Pharmacotherapeutic advances in the treatment of erectile dysfunction

Autophagy in erectile dysfunction: focusing on apoptosis and fibrosis

ABSTRACT

In most types of erectile dysfunction, particularly in advanced stages, typical pathological features observed are reduced parenchymal cells coupled with increased tissue fibrosis. However, the current treatment methods have shown limited success in reversing these pathologic changes. Recent research has revealed that changes in autophagy levels, along with alterations in apoptosis and fibrosis-related proteins, are linked to the progression of erectile dysfunction, suggesting a significant association. Autophagy, known to significantly affect cell fate and tissue fibrosis, is currently being explored as a potential treatment modality for erectile dysfunction. However, these present studies are still in their nascent stage, and there are limited experimental data available. This review analyzes erectile dysfunction from a pathological perspective. It provides an in-depth overview of how autophagy is involved in the apoptotic processes of smooth muscle and endothelial cells and its role in the fibrotic processes occurring in the cavernosum. This study aimed to develop a theoretical framework for the potential effectiveness of autophagy in preventing and treating erectile dysfunction, thus encouraging further investigation among researchers in this area.

Prostaglandins as a Topical Therapy for Erectile Dysfunction: A Comprehensive Review

INTRODUCTION

Erectile dysfunction (ED) is a substantial cause of dissatisfaction among many men. This discontentment has led to the emergence of various drug treatment options for this problem.

OBJECTIVES

Unfortunately, due to various interactions, contraindications, and side effects, systemic therapies such as phosphodiesterase-5 inhibitors (including sildenafil, tadalafil, vardenafil, avanafil, etc.) are not welcomed in many patients. These problems have led researchers to look for other ways to reduce these complications.

METHODS

This article holistically reviews the efficacy of topical prostaglandins and their role in treating ED. We sought to provide a comprehensive overview of recent findings on the current topic by using the extensive literature search to identify the latest scientific reports on the topic.

RESULTS

In this regard, topical and transdermal treatments can be suitable alternatives. In diverse studies, prostaglandins, remarkably PGE1 (also known as alprostadil), have been suggested to be an acceptable candidate for topical treatment.

CONCLUSION

Numerous formulations of PGE1 have been used to treat patients so far. Still, in general, with the evolution of classical formulation methods toward modern techniques (such as using nanocarriers and skin permeability enhancers), the probability of treatment success also increases.

The impact of diabetes mellitus on penile length in men undergoing inflatable penile prosthesis implantation

OBJECTIVE

To evaluate the changing cavernosal length of patients with diabetes mellitus (DM) and organic erectile dysfunction (ED) who were treated with inflatable, three-piece penile prostheses, a current surgical treatment option in our clinic, over the course of 12 years.

MATERIALS AND METHODS

Between April 2000 and December 2012, we retrospectively investigated data from patients who were diagnosed with organic ED and undergone penile prosthesis implantation (PPI). Of the 239 patients, 235 of them were included in the study. Four patients who were operated on for trans-sexuality were excluded from the study. All patients were divided into two groups as those with (Group 1) or without DM (Group 2). Data, including age, body mass index (BMI) in kg/m(2), surgical history, comorbidities, International Index of Erectile Function (IIEF) questionnaire scores, combined intracavernous injection and stimulation (CIS) test results, length of corpus cavernosum while implanting the penile prosthesis, complications, operative times, mean hospital stay, and satisfaction of the patient and partner, were recorded. Kruskal-Wallis and Mann-Whitney U tests were used for statistical analysis. A p-value of <0.05 was considered to be statistically signifcant.

RESULTS

The mean age was 57.9±10.5 years. Study population consisted of patients with DM (n=65), hypertension (n=21), DM, and hypertension (n=28), hyperlipidemia (n=5), a history of previous radical pelvic surgery with (n=4) or without DM (n=51) or cases without any comorbidity (n=62). Mean length of the corpus cavernosum was 17.277±0.1509 cm in Group 1 and 17289±0.1598 cm in Group 2 (p<0.05). Additionally, the other parameters, including age, operative time, and the satisfaction of the patient and partner, were not different between these groups (p>0.05).

CONCLUSION

The length of the corpus cavernosum and the destruction of cavernosal tissues do not depend only on DM. We conclude that these features may have multifactorial causes.

Usage of neck circumference as novel indicator of erectile dysfunction: a pilot study in Turkish population

Erectile dysfunction (ED) is the most common male sexual problem worldwide. The association between ED and components of metabolic syndrome (MtS) is well established. This study examined neck circumference (NC) as a possible indicator of MtS and also of ED. Ninety-two patients were included and divided into two groups. Group 1 consisted of 47 patients with ED and Group 2 consisted of 45 healthy volunteers. Questionnaires, differences in anthropometric and laboratory measurements between patients with ED and the control group, and a cut-off value for NC were investigated. The mean NC in ED patients was higher in Group 1 than in Group 2 (P = 0.001), and Group 1 also demonstrated more MtS criteria than Group 2 (P < 0.001). The cut-off point of NC was defined as 34.75 cm for ED and MtS. The cut-off values of waist circumference for ED and MtS were 105.5 and 102.5 cm respectively. In the light of these findings, NC may be a new component of MtS in ED patients. Additionally, NC may be a novel indicator of central obesity and ED. We suggest that NC values of 35 cm and over may predict ED in patients with MtS.

Estrogen-induced maldevelopment of the penis involves down-regulation of myosin heavy chain 11 (MYH11) expression, a biomarker for smooth muscle cell differentiation

Cavernous smooth muscle cells are essential components in penile erection. In this study, we investigated effects of estrogen exposure on biomarkers for smooth muscle cell differentiation in the penis. Neonatal rats received diethylstilbestrol (DES), with or without the estrogen receptor (ESR) antagonist ICI 182,780 (ICI) or the androgen receptor (AR) agonist dihydrotestosterone (DHT), from Postnatal Days 1 to 6. Tissues were collected at 7, 10, or 21 days of age. The smooth muscle cell biomarker MYH11 was studied in depth because microarray data showed it was significantly down-regulated, along with other biomarkers, in DES treatment. Quantitative real time-PCR and Western blot analyses showed 50%-80% reduction (P ≤ 0.05) in Myh11 expression in DES-treated rats compared to that in controls; and ICI and DHT coadministration mitigated the decrease. Temporally, from 7 to 21 days of age, Myh11 expression was onefold increased (P ≥ 0.05) in DES-treated rats versus threefold increased (P ≤ 0.001) in controls, implying the long-lasting inhibitory effect of DES on smooth muscle cell differentiation. Immunohistochemical localization of smooth muscle alpha actin, another biomarker for smooth muscle cell differentiation, showed fewer cavernous smooth muscle cells in DES-treated animals than in controls. Additionally, DES treatment significantly up-regulated Esr1 mRNA expression and suppressed the neonatal testosterone surge by 90%, which was mitigated by ICI coadministration but not by DHT coadministration. Collectively, results provided evidence that DES treatment in neonatal rats inhibited cavernous smooth muscle cell differentiation, as shown by down-regulation of MYH11 expression at the mRNA and protein levels and by reduced immunohistochemical staining of smooth muscle alpha actin. Both the ESR and the AR pathways probably mediate this effect.

Male sexual dysfunction and infertility associated with neurological disorders

Normal sexual and reproductive functions depend largely on neurological mechanisms. Neurological defects in men can cause infertility through erectile dysfunction, ejaculatory dysfunction and semen abnormalities. Among the major conditions contributing to these symptoms are pelvic and retroperitoneal surgery, diabetes, congenital spinal abnormalities, multiple sclerosis and spinal cord injury. Erectile dysfunction can be managed by an increasingly invasive range of treatments including medications, injection therapy and the surgical insertion of a penile implant. Retrograde ejaculation is managed by medications to reverse the condition in mild cases and in bladder harvest of semen after ejaculation in more severe cases. Anejaculation might also be managed by medication in mild cases while assisted ejaculatory techniques including penile vibratory stimulation and electroejaculation are used in more severe cases. If these measures fail, surgical sperm retrieval can be attempted. Ejaculation with penile vibratory stimulation can be done by some spinal cord injured men and their partners at home, followed by in-home insemination if circumstances and sperm quality are adequate. The other options always require assisted reproductive techniques including intrauterine insemination or in vitro fertilization with or without intracytoplasmic sperm injection. The method of choice depends largely on the number of motile sperm in the ejaculate.

Phosphodiesterase inhibitors for erectile dysfunction in patients with diabetes mellitus

BACKGROUND

Erectile dysfunction is a common multi-factorial complication of diabetes mellitus. Numerous strategies have been tried to overcome this diabetic complication. In recent years, phosphodiesterase type 5 (PDE-5) inhibitors have been introduced in the management of erectile dysfunction.

OBJECTIVES

The objective of this review was to assess the effect of PDE-5 inhibitors on the management of erectile dysfunction in diabetic men.

SEARCH STRATEGY

Studies were obtained from computerised searches of MEDLINE, EMBASE and The Cochrane Library.

SELECTION CRITERIA

Randomised controlled trials, in which treatment with PDE-5 inhibitors was compared to control, in diabetic patients with erectile dysfunction.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed trial quality.

MAIN RESULTS

Eight randomised controlled trials were identified. A total 976 men were allocated to receive a PDE-5 inhibitor and 741 were randomised to the control groups. Overall, 80% of the participants suffered from type 2 diabetes mellitus. The weighted mean difference (WMD) for the International Index of Erectile Function (IIEF) questions 3 and 4 (frequency of penetration during and maintaining erection to completion of intercourse) was 0.9 (95% CI 0.8 to 1.1) and 1.1 (95% CI 1.0 to 1.2) at the end of the study period, in favour of the intervention group. The WMD for the IIEF erectile dysfunction domain at the end of the study period was 6.6 (95% CI 5.2 to 7.9) in favour of the PDE-5 inhibitors arm. The relative risk (RR) for answering "yes" to a global efficacy question ( "did the treatment improve your erections?") was 3.8 (CI 95% 3.1 to 4.5) in the PDE-5 inhibitors compared with the control arm. The WMD between the percentage of successful attempts in the PDE-5 inhibitors and in the control arm was 26.7 (95% CI 23.1 to 30.3). Mortality was not reported in any of the included trials. Adverse cardiovascular effects were reported in one study. Headache was the most frequent adverse event reported, flushing was the second most common event, with upper respiratory tract complaints and flu like syndromes, dyspepsia, myalgia, abnormal vision and back pain also reported in a descending order of frequency. The overall risk ratio for developing any adverse reaction was 4.8 (CI 95% 3.74 to 6.16) in the PDE-5 inhibitors arm as compared to the control.

AUTHORS' CONCLUSIONS

Sufficient evidence exists that PDE-5 inhibitors form a care that improves erectile dysfunction in diabetic men.

Future options for combination therapy in the management of erectile dysfunction in older men

The prevalence of erectile dysfunction (ED) has dramatically increased in parallel with the aging of the Western industrialised population. The estimated prevalence of ED worldwide in 1995 was 152 million men. As the population in industrial nations ages, an estimated 322 million men will be affected by ED by the year 2025. Oral drug therapy with the phosphodiesterase (PDE) type 5 inhibitor sildenafil fails in some patients with ED; however, several different classes of drugs demonstrate efficacy in treating ED, creating the potential for pharmacological combination therapy. Pharmaceutical products that lead to the activation of or an increase in cyclic nucleotides (cyclic adenosine monophosphate and cyclic guanosine monophosphate), with or without nitric oxide donors or nitrates, as well as alpha-adrenoceptor antagonists, have been used to treat ED. Sildenafil has been used in combination with alprostadil (prostaglandin E1) and administered via intraurethral or intracavernous route. Successful intercourse using this combination of agents varies from 47% to 100% following failed monotherapy. Various combination therapies for ED are being studied using PDE5 inhibitors, together with other agents, alpha-adrenoceptor antagonists, and testosterone replacement therapy for men with hypogonadism. The combination of centrally acting agents with PDE5 inhibitors, e.g. a regimen of apomorphine plus PDE5 inhibitor, is an attractive approach because the two therapies target different mechanisms. New PDE5 inhibitors such as vardenafil should be tried first as therapy for sildenafil nonresponders before exploring any combination therapy options. Preliminary observations of combination therapy have been encouraging and provide a scientific rationale for prospective, randomised clinical trials with adequate numbers of patients.

Vardenafil: a review of its use in erectile dysfunction

Vardenafil (Levitra) is a potent and highly selective oral phosphodiesterase type 5 (PDE5) inhibitor. Vardenafil improved erectile function in men with mild to severe erectile dysfunction (ED) of varying aetiology in two randomised, double-blind, multicentre, fixed-dose studies of 12 or 26 weeks' duration. Men receiving vardenafil 10 or 20 mg had significantly greater improvements in International Index of Erectile Function (IIEF) questionnaire erectile function domain scores than placebo recipients. Moreover, improvements in penetration and maintenance of erection (assessed using IIEF or Sexual Encounter Profile [SEP] questions) were significantly greater with vardenafil 5-20 mg than with placebo. Improvements in IIEF intercourse satisfaction and orgasmic function domain scores were significantly greater with vardenafil 10 or 20 mg than with placebo and the proportion of patients with a positive response to a Global Assessment Question (GAQ) concerning improvement in erections after 12 or 26 weeks' therapy was significantly higher with vardenafil 5-20 mg than with placebo. Vardenafil improved erectile function in men with ED associated with diabetes mellitus or ED following unilateral or bilateral nerve-sparing radical retropubic prostatectomy in two randomised, double-blind, multicentre, fixed-dose, 3-month studies. In both studies, improvements from baseline in the erectile function domain score of the IIEF and in positive responses to SEP questions were significantly greater with vardenafil 10 or 20 mg than with placebo. In addition, a significantly higher proportion of vardenafil 10 or 20 mg recipients than placebo recipients had positive GAQ responses. Vardenafil was generally well tolerated in men with ED; treatment-emergent adverse events were of mild to moderate intensity and transient in nature. The most commonly reported adverse events (typical of those seen with PDE5 inhibitors) in vardenafil 5-20 mg recipients included headache, flushing, rhinitis, dyspepsia and sinusitis. There were no reports of abnormal colour vision in men with ED taking vardenafil at clinically recommended doses (5-20 mg).

CONCLUSION

Vardenafil is a potent and highly selective oral PDE5 inhibitor. It is effective and generally well tolerated in men with mild to severe ED of varying aetiology, as well as in men with ED associated with diabetes mellitus or ED after radical prostatectomy. Vardenafil should be considered a first-line treatment option in men with ED who are suitable candidates for oral PDE5 inhibitor therapy.

Muscarinic receptor subtypes mediate vasorelaxation in isolated horse deep dorsal penile vein

OBJECTIVES

To investigate the effect of acetylcholine (ACh) on horse deep dorsal penile vein and to characterize the muscarinic receptor subtypes involved in this response.

METHODS

Vein rings were mounted in an organ bath chamber, and the isometric tension was recorded.

RESULTS

In phenylephrine-contracted veins, ACh (1 nM to 1 microM) induced endothelium-dependent relaxation. The muscarinic receptor antagonist, atropine, produced parallel rightward shifts of the ACh response curves (pA2 = 10.04; pK(B) = 9.98). Carbachol (10 nM to 100 microM) also evoked relaxation in the vein segments, but showed a lower potency and similar relaxation to that induced by ACh. Pirenzepine, the high, intermediate, and low-affinity antagonist for M1, M3, and M2 receptors, respectively, inhibited ACh and carbachol-induced relaxation, yielding pA2 values of 7.51 and 7.37, and pK(B) values of 7.38 and 7.28, respectively. Methoctramine, a high-affinity M2 antagonist, showed no significant effect on the response to ACh. However, a high-affinity M3 antagonist, pFHHSiD, potently blocked the relaxation induced by carbachol and ACh, yielding pA2 and pK(B) values of 7.72 and 7.70 for pFHHSiD against ACh, respectively, and of 7.77 and 7.65 against carbachol, respectively.

CONCLUSIONS

These results indicate that ACh induces an endothelium-dependent relaxation in horse deep dorsal penile vein. The antagonist profile suggests that M3 muscarinic receptors mediate ACh-induced relaxation in this tissue.

Expression of functional prostaglandin D (DP) receptors in human corpus cavernosum smooth muscle

Prostaglandin D(2) (PGD(2)) binds to specific G-protein coupled receptors (DP) and induces smooth muscle relaxation by stimulating the synthesis of intracellular cAMP. In this study, we examined the role of PGD(2) and DP receptors in regulating human penile smooth muscle contractility. We determined that human corpus cavernosum tissue and smooth muscle cells in culture expressed functional DP receptor and lipocalin-like prostaglandin D synthase by reverse-transcribed polymerase chain reaction (RT-PCR). Functional PGD synthase activity was confirmed by the synthesis of PGD(2) in human corpus cavernosum smooth muscle cells upon addition of exogenous arachidonic acid. Organ bath preparations of human corpus cavernosum tissue strips, contracted with phenylephrine, relaxed in a dose-dependent fashion to either PGD(2) or the DP selective agonist BW245C. Cultures of human corpus cavernosum smooth muscle cells treated with BW245C showed a two-fold increase in cAMP synthesis. These data are consistent with the expression of functional DP receptors in human corpus cavernosum. This suggests the presence of an intact prostanoid autocrine system that may play a role in regulating penile erectile function.

Combination therapy for erectile dysfunction: where we are and what's in the future

Penile erection occurs in response to visual, olfactory, imaginative, and tactile stimuli initiated within the brain and/or on the periphery. Responses to these stimuli are mediated by efferent autonomic outflow originating in the sacral spinal cord and transmitted by the cavernosal and penile nerves. A number of neurotransmitters can play an integral role in corpus cavernosum smooth muscle relaxation, in part regulating penile erection through increased smooth muscle synthesis of the secondary messengers cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). In addition to direct-acting agents, there are indirect-acting smooth muscle-relaxing agents. Phosphodiesterase (PDE) inhibitors such as sildenafil act indirectly and require sexual stimulation and endogenous nitric oxide production to activate the cGMP pathway effectively. In contrast, agents such as prostaglandin E(1) (PGE(1)) act directly on the trabecular smooth muscle, binding to specific e-prostanoid receptors and increasing cAMP synthesis. For this reason the direct-acting agents do not require sexual stimulation for efficacy. Combination pharmacotherapy has been used experimentally to treat erectile dysfunction for 25 years, using combinations of cAMP synthesis augmentors, smooth muscle relaxants and PDE inhibitors, and alpha-blockers administered via intracavernosal injection. The present era of oral pharmacotherapy treatment has resulted in significant awareness in the field of sexual dysfunction; however, a single agent may not be ideal to sustain penile rigidity, especially if comorbidities and severity of erectile dysfunction are accounted for. The rationale for and recent reports on combination therapy are presented in this review.

Erosion of a penile prosthesis due to an indwelling urethral catheter as a late complication

A case of erosion of a penile prosthesis caused by indwelling of a catheter in the urethra is reported. A 73-year-old man had maintained sexual intercourse with penile prostheses (Jonas prosthesis, 19 cm) for 11 years without any complications until he developed cerebral infarction. One month after starting an indwelling urethral catheter in a neurosurgery clinic, the left-side penile prosthesis eroded from the area of the fossa navicularis, and was immediately removed. This type of complication is not unusual in patients with a neurogenic bladder. However, it is not well recognized in patients who suddenly develop a neurogenic bladder following a long-term uneventful period after the implantation of penile prostheses. Therefore, urologists should inform patients who receive this type of treatment that erosion of the prosthesis may develop when they need an indwelling urethral catheter as a late complication.

The hemodynamics of erection and the pharmacotherapies of erectile dysfunction

The past few years have been witness to a sea of change in understanding the diagnosis and treatment of erectile dysfunction. In the wake of Viagra, effective orally administered therapies are now the expected gold standard. Currently available therapies include both peripherally (at the level of the penis) and centrally (brain, e.g., hypothalamic nuclei) acting compounds. When all modes of pharmacotherapy are considered, ranging from oral, to topical, to intraurethral, to intracavernous injection, it is clear that the vast majority of men with mild to moderate erectile dysfunction can now be effectively treated. However, all forms of pharmacotherapy have the lowest efficacy and greatest side effect profiles (including cardiovascular events) in the patients that need the therapy most, that is, those with relatively severe and longstanding erectile dysfunction. The newer generation of pharmacotherapies, which will likely include gene therapy techniques as well, will therefore have to target this latter group. Improved mechanism-based, perhaps patient-specific therapies are foreseen that will dramatically increase the number of patients seeking treatment, as well as the quality of their lives.

Impact of chronic renal failure and peritoneal dialysis fluids on advanced glycation end product and iNOS levels in penile tissue: an experimental study

OBJECTIVES

To investigate the impact of chronic renal failure (CRF) on advanced glycation end product and inducible nitric oxide synthase (iNOS) in penile tissue, we examined the advanced glycation end product 5-hydroxy methyl furfural (5-HMF) content and iNOS expression in rats in which uremia had been produced by greater than 85% nephrectomy. In addition, the contribution of peritoneal dialysis (PD) fluids to the elevation of penile tissue 5-HMF levels and iNOS staining scores has been investigated.

METHODS

Adult male Wistar rats, aged between 10 and 12 weeks and weighing 200 to 330 g, were divided into five groups that each included 6 animals. The first group served as a control group. In the second group, CRF was induced and a peritoneal catheter was implanted, but PD was not performed. In group 3, CRF was induced and PD was performed using dialysis fluids containing 1.36% glucose and icodextrin. In group 4, CRF was also induced and PD was performed using 3.86% glucose and icodextrin. Finally, in group 5, without CRF, an indwelling catheter was implanted, and the PD procedure was performed using dialysis fluids containing 3.86% glucose and icodextrin.

RESULTS

The elevation in 5-HMF levels and iNOS staining scores in penile tissue from groups 2, 3, 4, and 5 was significant compared with group 1 (P <0.05). The elevation in 5-HMF levels and iNOS staining scores was also significant between groups 2 and 3, 2 and 4, 3 and 4, 3 and 5, and 4 and 5 (P <0.05). Moreover, the correlation between the 5-HMF levels and iNOS staining scores was statistically significant (r = 0.525, P = 0.003).

CONCLUSIONS

In the present experimental study, we found that 5-HMF levels and iNOS staining scores were significantly elevated in rat penile tissue in which uremia had been produced compared with the groups without CRF. Additionally, PD fluids containing glucose had an effect on the elevation of penile tissue 5-HMF levels and iNOS staining scores.

Neurogenic erectile dysfunction

Penile erection is a neurovascular event modulated by psyche and hormones. Erectile dysfunction (ED) has been classified as psychogenic, arteriogenic, neurogenic, endocrinologic, and cavernosal, based on the organs that are involved in penile erection. Among these types, neurogenic ED may be the most common, probably because a deficiency of neurotransmitters is the final common pathway in many diseases and conditions. This review discusses the physiology, pathophysiology, diagnosis, and treatment of erectile function and dysfunction, as well as strategies for future research.

O2-dependent prostanoid synthesis activates functional PGE receptors on corpus cavernosum smooth muscle

We have previously demonstrated that decreased O2 tension inhibits prostaglandin synthesis from human corpus cavernosum smooth muscle cells in static culture over 8-18 h (R. B. Moreland et al., Molecular Urology 2: 41-47, 1998). In this report, an experimental system was designed that allowed determination of the effects of O2 tension changes over the time frame of physiological penile erection. Human corpus cavernosum smooth muscle cells were cultured on microcarrier beads in enclosed stirrer flasks so that rapid changes of O2 tension could be modulated. After 18 h of equilibration at 30-40 mmHg to simulate blood PO2 at penile flaccidity, O2 tension was increased to 100 mmHg for 1 h and then returned to 30-40 mmHg. Media samples were withdrawn for prostanoid synthesis and cell samples were taken for cAMP determinations. After 18 h of 30-40 mmHg PO2 values, prostanoid synthesis by human corpus cavernosum smooth muscle cells was low (0.1-0.7 pmol/10(6) cells). When PO2 was increased to 100 mmHg, a rapid increase in PGE2 >> PGF2alpha > PGD2 was observed (thromboxane A2 was undetectable), which peaked at 5.7 pmol PGE2/10(6) cells. Increased O2 tension correlated with increased PGE2 and increased intracellular synthesis of cAMP. The prostaglandin G/H synthase inhibitor indomethacin or the E prostanoid (EP2)-selective antagonist AH-6809 each inhibited the O2-tension-dependent increases in cAMP. These data support a role of differential O2 tension in the penis in the smooth muscle synthesis of PGE2, which in turn increases cAMP synthesis via EP2 receptors.

A conscious-rabbit model to study vardenafil hydrochloride and other agents that influence penile erection

Experimental models to study the effect of agents on penile erection usually include electrical stimulation of peripheral nerves in anesthetized animals combined with systemic or intracavernous injection of drugs. The objective of this study was to demonstrate that conscious rabbits can be used as a simple and quantitative model for the assessment of compounds that show potential for the treatment of erectile dysfunction. Erection was assessed by measuring the length of uncovered penile mucosa before and after the intravenous (i.v.) administration of agents. Animals did not require anesthesia during the course of the study. The phosphodiesterase 5 (PDE5) inhibitors vardenafil x HCl (hereafter called vardenafil) and sildenafil were given intravenously, and measurements were taken for 0-5 h. The effects of phentolamine and milrinone were also evaluated. Vardenafil (0.1-3 mg/kg) induced dose-dependent penile erections in conscious rabbits following i.v. administration. The efficacy of vardenafil was potentiated, and the minimal effective dose was reduced significantly to 0.01 mg/kg by simultaneous administration of the nitric oxide (NO) donor sodium nitroprusside (SNP). Administration of the NO-synthase inhibitor L-NAME abolished the effect. Sildenafil was effective in this model after i.v. administration. The alpha-adrenergic receptor antagonist phentolamine (0.1, 0.3 and 1 mg/kg i.v.) induced erections with a slower t(max) compared with vardenafil and sildenafil. Intravenous administration of the PDE3 inhibitor milrinone (1 mg/kg i.v.) was less effective than the PDE5 inhibitor vardenafil. The conscious rabbit is a suitable and reliable model for the evaluation of compounds with potential for the treatment of erectile dysfunction. This was demonstrated using compounds that target different signaling pathways that induce smooth muscle relaxation in the penis.

Neurologic erectile dysfunction

Neurologic erectile dysfunction presents a diagnostic and treatment challenge to the internist and urologist. Multiple chronic disease modalities and traumatic etiologies exist. Education regarding these conditions and a detailed and thorough history and office work-up are the best resources for the clinician. Treatment can follow the model of proceeding from the least to most invasive procedure (process of care), taking into account patient and partner satisfaction. Because the psychology of grief and loss may enter into treatment of some neurologic conditions (e.g., erectile dysfunction after radical retropubic prostatectomy, spinal cord injury, or chronic diseases), a whole-patient approach encompassing psychotherapy is warranted.

Honeymoon impotence: psychogenic or organic in origin?

OBJECTIVES

Honeymoon impotence is the inability to perform successful sexual intercourse during the initial experience, especially during the first nights of marriage, and it is relatively frequent in Turkey. We investigated the underlying penile vascular abnormalities in patients presenting with honeymoon impotence and sought to differentiate between psychogenic and organic etiologies.

METHODS

Between 1989 and 1999, 90 patients sought urologic help for honeymoon impotence. Patient age ranged from 18 to 39 years (mean 28.06 +/- 3.4). All patients were given an intracavernous injection of 60 mg papaverine combined with self-manual genital stimulation (CIS test) to assess the degree of tumescence. Patients with a positive response to the CIS test were later evaluated with nocturnal penile tumescence (NPT) monitoring. Patients with a negative response to the CIS test and/or NPT monitoring were evaluated further using penile color Doppler ultrasound.

RESULTS

A psychogenic etiology was found in 61 patients (67.7%), 50 (55.5%) of whom achieved satisfactory sexual intercourse after intracavernous injection. Twenty-five patients (27.7%) exhibited penile vascular abnormalities by color Doppler ultrasound. Neurogenic erectile dysfunction was considered in the remaining 4 patients (4.4%) with a positive response to the CIS test, abnormal findings on NPT monitoring, and a normal vascular system with color Doppler ultrasound.

CONCLUSIONS

The present study is the first to report penile vascular abnormalities in patients presenting with honeymoon impotence, which was previously believed to be exclusively psychogenic in origin. The evaluation of the penile vascular system in patients with honeymoon impotence may reveal underlying penile vascular abnormalities, allowing the choice of the appropriate therapeutic option.

Pharmacotherapy for erectile dysfunction

Erectile dysfunction (ED) is defined as the consistent inability to obtain or maintain an erection for satisfactory sexual relations. An estimated 20-30 million men suffer from some degree of sexual dysfunction. The past 20 years of research on erectile physiology have increased our understanding of the biochemical factors and intracellular mechanisms responsible for corpus cavernosal smooth muscle contraction and relaxation, and revealed that ED is predominantly a disease of vascular origin. Since the advent of sildenafil (Viagra), there has been a resurgence of interest in ED, and an increase in patients presenting with this disease. A thorough knowledge of the physiology of erection is essential for future pharmacological innovations in the field of male ED.