Time-of-day dependent changes in guinea pig bladder afferent mechano-sensitivity.

The voiding of urine has a clear circadian rhythm with increased voiding during active phases and decreased voiding during inactive phases. Bladder spinal afferents play a key role in the regulation of bladder storage and voiding, but it is unknown whether they exhibit themselves a potential circadian rhythm. Therefore, this study aimed to determine the mechano- and chemo- sensitivity of three major bladder afferent classes at two opposite day-night time points. Adult female guinea pigs underwent conscious voiding monitoring and bladder ex vivo single unit extracellular afferent recordings at 0300 h and 1500 h to determine day-night modulation of bladder afferent activity. All guinea pigs voided a higher amount of urine at 1500 h compared to 0300 h. This was due to an increased number of voids at 1500 h. The mechano-sensitivity of low- and high-threshold stretch-sensitive muscular-mucosal bladder afferents to mucosal stroking and stretch was significantly higher at 1500 h compared to 0300 h. Low-threshold stretch-insensitive mucosal afferent sensitivity to stroking was significantly higher at 1500 h compared to 0300 h. Further, the chemosensitivity of mucosal afferents to N-Oleoyl Dopamine (endogenous TRPV1 agonist) was also significantly increased at 1500 h compared to 0300 h. This data indicates that bladder afferents exhibit a significant time-of-day dependent variation in mechano-sensitivity which may influence urine voiding patterns. Further studies across a 24 h period are warranted to reveal potential circadian rhythm modulation of bladder afferent activity.

Transient receptor potential channels in sensory mechanisms of the lower urinary tract.

Disruptions to sensory pathways in the lower urinary tract commonly occur and can give rise to lower urinary tract symptoms (LUTS). The unmet clinical need for treatment of LUTS has stimulated research into the molecular mechanisms that underlie neuronal control of the bladder and transient receptor potential (TRP) channels have emerged as key regulators of the sensory processes that regulate bladder function. TRP channels function as molecular sensors in urothelial cells and afferent nerve fibres and can be considered the origin of bladder sensations. TRP channels in the lower urinary tract contribute to the generation of normal and abnormal bladder sensations through a variety of mechanisms, and have demonstrated potential as targets for the treatment of LUTS in functional disorders of the lower urinary tract.

Therapeutic Efficacy of onabotulinumtoxinA Delivered Using Various Approaches in Sensory Bladder Disorder.

Cystoscopic onabotulinumtoxinA (onaBoNTA) intradetrusor injection is an efficient and durable modality for treating sensory bladder disorders. However, the inconvenience of using the cystoscopic technique and anesthesia, and the adverse effects of direct needle injection (e.g., haematuria, pain, and infections) have motivated researchers and clinicians to develop diverse injection-free procedures to improve accessibility and prevent adverse effects. However, determining suitable approaches to transfer onaBoNTA, a large molecular and hydrophilic protein, through the impermeable urothelium to reach therapeutic efficacy remains an unmet medical need. Researchers have provided potential solutions in three categories: To disrupt the barrier of the urothelium (e.g., protamine sulfate), to increase the permeability of the urothelium (e.g., electromotive drug delivery and low-energy shock wave), and to create a carrier for transportation (e.g., liposomes, thermosensitive hydrogel, and hyaluronan-phosphatidylethanolamine). Thus far, most of these novel administration techniques have not been well established in their long-term efficacy; therefore, additional clinical trials are warranted to validate the therapeutic efficacy and durability of these techniques. Finally, researchers may make progress with new combinations or biomaterials to change clinical practices in the future.

Afferent nerve fibres in the wall of the rat urinary bladder.

Structure and distribution of afferent nerve fibres in the rat bladder were studied by fluorescence microscopy after selective staining with antibodies against neuropeptide CGRP. Afferent fibres are very abundant (by comparison with other viscera) and interconnected in all bladder parts: muscle, urothelium, connective tissue, blood vessels, serosa. Their highest concentration is beneath the urothelium in equatorial and caudal regions, where they form a plexus, while individually maintaining a tree-like structure with innumerable branches running without preferential orientation. In cranial regions, mucosal afferent fibres become rare or absent. Abundant fibres are found in the detrusor, within each muscle bundle, with long strings of varicosities parallel to muscle cells. Afferent fibres, invariably varicose over hundreds of micrometres of their terminal parts and while still branching, comprise chains of hundreds of varicosities. Varicosities are irregular in size, frequency and separation, without specialised terminal structures around them, or within or around the fibre's ending. The possibility that varicosities are transduction points for sensory inputs is discussed, with the implication of a process taking place over considerable length in each branch of each fibre. Interconnectedness of afferent nerves of various bladder tissues, distribution of varicosities over hundreds of micrometres along axonal branches, absence of clear target structures for the fibres, apparent irregularity in the size and sequence of varicosities suggest an innervation that is not rigidly wired with distinct sensory pathways. In fact, the structural evidence suggests extensive afferent integration at the periphery, with wide distribution of source points and broad range of physical detectors.

Urothelial bladder afferent neurons in the rat are anatomically and neurochemically distinct from non-urothelial afferents.

There is mounting evidence underscoring a role for the urothelium in urinary bladder sensation. Previous functional studies have identified bladder primary afferents with mechanosensitive properties suggesting urothelial innervation and/or communication. The current study identifies a group of urothelium-innervating afferent neurons in rat, and characterizes and compares the properties of these and non-urothelial afferent neuron populations. Lumbosacral (LS) primary afferent neurons were retrogradely labeled using intraparenchymal (IPar) microinjection or intravesical (IVes) infusion of tracer into the bladder. Using these techniques, separate populations of neurons were differentiated by dorsal root ganglion (DRG) somata labeling and dye distribution within the bladder. IPar- and IVes-labeled neurons accounted for 85.0% and 14.4% of labeled L6-S1 neurons (P < .001), respectively, with only 0.6% of neurons labeled by both techniques. Following IVes labeling, dye was contained only within the periurothelial bladder region in contrast to non-urothelial distribution of dye after IPar labeling. Electrophysiological characterization by in situ patch-clamp recordings from whole-mount DRG preparations indicated no significant difference in passive or active membrane properties of IPar and IVes DRG neurons. However, calcium imaging of isolated neurons indicates that a greater proportion of IPar- than IVes-labeled neurons express functional TRPA1 (45.7% versus 25.6%, respectively; P < .05). This study demonstrates that two anatomically distinct groups of LS bladder afferents can be identified in rat. Further studies of urothelial afferents and the phenotypic differences between non-/urothelial afferents may have important implications for normal and pathophysiological bladder sensory processing.

Computer-assisted three-dimensional tracking of sensory innervation in the murine bladder mucosa with two-photon microscopy.

A strong association between functional bladder disorders and bladder sensation is well-known, with a relationship between malfunctioning detrusor muscle and abnormal sensation arising from the sub-urothelium and the lamina propria (LP), has been suggested. However, the exact underlying pathophysiology of these bladder disorders is not completely understood. Therefore, it is important to gain knowledge on sensory innervation of the urinary bladder in order to understand the neural network function in healthy and diseased bladder. In the present study we aim at the development of a computer-assisted method for 3D-tracking of sensory innervation in the murine bladder mucosa using two-photon laser scanning microscopy (TPLSM). TPLSM was performed on 10 fixed, stained (CGRP) bladder samples in both the trigone and dome. Nerve tracking was performed in subvolumes (6.3±2.9106µm3; median±IQR) of 22 stacks with determining total nerve length, nerve segment lengths, curviness, straightness, and locations of branching and ending points in the lamina propria (LP). The results show that the highest concentration of afferent fibres was found at the urothelium-LP interface. Nerve curviness, a presumed indicator of nerve activity, showed an equal value throughout the complete LP. We found a significantly higher median nerve segment length in the LP of the trigone and significantly more curved nerves in the dome of the bladder. This indicates an adaptation to, or an involvement in the detection of, bladder volume changes. Conclusively, we successfully developed a computer-assisted method for 3D tracking of sensory nerve fibres in the LP of the murine bladder wall.

Urothelial proliferation and regeneration after spinal cord injury.

The basal, intermediate, and superficial cell layers of the urothelium undergo rapid and complete recovery following acute injury; however, the effects of chronic injury on urothelial regeneration have not been well defined. To address this discrepancy, we employed a mouse model to explore urothelial changes in response to spinal cord injury (SCI), a condition characterized by life-long bladder dysfunction. One day post SCI there was a focal loss of umbrella cells, which are large cells that populate the superficial cell layer and normally express uroplakins (UPKs) and KRT20, but not KRT5, KRT14, or TP63. In response to SCI, regions of urothelium devoid of umbrella cells were replaced with small superficial cells that lacked KRT20 expression and appeared to be derived in part from the underlying intermediate cell layer, including cells positive for KRT5 and TP63. We also observed KRT14-positive basal cells that extended thin cytoplasmic extensions, which terminated in the bladder lumen. Both KRT14-positive and KRT14-negative urothelial cells proliferated 1 day post SCI, and by 7 days, cells in the underlying lamina propria, detrusor, and adventitia were also dividing. At 28 days post SCI, the urothelium appeared morphologically patent, and the number of proliferative cells decreased to baseline levels; however, patches of small superficial cells were detected that coexpressed UPKs, KRT5, KRT14, and TP63, but failed to express KRT20. Thus, unlike the rapid and complete restoration of the urothelium that occurs in response to acute injuries, regions of incompletely differentiated urothelium were observed even 28 days post SCI.

A three dimensional nerve map of human bladder trigone.

AIM: Central efferent and afferent neural pathways to and from the human urinary bladder are well-characterized, but the location and arborization of these nerves as they traverse the serosa, muscularis, and urothelial layers are not clearly defined. The purpose of this study was to create a three dimensional map of the innervation of the human bladder trigone from the extrinsic perivesical adventitial nerve trunks to the urothelium. METHODS: A male and a female human bladder were harvested from fresh frozen cadavers and fixed in formalin. The bladder neck and trigone region were serially sectioned (5 µm) and every 20th slide was stained (S100), scanned and aligned to create 3D maps. RESULTS: Nerve penetration into the detrusor muscle occurs with the highest frequency at the bladder neck and interureteric ridge. Nerves traveling parallel to the bladder lumen do so in the adventitia, beyond the outer border of detrusor. In females, the depth of these nerve bands is uniform at 0.7-1.7 cm below the luminal surface, the outer limits of which include the anterior vaginal wall. In the male, depth is more variable owing to detrusor hypertrophy with the minimum depth of nerves approximately 0.5 cm near the interureteric ridge and over 1 cm near the bladder neck. CONCLUSIONS: Myelinated neural pathways traversing in the human bladder in the region of the trigone have a discreet regional density. This 3D map of trigonal innervation may provide guidance to more precisely direct therapies for urinary incontinence or pelvic pain. Neurourol. Urodynam. 36:1015-1019, 2017. © 2016 Wiley Periodicals, Inc.

The Role of the Mucosa in Normal and Abnormal Bladder Function.

The internal face of the detrusor smooth muscle wall of the urinary bladder is covered by a mucosa, separating muscle from the hostile environment of urine. However, the mucosa is more than a very low permeability structure and offers a sensory function that monitors the extent of bladder filling and composition of the urine. The mucosa may be considered as a single functional structure and comprises a tight epithelial layer under which is a basement membrane and lamina propria. The latter region itself is a complex of afferent nerves, blood vessels, interstitial cells and in some species including human beings a muscularis mucosae. Stress on the bladder wall through physical or chemical stressors elicits release of chemicals, such as ATP, acetylcholine, prostaglandins and nitric oxide that modulate the activity of either afferent nerves or the muscular components of the bladder wall. The release and responses are graded so that the mucosa forms a dynamic sensory structure, and there is evidence that the gain of this system is increased in pathologies such as overactive bladder and bladder pain syndrome. This system therefore potentially provides a number of drug targets against these conditions, once a number of fundamental questions are answered. These include how is mediator release regulated; what are the intermediate roles of interstitial cells that surround afferent nerves and blood vessels; and what is the mode of communication between urothelium and muscle - by diffusion of mediators or by cell-to-cell communication?

Receptors, channels, and signalling in the urothelial sensory system in the bladder.

The storage and periodic elimination of urine, termed micturition, requires a complex neural control system to coordinate the activities of the urinary bladder, urethra, and urethral sphincters. At the level of the lumbosacral spinal cord, lower urinary tract reflex mechanisms are modulated by supraspinal controls with mechanosensory input from the urothelium, resulting in regulation of bladder contractile activity. The specific identity of the mechanical sensor is not yet known, but considerable interest exists in the contribution of transient receptor potential (TRP) channels to the mechanosensory functions of the urothelium. The sensory, transduction, and signalling properties of the urothelium can influence adjacent urinary bladder tissues including the suburothelial nerve plexus, interstitial cells of Cajal, and detrusor smooth muscle cells. Diverse stimuli, including those that activate TRP channels expressed by the urothelium, can influence urothelial release of chemical mediators (such as ATP). Changes to the urothelium are associated with a number of bladder pathologies that underlie urinary bladder dysfunction. Urothelial receptor and/or ion channel expression and the release of signalling molecules (such as ATP and nitric oxide) can be altered with bladder disease, neural injury, target organ inflammation, or psychogenic stress. Urothelial receptors and channels represent novel targets for potential therapies that are intended to modulate micturition function or bladder sensation.

Implications for bidirectional signaling between afferent nerves and urothelial cells-ICI-RS 2014.

AIMS: To present a synopsis of the presentations and discussions from Think Tank I, "Implications for afferent-urothelial bidirectional communication" of the 2014 International Consultation on Incontinence-Research Society (ICI-RS) meeting in Bristol, UK. METHODS: The participants presented what is new, currently understood or still unknown on afferent-urothelial signaling mechanisms. New avenues of research and experimental methodologies that are or could be employed were presented and discussed. RESULTS: It is clear that afferent-urothelial interactions are integral to the regulation of normal bladder function and that its disruption can have detrimental consequences. The urothelium is capable of releasing numerous signaling factors that can affect sensory neurons innervating the suburothelium. However, the understanding of how factors released from urothelial cells and afferent nerve terminals regulate one another is incomplete. Utilization of techniques such as viruses that genetically encode Ca(2+) sensors, based on calmodulin and green fluorescent protein, has helped to address the cellular mechanisms involved. Additionally, the epithelial-neuronal interactions in the urethra may also play a significant role in lower urinary tract regulation and merit further investigation. CONCLUSION: The signaling capabilities of the urothelium and afferent nerves are well documented, yet how these signals are integrated to regulate bladder function is unclear. There is unquestionably a need for expanded methodologies to further our understanding of lower urinary tract sensory mechanisms and their contribution to various pathologies.

Mucosal signaling in the bladder.

The bladder mucosa is comprised of the multilayered urothelium, lamina propria (LP), microvasculature, and smooth muscle fibers (muscularis mucosae). The muscularis mucosae is not always present in the mucosa, and its presence is related to the thickness of the LP. Since there are no mucus secreting cells, "mucosa" is an imprecise term. Nerve fibers are present in the LP of the mucosa. Efferent nerves mediate mucosal contractions which can be elicited by electrical field stimulation (EFS) and various agonists. The source of mucosal contractility is unknown, but may arise from the muscularis mucosae or myofibroblasts. EFS also increases frequency of mucosal venule contractions. Thus, efferent neural activity has multiple effects on the mucosa. Afferent activity has been measured when the mucosa is stimulated by mechanical and stretch stimuli from the luminal side. Nerve fibers have been shown to penetrate into the urothelium, allowing urothelial cells to interact with nerves. Myofibroblasts are specialized cells within the LP that generate spontaneous electrical activity which then can modulate both afferent and efferent neural activities. Thus mucosal signaling is defined as interactions between bladder autonomic nerves with non-neuronal cells within the mucosa. Mucosal signaling is likely to be involved in clinical functional hypersensory bladder disorders (e.g. overactive bladder, urgency, urgency incontinence, bladder pain syndrome) in which mechanisms are poorly understood despite high prevalence of these conditions. Targeting aberrant mucosal signaling could represent a new approach in treating these disorders.

Redefining the Autonomic Nerve Distribution of the Bladder Using 3-Dimensional Image Reconstruction.

PURPOSE: We sought to create a 3-dimensional reconstruction of the autonomic nervous tissue innervating the bladder using male and female cadaver histopathology. MATERIALS AND METHODS: We obtained bladder tissue from a male and a female cadaver. Axial cross sections of the bladder were generated at 3 to 5 mm intervals and stained with S100 protein. We recorded the distance between autonomic nerves and bladder mucosa. We manually demarcated nerve tracings using ImageScope software (Aperio, Vista, California), which we imported into Blender™ graphics software to generate 3-dimensional reconstructions of autonomic nerve anatomy. RESULTS: Mean nerve density ranged from 0.099 to 0.602 and 0.012 to 0.383 nerves per mm2 in female and male slides, respectively. The highest concentrations of autonomic innervation were located in the posterior aspect of the bladder neck in the female specimen and in the posterior region of the prostatic urethra in the male specimen. Nerve density at all levels of the proximal urethra and bladder neck was significantly higher in posterior vs anterior regions in female specimens (0.957 vs 0.169 nerves per mm2, p<0.001) and male specimens (0.509 vs 0.206 nerves per mm2, p=0.04). CONCLUSIONS: Novel 3-dimensional reconstruction of the bladder is feasible and may help redefine our understanding of human bladder innervation. Autonomic innervation of the bladder is highly focused in the posterior aspect of the proximal urethra and bladder neck in male and female bladders.

Therapeutic modulation of urinary bladder function: multiple targets at multiple levels.

Storage dysfunction of the urinary bladder, specifically overactive bladder syndrome, is a condition that occurs frequently in the general population. Historically, pathophysiological and treatment concepts related to overactive bladder have focused on smooth muscle cells. Although these are the central effector, numerous anatomic structures are involved in their regulation, including the urothelium, afferent and efferent nerves, and the central nervous system. Each of these structures involves receptors for­and the urothelium itself also releases­many mediators. Moreover, hypoperfusion, hypertrophy, and fibrosis can affect bladder function. Established treatments such as muscarinic antagonists, ß-adrenoceptor agonists, and onabotulinumtoxinA each work in part through their effects on the urothelium and afferent nerves, as do α1-adrenoceptor antagonists in the treatment of voiding dysfunction associated with benign prostatic hyperplasia; however, none of these treatments are specifically targeted to the urothelium and afferent nerves. It remains to be explored whether future treatments that specifically act at one of these structures will provide a therapeutic advantage.

Can the adrenergic system be implicated in the pathophysiology of bladder pain syndrome/interstitial cystitis? A clinical and experimental study.

AIMS: To evaluate sympathetic system activity in bladder pain syndrome/interstitial cystitis (BPS/IC) patients and to investigate if chronic adrenergic stimulation in intact rats induces BPS/IC-like bladder modifications. METHODS: Clinical study--In BPS/IC patients and aged and body mass index matched volunteers TILT test was undertaken and catecholamines were measured in plasma and 24 hr urine samples. Experimental study--Phenylephrine was injected subcutaneously (14 days) to female Wistar rats. Pain behavior, spinal Fos expression, urinary spotting, number of fecal pellets expelled, frequency of reflex bladder contractions, and urothelial height were analyzed. Urothelium permeability was investigated by trypan blue staining. Immunoreactivity against caspase 3 and bax were studied in the urothelium and against alpha-1-adrenoreceptor and TRPV1 in suburothelial nerves. Mast cell number was determined in the sub-urothelium. In rats with lipopolysaccharide-induced cystitis, urinary catecholamines, and Vesicular Monoamine Transporter 2 (VMAT2) expression in bladder nerves were analyzed. RESULTS: The TILT test showed an increase of sympathetic activity. Noradrenaline levels in blood at resting conditions and in 24-hr urine samples were higher in BPS/IC patients. Phenylephrine administration increased visceral pain, spinal Fos expression, bladder reflex activity, urinary spotting and the number of expelled fecal pellets. The mucosa showed urothelial thinning and increased immunoreactivity for caspase 3 and bax. Trypan blue staining was only observed in phenylephrine treated animals. Suburothelial nerves co-expressed alpha1 and TRPV1. Mastocytosis was present in the suburothelium. Cystitis increased sympathetic nerve density and urinary noradrenaline levels. CONCLUSIONS: Excessive adrenergic stimulation of the bladder may contribute to the pathophysiological mechanisms of BPS/IC.

Bladder dysfunction induced by cerebral hypoperfusion after bilateral common carotid artery occlusion in rats.

AIMS: The role of forebrain in controlling micturition has been studied extensively using rat model with ischemic injury; however, the influence of cerebral hypoperfusion on voiding function remains unclear. The study was conducted to evaluate the bladder dysfunction and the temporal expression of bladder nerve growth factor (NGF) after cerebral hypoperfusion induced by bilateral common carotid artery occlusion (BCCAO). MATERIALS AND METHODS: Forty female rats were subjected to either BCCAO or sham operation. Cerebral T2-weighted magnetic resonance images (MRI) and diffusion and perfusion change were studied to characterize the extent of the ischemic injury in the cortex and hippocampus. On 1, 7, and 28 days after BCCAO, the bladder dysfunction was assessed by cystometric studies, and the expressions of NGF in bladder muscle and urothelium were measured by immunohistochemistry and real-time polymerase chain reaction. RESULTS: In the MRI study, cerebral blood flow in the cortex and hippocampus was significantly decreased from 1 day and subsequently returned to sham-operated level at 28 days after BCCAO. Compared with the sham-operated group, significant reduction in voided volume and intercontraction interval was found from 1 to 28 days after cerebral hypoperfusion. The NGF immunoreactivity and mRNA in the bladder muscle and urothelium were transiently increased at 1 day, and declined significantly at 28 days after BCCAO. CONCLUSIONS: Our results indicate that bladder dysfunction may be caused by cerebral hypoperfusion and is less likely related to bladder NGF expression.

Continence and micturition: an anatomical basis.

Urinary incontinence remains an important clinical problem worldwide, having a significant socio-economic, psychological, and medical burden. Maintaining urinary continence and coordinating micturition are complex processes relying on interaction between somatic and visceral elements, moderated by learned behavior. Urinary viscera and pelvic floor must interact with higher centers to ensure a functionally competent system. This article aims to describe the relevant anatomy and neuronal pathways involved in the maintenance of urinary continence and micturition. Review of relevant literature focusing on pelvic floor and urinary sphincters anatomy, and neuroanatomy of urinary continence and micturition. Data obtained from both live and cadaveric human studies are included. The stretch during bladder filling is believed to cause release of urothelial chemical mediators, which in turn activates afferent nerves and myofibroblasts in the muscosal and submucosal layers respectively, thereby relaying sensation of bladder fullness. The internal urethral sphincter is continuous with detrusor muscle, but its arrangement is variable. The external urethral sphincter blends with fibers of levator ani muscle. Executive decisions about micturition in humans rely on a complex mechanism involving communication between several cerebral centers and primitive sacral spinal reflexes. The pudendal nerve is most commonly damaged in females at the level of sacrospinous ligament. We describe the pelvic anatomy and relevant neuroanatomy involved in maintaining urinary continence and during micturition, subsequently highlighting the anatomical basis of urinary incontinence. Comprehensive anatomical understanding is vital for appropriate medical and surgical management of affected patients, and helps guide development of future therapies.

New horizons: urinary incontinence in older people.

Urinary incontinence is a common complaint in older people, and is associated with significant impact on the individual, their carers and the wider healthcare system. As the numbers of frail elderly people increase, so will the burden of incontinence. This review examines recent developments in research into the aetiology, physiology, pathology and treatment of urinary incontinence and lower urinary tract symptoms in older people, and explores potential future developments which might reduce or ameliorate both urinary incontinence and its effects on frail older people. These include increasing understanding of the importance of central control of continence, the role of the urothelium as a sensory organ, novel targets for pharmacological treatments and surgical and invasive interventions.

Urinary bladder, cystitis and nerve/urothelial interactions.

A hallmark of functional pain syndromes, such as bladder pain syndrome/interstitial cystitis (BPS/IC) is pain in the absence of demonstrable infection or pathology of the viscera or associated nerves. There are no clear definitions of this syndrome, no proven etiologies and no effective treatments able to eradicate the symptoms. This condition is characterized by suprapubic pain, associated with bladder filling and can also be accompanied by a persistent strong desire to void, increased frequency of urination and nocturia. Severe cases of this disorder, which affects primarily women, can have considerable impact on the quality of life of patients due to extreme pain and urinary frequency, which are often difficult to treat. In addition, BPS/IC patients may also suffer co-morbid conditions where pain is a common symptom (such as irritable bowel syndrome, fibromyalgia). Theories explaining the pathology of bladder pain syndrome are many and include an altered bladder lining and possible contribution of a bacterial agent.

Expression and functional role of ß3 -adrenoceptors in the human ureter.

OBJECTIVES: To investigate the presence of ß-adrenoceptor subtypes in the human ureter, and to examine whether ß(3) -adrenoceptors modulate relaxation of the human ureter. METHODS: Expression of messenger ribonucleic acid of ß-adrenoceptors in the human ureter was determined by reverse transcription polymerase chain reaction, and distribution of ß-adrenoceptors was examined by immunohistochemistry. In functional studies, the relaxant effects of isoproterenol, procaterol, TRK-380, salbutamol and BRL 37344 on KCl-induced contraction of the human ureter were evaluated, and the inhibitory effects of isoproterenol, procaterol and TRK-380 on electrical field stimulation-induced contractions were determined. RESULTS: Expression of ß(1) -, ß(2) - and ß(3) -adrenoceptor messenger ribonucleic acid in the human ureter was confirmed by reverse transcription polymerase chain reaction. Positive staining for ß(1) -, ß(2) - and ß(3) -adrenoceptor was identified not only in smooth muscle, but also in the urothelium of the human ureter. All ß-adrenoceptor agonists decreased the tone of KCl-induced contractions of the human ureter with a rank order of relaxant effects of isoproterenol > procaterol > TRK-380 > salbutamol > BRL 37344. Furthermore, isoproterenol, procaterol and TRK-380 significantly decreased the amplitude of electrical field stimulation-induced contractions with a rank order of inhibitory effects of isoproterenol > procaterol > TRK-380. CONCLUSIONS: Human ureteral relaxation is mediated by both ß(2) - and ß(3) -adrenoceptor stimulation. ß(3) -Adrenoceptor agonists have the potential to relax the human ureter, and their clinical application in the treatment of ureteral stones is expected.