J. Bernabé

Ejaculation induced by I.C.V. injection of the preferential dopamine D3 receptor agonist 7-hydroxy-2-(Di-N-propylamino)tetralin in anesthetized rats

In addition to serotonin, dopamine within the CNS is known to play a primary role in the control of ejaculation. However, whether D(2) and/or D(3) dopamine receptor subtypes mediate this effect is still unclear. In order to clarify this issue, a pharmacological competitive study using the preferential D(3) agonist 7-hydroxy-2-(di-N-propylamino)tetralin (7-OH-DPAT) alone or in combination with competitive nonpreferential or preferential D(2) and D(3) antagonists delivered intracerebroventricularly (i.c.v.) was undertaken in anesthetized rats. Urethane-anesthetized male rats were implanted into the cerebral ventricle with a cannula for i.c.v. injections, and recording electrodes were placed within the bulbospongiosus (BS) muscle to monitor BS muscle contractions, which were used as a marker for the expulsion phase of ejaculation. Following i.c.v. injection, 7-OH-DPAT induced ejaculation and rhythmic BS muscle contractions. Co-injected i.c.v. with 7-OH-DPAT, the nonselective D(2)/D(3) antagonist (raclopride), and the preferential D(3) antagonist (S(-)-N[n-butyl-2-pyrrolidinyl)methyl]-1-methoxy-4-cyanonaphtalene-2-carboxamide; nafadotride) but not the preferential D(2) antagonist ((+/-)-3-[4-(4-chlorophenyl)-4-hydroxypiperidinyl]methylindole; L 741,626) inhibited the occurrence of ejaculation and BS muscle contractions. These results suggest that i.c.v. delivery of 7-OH-DPAT does represent a pertinent model to investigate the physio-pharmacology of ejaculation. It is inferred that targeting brain D(3) receptors may provide a therapeutic approach for treating ejaculatory disorders in humans.

Microinjection of the preferential dopamine receptor D3 agonist 7-hydroxy-N,N-di-N-propylaminotetralin hydrobromide into the hypothalamic medial preoptic area induced ejaculation in anesthetized rats

The pivotal role of the medial preoptic area (MPOA) of the hypothalamus in the dopaminergic cerebral control of ejaculation has been investigated for years; nevertheless the function of different dopamine receptors subclasses and their exact interrelations merit additional research. One hundred nanograms of a preferential D(3) agonist 7-OH-DPAT (7-hydroxy-N,N-di-n-propylaminotetralin hydrobromide) was microinjected unilaterally into the MPOA of male rats anesthetized with urethane. An ejaculation-related response (bulbospongiosus muscles rhythmic contractions and/or seminal vesicle pressure increases and/or expulsion of a semen plug) was observed in 8 of 10 rats devoid of sexual stimuli, while a similar response was observed in only one rat administered with 10 ng of 7-OH-DPAT. The effect of 7-OH-DPAT 100 ng was mostly abolished by simultaneous MPOA microinjection of 300 ng of a preferential D(3) antagonist N-[(n-butyl-2-pyrrolidinyl) methyl]-1-methoxy-4-cyanonaphthalene-2-carboxamide tartrate (nafadotride). Our results support the hypothesis that supraspinal command of ejaculation is mediated by D(2)-like receptors, probably by D(3) receptors, in the MPOA, and draw attention to the idea of these receptors serving as a promising target for pharmacological treatment of human ejaculatory disorders.

INFLUENCE OF THE INHIBITION OF CYCLIC NUCLEOTIDE PHOSPHODIESTERASE TYPE 4 ON HUMAN DETRUSOR SMOOTH MUSCLE CONTRACTIONS

Human bladder strip preparation Bladders samples were obtained from donors undergoing cystectomy for bladder cancer with no known bladder dysfunction according to their medical chart. Serosal and mucosal layers were removed from the bladder sample, and detrusor strips were mounted in 5 ml organ baths filled with Krebs-HEPES buffer maintained at 37°C and continuously bubbled with 95%O2-5%CO2. The strips were connected to force transducers for isometric tension recordings (Pioden Controls Ltd, UK). Following amplification, the tension changes were computerized via MacLabTM/8 using ChartTM 5 software (AD Instruments Ltd).

269 RHO-KINASE INHIBITION RELAXES DETRUSOR FROM NEUROGENIC PATIENTS

Hypothesis / aims of study Rho-kinases have a central role in the regulation of bladder smooth muscle from human and various animal species. In vitro or in vivo data from animal models of overactive bladder (OAB) indicate that rho-kinases could be involved in the pathophysiology of OAB. To date, the role of rho-kinases in patients with neurogenic detrusor overactivity has not yet been explored. We aimed to evaluate the effect of Rho-kinase inhibition on detrusor from neurogenic patients pre-contracted with either carbachol or KCl.

278 IS RELAXATION OF HUMAN DETRUSOR BY SILDENAFIL RELYING ON PDE 5 INHIBITION

INTRODUCTION AND OBJECTIVES: We evaluate the efficacy and safety of propiverine hydrochloride (antimuscarinics), naftopidil ( 1adrenoceptor antagonists), or both in patients with male lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH) and concomitant overactive bladder (OAB). METHODS: Older than fifty years old male who had a total International Prostate Symptom Score (IPSS) of 8 or higher and bladder dairy documenting micturition frequency (more than 8 micturitions per 24 hours) and urgency (more than 1 episode per one day), with or without urgency urinary incontinence and residual post-void residual urine volume (PVR) 50 ml were randomized into 3 groups, group Nnaftopidil (50mg once daily) only, group P-propiverine hydrochloride (20mg once daily) only, and group NPnaftopidil (50mg once daily) plus propiverine hydrochloride (20mg once daily) for a 4-week treatment regimen. Before and after administration, subjective symptoms were assessed using the IPSS and QOL index, and urinary urgency was assessed in four grades by referring to the Urgency Perception Scale. RESULTS: A total of 66 men, including 20 in group N, 23 in group P, and 23 in group NP were treated and 58 (87.9 %) completed the 4 weeks of treatment. IPSS were significantly improved in group N and NP. Urinary frequency was markedly improved in group P and NP. Severity of urgency improved after therapy in all 3 groups, and no significant difference existed in the degree of change among the 3 groups. PVR increased in group P and NP. Significant improvements were noted in each group in urgency episodes. As to adverse event, one patient required catheterization due to acute urinary retention and one patient stopped medication because of complaining of difficulty on voiding in group P. CONCLUSIONS: In patients with male LUTS suggestive of BPH and concomitant OAB, naftopidil monotherapy was the safest, while combination therapy with naftopidil and anticholinergic agent was the most effective. Anticholinergic agent monotherapy was the least effective and safe. As a result, blocker monotherapy should be administered initially to male LUTS suggestive of BPH and concomitant OAB.

BRAIN OXYTOCIN RECEPTOR BLOCKADE INHIBITS PHARMACOLOGICALLY INDUCED SEXUAL RESPONSES IN ANAESTHETISED MALE RATS

For this purpose, ejaculatory and erectile responses were elicited by delivering the dopamine D3 receptor preferring agonist [R(+)7-hydroxy-2-(di-N-propylamino)tetralin; 7-OH-DPAT] into the cerebral ventricle (i.c.v.). The effects of a peptide OT antagonist administered via different routes [i.c.v., intrathecal (i.t.), i.v.] were tested on 7-OH-DPAT-induced sexual responses. Pierre Clément1, Magali Peeters1, Jacques Bernabé1, Miguel Laurin1, Pierre Denys2, François Giuliano1,2*

999 THE PHOSPHODIESTERASE TYPE 4 INHIBITOR, ROLIPRAM, IS MORE EFFICIENT TO RELAX DETRUSOR SMOOTH MUSCLE IN RATS WITH OVERACTIVE BLADDER THAN IN CONTROL RATS

Hypothesis / aims of study Detrusor smooth muscle relaxation is mainly mediated by the cyclic adenosine monophosphate (cAMP) pathway. Elevation of cAMP levels by phophodiesterase type 4 inhibition relaxes smooth muscle of various origins. The aim of this study was to evaluate the effect of the PDE4 inhibitor rolipram on detrusor smooth muscle tone in a rat pathological model of overactive bladder (OAB) i.e with partial bladder outlet obstruction (BOO).

Chronic inhibition of cyclic GMP phosphodiesterase 5A prevents and reverses endothelial dysfunction and oxidative stress associated with the metabolic syndrome

Materials and methods Wistar rats (n = 10–14 per group) were fed a standard chow (CONT) or a 60% fructose/5% fat (% by weight)enriched diet for 8 weeks (FFR). From week 5 through 8, sildenafil was administered twice a day (sc, 20 mg/kg, FFR+SIL), thus reaching clinically relevant plasma concentrations circa 20 nM unbound known to give efficacy in man (Pfizer Inc., data on file), then a 1-week wash-out period from sildenafil was observed. Isometric tension studies were performed on isolated aortic and superior mesenteric arterial (SMA) rings precontracted with noradrenaline to build concentration-response curves (CRC) to endothelium-dependent (ACh and A23187) and -independent (SNP) relaxants in presence of indomethacin. Urinary 8-isoprostanes (IPT) and plasma levels of IL-6 and TNF-α were also evaluated. Results Relaxations to ACh were reduced in aortas of FFR (10-5 M: -102.6 ± -2.4% vs -89.2 ± 4.7, p < 0.001) while only slightly affected in SMA rings. Relaxations to A23187 were significantly reduced both in aortic and SMA rings of FFR. In aortas, sildenafil treatment restored normal endothelium-dependent relaxations to ACh (10-5 M: -104.2 ± 3.0%, p < 0.001) even after one week of wash-out from treatment. In SMA rings, a leftward shift of the CRC to ACh could be detected (pD2: -8.12 ± 0.11 vs -8.60 ± 0.08, p < 0.05). Relaxations to A23187 were also restored by sildenafil in both aortic and SMA rings of FFR. Enhanced compensatory endothelium-independent relaxations to SNP in FFR were not modified by sildenafil treatment. Neither IL-6 nor TNF-α were modified by the fructose or sildenafil treatment. Urinary IPT levels was normalized by the sildenafil treatment (FFR: 2.07 ± 0.36 vs CONT:0.95 ± 0.14 vs FFR+SIL: 0.88 ± 0.13 ng/ml/24 h, p < 0.05).

Daily treatment with sildenafil, an inhibitor of cGMP-dependent phosphodiesterase, normalizes the exaggerated hemodynamic response to norepinephrine in fructose-fed rats

Background Enhanced responsiveness of the vascular smooth muscle cell to vasoconstrictor stimuli has been described in insulin-resistant states. Fructose overload leads to the development of the metabolic syndrome and its associated cardiovascular disorders including hypertension. We postulated that chronic treatment with sildenafil would regulate the abnormally increased pressor response to a norepinephrine challenge in fructose-fed rats. Material and methods Wistar rats were fed a standard chow (CONT, n = 12) or a 60% fructose-enriched diet containing 5% fat (% by weight) for 8 weeks (FFR, n = 12). From week 5 through 8, sildenafil (twice a day sc, 20 mg/kg) was administered (FFR+SIL, n = 14), thus reaching clinically relevant plasma concentrations circa 20 nM unbound (Pfizer Inc., data on file), followed by a 1-week wash-out period (W9). On W9, in a sub-group of these conscious rats (n = 5) that had previously been implanted with telemetric devices, AP was recorded following cumulative infusion of noradrenaline (NA 50, 100, 200, 400 ng/kg/min). In all rats, urinary 8-isoprostane (IPT) and TxB2 levels were determined during a 24-hour period. Tissue ET-1 content was measured in segments of aortic and mesenteric artery. Results Fasting glycemia was unchanged in all rats while triglyceridemia were elevated in FFR compared to CONT (2.0 ± 0.4 mM vs 1.2 ± 0.2, p < 0.05) and corrected by sildenafil treatment (1.3 ± 0.2, NS vs CONT). Resting AP was similar in all rats. Pressor responses to NA were exacerbated in FFR (maximal increase from basal MAP: +22.8 ± 1.7 vs +38.0 ± 7.3 mmHg, respectively, p < 0.05) and normalized by sildenafil treatment (+24.9 ± 5.2 mmHg, NS vs CONT). Vascular ET-1 levels were not modified by the fructose nor sildenafil treatment whereas the increased production of urinary IPT and TxB2 in FFR versus CONT (2.07 ± 0.36 ng/ml/24 h vs 0.88 ± 0.13 and 12.86 ± 1.91 pg/ml/24 h vs 7.25 ± 0.59, respectively, p < 0.05) were corrected following sildenafil treatment (0.95 ± 0.14 ng/ ml/24 h and 8.74 ± 1.06 pg/ml/24 h, respectively, NS vs CONT).

APOLIPOPROTEIN E KNOCKOUT MICE AS A NEW MODEL OF HYPERCHORESTOROLAEMIA AND ATHEROSCLEROSIS ASSOCIATED ERECTILE DYSFUNCTION

Erectile dysfunction (ED) and cardiovascular diseases share the same risk factors including hypercholesterolemia and atherosclerosis, but there are few available animal models allowing to study hypercholesterolemia-associated ED. Although the use of hypercholesterolemic rabbit models has proven to be useful to illustrate the link between ED and hypercholesterolemia, the cost of daily maintenance of the animals and necessity for important amounts of drug in view of proof of concept studies to prevent or slow down these disorders have limited their use.