Brain oxytocin receptors mediate ejaculation elicited by 7-hydroxy-2-(di-N-propylamino) tetralin (7-OH-DPAT) in anaesthetized rats

BACKGROUND AND PURPOSE

The involvement of the neuropeptide oxytocin in the control of male sexual responses is documented although its exact mechanisms of action, and especially the site(s) of action, are not fully delineated. In order to clarify this issue, we tested the effects of a peptide oxytocin antagonist delivered through different routes on sexual responses elicited, in anaesthetized male rats, by i.c.v. 7-hydroxy-2-(di-N-propylamino) tetralin (7-OH-DPAT), a dopamine agonist, preferentially active on D3 receptors.

EXPERIMENTAL APPROACH

Seminal vesicle pressure (SVP) and bulbospongiosus muscle (BS) electromyograms were recorded as physiological markers of emission and expulsion phases of ejaculation respectively and intracavernosal pressure (ICP) was monitored as a physiological marker of erection.

KEY RESULTS

When injected i.v., the oxytocin antagonist did not impair 7-OH-DPAT-induced SVP and ICP responses while BS burst frequency was diminished. When delivered i.c.v., the oxytocin antagonist dose-dependently inhibited occurrence of 7-OH-DPAT-induced sexual responses. When delivered intrathecally (i.t.) at the level of the 6th lumbar (L6) segment, but not the 13th thoracic (T13) segment, the oxytocin antagonist reduced the duration of BS responses and the occurrence of ejaculation without impairing ICP responses.

CONCLUSIONS AND IMPLICATIONS

Brain oxytocin receptors mediate male sexual responses elicited by i.c.v. 7-OH-DPAT in anaesthetized rats whereas L6 spinal oxytocin receptors only impair the occurrence of ejaculation. Peripheral oxytocin receptors are marginally involved in 7-OH-DPAT-induced sexual responses. These findings should be considered for the development of potential pharmacological treatment of premature ejaculation in man.

Cardiovascular outcomes among sildenafil users: results of the International Men's Health Study

AIM

To assess the incidence of serious cardiovascular disease (CVD) events [i.e. myocardial infarction (MI) and stroke] and all-cause mortality in men with erectile dysfunction (ED) who received prescriptions for sildenafil.

METHODS

The International Men's Health Study (IMHS) was a prospective, observational cohort study of patients with ED and a new or existing prescription for sildenafil. Baseline and follow-up questionnaires provided information on demographics, CVD risk factors and ED. Postevent questionnaires were mailed to patients following possible nonfatal CVD events to collect information related to exposure to sildenafil/ED treatments before the event.

RESULTS

Thirty-five CVD events were reported in 30 patients in the analysis set (n = 3813). The incidence of all-cause mortality, MI and stroke was 0.4, 0.6 and 0.1 per 100 patient-years of observation respectively. Among the six men who reported using sildenafil in the month before a nonfatal CVD event, two reported use in the 24 h before the event.

CONCLUSION

The results of the IMHS support previous reports that ED and CVD are often comorbid and share risk factors.

The three stages of epilepsy in patients with CDKL5 mutations

Mutations in the X-linked cyclin-dependent kinase-like 5 (CDKL5) gene are responsible for a severe encephalopathy with early epilepsy. So far, the electroclinical phenotype remains largely unknown and no clear genotype-phenotype correlations have been established.

PURPOSE

To characterize the epilepsy associated with CDKL5 mutations and to look for a relationship between the genotype and the course of epilepsy.

METHODS

We retrospectively analyzed the electroclinical phenotypes of 12 patients aged from 2.5 to 19 years diagnosed with pathogenic CDKL5 mutations and one patient with a novel intronic sequence variation of uncertain pathogenicity and examined whether the severity of the epilepsy was linked to the type and location of mutations.

RESULTS

The epilepsy course reveals three successive stages: (Stage I) early epilepsy (onset 1-10 weeks) with normal interictal electroencephalogram (EEG) (10/13) despite frequent convulsive seizures; (Stage II) epileptic encephalopathy with infantile spasms (8/8) and hypsarrhythmia (8/8). At the age of evaluation, seven patients were seizure free and six had developed refractory epilepsy (stage III) with tonic seizures and myoclonia (5/6). Interestingly, the patients carrying a CDKL5 mutations causing a truncation of the catalytic domain tended to develop a more frequent refractory epilepsy than patients with mutations located downstream (4/6, 66.6% versus 1/6, 16%) although, these trends are not yet significant.

DISCUSSION

Our data contribute to a better definition of the epileptic phenotype in CDKL5 mutations, and might give some clues to a potential relationship between the phenotype and the genotype in these patients.

Acrocallosal syndrome in fetus: focus on additional brain abnormalities

Acrocallosal syndrome (ACS) is an autosomal recessive disorder characterized by craniofacial dysmorphism, agenesis or hypoplasia of the corpus callosum, duplication of the phalanges of the hallux, more rarely the thumbs, post-axial polydactyly, syndactyly and severe mental retardation. Here we report the two first descriptions of acrocallosal syndrome in fetus with extensive neuropathological study and provide new data regarding additional brain abnormalities in ACS. The first case was a 25-gestational week male fetus displaying craniofacial and limb abnormalities, with bilateral syndactyly of the fourth and fifth fingers, preaxial polydactyly of the left foot and an inter-frontal extra-bone. The second fetus was a 33-gestational week male fetus. His left hand displayed a broad thumb and 4/5 syndactyly. In both cases, gross examination of the brain showed an absence of corpus callosum associated with interhemispheric cysts. The cerebral cortex in front of the cysts was nodular. Upon microscopic examination, the nodular masses corresponded to large dysplastic areas represented by clusters of undifferentiated neurons in the white matter. The cyst wall showed arachnoidal and ependymal covering and contained numerous choroid plexus, suggesting a developmental abnormality of the ventricles. The pons and the cerebellum were hypoplastic. The dentate nuclei were fragmented. Numerous neuronal heterotopias associated with ectopic ependymal cavities were observed in the vermis in one case. The olivary nuclei were severely dysplastic too. We hope that these new data will make both the ante- and post-natal diagnosis easier, facilitate comparisons with animal models and encourage the identification of the genes responsible for this syndrome.

Urethral closure mechanisms during sneezing-induced stress in anesthetized female cats

During stress-induced increase in abdominal pressure, urinary continence is maintained by urethral closure mechanisms. Active urethral response has been studied in dogs and rats. Such an active urethral response is also believed to occur in humans during stress events. We aimed to investigate urethral closure mechanisms during sneezing in cats. Urethral pressures along the urethra (UP1-UP4), with microtip transducer catheters with UP4 positioned in the distal urethra where the external urethral sphincter (EUS) is located, and intravesical pressure were measured, and abdominal wall, anal sphincter (AS), levator ani (LA), and EUS electromyograms (EMGs) were recorded during sneezing under closed-abdomen and open-abdomen conditions in eight anesthetized adult female cats. Proximal and middle urethral response induced by sneezing was not different from bladder response. Distal urethral response was greater compared with proximal and middle urethral and bladder response. In the open-abdomen bladder, proximal and middle urethral responses were similarly decreased and distal urethral response was unchanged compared with the closed-abdomen bladder. Bladder and urethral responses were positively correlated to sneeze strength. EUS, LA, and AS EMGs increased during sneezing. No urine leakage was observed, regardless of the strength of sneeze. In cats urethral closure mechanisms are partly passive in the proximal and middle urethra and involve an active component in the distal urethra that is believed to result from EUS and possibly LA contractions. Because central serotonin exerts similar effects on the lower urinary tract in cats and humans, the cat may represent a relevant model for pharmacological studies on continence mechanisms.

Further evidence of the reliability and validity of the premature ejaculation diagnostic tool

This study details the further validation of the Premature Ejaculation Diagnostic Tool (PEDT), a five-item tool, developed to systematically apply the Diagnostic and Statistical Manual of Mental Disorders, revised version 4 (DSM-IV-TR), criteria in diagnosing presence or absence of premature ejaculation (PE). A total of 102 men completed the PEDT and were then interviewed by one of the seven clinical experts, who made a diagnosis of presence or absence of PE. The diagnoses from these two methods were compared to assess the convergent validity of PEDT. Retest reliability was also assessed, by men completing the PEDT a second time, approximately 2 weeks after the first administration. The level of agreement between clinical expert and PEDT diagnoses was very high (kappa-statistic=0.80 (95% CI=0.68-0.92)), and retest reliability was very good - Intraclass correlation coefficient=0.88. In summary, the PEDT is extensively validated, self-report measure that can systematically assess DSM-IV-TR criteria to provide accurate diagnoses of PE/no-PE.

Chapitre A - Les dysfonctions sexuelles masculines et leurs traitements en neuro-urologie

The management of sexual dysfunction has been revolutionized over recent years with the arrival of new treatments for erectile dysfunction. In parallel, groups specialized in neurosexology have gradually emerged in order to improve the patient's fertility. This article presents the disorders most frequently encountered in spinal cord injury and the main approaches to management.

Chapitre A-2 - Traitements pharmacologiques per-os à visée sphinctérienne en neuro-urologie

Sphincter dysfunction is an almost constant pathological process in neurourology. No oral pharmacological treatment is available to treat stress urinary incontinence secondary to sphincter incompetence or to relieve urethral hypertonia usually induced by detrusor-sphincter dyssynergia. The few treatments that induce sphincter relaxation are not sufficient to justify a routine therapeutic indication.

Effect of acute dapoxetine administration on the pudendal motoneuron reflex in anesthetized rats: comparison with paroxetine

PURPOSE

Pudendal motoneuron reflex discharges elicited by bilateral electrical stimulation of the dorsal nerves of the penis were used as an experimental model of the expulsion reflex of ejaculation to investigate the effect of acute intravenous delivery of dapoxetine, a short acting selective serotonin reuptake inhibitor, in anesthetized rats. Dapoxetine was compared with paroxetine, the selective serotonin reuptake inhibitor of reference.

MATERIALS AND METHODS

Stimulating electrodes were placed bilaterally on the dorsal nerves of the penis and a recording electrode was placed on the motor branch of the pudendal nerve to monitor pudendal motoneuron reflex discharges in urethane anesthetized rats. Pudendal motoneuron reflex discharges induced by penile dorsal nerve stimulation were measured before and 60 minutes after a single intravenous injection of dapoxetine or paroxetine, each tested at 3 doses (1, 3 and 10 mg/kg) or after a single injection of vehicle.

RESULTS

At all doses tested dapoxetine significantly lengthened the latency of pudendal motoneuron reflex discharges following bilateral stimulation of the dorsal nerves of the penis in comparison with vehicle, whereas only the 1 mg/kg dose of paroxetine was effective. The amplitudes of pudendal motoneuron reflex discharges were significantly decreased only in rats treated with 3 mg/kg dapoxetine compared to vehicle.

CONCLUSIONS

Acute systemic delivery of selective serotonin reuptake inhibitors is capable of modulating the expulsion reflex of ejaculation in anesthetized rats with dapoxetine appearing to be more effective than paroxetine. These findings support the beneficial effect of on-demand administration of dapoxetine for premature ejaculation.

Mutations in PHD-like domain of the ATRX gene correlate with severe psychomotor impairment and severe urogenital abnormalities in patients with ATRX syndrome

Mutations in ATRX are associated with a wide and clinically heterogeneous spectrum of X-linked mental retardation syndromes. The ATRX protein, involved in chromatin remodelling, belongs to the family of SWI/SNF DNA helicases and contains a plant homeodomain (PHD)-like domain. To date, more than 60 different mutations have been reported in ATRX. One of them is recurrent and accounts for 20% of all the reported mutations, whereas all others are private. Most mutations are clustered in the two major functional domains, the helicase and the PHD-like domain. So far, no clear genotype-phenotype correlation has been established, with exception to the rare truncating mutations located at the C-terminal part of the protein, which are consistently associated with severe urogenital defects. In this study, we report the molecular analysis performed in 16 families positive for ATRX. Our findings indicate that, in addition to the previously described mutation 'hotspot' in the PHD-like domain, two other protein sections emerge as minor 'hotspots' in the helicase region encoded by exons 18-20 and 26-29, respectively, gathering 33% of all described mutations. Additionally, based on the clinical data collected for 22 patients from the 16 families, we observe that mutations in the PHD-like domain produce severe and permanent psychomotor deficiency, usually preventing patients from walking, as well as constant urogenital abnormalities, while mutations in the helicase domain lead to delayed but correct psychomotor acquisitions together with mild or absent urogenital abnormalities. In summary, mutations in the helicase domain are associated with milder phenotypes than mutations in the PHD-like domain.

Unbalanced inherited complex chromosome rearrangement involving chromosome 8, 10, 11 and 16 in a patient with congenital malformations and delayed development

Complex chromosome rearrangements (CCR) are rare structural chromosome aberrations that can be found in patients with phenotypic abnormalities or in phenotypically normal patients presenting, however, recurrent miscarriages or infertility. Conventional karyotype generally allows their identification. However, molecular cytogenetic methods can reveal subtle rearrangements. We report, here, the identification of an unbalanced maternally inherited CCR in a boy with multiple congenital malformations and delayed development. High-resolution karyotype completed by molecular cytogenetic prompted us to precise the rearrangements. The healthy mother was found to carry a balanced de novo CCR that implicates four chromosomes (8, 10, 11 and 16), six breakpoints, three translocations and an insertion. The malsegregation of this CCR had led, in her son, to partial 10p12.3 to 10p14 deletion, a chromosomal region associated with the DiGeorge like phenotype.

Efficacy and safety of vardenafil in men with erectile dysfunction caused by spinal cord injury

OBJECTIVE

To assess the efficacy and tolerability of vardenafil in men with erectile dysfunction (ED) due to traumatic spinal cord injury (SCI).

METHODS

In this multicenter, double-blind, placebo-controlled, parallel-group 12-week study, 418 men aged 18 years and older with ED for more than 6 months consequent to SCI were randomized to vardenafil (n = 207) or placebo (n = 211) (10 mg for 4 weeks, then maintained or titrated to 5 or 20 mg at weeks 4 and 8). Efficacy assessments included the erectile function (EF) domain score of the International Index of Erectile Function questionnaire and diary questions regarding penetration, maintenance of erection to completion of intercourse, and ejaculation.

RESULTS

Baseline patient characteristics were similar in the vardenafil (mean age 40 years) and placebo (mean age 39 years) groups. Mean baseline EF domain scores were 11.6 in the vardenafil group and 12.1 (moderate ED) in the placebo group. EF domain score in the vardenafil group improved to 22.0 (mild ED) at last observation carried forward vs 13.5 in the placebo group (p < 0.001). Over 12 weeks of treatment, mean per-patient penetration (76% vs 41%), maintenance (59% vs 22%), and ejaculation (19% vs 10%) success rates were significantly greater vs placebo (all p < 0.001). The most frequently reported drug-related adverse events were headache (vardenafil 15%, placebo 4%), flushing (vardenafil 6%, placebo 0%), nasal congestion (vardenafil 5%, placebo 0%), and dyspepsia (vardenafil 4%, placebo 0%).

CONCLUSION

Vardenafil significantly improved erectile and ejaculatory function and was generally well tolerated in men with erectile dysfunction due to spinal cord injury.

Identification of lumbar spinal neurons controlling simultaneously the prostate and the bulbospongiosus muscles in the rat

Lumbar spinothalamic neurons in the lamina X of the L3-L4 spinal cord segment have been proposed to constitute the spinal ejaculation generator in male rats. Lumbar spinothalamic cells are immunoreactive for galanin and neurokinin-1 receptors. We previously showed that after injection of pseudorabies virus either in the bulbospongiosus muscle or in the prostate, retrogradely labeled cells in the L3-L4 segment also displayed galanin or neurokinin-1 receptor immunoreactivities, demonstrating a direct link between lumbar spinothalamic cells and two anatomical structures involved in the two phases of ejaculation i.e. the emission and the expulsion phases. In order to provide with a more precise anatomical support for the role of lumbar spinothalamic cells in controlling ejaculation, we injected simultaneously in male adult rats two strains of recombinant pseudorabies virus, expressing either beta-galactosidase (PRV-BaBlu) or green fluorescent protein (PRV-152) in the prostate and in the bulbospongiosus muscle, respectively. After 5 days, we performed multiple immunofluorescence experiments to detect PRV-BaBlu, PRV-152 and galanin or neurokinin-1 receptors in transverse sections of the L1-S1 segment. Double- and triple-labeled cells were counted using confocal laser scanning microscope. Double-labeled neurons with the two strains of pseudorabies virus were mainly found at the L3-L4 segment lateral to the central canal in lamina X and represented about 60% of the total number of pseudorabies virus-labeled neurons. All the double pseudorabies virus-labeled neurons also expressed lumbar spinothalamic and most of them neurokinin-1 receptor, identifying them as lumbar spinothalamic neurons. The convergence of retrograde labeling from prostate and bulbospongiosus muscle on the same lumbar spinothalamic cells strongly reinforce their role in the spinal control and coordination of the emission and expulsion of sperm.

Melanotan-II: Investigation of the inducer and facilitator effects on penile erection in anaesthetized rat

The effects of melanotan-II, a non-specific agonist of melanocortin receptors, on erection and its possible sites of action were investigated in anesthetized rats. Delivered i.v. (0.1, 0.3 and 1 mg/kg) or within the paraventricular nucleus of the hypothalamus (0.1 and 1 microg), melanotan-II exerted a dose-dependent inducer activity on erection by eliciting erectile events and shortening latency of the first erectile event to occur. Erectile events were of higher amplitude in rats treated with melanotan-II i.t. (0.2 microg) delivered at the L6-S1 level than in animals treated with the vehicle i.t. delivered. Erectile responses elicited by cavernous nerve stimulation were increased after i.v. melanotan-II (1 mg/kg), thereby exerting facilitator effect on erection. In contrast, melanotan-II injected within the corpus cavernosum (1 microg) did not display any facilitator activity. To investigate the neural pathways involved in the facilitator effect of melanotan-II, we performed acute spinalization (T8 level) and differential selective nerve transections. Neither spinalization nor bilateral transection of pelvic nerves or dorsal penile nerves impaired facilitator activity of i.v. melanotan-II (1 mg/kg). Conversely, the facilitator effect of melanotan-II was abolished after acute removal of the lumbar paravertebral sympathetic chain. These results lead to the conclusion that central and peripheral melanocortin pathways are recruited by melanotan-II, depending on its route of delivery, to exert both inducer and facilitator activities on erection.

[ATR-X syndrome: a new mutation in the XNP/ATRX gene near the helicase domain]

The alpha-thalassemia/mental retardation syndrome, X linked, also named ATR-X syndrome is a X-linked mental retardation syndrome. Mutations have been found in the ATRX gene in about one half of the patients. We report a typical clinical case. The clinical evidence leads us to continue the analysis of the gene despite a negative first screening. Indeed a new mutation was found, just behind the helicase domain, bringing up the interest of an effective collaboration between physicians and biologists.

The Use of Telemetry Technology to Test the Proerectile Effect of Melanotan-II (MT-II) in Conscious Rats

OBJECTIVE

The aim of this study is to demonstrate that monitoring, by means of telemetry technology, the increases in intracavernosal pressure (ICP) in freely moving rats using melanotan-II (MT-II) as a proerectile inducer compound is a relevant experimental model to investigate the effects of pharmacological agents on erection.

METHODS

Adult rats were implanted in the corpus cavernosum with a pressure sensor which permitted telemetric monitoring of ICP in freely moving animals following MT-II (0.1, 0.3 and 1 mg/kg) or saline i.v. injections. ICP was also measured after MT-II (0.1, 0.3 or 1 mg/kg) or saline i.v. delivery in anesthetized rats.

RESULTS

In conscious rats, MT-II (1 mg/kg) significantly increased overall erectile activity compared to saline. In anesthetized rats, MT-II-induced increase in overall erectile activity was not statistically significant but displayed a similar pattern.

CONCLUSIONS

The use of telemetry technology allowed to collect quantifiable and reliable data regarding the proerectile activity of MT-II in physiological conditions. The telemetry model appears suitable for investigating the potential inducer proerectile properties of pharmacological agents.

Piboserod (SB 207266), a selective 5-HT4 receptor antagonist, reduces serotonin potentiation of neurally-mediated contractile responses of human detrusor muscle

The aim of this study is to evaluate the potency of piboserod (SB 207266), a selective 5-HT(4) receptor antagonist, at inhibiting the 5-HT(4)-mediated potentiating effect of serotonin (5-HT) on the neurally-mediated contractile responses of human detrusor strips to electrical field stimulations (EFS). Strips of human detrusor muscle were mounted in Krebs-HEPES buffer under a resting tension of 500 mg and EFS (20 Hz, 1 ms duration at 300 mA for 5 s) was applied continuously at 1 min intervals. After stabilization of the EFS-induced contractions, concentration-response curves to 5-HT (0.1 nM-100 microM) were constructed in the absence or presence of 1 or 100 nM of piboserod. The experiments were performed in the presence of methysergide (1 microM) and ondansetron (3 microM) to block 5HT(1)/5HT(2) and 5-HT(3) receptors, respectively. 5-HT potentiated the contractile responses to EFS of human bladder strips in a concentration-dependent manner, with a maximum mean of 60.0+/-19.9% of the basal EFS-evoked contractions. Piboserod did not modify the basal contractions but concentration-dependently antagonized the ability of 5-HT to enhance bladder strip contractions to EFS. In presence of 1 and 100 nM of piboserod, the maximal 5-HT-induced potentiations were reduced to 45.0+/-7.9 and 38.7+/-8.7%, respectively. A mean apparent antagonist dissociation constant value (K(B)) of 0.56+/-0.09 nM was determined. These data show the ability of piboserod to antagonize with high potency the enhancing properties of 5-HT on neurally-mediated contractions of isolated human bladder strips. Therefore, the 5-HT(4) receptor might represent an attractive pharmacological target for the treatment of overactive bladder.

Loss of ZMPSTE24 (FACE-1) causes autosomal recessive restrictive dermopathy and accumulation of Lamin A precursors

Restrictive dermopathy (RD) is characterized by intrauterine growth retardation, tight and rigid skin with prominent superficial vessels, bone mineralization defects, dysplastic clavicles, arthrogryposis and early neonatal death. In two patients affected with RD, we recently reported two different heterozygous splicing mutations in the LMNA gene, leading to the production and accumulation of truncated Prelamin A. In other patients, a single nucleotide insertion was identified in ZMPSTE24. This variation is located in a homopolymeric repeat of thymines and introduces a premature termination codon. ZMPSTE24 encodes an endoprotease essential for the post-translational cleavage of the Lamin A precursor and the production of mature Lamin A. However, the autosomal recessive inheritance of RD suggested that a further molecular defect was present either in the second ZMPSTE24 allele or in another gene involved in Lamin A processing. Here, we report new findings in RD linked to ZMPSTE24 mutations. Ten RD patients were analyzed including seven from a previous series and three novel patients. All were found to be either homozygous or compound heterozygous for ZMPSTE24 mutations. We report three novel 'null' mutations as well as the recurrent thymine insertion. In all cases, we find a complete absence of both ZMPSTE24 and mature Lamin A associated with Prelamin A accumulation. Thus, RD is either a primary or a secondary laminopathy, caused by dominant de novo LMNA mutations or, more frequently, recessive null ZMPSTE24 mutations, most of which lie in a mutation hotspot within exon 9. The accumulation of truncated or normal length Prelamin A is, therefore, a shared pathophysiological feature in recessive and dominant RD. These findings have an important impact on our knowledge of the pathophysiology in Progeria and related disorders and will help direct the development of therapeutic approaches.