Lacking the Gene for Endothelial Nitric Oxide Synthase (eNOS−/−)

Nitric oxide (NO) has been established as a neurotransmitter in both the central and peripheral nervous systems. Three isoforms of its synthetic enzyme, NO synthase (NOS), have been identified: 1) in the endothelial lining of blood vessels (eNOS), 2) an inducible form found in macrophages (iNOS), and 3) in neurons (nNOS). Previous studies using pharmacological agents that block all three isoforms of NOS have revealed that NO mediates several aspects of reproductive physiology and behavior, including anomalies in male sexual behavior and erectile function. To determine the specific contribution of the endothelial isoform of NOS in male reproductive behavior, we studied mice missing the gene for only eNOS (eNOS−/−). Wild-type (WT) and eNOS−/− animals were placed with an estrous WT female and observed for 45 min. Both WT and eNOS−/− mice displayed equivalent motivation to mount the stimulus female. However, eNOS−/− mice exhibited striking anomalies in ejaculatory function. A higher percentage of eNOS−/− than WT mice ejaculated during the testing period ( p < 0.001). This increased propensity to ejaculate was apparently due to reduced stimulation required to elicit ejaculation; eNOS−/− mice required significantly fewer mounts ( p < 0.003) and intromissions ( p < 0.001) to ejaculate compared to WT mice. Taken together, these results suggest that NO synthesized by eNOS may be involved in ejaculatory physiology, but not sexual motivation.

Some Developments on the International Index of Erectile Function (IIEF)

This manuscript covers two complementary topics. For both topics, data from clinical studies and control samples were used. The first topic provides an overview of the development and validation of the International Index of Erectile Function (IIEF), a 15-item questionnaire, for male erectile and sexual function. A principal components analysis revealed five factors (erectile function, orgasmic function, sexual desire, intercourse satisfaction, and overall satisfaction). The IIEF demonstrated reliability, validity, and sensitivity and specificity with regard to treatment effect. The second topic presents, among men who reported having had sexual intercourse, the methodology and results on the evaluation of the erectile function (EF) domain of the IIEF, which has a range of scores from 6–30 for these men, as a diagnostic tool to help discriminate between men with and without erectile dysfunction (ED). For a prevalence rate of ED equal to 0.5 in a clinical population, the Classification and Regression Trees program gave a cutoff score of 25: men with EF scores of 25 or less were retrospectively classified as having ED, while those with scores above 25 were classified as not having ED (sensitivity = 0.97, specificity = 0.88). The IIEF has been developed and validated as a scale that is reliable, brief, self-administered, and psychometrically sound. Its EF domain showed desirable diagnostic properties. More research is encouraged in this area.