THE INCIDENCE OF A POSITIVE ICE WATER TEST IN BLADDER OUTLET OBSTRUCTED PATIENTS: EVIDENCE FOR BLADDER NEURAL PLASTICITY

Acute Intravesical Capsaicin for the Study of TRPV1 in the Lower Urinary Tract: Clinical Relevance and Potential for Innovation

Capsaicin acts on sensory nerves via vanilloid receptors. TRPV1 has been extensively studied with respect to functional lower urinary tract (LUT) conditions in rodents and humans. We aimed to (1) provide background information on capsaicin and TRPV1 and its mechanisms of action and basis for clinical use, (2) review the use of acute intravesical capsaicin instillation (AICI) in rodents to mimic various LUT disorders in which capsaicin sensitive C-fibers are involved and (3) discuss future innovative treatments. A comprehensive search of the major literature databases until June 2022 was conducted. Both capsaicin-sensitive and resistant unmyelinated bladder afferent C-fibers are involved in non-neurogenic overactive bladder/detrusor overactivity (OAB/DO). AICI is a suitable model to study afferent hyperactivity mimicking human OAB. Capsaicin-sensitive C-fibers are also involved in neurogenic DO (NDO) and potential targets for NDO treatment. AICI has been successfully tested for NDO treatment in humans. Capsaicin-sensitive bladder afferents are targets for NDO treatment. TRPV1-immunoreactive nerve fibers are involved in the pathogenesis of interstitial cystitis/painful bladder syndrome (IC/PBS). The AICI experimental model appears relevant for the preclinical study of treatments targeting bladder afferents for refractory IC/BPS. The activity of capsaicin-sensitive bladder afferents is increased in experimental bladder outlet obstruction (BOO). The AICI model may also be relevant for bladder disorders resulting from C-fiber hyperexcitabilities related to BOO. In conclusion, there is a rationale for the selective blockade of TRPV1 channels for various bladder disorders. The AICI model is clinically relevant for the investigation of pathophysiological conditions in which bladder C-fiber afferents are overexcited and for assessing innovative treatments for bladder disorders based on their pathophysiology.

Voiding and Storage Domain-Specific Symptom Score Outcomes After Prostate Artery Embolization for Lower Urinary Tract Symptoms and Urinary Retention

OBJECTIVE

To characterize voiding and storage symptom domain-specific outcomes after prostate artery embolization (PAE) to treat lower urinary tract symptoms (LUTS) or urinary retention caused by benign prostatic hyperplasia (BPH).

METHODS

Two hundred forty patients (age = 74.5 ± 8.6 years) underwent PAE between May 2013 and March 2020 at a single center for LUTS (n = 161) or urinary retention (n = 79). Total International Prostate Symptom Score (IPSS-t), voiding domain score (IPSS-v), storage domain score (IPSS-s), and Quality of Life score (QoL) were obtained pre-PAE for LUTS patients (IPSS-t = 21.7 ± 6.2, IPSS-v = 11.9 ± 4.3, IPSS-s = 9.6 ± 3.1, QoL = 4.5 ± 1.2), and post-PAE through 36 months (mean = 22.9 ± 15.2 months) for LUTS and retention patients. Mean relative changes in IPSS-t, IPSS-v, IPSS-s, and QoL were calculated for LUTS patients. Mean voiding or storage component scores were calculated for retention patients.

RESULTS

For evaluable LUTS patients (n = 147), IPSS-t showed sustained substantial improvement through 36 months (6.3 ± 4.2-8.6 ± 7.6), as did QoL (1.1 ± 1.1-1.8 ± 1.5). One month after PAE, improvements in IPSS-v (69% ± 29%) were greater than in IPSS-s (46% ± 33%; P < .000001), and remained so through 36 months (68% ± 31% vs 53% ± 28%, P = .004). Among evaluable retention patients (n = 75), 84% passed voiding trials. Both IPSS-t (6.0 ± 3.9-8.2 ± 6.7) and QoL (0.9 ± 1.2-1.5 ± 1.6) remained low through 36 months. One month after PAE, mean IPSS-v component score (0.9 ± 1.3) was lower than mean IPSS-s component score (1.7 ± 1.4; P = .003) and remained so through 24 months (0.9 ± 1.2 vs 1.3 ± 1.1, P = .02), with similar trend at 36 months (0.7 ± 1.1 vs 1.1 ± 1.1, P = .07).

CONCLUSIONS

PAE effectively treated BPH-related LUTS and retention. IPSS-v improved more than IPSS-s in LUTS patients, and remained lower in LUTS and retention patients through 36 months.

Persistent storage symptoms after TURP can be predicted with a nomogram derived from the ice water test

PURPOSE

To predict the persistence of storage symptoms after transurethral resection of the prostate (TURP) using a nomogram derived from the ice water test (IWT).

METHODS

The IWTs of 73 men with lower urinary tract symptoms and prostatic bladder outlet obstruction were retrospectively analyzed. The strength of the detrusor contraction was approximated by using the detrusor gradient of Δp_det /Δt at maximum detrusor pressure and the area under the curve. The parameters were utilized in a nomogram, which facilitated a severity categorization from 1 to 10. Patients with a positive IWT in the categories 1 to 2 were assigned to group A, categories 3 to 4 to group B and categories 5 and higher to group C. After TURP, patients with persisting storage symptoms were offered a botulinum toxin injection.

RESULTS

There were 32 patients (44%) with negative and 41 patients (56%) with positive IWTs. Patients with negative IWTs were classified in category 1. Regarding patients with positive IWTs, 14 (34%) were correlated to group A, 14 (34%) to group B, and 13 (32%) to group C. The necessity of a subsequent botulinum toxin injection correlated significantly with a higher nomogram category (P < .001) as well as higher severity categorization (P < .001). In multivariate analysis, the nomogram category was an independent predictor for botulinum toxin injection (P = .002, OR, 6.9, CI, 2.0-23.9).

CONCLUSION

The quantification of the detrusor contraction during the IWT allowed stratification of patients in risk categories for persistent storage symptoms after TURP and the potential need for later botulinum toxin injections.

Role of neurogenic inflammation in local communication in the visceral mucosa

Intense research has focused on the involvement of the nervous system in regard to cellular mechanisms underlying neurogenic inflammation in the pelvic viscera. Evidence supports the neural release of inflammatory factors, trophic factors, and neuropeptides in the initiation of inflammation. However, more recently, non-neuronal cells including epithelia, endothelial, mast cells, and paraneurons are likely important participants in nervous system functions. For example, the urinary bladder urothelial cells are emerging as key elements in the detection and transmission of both physiological and nociceptive stimuli in the lower urinary tract. There is mounting evidence that these cells are involved in sensory mechanisms and can release mediators. Further, localization of afferent nerves next to the urothelium suggests these cells may be targets for transmitters released from bladder nerves and that chemicals released by urothelial cells may alter afferent excitability. Modifications of this type of communication in a number of pathological conditions can result in altered release of epithelial-derived mediators, which can activate local sensory nerves. Taken together, these and other findings highlighted in this review suggest that neurogenic inflammation involves complex anatomical and physiological interactions among a number of cell types in the bladder wall. The specific factors and pathways that mediate inflammatory responses in both acute and chronic conditions are not well understood and need to be further examined. Elucidation of mechanisms impacting on these pathways may provide insights into the pathology of various types of disorders involving the pelvic viscera.

Non-invasive characterization of real-time bladder sensation using accelerated hydration and a novel sensation meter: An initial experience

AIMS

The purpose of this investigation was to develop a non-invasive, objective, and unprompted method to characterize real-time bladder sensation.

METHODS

Volunteers with and without overactive bladder (OAB) were prospectively enrolled in a preliminary accelerated hydration study. Participants drank 2L Gatorade-G2® and recorded real-time sensation (0-100% scale) and standardized verbal sensory thresholds using a novel, touch-screen "sensation meter." 3D bladder ultrasound images were recorded throughout fillings for a subset of participants. Sensation data were recorded for two consecutive complete fill-void cycles.

RESULTS

Data from 14 normal and 12 OAB participants were obtained (ICIq-OAB-5a = 0 vs. ≥3). Filling duration decreased in fill2 compared to fill1, but volume did not significantly change. In normals, adjacent verbal sensory thresholds (within fill) showed no overlap, and identical thresholds (between fill) were similar, demonstrating effective differentiation between degrees of %bladder capacity. In OAB, within-fill overlaps and between-fill differences were identified. Real-time %capacity-sensation curves left shifted from fill1 to fill2 in normals, consistent with expected viscoelastic behavior, but unexpectedly right shifted in OAB. 3D ultrasound volume data showed that fill rates started slowly and ramped up with variable end points.

CONCLUSIONS

This study establishes a non-invasive means to evaluate real-time bladder sensation using a two-fill accelerated hydration protocol and a sensation meter. Verbal thresholds were inconsistent in OAB, and the right shift in OAB %capacity-sensation curve suggests potential biomechanical and/or sensitization changes. This methodology could be used to gain valuable information on different forms of OAB in a completely non-invasive way.

[The ice water test and bladder cooling reflex. Physiology, pathophysiology and clinical importance]

BACKGROUND

Urodynamic studies are utilised for identification and follow-up of functional disorders of the lower urinary tract. Provocation tests are used to determine disorders which could not be revealed in standard cystometry. The ice water test is a simple test to identify neurogenic bladder dysfunction and to screen the integrity of the upper motor neuron in neurogenic bladder dysfunction.

OBJECTIVES

Development and significance of the ice water test is presented in this review against the background of physiology and pathophysiology of the lower urinary tract.

MATERIALS AND METHODS

A systematic review of PubMed and ScienceDirect databases was performed in April 2015. No language or time limitation was applied. The following key words and Medical Subject Heading terms were used to identify relevant studies: "ice water test", "bladder cooling reflex", "micturition" and "neuronal control". Review articles and bibliographies of other relevant studies identified were hand searched to find additional studies.

RESULTS

The ice water test is performed by rapid instillation of 4-8 °C cold fluid into the urinary bladder. Hereby, afferent C fibers are activated by cold receptors in the bladder leading to the bladder cooling reflex. It is a spinal reflex which causes an involuntarily contraction of the urinary bladder. The test is normally positive in young infants during the first 4 years of life and become negative with maturation of the central nervous system afterwards by inhibition of the reflex. The damage of the upper motor neuron causes the recurrence of the reflex in the adulthood and indicates spinal and cerebral lesions.

DISCUSSION

The ice water test is utilised to identify lesions of the upper motor neuron. However, in the case of detrusor acontractility the test will always be negative and can not be utilized to distinguish between neurogenic or muscular causes. Furthermore, the test is also positive in a small percentage of cases of non-neurogenic diseases, e.g. in prostate-related bladder outlet obstruction or idiopathic overactive bladder. Although no clear explanation exists, a positive ice water test could be the first sign of an otherwise asymptomatic neurological disease.

CONCLUSIONS

Due to the simple procedure, the ice water test is a reliable possibility to identify neurologic bladder hyperactivity subsequent to standard cystometry.

Usefulness of ice water test to unmask detrusor overactivity

PURPOSE

Ice Water Test (IWT) is not frequently used today. IWT triggers a non-inhibited involuntary detrusor contraction (NIDC) when the bladder is being filled with cold saline solution. NIDC is unmasked via a segmental reflex loop different from the physiological micturition reflex. Our purpose was to search for usefulness of IWT to expose detrusor overactivity (DO).

METHODS

One hundred and seventy-nine IWT performed in patients with overactive bladder syndrome (OAB) and conventional cystometry (CC) non-contributive to diagnosis were retrospectively analyzed. An increase of detrusor pressure of 15cm H2O allowed defining positive IWT (with leakage) or intermediate (without leakage).

RESULTS

The population comprised of 131 women (58.2±17.3 years) and 48 men (56.1±15.3 years). Main complaints were mixed or urge incontinence (76/179). Hundred and twenty-four patients had a history of neurological disease. From CC, detrusor behavior was founded uncategorized for 106, normal for 53 patients and underactive for 20. These results did not contribute to diagnose a DO. IWT was positive for 22 patients and intermediate for 20. DO was unmasked by IWT for 42 patients (23.4%) of whom 34 had neurological disease. The positive predictive value was 80.9%, the negative predictive value was 34.3%.

CONCLUSION

In patients with OAB syndrome, IWT is contributory to unmask DO when CC is not contributive. Our study underlines the interest to perform IWT when urodynamic diagnosis is unclear.

Neural control of the lower urinary tract

This article summarizes anatomical, neurophysiological, pharmacological, and brain imaging studies in humans and animals that have provided insights into the neural circuitry and neurotransmitter mechanisms controlling the lower urinary tract. The functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain, spinal cord, and peripheral autonomic ganglia that coordinates the activity of smooth and striated muscles of the bladder and urethral outlet. The neural control of micturition is organized as a hierarchical system in which spinal storage mechanisms are in turn regulated by circuitry in the rostral brain stem that initiates reflex voiding. Input from the forebrain triggers voluntary voiding by modulating the brain stem circuitry. Many neural circuits controlling the lower urinary tract exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. The major component of the micturition switching circuit is a spinobulbospinal parasympathetic reflex pathway that has essential connections in the periaqueductal gray and pontine micturition center. A computer model of this circuit that mimics the switching functions of the bladder and urethra at the onset of micturition is described. Micturition occurs involuntarily in infants and young children until the age of 3 to 5 years, after which it is regulated voluntarily. Diseases or injuries of the nervous system in adults can cause the re-emergence of involuntary micturition, leading to urinary incontinence. Neuroplasticity underlying these developmental and pathological changes in voiding function is discussed.

Neural mechanisms underlying lower urinary tract dysfunction

This article summarizes anatomical, neurophysiological, and pharmacological studies in humans and animals to provide insights into the neural circuitry and neurotransmitter mechanisms controlling the lower urinary tract and alterations in these mechanisms in lower urinary tract dysfunction. The functions of the lower urinary tract, to store and periodically release urine, are dependent on the activity of smooth and striated muscles in the bladder, urethra, and external urethral sphincter. During urine storage, the outlet is closed and the bladder smooth muscle is quiescent. When bladder volume reaches the micturition threshold, activation of a micturition center in the dorsolateral pons (the pontine micturition center) induces a bladder contraction and a reciprocal relaxation of the urethra, leading to bladder emptying. During voiding, sacral parasympathetic (pelvic) nerves provide an excitatory input (cholinergic and purinergic) to the bladder and inhibitory input (nitrergic) to the urethra. These peripheral systems are integrated by excitatory and inhibitory regulation at the levels of the spinal cord and the brain. Therefore, injury or diseases of the nervous system, as well as disorders of the peripheral organs, can produce lower urinary tract dysfunction, leading to lower urinary tract symptoms, including both storage and voiding symptoms, and pelvic pain. Neuroplasticity underlying pathological changes in lower urinary tract function is discussed.

Pharmacological approach to overactive bladder and urge urinary incontinence in women: an overview

Besides life-style changes, electrical stimulation or surgery, pharmacological treatment is becoming the first-choice approach in women suffering from lower urinary tract symptoms (LUTS), including urge urinary incontinence (UUI) and overactive bladder (OAB). Several drugs for the treatment of bladder storage and voiding disorders are currently available and, in the near future, novel compounds with higher specificity for the lower urinary tract receptors will be accessible. This will bring optimization of therapy, reducing side effects and increasing compliance, especially in patients with comorbidities and in women. The purpose of this paper is to give an overview on the pharmacotherapy of two common inter-correlated urological conditions, UUI and OAB. The study was conducted by analyzing and comparing the data of the recent international literature on this topic. Advances in the discovery of pharmacological options have dramatically improved the quality of life of patients affected by incontinence, but further studies are needed to increase the effectiveness and safety of the therapies used in this field.

Central nervous targets for the treatment of bladder dysfunction

BACKGROUND

The functions of the lower urinary tract, to store and periodically release urine, are dependent on the activity of smooth and striated muscles in the urinary bladder, urethra, and external urethral sphincter. This activity is in turn controlled by neural circuits in the brain, spinal cord, and peripheral ganglia.

AIMS

This paper will review recent advances in our understanding of the pathophysiology of voiding disorders, especially focusing on the central nervous system.

METHODS

Various neurotransmitters, including acetylcholine, norepinephrine, dopamine, serotonin, excitatory and inhibitory amino acids, adenosine triphosphate, nitric oxide, and neuropeptides, have been implicated in the neural regulation of the lower urinary tract.

RESULTS

Injuries or diseases of the nervous system, as well as drugs and disorders of the peripheral organs, can produce voiding dysfunctions such as urinary frequency, urgency, or incontinence.

CONCLUSION

We discuss the potential targets in the central nervous system and new modalities for the treatment of voiding dysfunction.

Urothelial signaling

The urothelium, which lines the inner surface of the renal pelvis, the ureters, and the urinary bladder, not only forms a high-resistance barrier to ion, solute and water flux, and pathogens, but also functions as an integral part of a sensory web which receives, amplifies, and transmits information about its external milieu. Urothelial cells have the ability to sense changes in their extracellular environment, and respond to chemical, mechanical and thermal stimuli by releasing various factors such as ATP, nitric oxide, and acetylcholine. They express a variety of receptors and ion channels, including P2X3 purinergic receptors, nicotinic and muscarinic receptors, and TRP channels, which all have been implicated in urothelial-neuronal interactions, and involved in signals that via components in the underlying lamina propria, such as interstitial cells, can be amplified and conveyed to nerves, detrusor muscle cells, and ultimately the central nervous system. The specialized anatomy of the urothelium and underlying structures, and the possible communication mechanisms from urothelial cells to various cell types within the bladder wall are described. Changes in the urothelium/lamina propria ("mucosa") produced by different bladder disorders are discussed, as well as the mucosa as a target for therapeutic interventions.

Function and expression pattern of TRPM8 in bladder afferent neurons associated with bladder outlet obstruction in rats

We investigated the function and expression pattern of the transient receptor potential melastatin-8 (TRPM8) in urinary bladder afferent neurons from control and bladder outlet obstruction (BOO) rats. BOO was produced and, after six weeks, the effects of intravesical infusion of menthol, the agonist of TRPM8, were investigated using unanesthetized cystometry. The intravesical infusion of menthol produced an increase in the micturition pressure in both sham surgery and BOO rats. In BOO rats, increased basal and threshold pressure and a decreased micturition interval were observed. Next, the population of TRPM8-positive and the co-expression proportion of TRPM8 with neurochemical markers (NF200 or TRPV1) in the bladder afferent neurons were each compared between the control and BOO rats using retrograde tracing and immunohistochemistry. The population of TRPM8-immunoreactive bladder afferent neurons was larger in BOO rats (3.28±0.43%) than in the control rats (1.33±0.18%). However, there were no statistical differences between the control and BOO rats in the co-expression proportion of neither TRPM8-NF200 (84.1±4.3% vs 79.7±2.7%, p=0.41) nor TRPM8-TRPV1 (33.3±3.6% vs 40.8±2.6%, p=0.08) in the bladder afferent neurons. The present results suggest that the neuronal input through TRPM8-positive bladder afferent neurons are augmented after BOO, however, the neurochemical phenotype of the up-regulated TRPM8-positive bladder afferent neurons is not changed after BOO.

Effect of botulinum toxin on expression of nerve growth factor and transient receptor potential vanilloid 1 in urothelium and detrusor muscle of rats with bladder outlet obstruction-induced detrusor overactivity

OBJECTIVE

To investigate the effects of botulinum toxin A (BoNT/A) on the expression of nerve growth factor (NGF) and transient receptor potential vanilloid 1 (TRPV1) in the urothelium and detrusor muscle of rats with partial bladder outlet obstruction (BOO)-induced detrusor overactivity.

METHODS

Male Sprague-Dawley rats were allocated to a control group, a BOO group, or a BoNT/A-treated BOO group. BoNT/A (1 U) was injected into the detrusor muscle simultaneously with the induction of BOO. The rats were assessed by cystometrography 3 weeks later. The bladder was then removed. Immunofluorescence staining and Western blotting was performed to localize and quantify the expression of NGF and TRPV1 in the urothelium and detrusor muscle.

RESULTS

Cystometrography revealed induction of an unstable bladder in the BOO group and recovery of bladder stability after BoNT/A treatment. Expression of the NGF and TRPV1 proteins in the urothelium was significantly greater in the BOO group than in the control group and had decreased significantly with BoNT/A treatment in BOO-induced rat. The expression of NGF in detrusor muscle was significantly greater in the BOO group than in the control group and subsequently decreased significantly with BoNT/A treatment in the BOO-induced rat. In contrast, TRPV1 expression in the detrusor muscle did not differ significantly among the 3 groups.

CONCLUSION

Our experiments showed that detrusor wall injection of BoNT/A can modulate the expression of NGF and TRPV1, particularly in the urothelium, in accordance with recovery of bladder function.

The role of the transient receptor potential (TRP) superfamily of cation-selective channels in the management of the overactive bladder

• The pathophysiology of lower urinary tract symptoms (LUTS), detrusor overactivity (DO), and the overactive bladder (OAB) syndrome is multifactorial and remains poorly understood. • The transient receptor potential (TRP) channel superfamily has been shown to be involved in nociception and mechanosensory transduction in various organ systems, and studies of the LUT have indicated that several TRP channels, including TRPV1, TRPV2, TRPV4, TRPM8, and TRPA1, are expressed in the bladder, and may act as sensors of stretch and/or chemical irritation. • However, the roles of these individual channels for normal LUT function and in LUTS/DO/OAB, have not been established. • TRPV1 is the channel best investigated. It is widely distributed in LUT structures, but despite extensive information on morphology and function in animal models, the role of this channel in normal human bladder function is still controversial. Conversely, its role in the pathophysiology and treatment of particularly neurogenic DO is well established. • TRPV1 is co-expressed with TRPA1, and TRPA1 is known to be present on capsaicin-sensitive primary sensory neurones. Activation of this channel can induce DO in animal models. • TRPV4 is a Ca(2+)-permeable stretch-activated cation channel, involved in stretch-induced ATP release, and TRPV4-deficient mice exhibit abnormal frequencies of voiding and non-voiding contractions in cystometric experiments. • TRPM8 is a cool receptor expressed in the urothelium and suburothelial sensory fibres. It has been implicated in the bladder-cooling reflex and in idiopathic DO. • The occurrence of other members of the TRP superfamily in the LUT has been reported, but information on their effects on LUT functions is scarce. There seem to be several links between activation of different members of the TRP superfamily and LUTS/DO/OAB, and further exploration of the involvement of these channels in LUT function, normally and in dysfunction, may be rewarding.

Modulation of urinary bladder innervation: TRPV1 and botulinum toxin A

The persisting interest around neurotoxins such as vanilloids and botulinum toxin (BoNT) derives from their marked effect on detrusor overactivity refractory to conventional antimuscarinic treatments. In addition, both are administered by intravesical route. This offers three potential advantages. First, intravesical therapy is an easy way to provide high concentrations of pharmacological agents in the bladder tissue without causing unsuitable levels in other organs. Second, drugs effective on the bladder, but inappropriate for systemic administration, can be safely used as it is the case of vanilloids and BoNT. Third, the effects of one single treatment might be extremely longlasting, contributing to render these therapies highly attractive to patients despite the fact that the reasons to the prolonged effect are still incompletely understood. Attractive as it may be, intravesical pharmacological therapy should still be considered as a second-line treatment in patients refractory to conventional oral antimuscarinic therapy or who do not tolerate its systemic side effects. However, the increasing off-label use of these neurotoxins justifies a reappraisal of their pharmacological properties.

Urothelial signaling

The urinary bladder "mucosa" or innermost portion of the bladder is composed of transitional epithelium, basement membrane, and the lamina propria. This chapter reviews the specialized anatomy of the bladder epithelium (urothelium) and speculates on possible communication mechanisms from urothelial cells to various cell types within the bladder wall. For example, beyond serving as a simple barrier, there is growing evidence that the urinary bladder urothelium exhibits specialized sensory properties and plays a key role in the detection and transmission of both physiological and nociceptive stimuli. Findings from a number of studies suggest that the urothelium exhibits both "sensor" (expressing receptors/ion channels capable of responding to thermal, mechanical, and chemical stimuli) and "transducer" (ability to release chemicals) properties. Thus, urothelial cells exhibit the ability to sense changes in their extracellular environment including the ability to respond to chemical, mechanical, and thermal stimuli that may communicate the state of the urothelial environment to the underlying nervous and muscular systems.

Is the urothelium intelligent?

The urothelium separates the urinary tract lumen from underlying tissues of the tract wall. Previously considered as merely an effective barrier between these two compartments it is now recognized as a more active tissue that senses and transduces information about physical and chemical conditions within the urinary tract, such as luminal pressure, urine composition, etc. To understand this sensory function it is useful to consider the urothelium and suburothelium as a functional unit; containing uroepithelial cells, afferent and efferent nerve fibers and suburothelial interstitial cells. This structure responds to alterations in its external environment through the release of diffusible agents, such as ATP and acetylcholine, and eventually modulates the activity of afferent nerves and underlying smooth muscles. This review considers different stresses the urothelium/suburothelium responds to; the particular chemicals released; the cellular receptors that are consequently affected; and how nerve and muscle function is modulated. Brief consideration is also to regional differences in the urothelium/suburothelium along the urinary tract. The importance of different pathways in relaying sensory information in the normal urinary tract, or whether they are significant only in pathological conditions is also discussed. An operational definition of intelligence is used, whereby a system (urothelium/suburothelium) responds to external changes, to maximize the possibility of the urinary tract achieving its normal function. If so, the urothelium can be regarded as intelligent. The advantage of this approach is that input-output functions can be mathematically formulated, and the importance of different components contributing to abnormal urinary tract function can be calculated.

Changes in afferent activity after spinal cord injury

AIMS

To summarize the changes that occur in the properties of bladder afferent neurons following spinal cord injury.

METHODS

Literature review of anatomical, immunohistochemical, and pharmacologic studies of normal and dysfunctional bladder afferent pathways.

RESULTS

Studies in animals indicate that the micturition reflex is mediated by a spinobulbospinal pathway passing through coordination centers (periaqueductal gray and pontine micturition center) located in the rostral brain stem. This reflex pathway, which is activated by small myelinated (Adelta) bladder afferent nerves, is in turn modulated by higher centers in the cerebral cortex involved in the voluntary control of micturition. Spinal cord injury at cervical or thoracic levels disrupts voluntary voiding, as well as the normal reflex pathways that coordinate bladder and sphincter function. Following spinal cord injury, the bladder is initially areflexic but then becomes hyperreflexic due to the emergence of a spinal micturition reflex pathway. The recovery of bladder function after spinal cord injury is dependent in part on the plasticity of bladder afferent pathways and the unmasking of reflexes triggered by unmyelinated, capsaicin-sensitive, C-fiber bladder afferent neurons. Plasticity is associated with morphologic, chemical, and electrical changes in bladder afferent neurons and appears to be mediated in part by neurotrophic factors released in the spinal cord and the peripheral target organs.

CONCLUSIONS

Spinal cord injury at sites remote from the lumbosacral spinal cord can indirectly influence properties of bladder afferent neurons by altering the function and chemical environment in the bladder or the spinal cord.

Urothelial signaling

Beyond serving as a simple barrier, there is growing evidence that the urinary bladder urothelium exhibits specialized sensory properties and play a key role in the detection and transmission of both physiological and nociceptive stimuli. These urothelial cells exhibit the ability to sense changes in their extracellular environment including the ability to respond to chemical, mechanical and thermal stimuli that may communicate the state of the urothelial environment to the underlying nervous and muscular systems. Here, we review the specialized anatomy of the urothelium and speculate on possible communication mechanisms from urothelial cells to various cell types within the bladder wall.

Persistent detrusor overactivity after transurethral resection of the prostate

Detrusor overactivity is associated with aging and benign prostatic obstruction and often causes the troublesome symptoms of urgency and urgency incontinence (overactive bladder), persistent detrusor overactivity after transurethral resection of the prostate being the cause of more than a third of poor symptomatic outcomes following surgery. Most of the evidence currently suggests that neurons of the urothelium at the bladder neck play a significant role in the genesis of detrusor overactivity. Treatment options including botulinum toxin injections and intravesical vanilloids have been studied in the treatment of persistent detrusor overactivity, but further studies are needed specifically in patients with persistent detrusor overactivity after transurethral resection of the prostate. As urodynamic studies are able to predict a proportion of postoperative failures, more widespread use is advocated by many in the routine assessment of lower urinary tract symptoms thought to be due to benign prostatic obstruction.

Afferent nerve regulation of bladder function in health and disease

The afferent innervation of the urinary bladder consists primarily of small myelinated (Adelta) and unmyelinated (C-fiber) axons that respond to chemical and mechanical stimuli. Immunochemical studies indicate that bladder afferent neurons synthesize several putative neurotransmitters, including neuropeptides, glutamic acid, aspartic acid, and nitric oxide. The afferent neurons also express various types of receptors and ion channels, including transient receptor potential channels, purinergic, muscarinic, endothelin, neurotrophic factor, and estrogen receptors. Patch-clamp recordings in dissociated bladder afferent neurons and recordings of bladder afferent nerve activity have revealed that activation of many of these receptors enhances neuronal excitability. Afferent nerves can respond to chemicals present in urine as well as chemicals released in the bladder wall from nerves, smooth muscle, inflammatory cells, and epithelial cells lining the bladder lumen. Pathological conditions alter the chemical and electrical properties of bladder afferent pathways, leading to urinary urgency, increased voiding frequency, nocturia, urinary incontinence, and pain. Neurotrophic factors have been implicated in the pathophysiological mechanisms underlying the sensitization of bladder afferent nerves. Neurotoxins such as capsaicin, resiniferatoxin, and botulinum neurotoxin that target sensory nerves are useful in treating disorders of the lower urinary tract.

AMTB, a TRPM8 channel blocker: evidence in rats for activity in overactive bladder and painful bladder syndrome

The activation of the TRPM8 channel, a member of the large class of TRP ion channels, has been reported to be involved in overactive bladder and painful bladder syndrome, although an endogenous activator has not been identified. In this study, N-(3-aminopropyl)-2-{[(3-methylphenyl) methyl]oxy}-N-(2-thienylmethyl)benzamide hydrochloride salt (AMTB) was evaluated as a TRPM8 channel blocker and used as a tool to evaluate the effects of this class of ion channel blocker on volume-induced bladder contraction and nociceptive reflex responses to noxious bladder distension in the rat. AMTB inhibits icilin-induced TRPM8 channel activation as measured in a Ca(2+) influx assay, with a pIC(50) of 6.23. In the anesthetized rat, intravenous administration of AMTB (3 mg/kg) decreased the frequency of volume-induced bladder contractions, without reducing the amplitude of contraction. The nociceptive response was measured by analyzing both visceromotor reflex (VMR) and cardiovascular (pressor) responses to urinary bladder distension (UBD) under 1% isoflurane. AMTB (10 mg/kg) significantly attenuated reflex responses to noxious UBD to 5.42 and 56.51% of the maximal VMR response and pressor response, respectively. The ID50 value on VMR response was 2.42 +/- 0.46 mg/kg. These results demonstrate that TRPM8 channel blocker can act on the bladder afferent pathway to attenuate the bladder micturition reflex and nociceptive reflex responses in the rat. Targeting TRPM8 channel may provide a new therapeutic opportunity for overactive bladder and painful bladder syndrome.

The neural control of micturition

Micturition, or urination, occurs involuntarily in infants and young children until the age of 3 to 5 years, after which it is regulated voluntarily. The neural circuitry that controls this process is complex and highly distributed: it involves pathways at many levels of the brain, the spinal cord and the peripheral nervous system and is mediated by multiple neurotransmitters. Diseases or injuries of the nervous system in adults can cause the re-emergence of involuntary or reflex micturition, leading to urinary incontinence. This is a major health problem, especially in those with neurological impairment. Here we review the neural control of micturition and how disruption of this control leads to abnormal storage and release of urine.

Association of overactive bladder and stress urinary incontinence in rats with pudendal nerve ligation injury

Approximately one-third of patients with stress urinary incontinence (SUI) also suffer from urgency incontinence, which is one of the major symptoms of overactive bladder (OAB) syndrome. Pudendal nerve injury has been recognized as a possible cause for both SUI and OAB. Therefore, we investigated the effects of pudendal nerve ligation (PNL) on bladder function and urinary continence in female Sprague-Dawley rats. Conscious cystometry with or without capsaicin pretreatment (125 mg/kg sc), leak point pressures (LPPs), contractile responses of bladder muscle strips to carbachol or phenylephrine, and levels of nerve growth factor (NGF) protein and mRNA in the bladder were compared in sham and PNL rats 4 wk after the injury. Urinary frequency detected by a reduction in intercontraction intervals and voided volume was observed in PNL rats compared with sham rats, but it was not seen in PNL rats with capsaicin pretreatment that desensitizes C-fiber-afferent pathways. LPPs in PNL rats were significantly decreased compared with sham rats. The contractile responses of detrusor muscle strips to phenylephrine, but not to carbachol, were significantly increased in PNL rats. The levels of NGF protein and mRNA in the bladder of PNL rats were significantly increased compared with sham rats. These results suggest that pudendal nerve neuropathy induced by PNL may be one of the potential risk factors for OAB, as well as SUI. Somato-visceral cross sensitization between somatic (pudendal) and visceral (bladder) sensory pathways that increases NGF expression and alpha(1)-adrenoceptor-mediated contractility in the bladder may be involved in this pathophysiological mechanism.

Effect of Thalamic Deep Brain Stimulation on Lower Urinary Tract Function

OBJECTIVE

The precise mechanisms underlying cerebral regulation of lower urinary tract function are still poorly understood. In patients with disabling essential tremor (ET) refractory to pharmacotherapy, thalamic deep brain stimulation (DBS) is an effective treatment for tremor control. Here, we evaluated the effect of thalamic DBS on urodynamic parameters in patients with ET.

PATIENTS AND METHODS

We investigated seven patients (two females, five males) with ET 15-85 mo after implantation of DBS leads into the ventral intermediate nucleus of the thalamus. We compared urodynamic parameters during thalamic DBS (ON state) and 30 min after turning the stimulator off (OFF state).

RESULTS

In the ON compared with the OFF state, there was a significant decrease in bladder volume at first desire to void (median, 218 ml vs. 365 ml, p=0.031), at strong desire to void (median, 305 ml vs. 435 ml, p=0.031), and at maximum cystometric capacity (median, 345 ml vs. 460 ml, p=0.016). No significant differences between the ON and OFF state were detected for changes in detrusor pressure during filling cystometry, bladder compliance, maximum detrusor pressure, detrusor pressure at maximum flow rate, maximum flow rate, voided volume, and postvoid residual.

CONCLUSIONS

Thalamic deep brain stimulation resulted in an earlier desire to void and decreased bladder capacity, suggesting a regulatory role of the thalamus in lower urinary tract function. Therefore, the thalamus may be a promising target for the development of new therapies for lower urinary tract dysfunction.

Resiniferatoxin and botulinum toxin type A for treatment of lower urinary tract symptoms

Resiniferatoxin (RTX) and botulinum toxin subtype A (BTX-A) are increasingly viewed as potential treatments for lower urinary tract symptoms (LUTS) refractory to conventional therapy. RTX, a capsaicin analogue devoid of severe pungent properties, acts by desensitizing the transient receptor potential vanilloid type 1 (TRPV1) receptor and inactivating C-fibers. BTX-A cleaves soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins in afferent and efferent nerve endings, therefore impeding the fusion of synaptic vesicles with the neuronal membrane necessary for the release of neurotransmitters. In patients with neurogenic and idiopathic detrusor overactivity, RTX and BTX-A have been shown to increase the volume to first detrusor contraction, increase bladder capacity, and improve urinary incontinence and quality of life. Recent data also suggest a role for these neurotoxins in treating urgency, the primary symptom in overactive bladder (OAB) syndrome. Furthermore, experimental data strongly support the use of both neurotoxins in the treatment of pain and frequency in patients with interstitial cystitis/painful bladder syndrome (IC/PBS), although the results from available clinical trials for this use are still inconclusive. In spite of promising results overall, it should be made clear that the administration of these neurotoxins is still considered an experimental procedure and that more clinical studies are necessary before a license for their use will be issued by health authorities.

Therapeutic receptor targets for lower urinary tract dysfunction

The functions of the lower urinary tract, to store and periodically release urine, are dependent on the activity of smooth and striated muscles in the bladder, urethra, and external urethral sphincter. During urine storage, the outlet is closed, and the bladder smooth muscle is quiescent. When bladder volume reaches the micturition threshold, activation of a micturition center in the dorsolateral pons (the pontine micturition center) induces a bladder contraction and a reciprocal relaxation of the urethra, leading to bladder emptying. During voiding, sacral parasympathetic (pelvic) nerves provide an excitatory input (cholinergic and purinergic) to the bladder and inhibitory input (nitrergic) to the urethra. These peripheral systems are integrated by excitatory and inhibitory regulation at the levels of the spinal cord and the brain. Injury or diseases of the nervous system, as well as drugs and disorders of the peripheral organs, can produce lower urinary tract dysfunction. In the overactive bladder (OAB) condition, therapeutic targets for facilitation of urine storage can be found at the levels of the urothelium, detrusor muscles, autonomic and afferent pathways, spinal cord, and brain. There is increasing evidence showing that the urothelium has specialized sensory and signaling properties including: (1) expression of nicotinic, muscarinic, tachykinin, adrenergic, bradykinin, and transient receptor potential (TRP) receptors, (2) close physical association with afferent nerves, and (3) ability to release chemical molecules such as adenosine triphosphate (ATP), acetylcholine, and nitric oxide. Increased expression and/or sensitivity of these urothelial-sensory molecules that lead to afferent sensitization have been documented as possible pathogenesis of OAB. Targeting afferent pathways and/or bladder smooth muscles by modulating activity of ligand receptors (e.g., neurokinin, ATP, or beta3-adrenergic receptors) and ion channels (e.g., TRPV1 or K) could be effective to suppress OAB. In the stress urinary incontinence condition, pharmacotherapies targeting the neurally mediated urethral continence reflex during stress conditions such as sneezing or coughing could be effective for increasing the outlet resistance. Therapeutic targets include adrenergic and serotonergic receptors in the spinal cord as well as adrenergic receptors at the urethral sphincter, which can enhance urethral reflex activity during stress conditions and increase baseline urethral pressure, respectively.

Diabetes mellitus: does it impair urinary continence after radical cystoprostatectomy and ileal orthotopic bladder substitution?

OBJECTIVE

To assess the effect of diabetes mellitus (DM) on urinary continence after radical cystoprostatectomy and ileal orthotopic bladder substitution.

METHODS

Patients with DM undergoing radical cystoprostatectomy and ileal orthotopic bladder substitution without prior radiotherapy and with a minimum follow-up of 12 mo were identified from our database. Twenty-two men met the inclusion criteria and were randomly matched to 22 nondiabetic controls for age, ileum length used for reservoir construction, attempted nerve-sparing surgery, pathologic tumour stage, and pathologic lymph node status to assess the effect of DM on urinary continence.

RESULTS

All 22 diabetic patients suffered from type 2 DM. Twelve were treated with oral antidiabetics and 10 required insulin. Daytime continence was significantly worse in the diabetic patients compared to nondiabetic controls 3 mo (odds ratio [OR] 21; 95% confidence interval [CI], 2.4-185; p=0.001) and 6 mo (OR 17.5; 95% CI, 2-154; p=0.002) postoperatively. Thereafter no significant difference was detectable. In diabetic patients nighttime continence was worse. The difference was statistically significant at 3 mo (OR 7.3; 95% CI, 1.9-28; p=0.002), 6 mo (OR 9.1; 95% CI, 2.3-36; p=0.001), 12 mo (OR 7.1; 95% CI, 1.9-27; p=0.003), and 24 mo (OR 5.7; 95% CI, 1.3-26; p=0.018) after surgery.

CONCLUSIONS

Patients with DM take longer to regain daytime and, even more so, nighttime continence than nondiabetic patients. Diabetic patients undergoing radical cystoprostatectomy should be informed of the potential negative impact of DM on the recovery of urinary continence after an ileal orthotopic bladder substitution.

Can the ice-water test predict the outcome of intradetrusor injections of botulinum toxin in patients with neurogenic bladder dysfunction?

The aim of this project was to evaluate the ice-water test as a predictor of the response to intradetrusor botulinum toxin injection in patients with neurogenic detrusor overactivity. We retrospectively evaluated the urodynamic parameters in 22 patients with neurogenic bladder dysfunction and positive ice-water test. Maximum cystometric capacity (MCC), reflex volume (RV), maximum detrusor pressure during voiding (MVP) and bladder compliance (BC) were compared before and after intradetrusor injection of 300 units botulinum toxin and calculated as a quotient. The ice-water test was performed before the injection, and the maximum pressure rise and the time to maximum pressure were measured. Furthermore, the ratio between maximum pressure and time to reach maximum pressure was calculated as the velocity of pressure rise. Correlations between the ice-water test criteria and the quotients of the cystometric data before and after injection were determined by the Spearmen's Rho coefficient. The increase in MCC and RV after botulinum toxin A injection showed a small positive, but insignificant correlation of 0.25 and 0.2 to the velocity of pressure rise of the ice-water test. A small negative, but insignificant correlation was found in change of BC and MVP with -0.17 and -0.2, respectively. Based on our population the ice-water test cannot predict the efficacy of intradetrusor botulinum toxin injections in patients with neurogenic detrusor overactivity.

TRPs in bladder diseases

This review attempts to provide an overview of the current knowledge of TRP proteins and their possible role in bladder function and disease. At present, there are 28 transient receptor potential (TRP) channels (subdivided into 7 categories or families) which are involved in a number of functions [G.A. Hicks, TRP channels as therapeutic targets: hot property, or time to cool down? Neurogastroenterology and Motility 18, (2006) 590-594., J.D. Levine, N. Alessandri-Haber, TRP channels: targets for the relief of pain, Biochimica et Biophysica Acta 1772, (2007) 989-1003.]. Of those belonging to the group 1 subfamily, a number of TRPV, TRPM and TRPA proteins associated with osmoregulation, thermal, chemical and mechanical signaling mechanisms have been shown to be expressed within the lower urinary tract. Though the biological role of many of these channels in urinary bladder function still remains elusive, TRPV1 is by far the best characterized and is thought to be involved in a number of bladder disorders [A. Szallasi, P.M. Blumberg, Vanilloid (Capsaicin) Receptors and Mechanisms, Pharmacological Reviews 51, (1999) 150-221., I. Nagy, P. Santha, G. Jansco, L. Urban, The role of the vanilloid (capsaicin) receptor (TRPV1) in physiology and pathology, European Journal of Pharmacology 500, (2004) 351-369.].

Lower urinary tract symptoms (LUTS) and bladder afferent activity

AIMS

Dysregulation of bladder afferent activity and detrusor smooth muscle behavior leads to a constellation of lower urinary tract symptoms (LUTS), which includes overactive bladder (OAB). Current treatments for LUTS are poorly tolerated and may be associated with substantial adverse effects.

METHODS

Major advances in the understanding of bladder neuroanatomy and the role of bladder afferent pathways in symptom generation suggest a range of targets for new therapeutic agents.

RESULTS

A sensory role for urothelial and suburothelial structures has been established, as well as a cascade of afferent bladder signaling involving the bladder epithelium and detrusor muscle. Numerous inhibitory and stimulatory neurotransmitters and chemical mediators interact with a variety of specialized receptors and participate in signal transduction leading to wider neuroactivation. The blockade of muscarinic receptors, possibly mediated by muscarinic 2 (M(2)) receptors residing in the urothelium, has been shown to affect bladder afferent fibers, challenging the traditional concept that antimuscarinic therapy involves M(3) receptor-mediated effects on detrusor smooth muscle. The propagation of impulses to spinal and higher centers utilizes axonal fiber tracts remarkable for their morphologic and functional plasticity as bladder function becomes increasingly disordered.

CONCLUSIONS

These findings suggest that the etiology of LUTS includes enhanced, dysregulated, and perhaps maladaptive sensory signaling arising from numerous pelvic locales, including the most superficial epithelium of the bladder.

LUTS treatment: Future treatment options

Lower urinary tract symptoms (LUTS) are commonly divided into storage, voiding, and postmicturition symptoms, and may occur in both men and women. Male LUTS have historically been linked to benign prostatic hyperplasia (BPH), but are not necessarily prostate related. The focus of treatment for LUTS has thus shifted from the prostate to the bladder and other extraprostatic sites. LUTS include symptoms of the overactive bladder (OAB), which are often associated with detrusor overactivity. Treatment for LUTS suggestive of BPH has traditionally involved the use of alpha(1)-adrenoceptor (AR) antagonists; 5alpha-reductase inhibitors; and phytotherapy-however, several new therapeutic principles have shown promise. Selective beta(3)-adrenoceptor agonists and antimuscarinics are potentially useful agents for treating LUTS, particularly for storage symptoms secondary to outflow obstruction. Other agents of potential or actual importance are antagonists of P2X(3) receptors, botulinum toxin type A, endothelin (ET)-converting enzyme inhibitors, and drugs acting at vanilloid, angiotensin, and vitamin D(3) receptor sites. Drugs interfering with the nitric oxide/cGMP-cAMP pathway, Rho-kinase and COX inhibitors, as well as drugs targeting receptors and mechanisms within the CNS, are also of interest and deserving of further study for the treatment of LUTS.

Intravesical resiniferatoxin for the treatment of women with idiopathic detrusor overactivity and urgency incontinence: A single dose, 4 weeks, double-blind, randomized, placebo controlled trial

AIMS

To assess the hypothesis that resiniferatoxin (RTX) can be useful in women with urgency incontinence and idiopathic detrusor overactivity (IDO), we conducted a prospective, double-blind, randomized, placebo-controlled, parallel trial comparing the effects of RTX and placebo.

MATERIALS AND METHODS

Fifty-eight patients were randomly assigned to receive a single intravesical dose of 100 ml of either RTX 50 nM or placebo. Safety and efficacy were evaluated over 4 weeks. The primary efficacy endpoints were voiding symptoms evaluated through the voiding diary. Secondary efficacy endpoint was urodynamic response. Quality of life was measured by the Kings' Health Questionnaire

RESULTS

Although improving trends were seen in both groups after the instillations, no statistically significant differences were found between the groups in any of the clinical or urodynamic parameters. RTX instillations were well tolerated with few and self-limited side-effects.

CONCLUSION

A single 50 nM intravesical dose of RTX was not better than placebo for the treatment of women with IDO and urgency incontinence.

Safety and efficacy of tramadol in the treatment of idiopathic detrusor overactivity: a double-blind, placebo-controlled, randomized study

AIM

To evaluate the efficacy and safety of tramadol in patients with idiopathic detrusor overactivity (IDO).

METHODS

A total of 76 patients 18 years or older with IDO were randomly assigned to receive 100 mg tramadol sustained release (group 1, n = 38) or placebo (group 2, n = 38) every 12 h for 12 weeks. Clinical evaluation was performed at baseline and every 2 weeks during treatment. All patients underwent urodynamics and ice water test at baseline and 12-week treatment. Main outcome measures were number of voids per 24 h, urine volume per void and episodes of urge incontinence per 24 h on a frequency volume chart and detailed recording of adverse effect.

RESULTS

After 12 weeks of treatment mean number of voids per 24 h +/- SD decreased from 9.3 +/- 3.2 to 5.1 +/- 2.1 (P < 0.001 vs. placebo) [95% confidence interval (CI) -5.1--0.4]. At that time mean urine volume per void increased from 158 +/- 32 to 198 +/- 76 ml (P < 0.001 vs. placebo) (95% CI 8-22), while mean number of incontinence episodes per 24 h decreased from 3.2 +/- 3.3 to 1.6 +/- 2.8 (P < 0.001 vs. placebo) (95% CI -2-0.3). Tramadol induced significant improvements in urodynamic parameters. More adverse effects were associated with tramadol treatment than with placebo (P < 0.05). The main adverse event with tramadol was nausea.

CONCLUSIONS

In patients with non-neurogenic IDO tramadol provided beneficial clinical and urodynamic results. Further studies are required to draw final conclusions on the efficacy of this drug in IDO.

TRPV1 (vanilloid receptor) in the urinary tract: expression, function and clinical applications

The transient receptor potential vanilloid subfamily 1 (TRPV1) is an ion channel activated by capsaicin, heat, protons and endogenous ligands such as anandamide. It is largely expressed in the urinary tract of mammals. Structures in which the receptor expression is firmly established include sensory fibers and urothelial cells, although the presence of TRPV1 in other cell types has been reported. As in other systems, pain perception was the first role attributed to TRPV1 in the urinary tract. However, it is now increasingly clear that TRPV1 also regulates the frequency of bladder reflex contractions, either through direct excitation of sensory fibers or through urothelial-sensory fiber cross talk involving the release of neuromediators from the epithelial cells. In addition, the recent identification of the receptor in urothelial and prostatic cancer cells raise the exciting hypothesis that TRPV1 is involved in cell differentiation. Desensitization of the receptor by capsaicin and resiniferatoxin has been investigated for therapeutic purposes. For the moment, lower urinary tract dysfunctions in which some benefit was obtained include painful bladder syndrome and overactive bladder of neurogenic and non-neurogenic origin. However, desensitization may become obsolete when non-toxic, potent TRPV1 antagonists become available.

Animal models in urological disease and sexual dysfunction

There are several conditions associated with dysfunction of the lower urinary tract or which result in a reduction in the ability to engage in satisfactory sexual function and result in significant bother to sufferers, partners and/or carers. This review describes some of the animal models that may be used to discover safe and effective medicines with which to treat them. While alpha adrenoceptor antagonists and 5-alpha-reductase inhibitors deliver improvement in symptom relief in benign prostatic hyperplasia sufferers, the availability of efficacious and well-tolerated medicines to treat incontinence is less well served. Stress urinary incontinence (SUI) has no approved medical therapy in the United States and overactive bladder (OAB) therapy is limited to treatment with muscarinic antagonists (anti-muscarinics). SUI and OAB are characterised by high prevalence, a growing ageing population and a strong desire from sufferers and physicians for more effective treatment options. High patient numbers with low presentation rates characterizes sexual dysfunction in men and women. The introduction of Viagra in 1998 for treating male erectile dysfunction and the success of the phosphodiesterase type 5 inhibitor class (PDE5 inhibitor) have indicated the willingness of sufferers to seek treatment when an effective alternative to injections and devices is available. The main value of preclinical models in discovering new medicines is to predict clinical outcomes. This translation can be established relatively easily in areas of medicine where there are a large number of drugs with different underlying pharmacological mechanisms in clinical usage. However, apart from, for example, the use of PDE5 inhibitors to treat male erectile dysfunction and the use of anti-muscarinics to treat OAB, this clinical information is limited. Therefore, current confidence in existing preclinical models is based on our understanding of the biochemical, physiological, pathophysiological and psychological mechanisms underlying the conditions in humans and how they are reflected in preclinical models. Confidence in both the models used and the pharmacological data generated is reinforced if different models of related aspects of the same disorder generate confirmatory data. However, these models will only be fully validated in retrospect once the pharmacological agents they have helped identify are tested in humans.

Improvement of bladder storage function by α1-blocker depends on the suppression of C-fiber afferent activity in rats

AIMS

Alpha1-blockers improve voiding symptoms through the reduction of prostatic and urethral smooth muscle tone; however, the underlying mechanism of improvement of storage symptoms is not known. Using a rat model of detrusor overactivity caused by cerebral infarction (CI), we undertook the present study to determine whether the effect of an alpha1-blocker, naftopidil, is dependent on the suppression of C-fiber afferents.

METHODS

To induce desensitization of C-fiber bladder afferents, we injected resiniferatoxin (0.3 mg/kg, RTX) sub-cutaneously to female Sprague-Dawley rats 2 days prior to left middle cerebral artery occlusion (MCAO) (RTX-CI rats). As controls we used rats without RTX treatment (CI rats). MCAO and insertion of a polyethylene catheter through the bladder dome were performed under halothane anesthesia. We investigated the effects on cystometrography (CMG) of intravenous (i.v.), intracerebroventricular (i.c.v.), or intrathecal (i.t.) administration of naftopidil in conscious CI rats.

RESULTS

Bladder capacity (BC) was markedly reduced after MCAO in both RTX-CI and CI rats. I.v. administration of naftopidil significantly increased BC in CI rats without an increase in residual volume, but it had no effects on BC in RTX-CI rats. I.t. administration of naftopidil significantly increased BC in CI but not in RTX-CI rats.

CONCLUSIONS

These results suggest that naftopidil has an inhibitory effect on C-fiber afferents in the lumbosacral spinal cord, improving BC during the storage phase.

Effect of botulinum toxin on detrusor overactivity induced by intravesical adenosine triphosphate and capsaicin in a rat model

OBJECTIVES

To assess the effects of intravesical injection of botulinum toxin type A (BTX) on a model of detrusor overactivity induced by intravesical infusions of adenosine triphosphate (ATP) and capsaicin. BTX has recently been used clinically to treat overactive bladder syndromes without a precise knowledge of the mechanism of action.

METHODS

Twelve Sprague-Dawley rats underwent BTX injections. Six received 1.0 U and 6 received 0.5 U. BTX injections were done at bladder tube placement. Ten rats received saline injections as controls. After 48 hours of recovery, all 22 animals underwent awake, conscious cystometrography (CMG), performed using both saline and ATP (20 mM) intravesical infusion at 0.074 mL/min. In another 4 rats, capsaicin (100 microM) was infused intravesically before and after the BTX injections. The CMG parameters calculated included bladder contraction pressures and contraction frequencies (contractions per minute or Herz).

RESULTS

Intravesical saline CMG produced a contraction frequency of 0.78 +/- 0.10 Hz. Intravesical ATP doubled this voiding frequency to 1.45 +/- 0.18 Hz (P = 0.003). BTX treatment at 1.0 U reduced the frequency to 0.91 +/- 0.13 Hz (P = 0.02). BTX injection significantly decreased the bladder contraction pressure during saline and ATP CMG. However, 0.5 U BTX did not decrease ATP-induced overactivity; therefore, in the capsaicin experiments, 1.0 U BTX was used. Although BTX tended to reverse detrusor overactivity secondary to intravesical capsaicin, this difference was not statistically significant.

CONCLUSIONS

Intravesical infusion of either ATP or capsaicin can induce detrusor overactivity. BTX was more effective in blocking the effect of ATP than of capsaicin, although BTX injection did show a trend in reducing the contraction frequencies and amplitudes induced by capsaicin. The clinical utility of using BTX to treat overactive bladder syndromes and bladder hypersensory states, especially those that may be caused by an augmentation of the purinergic pathway, should be studied further.

Nocturia in men with lower urinary tract symptoms is associated with both nocturnal polyuria and detrusor overactivity with positive response to ice water test

OBJECTIVES

To investigate whether detrusor overactivity (DO) and the response to the ice water test (IWT) influence nighttime urinary frequency in patients with lower urinary tract symptoms.

METHODS

A total of 114 patients with lower urinary tract symptoms, who were older than 50 years, with an International Prostate Symptom Score 8 or more points and a quality of life index of 2 or greater, were evaluated by a 48-hour frequency-volume chart, free flowmetry, pressure flow study, and IWT.

RESULTS

The DO-positive IWT responders had a significantly greater bladder outlet obstruction index than did the DO-positive IWT nonresponders and the DO-negative IWT nonresponders. The DO-positive IWT responders had significantly more frequent nocturia and smaller nighttime maximal and minimal voided volumes than did the DO-negative IWT nonresponders without any difference in the nocturnal voided volume. The patients with nocturia two or more times had a significantly larger nocturnal voided volume and smaller nighttime minimal voided volume than the patients with nocturia less than two times. The incidence of DO-positive IWT responders was significantly greater among the patients with nocturia three or more times than that among those with nocturia less than three times. In the multivariate logistic model, the nocturnal voided volume and nighttime minimal voided volume were independently associated with nocturia two or more times and the DO-positive IWT responders were independently associated with nocturia three or more times.

CONCLUSIONS

Once high-grade bladder outlet obstruction induces C-fiber-related DO, it is strongly suggested that this process, together with nocturnal polyuria, plays an important role in the consequent clinical manifestations of nocturia in patients with lower urinary tract symptoms.

Urinary Incontinence in Men

BACKGROUND

Despite similar rates of voiding dysfunction in older men and women, most funded research has focused on women. Strategic treatment plans for managing urinary incontinence and other lower urinary tract symptoms in men are limited by sparse or absent direct clinical evidence with most interventions supported by data extrapolated from studies in women.

OBJECTIVES

To explore what is known about the epidemiology and etiology of incontinence in men, highlight some of the gaps in the current knowledge, address limitations in existing research, and consider future directions in men's continence care.

METHODS

Existing literature on urinary incontinence in men was analyzed to generate a plan for future research.

RESULTS

Gaps in our knowledge of urinary incontinence in men remain in the areas of etiology, psychosocial consequences, and treatment efficacy.

CONCLUSIONS

Clinical research addressing incontinence in men is critical to explore the barriers or facilitators to seeking care, elucidate the biomechanical aspects of pelvic floor function, provide a clear description of the natural history of bladder dysfunction, and highlight the quality of life impact from incontinence.

Bladder C-Fiber Desensitization Induces a Long-Lasting Improvement of BPH-Associated Storage LUTS: A Pilot Study

OBJECTIVES

To evaluate the effect of bladder C-fiber desensitization on BPH-associated storage LUTS.

METHODS

Twelve patients with predominant BPH-associated storage LUTS gave written informed consent to enter the study. IPSS and QoL scores, micturition chart, uroflowmetry, cystometry and post-void residual (PVR) were obtained at baseline and at 1, 3 and 6 months after a single intravesical administration of 50 nM resiniferatoxin (RTX) solution.

RESULTS

Mean IPSS score decreased from 20.1 +/- 6.0 to 10.5 +/- 4.4 at 1 month (p = 0.0001), to 10.3 +/- 4.4 at 3 months (p = 0.00001) and to 9.8 +/- 5.7 at 6 months (p < 0.00001). Mean QoL score decreased from 4.5 +/- 1 to 2.5 +/- 1 at 1 month (p = 0.0001), to 2.3 +/- 1 at 3 months (p = 0.0004) and to 2.6 +/- 1.2 at 6 months (p = 0.0003). Mean urinary frequency decreased from 15.2 +/- 8.5 to 10.8 +/- 7.3 at 1 month (p = 0.0002), to 10.2 +/- 4.9 at 3 months (p = 0.002) and to 11.7 +/- 9.2 at 6 months (p = 0.005). Urge incontinence, which was present in six cases, disappeared in 4 patients and decreased to less than half in the other two. Mean first desire to void and maximal cystometric capacity increased significantly after RTX whereas uroflowmetry and PVR were not altered.

CONCLUSIONS

Intravesical desensitization of bladder C fibres with intravesical RTX might be useful in the treatment of patients with predominant BPH associated storage LUTS.

Mechanisms involved in new therapies for overactive bladder

During the last few years, vanilloid substances and botulinum-A toxin were extensively investigated as new therapies for overactive bladder. Intravesical administration of capsaicin or resiniferatoxin--2 members of the vanilloid family--has been shown to increase bladder capacity and decrease urge incontinence in patients with neurogenic, as well as nonneurogenic, forms of detrusor overactivity. In addition, vanilloids have been shown also to reduce bladder pain in patients with hypersensitive disorders. Vanilloids are exogenous ligands of vanilloid receptor type 1 (VR1), an ion channel present in the membrane of type C primary afferent nerve fibers. This receptor, which plays a key role in pain perception and control of the micturition reflex, may be upregulated by nerve growth factor (NGF), a neurotrophic molecule detected in high concentrations in overactive detrusor tissue. Vanilloids, by reducing uptake of NGF through sensory neurons, may counteract VR1 upregulation. Intravesical injections of botulinum-A toxin, a neurotoxin produced by Clostridium botulinum, were shown to increase bladder capacity and to decrease urge incontinence episodes in patients with neurogenic detrusor overactivity. Botulinum-A toxin impedes the release of acetylcholine from cholinergic nerve endings at the neuromuscular junction, leading to paralysis of the detrusor smooth muscle.