Stimulation of dopamine receptors in the paraventricular nucleus of the hypothalamus of male rats induces penile erection and increases extra-cellular dopamine in the nucleus accumbens: Involvement of central oxytocin

The effect of a pro-erectile dose of apomorphine, a mixed dopamine receptor agonist, and of PD-168077 (N-[4-(2-cyanophenyl)piperazin-1-ylmethyl]-3-methylbenzamide maleate), a selective dopamine D4 receptor agonist, injected into the paraventricular nucleus of the hypothalamus on the concentration of extra-cellular dopamine and its main metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the dialysate from the nucleus accumbens was studied in male rats. As expected, apomorphine (0.1microg) and PD-168077 (0.1microg) induced penile erection episodes, which occurred concomitantly to an increase in extra-cellular dopamine and DOPAC concentration in the dialysate from the shell of the nucleus accumbens, as measured by intracerebral microdialysis. When induced by apomorphine, these effects were reduced by 80% by raclopride, a selective D2/D3 receptor antagonist (1microg) and only by 40-45% by L-745,870 (1microg), a selective dopamine D4 receptor antagonist. When induced by PD-168077, these effects were reduced by more than 80% by L-745,870 (1microg), but only by 35-40% by raclopride. Irrespective of the dopamine agonist used to induce penile erection, the pro-erectile effect and the concomitant increase in dopamine and DOPAC concentration in the nucleus accumbens dialysate were almost completely abolished by d(CH(2))(5)Tyr(Me)(2)-Orn(8)-vasotocin(1microg), a potent oxytocin receptor antagonist, given into the lateral ventricles. The present results suggest that stimulation of dopamine receptors (mainly of the D2 to D4 subtype) in the paraventricular nucleus induces the release of oxytocin in brain areas that influence the activity of mesolimbic dopaminergic neurons mediating the appetitive and reinforcing effects of sexual activity. This provides evidence for a role of oxytocin in neural circuits that integrate the activity of neural pathways controlling the consummatory aspects of sexual behaviour (e.g., penile erection) with those controlling sexual motivation and sexual arousal.     

The natural history of Peyronie's disease: an ultrasonography-based study

OBJECTIVES: To define ultrasonographic patterns reflecting different states of Peyronie's disease (PD) and to use them to evaluate the natural history of the disease. MATERIAL AND METHODS: Diagnosis of PD was based on medical and sexual history, physical examination, intracavernosal injection test, and penile ultrasonography. Patients with penile fracture history were excluded from the study. Three groups were formed according to ultrasonographic patterns: solitary hyperechoic lesion without acoustic shadow (group A), moderately hyperechoic multiple scattered calcified lesions with acoustic shadows (group B), dense calcified hyperechoic plaque with acoustic shadow (group C). All patients entered a watchful waiting protocol for 1 yr followed by a new penile ultrasonography. RESULTS: Ninety-five 95 patients with PD were included in the study (mean age, 57.2+/-9.1 yr; mean duration of disease, 12.9+/-8.9 mo). Risk factors associated with cardiovascular disease were present in 79 of 95 patients (83.16%). Eleven (11.6%), 35 (36.8%), and 49 (51.6%) patients were classified into groups A, B and C, respectively. At the end of the study, in group A, reduction of fibrotic lesions and curvature angle was noticed in 9 of 11 (81.8%) patients, whereas plaque formation was noticed in 2 of 11 (18.2%) patients. In group B, plaque and curvature reduction was noticed in 15 of 35 (42.9%) and 12 of 35 (34.3%) respectively, whereas in the rest a dense calcified plaque was noticed. In group C, no ultrasonographic evidence of improvement was noticed; curvature angle was reduced in 4 of 49 (8.2%), owing to the extension of the plaque circumferentially. Significant hemodynamic changes were noticed at the two time points tested (30.53% diagnosed with vascular disease at baseline vs. 46.32% at the end of the study, p=0.03). CONCLUSIONS: Corporal ultrasonography in patients with PD allows objective evaluation and classification of disease. The density of echogenic areas and presence of acoustic shadows are predictors of disease stability.     

Neurofibromatosis type 1 with external genitalia involvement presentation of 4 patients

Genitourinary neurofibromas with clitoral involvement in neurofibromatosis type 1 are rare, and even more infrequent are the neurofibromas involving genitalia in males. The most frequent presenting sign of neurofibroma in females is clitoromegaly with pseudopenis, and enlarged penis is the most common sign in males. Labium majus neurofibroma not associated with clitoral involvement is extremely rare. Magnetic resonance imaging demonstration of the neurofibromas has seldom been reported. We report 4 children, 3 girls and 1 boy, with plexiform neurofibromas involving the external genitalia. Three of the 4 patients had histologic confirmation of neurofibroma. Two girls with clitoral hypertrophy had a neurofibroma that infiltrated the clitoris and extended unilaterally to the lower bladder wall. One girl had a plexiform neurofibroma that affected a labium. One boy with asymmetric penile hypertrophy since 2 years of age and ipsilateral gluteal hypertrophy had plexiform neurofibromas that extended between the left lumbogluteal and penile regions, infiltrating the left rectum wall and bladder with compression of both structures, the left prostate, and the left half of the cavernous corpi with hypertrophy of this part and asymmetry of the penis. Magnetic resonance imaging demonstrated in all patients that external genitalia and plexiform neurofibroma formed images of nondetachable structures. However, hermaphroditism was discarded by chromosomal study in all 3 girls before ratifying the diagnosis of external genitalia neurofibroma.