Characterisation of pomegranate juice effects on human corpus cavernosum

Pomegranate (POM) juice may benefit the erectile process, but the scientific evidence is lacking. This study evaluates the molecular characterisation and confirmation of POM's action on human corpus cavernosum (HCC) obtained from patients (n = 16) undergoing penile prosthesis implantation. After phenylephrine contraction, the relaxant effects of POM with various inhibitors in the presence and absence of palmitic acid (PA)-induced acute oxidative stress were investigated. Electrical field stimulation (EFS)- and acetylcholine (ACh)-induced relaxation were performed using organ bath preparation. Expression of neuronal nitric oxide synthase (nNOS), endothelial (eNOS), phosphodiesterase (PDE)-5A and cGMP levels were assessed in cells from ex vivo organ cultures of HCC, using RT-PCR, ELISA and immunohistochemistry techniques. POM induced marked relaxation of HCC (maximum response: 97.0 ± 3.1%) and reversed the PA-induced decrease of EFS (20 Hz). nNOS transcription was increased by 7-fold in POM-treated cells without influencing eNOS and PDE5A expressions. We conclude that POM induced marked relaxation of HCC via: (i) nNOS stimulation, and (ii) downstream relaxation stimulated by nNOS and cGMP and bypassing the NO and PDE5. This action provides a rationale for the therapeutic or preventative use of POM in men with erectile dysfunction who do not respond well to PDE5 inhibitors.

Therapeutic advances in the treatment of Peyronie's disease

Peyronie's disease (PD) is an under-diagnosed condition with prevalence in the male population as high as 9%. It is a localized connective tissue disorder of the penis characterized by scarring of the tunica albuginea. Its pathophysiology, however, remains incompletely elucidated. For the management of the acute phase of PD, there are currently numerous available oral drugs, but the scientific evidence for their use is weak. In terms of intralesional injections, collagenase clostridium histolyticum is currently the only Food and Drug Administration-approved drug for the management of patients with PD and a palpable plaque with dorsal or dorsolateral curvature >30°. Other available intralesional injectable drugs include verapamil and interferon-alpha-2B, however, their use is considered off-label. Iontophoresis, shockwave therapy, and radiation therapy have also been described with unconvincing results, and as such, their use is currently not recommended. Traction therapy, as part of a multimodal approach, is an underused additional tool for the prevention of PD-associated loss of penile length, but its efficacy is dependent on patient compliance. Surgical therapy remains the gold standard for patients in the chronic phase of the disease. In patients with adequate erectile function, tunical plication and/or incision/partial excision and grafting can be offered, depending on degree of curvature and/or presence of destabilizing deformity. In patients with erectile dysfunction non-responsive to oral therapy, insertion of an inflatable penile prosthesis with or without straightening procedures should be offered.

Erectile dysfunction in urethral stricture and pelvic fracture urethral injury patients: diagnosis, treatment, and outcomes

Urethral stricture disease, pelvic fracture urethral injury (PFUI), and their various treatment options are associated with erectile dysfunction (ED). The etiology of urethral stricture disease is multifactorial and includes trauma, inflammatory, and iatrogenic causes. Posterior urethral injuries are commonly associated with pelvic fractures. There is a spectrum in the severity of both conditions and this directly impacts the treatment options offered by the surgeon. Many published studies focus on the treatment outcomes and the relatively high recurrence rates after surgical repair. This communication reviews the current knowledge of the association between ED and urethral stricture disease, as well as PFUI. The incidence, pathophysiology, and clinical ramifications of both conditions on sexual function are discussed. The treatment options for ED in those patients are reviewed and summarized.

Effect of avanafil on rat and human corpus cavernosum

We compared the activity of a new phosphodiesterase-5 inhibitor (PDE5i) avanafil with sildenafil and tadalafil in human and rat corpus cavernosum (CC) tissues. The effect of avanafil with several inhibitors and electrical field stimulation (EFS) was evaluated on CC after pre-contraction with phenylephrine. With the PDE5i, sildenafil and tadalafil, concentration-response curves were obtained and cyclic guanosine monophosphate (cGMP) levels were measured in tissues. Avanafil induced relaxation with maximum response of 74 ± 5% in human CC. This response was attenuated by NOS inhibitor and soluble guanylate cyclase (sGC) inhibitor. Avanafil potentiated relaxation responses to acetylcholine and EFS in human CC and enhanced SNP-induced relaxation and showed 3-fold increase in cGMP levels. When compared with sildenafil, avanafil and tadalafil were effective at lower concentrations in human CC. In addition, Sprague-Dawley rats underwent in vivo intracavernosal pressure (ICP) and mean arterial pressure (MAP) measurements. Avanafil increased ICP/MAP that was enhanced by SNP and cavernous nerve (CN) stimulation in rat CC tissues. Also avanafil showed maximum relaxation response of 83 ± 7% in rat CC with 3-fold increase in cGMP concentration. Taken together, these results of our in vivo and in vitro studies in human and rat suggest that avanafil promotes the CC relaxation and penile erection via NO-cGMP pathway.

The pre-treatment prevalence and types of sexual dysfunction among patients diagnosed with prostate cancer

Erectile dysfunction (ED) following prostate cancer therapy is a common condition that is well documented in literature. Despite the significant focus placed on ED and prostate cancer, very little is known regarding the baseline prevalence of other aspects of sexual dysfunction (SD) in this specific cohort of patients. The objective of the current manuscript was to assess the prevalence of subtypes of SD, including ED, ejaculatory dysfunction (EjD) and decreased libido among men with newly diagnosed prostate cancer. To achieve this objective, patients presenting to our clinic with a new diagnosis of prostate cancer from July 2011 and May 2012 completed the Male Sexual Health Questionnaire (MSHQ) to assess baseline sexual function. A total of 60 patients completed an MSHQ, with a mean age of 60.28 ± 6.25 (range 44-73 years). Of patients surveyed, 14% reported no sexual activity within the previous month, while 53% had sex at least once weekly. The percentage of patients reporting ED, EjD and decreased sexual desire ≥50% of the time was 37, 26 and 48% respectively. Eleven to 18% of patients reported that these symptoms were 'very' or 'extremely' bothersome. Patients noted dissatisfaction with the quality of their sexual relationship, frequency of sexual activity and quality of sex in 18, 31 and 20%, respectively. Overall findings suggest that patients with newly diagnosed prostate cancer experience a high rate of SD at baseline. Knowledge of these prevalence rates may assist physicians managing patient's expectations with planned therapies.

Understanding the course of Peyronie's disease

AIMS

To correct common misconceptions about Peyronie's disease (PD) that present obstacles to early recognition and treatment.

METHODS

The prevalence, natural disease course, psychosocial effects and treatment considerations for patients with PD were reviewed.

RESULTS

Studies over the past decade have shown that the prevalence of PD may be higher (up to 20%) than previously thought. PD can lead to emotional and relationship distress. Nearly 10% of men who present with PD are younger than 40. Both younger age and comorbid vascular disease have been associated with more severe and progressive PD. In the majority of patients, symptoms will either deteriorate or remain stable. PD is often associated with erectile dysfunction (ED). Effective, minimally invasive treatments used early in the disease course include unapproved and/or investigational intralesional injection therapy with verapamil, interferon (IFN) α-2b, or collagenase clostridium histolyticum (CCH). Surgical intervention is considered in patients with ED and/or penile deformity that impairs sexual functioning; however, preoperative discussion of appropriate expectations is important.

DISCUSSION

The availability of effective minimally invasive and surgical therapies for PD suggests that active management should be considered over a 'wait-and-see' approach.

CONCLUSION

Providing early intervention and improved education/awareness of PD as a chronic and progressive disorder may result in improved physical and psychosocial outcomes for PD patients. As general practitioners are often the first contact for men with PD, they are well positioned to recognise symptoms early and promptly refer patients for further evaluation and treatment.

Update on treatments for premature ejaculation

Current and upcoming treatment options for premature ejaculation (PE) are of global clinical interest. In 2008, the International Society for Sexual Medicine published an evidence-based definition for PE. While there are no US Food and Drug Administration-approved therapies for PE, the American Urological Association 2004 guidelines state the serotonergic antidepressants paroxetine, sertraline, fluoxetine and clomipramine and the topical lidocaine-prilocaine cream are effective treatment options. However, there are limitations associated with their use, which may be overcome by PE-specific therapies currently in development. Two agents that are in advanced stages of clinical development include: (i) dapoxetine, an on-demand short-acting selective serotonin reuptake inhibitor, and (ii) PSD502, a metered-dose aerosol containing lidocaine and prilocaine, also for on-demand treatment. Another on-demand agent in development is tramadol, a weak opioid that is currently approved for treating pain. Coupled with efficient diagnosis, it is hoped that these newer agents will improve the quality of life for patients who suffer from PE.

Available and future therapies for premature ejaculation

Premature ejaculation (PE), the most common male sexual dysfunction, impacts the quality of life of not only the affected male but also his partner. Despite its prevalence, there are currently no United States Food and Drug Administration-approved therapies for PE. In 2004, the American Urological Association published treatment guidelines for PE that recommended the serotonergic antidepressants paroxetine, sertraline, clomipramine and fluoxetine, as well as topical lidocaine-prilocaine cream. None of these treatments were developed for PE, and all have limitations associated with their use. Therapies in development may have advantages over the currently available treatments. These include PSD-502, a metered-dose aerosol of lidocaine and prilocaine used as an on-demand local treatment, and dapoxetine, an on-demand short-acting selective serotonin reuptake inhibitor. Together with a recent, evidence-based definition of PE, these novel therapies should improve sexual function and quality of life in men suffering from PE.

Current safety and tolerability issues in men with erectile dysfunction receiving PDE5 inhibitors

AIMS

Treatment of erectile dysfunction (ED) has been greatly advanced by the advent of phosphodiesterase type-5 (PDE5) inhibitors. Upon the introduction of these agents, their cardiovascular (CV) safety was a major concern, mainly due to their vasodilatory effects. We conducted an electronic literature review of data concerning the safety and tolerability issues of men with ED receiving PDE5 inhibitors.

RESULTS

Although safety concerns have been raised, evaluation of CV safety and related adverse events in clinical trials has not revealed any atypical safety issues.

DISCUSSION

No causal association has been established to date between non-arteritic anterior ischaemic optic neuropathy (NAION) and PDE5 inhibitors. In addition, there are established guidelines which provide recommendations for the safe and effective use of these agents in treating men with ED and associated comorbidities.

CONCLUSIONS

Clinical trial and postmarketing surveillance data confirm the safety and tolerability profile of the PDE5 inhibitors, even in patients with endothelial dysfunction-associated comorbidities.

Gene and stem cell therapy for erectile dysfunction

Erectile dysfunction (ED) is defined as the inability to attain and/or maintain penile erection sufficient for satisfactory sexual performance. ED is a highly prevalent health problem with considerable impact on the quality of life of men and their partners. Although the treatment of ED with oral phosphodiesterase type V (PDE5) inhibitors is effective in a wide range of individuals, it is not efficacious in all patients. The failure of PDE5 inhibitors happens mainly in men with diabetes, non-nerve sparing radical prostatectomy, and high disease severity. Therefore, improved therapies based on a better understanding of the fundamental issues in erectile physiology and pathophysiology have recently been proposed. Here, we summarize studies on ED treatment using gene and stem cell therapies. Adenoviral-mediated intracavernosal transfer of therapeutic genes, such as endothelial nitric oxide synthase (eNOS), calcitonin gene-related peptide (CGRP), superoxide dismutase (SOD), and RhoA/Rho kinase and mesenchymal stem cell-based cell and gene therapy strategy for the treatment of age- and diabetes-related ED are the focus of this review.

Effect of combination endothelial nitric oxide synthase gene therapy and sildenafil on erectile function in diabetic rats

Erectile dysfunction associated with diabetes mellitus is caused in part by disordered endothelial smooth muscle relaxation, neuropathy, and a decrease in cavernosal nitric oxide synthase (NOS) activity. The purpose of this study was to determine whether a combination of sildenafil and adenoviral gene transfer of endothelial NOS (eNOS) could enhance the erectile response in diabetic rats. Five groups of animals were utilized: (1) age-matched control rats, (2) streptozotocin (STZ)-induced diabetic rats (60 mg/kg i.p.), (3) STZ-rats + sildenafil (2 mg/kg i.v.), (4) STZ-rats transfected with AdCMVbetagal or AdCMVeNOS, and (5) STZ-rats transfected with AdCMVeNOS +sildenafil (2 mg/kg i.v.). At 2 months after i.p. injection of STZ, groups 4 and 5 were transfected with the adenoviruses and 1-2 days after transfection, all animals underwent cavernosal nerve stimulation (CNS) to assess erectile function. Cyclic 3',5'-guanosine monophosphate (cGMP) levels were assessed in the cavernosal tissue. STZ-diabetic rats had a significant decrease in erectile function as determined by the peak intracavernosal pressure (ICP) and total ICP (area under the erectile curve; AUC) after CNS when compared to control rats. STZ-diabetic rats+AdCMVeNOS had a peak ICP and AUC, which were similar to control animals. STZ-diabetic rats administered sildenafil demonstrated a significant increase in peak ICP at the 5 and 7.5 V settings, while the AUC was significantly increased at all voltage (V) settings. The increase in both ICP and AUC of STZ-diabetic rats transfected with AdCMVeNOS at all V settings was greater than STZ-diabetic rats transfected with AdCMVbetagal. STZ-diabetic rats transfected with AdCMVeNOS and administered sildenafil had a significant increase in total ICP that was greater than eNOS gene therapy alone. Cavernosal cGMP levels were significantly decreased in STZ-diabetic rats, but were increased after transfection with AdCMVeNOS to values greater than control animals. In conclusion, overexpression of eNOS and cGMP in combination with sildenafil significantly increased both the peak ICP and total ICP to CNS in the STZ-diabetic rat, which was similar to the response observed in control rats. Moreover, the total erectile response was greater in STZ-diabetic rats receiving eNOS gene therapy plus sildenafil than STZ-rats receiving sildenafil or eNOS gene therapy alone.

Feline penile erection induced by topical glans penis application of combination alprostadil and SEPA (Topiglan)

The objective of this study was to evaluate the efficacy of topically applied prostaglandin E1 (PGE(1))+5% SEPA (soft enhancement of percutaneous absorption) on the glans penis in a feline erection model. Erectile response after glans penis administration of PGE(1)+5% SEPA cream (Topiglan, MacroChem Co., Lexington, MA, USA) was compared to the erectile response after intracavernosal administration of the triple-drug combination (1.65 mg papaverine, 25 microg phentolamine, and 0.5 microg PGE(1)). The placebo cream and increasing concentrations (0.25%, 2.5 mg/ml; 0.5%, 5 mg/ml; and 1%, 10 mg/ml) of PGE(1)+5% SEPA were applied in a total volume of 0.1 ml via a plastic needle-less syringe. The control triple-drug combination was administrated intracavernosally via a 30-gauge needle at the completion of each experiment to serve as a control reference. With each application of placebo, PGE(1)+SEPA, and the triple-drug combination, changes in intracavernosal pressure and systemic blood pressure were continuously monitored. Topical application of PGE(1)+SEPA induced increases in intracavernosal pressure in a dose-dependent manner, with minimal effects on systemic blood pressure. The increases obtained with 1% PGE(1) Topiglan cream were similar to the intracavernosal pressure values elicited by the standard intracavernosal triple-drug combination. These data demonstrate that topical glans penis application of PGE(1)+SEPA can induce an erectile response in cats with minimal systemic adverse effects. Oral pharmacological agents are the first-line treatment for male ED. Studies investigating the effectiveness of noninvasive modalities such as topical therapy should continue, because these agents have the potential to avoid the systemic effects commonly seen with oral therapies. Additionally, topical therapy may also benefit patients who are unresponsive to oral agents or have explicit contraindications. Topical PGE(1) application to the glans penis may become an important treatment option in selected patients suffering from erectile dysfunction.

Three-piece inflatable penile prosthesis components (surgical pearls on reservoirs, pumps, and rear-tip extenders)

Erectile dysfunction (ED) is a major quality-of-life disorder that affects greater than 30 million American men each year. Since the introduction of Viagra, more and more men are presenting with ED that is not responding to oral or local therapies. Penile prosthesis implantation is recognized as the most effective, although most invasive, ED therapy with a high satisfaction rate. With an aging population both aware of and requesting therapy for ED, the number of penile prosthesis implantations will remain stable, especially at centers specializing in ED treatment. Therefore, a better understanding of the techniques used for placement of the penile prosthesis is necessary. The following review will discuss the techniques and a few clinical pearls in the placements of inflatable penile prostheses.

Surgical approaches for advanced Peyronie's disease patients

Surgical therapy for Peyronie's disease (PD) is reserved for patients with severe penile deformity that fails to improve with medical treatment and impedes sexual intercourse. The surgical treatment of PD consists of either correction of the penile deformity or insertion of a penile prosthesis in patients with concomitant erectile dysfunction (ED). Plaque incision/excision combined with grafting procedures or plication techniques are suitable in Peyronie's patients having an adequate penile vascular supply. When patients with Peyronie's disease have both penile deformity and ED, penile prosthesis implantation with or without excision or incision of the tunica is the current standard of care.

History, epidemiology, and clinical presentation of Peyronie's disease

Peyronie's disease is a localized connective tissue disorder that involves the tunica albuginea of the penis. The formation of fibrotic plaques in the tunica albuginea and surrounding cavernosal tissue alters penile anatomy and can cause different degrees of bending and narrowing, as well as penile pain and erectile dysfunction. Although long recognized as an important clinical entity of the male genitalia, the etiology of this disease has remained poorly understood. Recent studies have demonstrated that this disorder may be more prevalent than previously reported. The following review will examine the history, epidemiology, and clinical presentation of Peyronie's disease.

Comparison of cadaveric pericardial, dermal, vein, and synthetic grafts for tunica albuginea substitution using a rat model

OBJECTIVE

To evaluate in an animal model the intermediate and long-term efficacy of cadaveric pericardium, dermis, vein and Gore-Tex per thousand as grafting materials for tunica albuginea substitution after plaque excision for Peyronie's disease.

MATERIALS AND METHODS

The study comprised 100 male Sprague-Dawley rats (300-325 g) divided into five equal groups: group 1, sham-operated controls; and groups 2-5 which underwent wedge excision of the tunica albuginea and replacement with either cadaveric pericardium, dermis, vein or Gore-Tex grafts. Ten rats in each group had the cavernosal nerve stimulated electrically to assess erectile function at 4 months, and the remaining 10 rats at 6 months. After death the sampled tissues were fixed in 10% formalin, paraffin-embedded, and stained with Masson's trichrome and Verhoff's van Giesen for collagen and elastic fibres.

RESULTS

Erectile function, assessed by cavernosal nerve stimulation, did not differ significantly in any of the groups (P > 0.05). The histological assessment of penile cross-sections showed minimal fibrosis surrounding the patch in the dermal and vein grafts, and moderate to severe fibrosis in the Gore-Tex graft at 4 and 6 months. In the pericardial graft there was a moderate degree of fibrosis at 4 months with only minimal fibrosis at 6 months.

CONCLUSIONS

These results show that cadaveric pericardium allows complete penile expansion and is strong enough to withstand normal intracorporal pressures. There was minimal fibrosis in the pericardial, dermal and vein grafts, and moderate fibrosis in the Gore-Tex graft at 6 months. The pericardial graft is a satisfactory grafting material when used for tunica albuginea substitution, including the surgical management of Peyronie's disease.

Penile epithelioid sarcoma and the case for a histopathological diagnosis in Peyronie's disease

OBJECTIVES

To devise a set of clinical criteria that would identify which penile abnormality could be malignant and warrant biopsy, between Peyronie's disease (a pathological fibrosis involving the tunica albuginea of the penis) and epithelioid sarcoma (ES) of the penis (a rare malignant condition which can resemble Peyronie's disease in clinical presentation).

PATIENTS AND METHODS

The pathology reports and histological slides of men with Peyronie's disease who underwent penile biopsy were reviewed for ES. The medical charts of suspicious cases were then reviewed by a pathologist, unaware of the origin, for consistencies in signs, symptoms and clinical findings. These consistencies were then to be used to develop criteria for biopsy. Thirty-two men underwent penile biopsy from 1992 to 2001.

RESULTS

Because there were no actual cases of ES, a specific set of criteria for ES could not be established. A review of previously published cases was then used for comparison with the present patients.

CONCLUSIONS

Many of the previously reported cases included signs and symptoms of urethral narrowing or compression, causing lower urinary tract symptoms. In addition, the penile nodule size was reported to progressively enlarge over time. Because of the high prevalence of Peyronie's disease and low prevalence of ES, biopsy of every penile nodule is not judicious. However, signs and symptoms of urethral obstruction, and a progressively growing and persistently painful nodule should suggest a possible malignancy and warrant biopsy.

Testicular-sparing surgery: a reasonable option in selected patients with testicular lesions

OBJECTIVE

To describe our experience of inguinal exploration in patients who had a reasonable chance of having a benign testicular lesion.

PATIENTS AND METHODS

From 1995 to 2002, 11 patients (mean age 43 years, range 27-63) with testicular masses that were suspected to be benign underwent inguinal exploration.

RESULTS

In nine of the 11 patients, frozen-section analysis and the final pathological results were similar, and two underwent inguinal orchidectomy. In seven patients the testicle was spared. Finally, because of an uncertain pathological diagnosis and patient age, two patients underwent orchidectomy.

CONCLUSIONS

Inguinal exploration and testicular-sparing surgery are reasonable options in patients with peripheral intratesticular lesions, on the basis of preoperative ultrasonographic characteristics, and if there is a possibility of the mass being benign because of age, race, physical examination and tumour markers.

Antimicrobial activity of antibiotic-soaked, Resist-coated Bioflex

This study investigates whether a hydrophilic coating (Resist), designed to inhibit bacterial adherence, applied to inflatable penile prostheses can prolong the effect of intraoperative antibiotics. The activity of antibiotic-soaked Bioflex (penile prosthetic substrate material) discs with and without Resist was examined by measuring the zone of inhibition following in vivo exposure in four groups of rabbits: 1, 2, 3 and 5 days' duration of disc implantation. Coated and uncoated discs were soaked in an aqueous solution of gentamicin and bacitracin. The implanted antibiotic-soaked discs were extracted, and the zone of inhibition against four microorganisms in vitro demonstrated that the Resist coating was especially effective against Staphylococcus epidermidis, and statistically significant improvements were observed for the coated over the uncoated substrate up to 3 days following implantation. This effect, and the anti-adherence properties of Resist, may prevent adhesion and colonization of some microorganisms to penile implants and reduce chances for infection.

Implications of nitric oxide synthase isoforms in the pathophysiology of Peyronie's disease

Peyronie's disease is an idiopathic, localized connective tissue disorder of the penis which involves the tunica albuginea of the corpus cavernosum and the adjacent areolar space. Peyronie's disease is characterized by local changes in the collagen and elastic fiber composition of the tunica albuginea. The formation of fibrotic plaques alters penile anatomy and can cause different degrees of bending and narrowing, as well as penile pain and erectile dysfunction. Though long recognized as an important clinical entity of the male genitalia, the etiology of this disease has remained poorly understood. Until recently there have been no studies to examine the role nitric oxide (NO) and nitric oxide synthase (NOS) isoforms may play in the onset and progression of Peyronie's disease. NO is a potent biological mediator with diverse physiological and pathophysiological roles. The purpose of this review is to describe each of the NOS isoforms and their potential roles in the pathophysiology of Peyronie's disease, with particular emphasis on the regulation of endothelial and inducible NOS isoforms.

Intralesional interferon-alpha-2b for the treatment of Peyronie's disease

Peyronie's disease can best be described as a localized connective tissue disorder that primarily affects the tunica albuginea of the penis. The disease may be attributed to repetitive vascular trauma that initiates an inflammatory process and ultimately leads to the formation of a fibrous penile plaque. The plaque consists mainly of collagen and can significantly alter penile anatomy and function. Patients with Peyronie's disease will most often present with penile curvature, pain on erection, a palpable nodule most commonly located on the dorsal shaft of the penis, and erectile dysfunction. There is no definitive treatment for Peyronie's disease and the treating physician has many options. They may wait for spontaneous resolution of the plaque, choose medical therapy (which includes both oral and intralesional regimens), or opt for surgical management. The main purpose of this article is to discuss the advances in medical therapy for Peyronie's disease, in particular intralesional injection of interferon-alpha-2b (IFN-alpha-2b). Several studies have concluded that IFN-alpha-2b can be an effective modality of treatment and that many patients placed on a regimen of IFN-alpha-2b experienced a significant reduction in penile curvature, diminished pain with erection, and decreased size of the plaque. Further clinical studies are currently being undertaken to determine the precise quantity and frequency of administration of IFN-alpha-2b that is most effective with the least amount of side effects.

Localization of peripheral dopamine D1 and D2 receptors in rat corpus cavernosum

OBJECTIVE

To detect and locate anatomically peripheral dopamine D1 and D2 receptors in rat cavernosa, as dopamine is important in sexual drive and penile erection through receptors located in the central nervous system.

MATERIALS AND METHODS

Corpora cavernosa were obtained from Sprague-Dawley rats; total RNA and membrane proteins were extracted and cryostat sections prepared. The rat brain hypothalamus was used as a control for dopamine D1 and D2 receptors. The presence and expression of peripheral dopamine D1 and D2 receptor mRNAs in rat corpus cavernosa was assessed using reverse transcription and polymerase chain reaction (RT-PCR), and Northern blot hybridization using (32)P-UTP-labelled RNA probes. Concurrently, corresponding proteins from D1 and D2 receptors were assayed and detected by a Western blotting technique. The anatomical location of dopamine D1 and D2 receptor mRNAs in rat penile tissues was identified by in situ hybridization using (35)S-UTP-labelled RNA probes in cryostat sections. Immunohistochemical staining was used to locate peripheral dopamine D1 and D2 receptor proteins in rat corpora cavernosa.

RESULTS

Dopamine D1 and D2 receptor gene expression was detected in rat corpora cavernosa. In situ hybridization signals for dopamine D1 and D2 receptor mRNAs were localized to corpus cavernosal tissues and dorsal vessels in the rat penis. Western blot analyses showed peripheral dopamine D1 and D2 receptor proteins in rat corpora cavernosa. Immunohistochemically, peripheral dopamine D1 and D2 receptor proteins were detected in dorsal nerves, dorsal vessels and corpus cavernosal smooth muscle of the rat penile tissues.

CONCLUSIONS

Peripheral dopamine D1 and D2 receptors are present in the corpora cavernosa of rats. The functional significance of these receptors and signal transduction pathways in modulating the vascular tone of the penis warrants further investigation.