Bladder and cutaneous sensory neurons of the rat express different functional P2X receptors.

The expression and functional responses of P2X receptors in bladder and cutaneous sensory neurons of adult rats and mice have been studied using immunohistochemistry and patch clamp techniques. Cell bodies of bladder pelvic afferents were identified in L6 and S1 dorsal root ganglia (DRG), following Fast Blue injection into the muscle wall of the urinary bladder. Similarly, cutaneous sensory neurons were identified in L3 and L4 DRG, following Fast Blue injection into the saphenous nerve innervating the skin. Bladder sensory neurons contained only weak to moderate P2X(3)-immunoreactivity (IR), in contrast to strong P2X(3)-IR observed in a sub-population of cutaneous afferents. Whole-cell patch-clamp recordings revealed that approximately 90% of bladder afferent neurons responded to alpha beta-methylene ATP (alpha beta meATP) and ATP (30 microM) with persistent currents, which were inhibited by 2',3'-O-trinitrophenyl-ATP (TNP-ATP) (0.3 microM) to 6.4+/-1.9% and 8.0+/-2.6% of control, respectively (n=8). The remaining bladder sensory neurons demonstrated biphasic, transient or no response to P2X agonists. In contrast, only 24% of cutaneous afferent neurons gave persistent currents to alpha beta meATP (30 microM), with 66% of cells giving transient or biphasic currents and the remaining 10% being non-responsive. Our results suggest that, in contrast to DRG neurons in general, bladder sensory neurons projecting via pelvic nerves express predominantly P2X(2/3) heteromeric receptors, which are likely to mediate the important roles of ATP as a signaling molecule of urinary bladder filling and nociception.

Discovery and synthesis of a novel and selective drug-like P2X(1) antagonist.

Although there is extensive literature to indicate that many different types of P2 purinoceptors are present in the lower urinary tract, the physiological role of these receptors in micturition is still uncertain. In part, this uncertainty has been caused by a lack of P2 subtype selective ligands. In this paper we report the discovery, gram scale synthesis, and binding results for 1, the first potent, drug-like, selective P2X(1) receptor antagonist described. Compound 1 was shown to be more than 30-fold selective over other purinergic receptor subtypes.

Decreased sensory receptors P2X3 and TRPV1 in suburothelial nerve fibers following intradetrusor injections of botulinum toxin for human detrusor overactivity.

PURPOSE: Botulinum neurotoxin type A (BoNT/A) is effective in the treatment of intractable detrusor overactivity (DO). In addition to its known inhibitory effect on presynaptic release of acetylcholine by motor terminals, there is increasing evidence that BoNT/A may affect sensory fibers. We investigated a possible effect of BoNT/A on human bladder afferent mechanisms by studying the sensory receptors P2X3 and TRPV1 in biopsies from patients with neurogenic or idiopathic DO. MATERIALS AND METHODS: A total of 38 patients (22 with neurogenic DO, 16 with idiopathic DO) with intractable DO were treated with intradetrusor BoNT/A, and bladder biopsies were taken at 4 and 16 weeks. Urodynamics and voiding diary were also recorded. Specimens were studied immunohistochemically for P2X3, TRPV1 and the pan-neuronal marker PGP9.5, in comparison with controls. RESULTS: P2X3-immunoreactive and TRPV1-immunoreactive (-IR) fibers were decreased at 4 weeks after BoNT/A, and more significantly at 16 weeks (paired t test p=0.0004 and p=0.0008, respectively), when significant improvements were observed in clinical and urodynamic parameters. P2X3-IR fiber decrease was significantly correlated with reduction of urgency episodes at 4 and 16 weeks (p=0.0013 at 4 weeks and p=0.02 at 16 weeks), but not maximum cystometric capacity or detrusor pressures. TRPV1-IR fiber decrease showed a similar trend. PGP9.5-IR suburothelial fibers remained unchanged after treatment at both followups (p=0.85 and p=0.21 at 4 and 16 weeks, respectively). Urothelial cell P2X3-IR and TRPV1-IR also appeared unchanged. CONCLUSIONS: Decreased levels of sensory receptors P2X3 and/or TRPV1 may contribute to the clinical effect of BoNT/A in detrusor overactivity.

A randomized crossover study to evaluate Ro 115-1240, a selective alpha1A/1L-adrenoceptor partial agonist in women with stress urinary incontinence.

OBJECTIVES: To investigate the potential therapeutic benefits of the selective alpha1A/1l-adrenoceptor partial agonist Ro 115-1240 in women with mild-to-moderate stress urinary incontinence (SUI). PATIENTS AND METHODS: Thirty-seven women with mild-to-moderate SUI were enrolled in a randomized, placebo-controlled crossover study. Patients received 1.5 mg Ro 115-1240 twice daily or matching placebo for 2 or 4 weeks. Voiding diaries were used to record the number of SUI episodes, urge incontinence episodes and pads used. Sitting blood pressures and heart rate were recorded at each visit. RESULTS: Ro 115-1240 was associated with a significantly lower mean weekly number of SUI episodes than placebo (8.4 vs 6.0; P= 0.0079), a 28% relative improvement over placebo. There was also a significantly lower mean number of pads used and wet pads changed/week with Ro 115-1240 than with placebo (P = 0.0055 and 0.0066, respectively). The most frequently reported treatment-emergent adverse events were scalp tingling, headache, chills, piloerection, and pruritus. Generally these events were transient and mild to moderate. There was a slightly lower mean sitting heart rate with Ro 115-1240 than with placebo, but no difference in mean systolic or diastolic blood pressure between treatments. CONCLUSIONS: This study suggests that selective alpha1A/1l-adrenoceptor partial agonists have the potential to improve the symptoms of SUI with little or no cardiovascular effect. These results are encouraging and a randomized controlled trial of Ro 115-1240 in a larger population with SUI is warranted to substantiate these findings.

Pharmacological characteristics of Ro 115-1240, a selective alpha1A/1L-adrenoceptor partial agonist: a potential therapy for stress urinary incontinence.

OBJECTIVE: To describe the preclinical pharmacology of Ro 115-1240, a peripherally acting selective alpha1A/1L-adrenoceptor (AR) partial agonist, compared with the alpha1A/1L-AR full agonist amidephrine, as AR agonists have some utility in the treatment of stress urinary incontinence (SUI) but are limited by undesirable cardiovascular and central nervous system side-effects. RESULTS: In radioligand-binding studies Ro 115-1240 had greater affinity for alpha1A than for alpha1B and alpha1D subtypes. The potency and intrinsic activity of amidephrine and Ro 115-1240 relative to noradrenaline were determined in native and cell-based assays using human recombinant alpha1-ARs; they acted as selective alpha1A/1L-AR full and partial agonists, respectively. In anaesthetized micropigs and rabbits, amidephrine and Ro 115-1240 produced non-selective, dose-dependent increases in intraurethral and arterial blood pressures but the magnitude of the pressure increases evoked by Ro 115-1240 were about a third of those with amidephrine. In conscious micropigs both agents produced dose-dependent increases in urethral tension. Again, the magnitude of the urethral response to Ro 115-1240 was about a third of that with amidephrine. More importantly, only amidephrine produced dose-dependent increases in blood pressure and decreases in heart rate. Ro 115-1240 produced a maximum increase in urethral tension with no effect on blood pressure or heart rate. CONCLUSION: These results show that by combining selectivity for the alpha1A/1L-AR subtype with a reduction in intrinsic agonist efficacy, Ro 115-1240 has reduced haemodynamic effects while retaining to some degree the contractile effects on urethral smooth muscle. These studies indicate that Ro 115-1240 may be useful as a novel treatment for SUI.

Alterations in P2X and P2Y purinergic receptor expression in urinary bladder from normal cats and cats with interstitial cystitis.

Purinergic mechanisms appear to be involved in motor as well as sensory functions in the urinary bladder. ATP released from efferent nerves excites bladder smooth muscle, whereas ATP released from urothelial cells can activate afferent nerves and urothelial cells. In the present study, we used immunohistochemical techniques to examine the distribution of purinoceptors in the urothelium, smooth muscle, and nerves of the normal cat urinary bladder as well as possible changes in the expression of these receptors in cats with a chronic painful bladder condition termed feline interstitial cystitis (FIC) in which ATP release from the urothelium is increased. In normal cats, a range of P2X (P2X(1), P2X(2), P2X(3), P2X(4), P2X(5), P2X(6), and P2X(7)) and P2Y (P2Y(1), P2Y(2), and P2Y(4)) receptor subtypes was expressed throughout the bladder urothelium. In FIC cats, there is a marked reduction in P2X(1) and loss of P2Y(2) receptor staining. Both P2X(3) and P2Y(4) are present in nerves in normal cat bladder, and no obvious differences in staining were detected in FIC. Smooth muscle in the normal bladder did not exhibit P2Y receptor staining but did exhibit P2X (P2X(2), P2X(1)) staining. In the FIC bladder smooth muscle, there was a significant reduction in P2X(1) expression. These findings raise the possibility that purinergic mechanisms in the urothelium and bladder smooth muscle are altered in FIC cats. Because the urothelial cells appear to have a sensory function in the bladder, it is possible that the plasticity in urothelial purinergic receptors is linked with the painful bladder symptoms in IC.

Synthesis, pharmacology and pharmacokinetics of 3-(4-aryl-piperazin-1-ylalkyl)-uracils as uroselective alpha1A-antagonists.

Predominance in the urethra and prostate of the alpha(1A)-adrenoceptor subtype, which is believed to be the receptor mediating noradrenaline induced smooth muscle contraction in these tissues, led to the preparation of alpha(1A)-selective antagonists to be tested as uroselective compounds for the treatment of benign prostatic hyperplasia. Thus, a number of selective alpha(1A)-adrenoceptor antagonists were synthesized and assayed in vitro for potency and selectivity. Dog pharmacokinetic parameters of 12 (RO700004) and its metabolite 40 (RO1104253) were established. The relative selectivity of intravenously administered 12, 40 and standard prazosin to inhibit hypogastric nerve stimulation-induced increases in intraurethral prostatic pressure versus phenylephrine-induced increases in diastolic blood pressure in anesthetized dogs was 76, 71 and 0.6, respectively.