Relief of pain following intravesical capsaicin in patients with hypersensitive disorders of the lower urinary tract

TRP channels in lower urinary tract dysfunction

Lower urinary tract dysfunction (LUTd) represents a major healthcare problem. Although it is mostly not lethal, associated social disturbance, medical costs, loss of productivity and especially diminished quality of life should not be underestimated. Although more than 15% of people suffer from a form of LUTd to some extent, pathophysiology often remains obscure. In the past 20 years, transient receptor potential (TRP) channels have become increasingly important in this field of research. These intriguing ion channels are believed to be the main molecular sensors that generate bladder sensation. Therefore, they are intensely pursued as new drug targets for both curative and symptomatic treatment of different forms of LUTd. TRPV1 was the first of its class to be investigated. Actually, even before this channel was cloned, it had already been targeted in the bladder, with clinical trials of intravesical capsaicin instillations. Several other polymodally gated TRP channels, particularly TRPM8, TRPA1 and TRPV4, also appear to play a prominent role in bladder (patho)physiology. With this review, we provide a brief overview of current knowledge on the role of these TRP channels in LUTd and their potential as molecular targets for treatment.

Effect of red pepper on symptoms of irritable bowel syndrome: preliminary study

BACKGROUND

Abdominal pain, that characterizes irritable bowel syndrome (IBS) together with bloating and disordered defecation, is mainly related to a visceral hypersensitivity due to an increase of TRPV(1) nociceptive nerve fiber activity.

AIM

As capsaicin contained in red pepper is able to desensitize the TRPV(1) fibres, we evaluated whether the red pepper oral administration can decrease the symptoms of visceral hypersensitivity in IBS patients.

METHODS

The study was performed on 50 patients with IBS diagnosed following Rome II criteria. After a 2-week washout period, 23 patients were planned to receive 4 pills/day, for 6 weeks randomly and in a double blind manner, each containing 150 mg of red pepper powder with a coat that dissolves in the colon, and 27 patients placebo. The patients scored each day in a diary the abdominal pain and bloating intensities following the 5-point Likert scale. The weekly symptom mean scores and the final patient subjective evaluation on treatment effectiveness were statistically compared among groups and intra-groups with appropriate tests.

RESULTS

Eight patients dropped from the study: 6 in the red pepper group for abdominal pain and 2 in the placebo group. In 8 patients, the pills were reduced to 2/day, because of the abdominal pain at the onset of treatment. The intra-group comparisons showed that in patients taking red pepper the abdominal pain and bloating mean score values of the last weeks of treatment were significantly improved with respect to pre-treatment values, unlike patients taking placebo. The final patient subjective evaluation on the treatment effectiveness showed that red pepper group scored significantly better than placebo.

CONCLUSIONS

The results of this preliminary study indicate that the chronic administration of red pepper powder in IBS patients with enteric-coated pills was significantly more effective than placebo in decreasing the intensity of abdominal pain and bloating and was considered by the patients more effective than placebo.

TRP family proteins in the lower urinary tract: translating basic science into new clinical prospective

The lower urinary tract (LUT) is densely innervated by capsaicin-sensitive primary afferent neurons, a sub set of sensory nerves, in a number of species including humans. These fibers exhibit both a sensory (afferent) function, including the regulation of the micturition reflex and the perception of pain, and an 'efferent' function, involved in the detrusor smooth muscle contractility and plasma protein extravasation. The discovery of specific binding sites for capsaicin, the pungent ingredient of red chilli, initiated a rush that ended up with the cloning of the 'vanilloid receptor', which belongs to the TRP (transient receptor potential) family. Here we reviewed the knowledge about the presumable functions of TRP family proteins in the LUT as regulators of bladder reflex activity, pain perception and cell differentiation. This review will focus on experimental evidence and promising clinical applications of targeting these proteins for the treatment of detrusor overactivity and bladder pain syndrome. As TRP receptor ligands may promote cellular death, and inhibit the growth of normal and neoplastic cells, the translation of basic science evidence into new clinical prospective for bladder and prostate cancer will be shown.

The sensory bladder (1): An update on the different sensations described in the lower urinary tract and the physiological mechanisms behind them

AIMS

To give an update of the actual information on sensory function in the lower urinary tract (LUT).

METHODS

We give an up-to-date review of the most modern and reasonable approach to the topic of physiological mechanisms involved in LUT sensory function and different sensations described in the LUT.

RESULTS

Although the sensory function of the LUT is a main player in the function of continence and micturition, it has been dealt with rather superficially for many decades. More recently the interest in this function grows and does so rapidly, both in basic as in clinical research. Sensation depends on neurophysiologic mechanisms in several different nerves, receptors, and transmitters. This knowledge creates a better understanding of sensory symptoms. Different stimuli can elicit sensations in the LUT such as bladder filling, micturition, noxious stimuli, external stimuli.

CONCLUSION

Sensation is the prerequisite of conscious bladder control and deserves full attention in the management of LUT dysfunction.

Activation of Urothelial Transient Receptor Potential Vanilloid 4 by 4α-Phorbol 12,13-Didecanoate Contributes to Altered Bladder Reflexes in the Rat

The ion channel transient receptor potential vanilloid (TRPV) 4 can be activated by hypo-osmolarity, heat, or certain lipid compounds. Here, we demonstrate expression of functional TRPV4 protein in the urothelium lining the renal pelvis, ureters, urinary bladder, and urethra. Exposure of cultured rat urothelial cells from the urinary bladder to the TRPV4-selective agonist 4alpha-phorbol 12,13-didecanoate (4alpha-PDD) promoted Ca2+ influx, evoked ATP release, and augmented the ATP release evoked by hypo-osmolarity. In awake rats during continuous infusion cystometrograms, intravesical administration of 4alpha-PDD (10-100 microM) increased maximal micturition pressure by 51%, specifically by augmenting the portion of each intravesical pressure wave that follows high-frequency urethral oscillations and voiding. This unusual pharmacological effect was prevented by intravesical pretreatment with the nonselective ATP receptor antagonist, pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (100 microM), systemic treatment with the selective P2X3 purinergic antagonist 5-([(3-phenoxybenzyl)[1S)-1,2,3,4-tetrahydro-1-naphthalenyl]amino]carbonyl)-1,2,4-benzenetricarboxylic acid (A317491) (250 micromol/kg), or urethane anesthesia, but was unaffected by capsaicin pretreatment (100 mg/kg s.c.) or denervation of the urethral sphincter. 4Alpha-PDD (1-100 microM) did not alter the contractility to electrical stimulation of excised bladder strips. We conclude that activation of urothelial TRPV4 by 4alpha-PDD and release of mediators such as ATP trigger a novel neural mechanism that regulates the late phase of detrusor muscle contraction after micturition. These data raise the possibility that TRPV4 channels in the urothelium could contribute to abnormal bladder activity.

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.

Interstitial cystitis

Interstitial cystitis (IC) is a debilitating chronic inflammatory disorder of the bladder. It affects predominantly middle-aged Caucasian women. The diagnosis, made from the combination of symptoms, cystoscopic findings and bladder biopsies, is often delayed in the gynaecology setting because of a low index of suspicion. The pathophysiology is incompletely understood, although mast cell activation, altered bladder epithelial permeability and sensory afferent nerve up-regulation are thought to play key roles. Recent theories include the role of an antiproliferative factor. A wide assortment of therapies is available and many more are under trial. Until the causes and pathogenesis of IC are unraveled, mainstream medical treatment will remain palliative and cystectomy with urinary diversion, the only potential cure. In addition to our long experience on managing this disorder, we present a comprehensive review of the current thoughts on the aetiology and management of IC.

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.

Spinal neurophysiologic correlates of the analgesic actions of intravesical dimethyl sulfoxide and capsaicin in the rat

Peripheral analgesia produced by the intravesical instillation of dimethyl sulphoxide (DMSO) and capsaicin has been used to treat visceral pain originating in the urinary bladder. The present study sought to determine the neurophysiologic consequences of the intravesical instillation of these compounds by measuring spinal neuronal responses evoked by urinary bladder distension (UBD) in the rat. Subjects were spinally transected, decerebrate female Sprague-Dawley rats. The effect of 0.5 mL of solution of 10% or 50% DMSO, 100 micromol/L capsaicin, or the same volume of saline instilled into the bladder on excitatory neuronal responses to UBD was studied by using single-unit extracellular recordings of L6-S2 dorsal horn spinal cord neurons. Fifty-six dorsal horn neurons that were excited by UBD in a graded fashion were identified. All neurons were also excited by noxious or non-noxious cutaneous stimuli. Two hours after intravesical instillation, solutions of 50% DMSO or 100 micromol/L of capsaicin produced a reduction of the slope of stimulus-response functions for neuronal activity evoked by graded UBD. These data support a local effect of intravesical 50% DMSO or capsaicin and suggest the use of this model to study novel peripheral treatment strategies for bladder pain.

The basics behind bladder pain: A review of data on lower urinary tract sensations

Interstitial cystitis is a syndrome consisting of frequency, urgency, and bladder pain that increases with bladder filling and improves temporarily after voiding. The exact cause or causes are not as yet fully understood. This leads to uncertainty in diagnosis and treatment. There is need for more knowledge, and to acquire this for more research. The fact that the condition causes pain, a pathologic stimulation of sensory fibres, makes understanding the basic sensory mechanisms in the lower urinary tract in normal and pathologic conditions mandatory. In this article we review the data on bladder sensation from the last 25 years and the possible relation with painful bladder syndrome.

Effectiveness of intravesical resiniferatoxin for anticholinergic treatment refractory detrusor overactivity due to nonspinal cord lesions

PURPOSE

Evidence suggests that unmyelinated C fibers become predominant in the mediation of the detrusor reflex in patients with chronic spinal cord lesions and possibly in idiopathic detrusor hyperactivity. Intravesical vanilloid therapy might be effective in treating refractory detrusor overactivity due to nonspinal cord lesion. This study investigated the clinical effect of intravesical resiniferatoxin in treating detrusor overactivity of nonspinal cord lesions refractory to anticholinergics.

MATERIALS AND METHODS

A total of 41 patients received intravesical resiniferatoxin therapy with 10 ml of 100 nM resiniferatoxin in 10% ethanol solution for 40 minutes. The clinical effects on a decrease in incontinence episodes and urodynamic study were evaluated at baseline and after treatment. Clinical improvement was considered if patients became dry or had a decrease in incontinence episodes of 50%. Therapeutic results were analyzed by disease category and type of initial detrusor response.

RESULTS

Of the 41 patients 10 had neurogenic lesions, 18 had previous transurethral prostatectomy and 13 had idiopathic detrusor overactivity. There were 20 women and 21 men with a mean age of 73.6 years (range 43 to 82) and a symptom duration of 3.6 +/- 4.5 years. After resiniferatoxin treatment 21 patients had clinical improvement (51.2%) including 5 with neurogenic (50%), 11 with previous transurethral prostatectomy (61.1%) and 5 with idiopathic detrusor overactivity (38.5%). An improvement was found in 11 patients with type I initial response (84.6%), 3 patients with type II response (23%) and 7 patients with type III response (46.7%). The 21 patients with improvement had a significant increase in cystometric capacity (208 +/- 80.7 vs 287.2 +/- 118.6 ml, p = 0.001) and a significant decrease in detrusor pressure (33.6 +/- 11.1 vs 27.4 +/- 11.8 cmH(2)O, p = 0.047), but no significant difference in maximal flow rate and residual urine volume.

CONCLUSIONS

Intravesical resiniferatoxin was effective in treating refractory detrusor overactivity in 51.2% of patients with nonspinal cord lesions. Patients with detrusor overactivity due to previous bladder outlet obstruction benefited the most. Detrusor contractility decreased after resiniferatoxin treatment in the group with improvement but did not influence voiding efficiency. The initial detrusor response to resiniferatoxin treatment might predict the clinical outcome.

Neurogenic inflammation of the bladder

Current evidence suggests multiple and redundant pathways through which the nervous system can initiate, amplify, and perpetuate inflammation. Many of the processes initiated by neurogenic inflammation have the capacity to recruit the participation of additional sensory nerves. These observations indicate that effective strategies for prevention or treatment of neurogenic inflammation of the bladder will entail or require intervention at multiple points. It has been observed that pain management in the future will be based on selective intervention tailored to the specific processes modulating pain perception in individual patients. It is exciting to contemplate the same approach to prevention and treatment of neurogenic bladder inflammation.

Effect of KW-7158, a putative afferent nerve inhibitor, on bladder and vesico-vascular reflexes in rats

The effects of KW-7158, a putative afferent nerve inhibitor, on reflex bladder activity and vesico-vascular reflexes were evaluated in urethane anesthetized SD rats with normal and xylene-irritated bladders. The bladder was filled with saline until the appearance of large amplitude spontaneous bladder contractions (LA-BC). Vesico-vascular reflexes were measured as increases in systolic arterial blood pressure during LA-BC or when the bladder was distended by a range of pressures. In normal rats, KW-7158 (10 and 100 microg/kg, i.v.) did not alter the amplitude or volume threshold for inducing LA-BC but increased the intercontraction interval. After xylene-irritation, which decreased volume threshold and intercontraction interval and induced small amplitude bladder contractions, KW-7158 increased volume threshold (65%) and intercontraction interval (150%) and decreased the number of small amplitude bladder contractions. Vesico-vascular reflexes induced during LA-BC or by bladder distension were suppressed (19.4-100%) by KW-7158. The effect of KW-7158 to depress vesico-vascular reflexes as well as xylene-induced bladder hyperactivity without altering the amplitude of contractions is consistent with the view that the drug affects reflex bladder activity at least in part by depressing afferent pathways.

The treatment of functional dyspepsia with red pepper

AIM

: To decrease the intensity of dyspeptic symptoms by impairing the visceral nociceptive C-type fibres with capsaicin, contained in red pepper powder.

METHODS

: The study was performed on 30 patients with functional dyspepsia and without gastro-oesophageal reflux disease and irritable bowel syndrome. After a 2-week washout period, 15 patients received, before meals randomly and in a double-blind manner, 2.5 g/day of red pepper powder for 5 weeks, and 15 patients received placebo. A diary sheet was given to each patient to record, each day, the scores of individual and overall symptom intensity, which subsequently were averaged weekly and over the entire treatment duration.

RESULTS

: The overall symptom score and the epigastric pain, fullness and nausea scores of the red pepper group were significantly lower than those of the placebo group, starting from the third week of treatment. The decrease reached about 60% at the end of treatment in the red pepper group, whilst placebo scores decreased by less than 30%.

CONCLUSIONS

: Red pepper was more effective than placebo in decreasing the intensity of dyspeptic symptoms, probably through a desensitization of gastric nociceptive C-fibres induced by its content of capsaicin. It could represent a potential therapy for functional dyspepsia.

Mast cell involvement in interstitial cystitis: a review of human and experimental evidence

Interstitial cystitis (IC) is a heterogeneous syndrome of unknown etiology. Altered bladder glycosaminoglycans lining and bladder mastocytosis have been documented in IC. The objective of this article is to critically examine the published data on bladder mastocytosis in clinical, experimental, and animal studies, with particular emphasis on morphologic evidence of mast cell increase and activation. The literature on bladder mastocytosis and mast cell activation in IC is critically reviewed with particular reference to staining methodology, tryptase immunoreactivity, and electron microscopy. Data from humans and animal models of IC are included. Mastocytosis in IC is best documented by tryptase immunocytochemical staining. Standard surgical stains such as Giemsa and toluidine blue routinely underestimate the degree of mastocytosis. Mast cells are 6- to 8-fold higher in the detrusor compared with controls in "classic IC," and 2- to 3-fold higher in "nonulcerative" IC. Detrusor mastocytosis occurs in both classic and nonulcer IC. Mucosal mast cell increase is present in nonulcerative IC. Mast cell activation without typical exocytosis occurs in the mucosa and submucosa. Activation of mast cells, irrespective of bladder location or degree of mastocytosis, is significant. Mast cell-derived vasoactive and proinflammatory molecules may contribute to the pathogenesis of IC.

New agents for the medical treatment of interstitial cystitis

Interstitial cystitis (IC) is a painful, sterile, disorder of the urinary bladder characterised by urgency, frequency, nocturia and pain. IC occurs primarily in women but also in men with recent findings indicating that chronic, abacterial prostatitis may be a variant of this condition. The prevalence of IC has ranged from about 8 - 60 cases/100,000 female patients depending on the population evaluated. About 10% of patients have severe symptoms that are associated with Hunner's ulcers on bladder biopsy; the rest could be grouped in those with or without bladder inflammation. Symptoms of IC are exacerbated by stress, certain foods and ovulatory hormones. Many patients also experience allergies, irritable bowel syndrome (IBS) and migraines. There have been various reports indicating dysfunction of the bladder glycosaminoglycan (GAG) protective layer and many publications showing a high number of activated bladder mast cells. Increasing evidence suggests that neurogenic inflammation and/or neuropathic pain is a major component of IC pathophysiology. Approved treatments so far include intravesical administration of dimethylsulphoxide (DMSO) or oral pentosanpolysulphate (PPS). New treatments focus on the combined use of drugs that modulate bladder sensory nerve stimulation (neurolytic agents), inhibit neurogenic activation of mast cells, or provide urothelial cytoprotection, together with new drugs with anti-inflammatory activity.

The capsaicin analogue SDZ249-665 attenuates the hyper-reflexia and referred hyperalgesia associated with inflammation of the rat urinary bladder

This study assessed the effects of the systemically administered capsaicin analogue SDZ249-665 in an animal model of visceral pain and hyper-reflexia. The effects of prophylactic administration of SDZ249-665 (in the dose range 0.05-1 mg/kg) on the viscero-visceral hyper-reflexia (VVH) and the referred viscero-somatic hyperalgesia to mechanical stimuli (VSH) associated with turpentine inflammation of the rat urinary bladder were evaluated. SDZ249-665 attenuated both the VVH and the VSH in a dose related fashion. In the VVH model, following solvent control administration, intra-vesical turpentine administration was associated with a significant reduction in micturition threshold to 43.7% (SEM 6.3) of baseline, indicating the presence of a VVH. This effect was not observed when animals were prophylactically treated with SDZ249-665 alone. At a dose of 0.1 mg/kg the micturition threshold was 90.7% (SEM 10.2) of baseline at 1 h after intra-vesical instillation of turpentine. In the VSH model, curves were plotted of the difference in fore and hind limb withdrawal latencies from a mechanical stimulus and the area under these curves (AUCs) were compared between different treatment protocols. Intra-vesical turpentine was associated with a negative deflection of the curve (AUC -5.2x10(3) SEM 1.7) in comparison with naïve animals (AUC -0.02x10(3) SEM 0.6), indicative of a referred hyperalgesia. This was prevented, in a dose-related manner, by prophylactic administration of SDZ249-665. For example, at a dose of 0.5 mg/kg the AUC was +0.4x10(3) (SEM 0.8). These findings support previous work indicating that capsaicin sensitive neurones participate in patho-physiological events occurring following inflammation of the bladder, and provides evidence that systemically active capsaicin based compounds may be developed for use in the clinical setting.

Acute effects of capsaicin on gastrointestinal vagal afferents

Capsaicin is an important tool for investigation of thin afferent fibres, but its acute effects on subtypes of vagal afferent endings are unknown. In the gastrointestinal tract, these subtypes are: muscle endings (thought to be purely tension sensitive), mucosal endings (sensitive to stroking and chemical stimuli) and endings in the oesophagus with both properties. Acute capsaicin sensitivity was investigated in ferrets using in vivo and in vitro methods. Single-fibre activity was recorded from 63 vagal afferents: 12 Adelta-fibres, 15 C-fibres and 36 unclassified fibres with endings in the oesophagus (n=42), stomach (n=19) and duodenum (n=2). Responses to capsaicin occurred independently of motility changes and were therefore due to direct activation of the receptor ending. In the oesophagus in vivo, two of 10 tension receptors and one of one mucosal receptor responded to intraluminal application of 3.25 mM capsaicin. In the stomach and duodenum, five of 14 tension receptors and two of four mucosal receptors responded to close-systemic (32-164 nmol) capsaicin. In an in vitro gastro-oesophageal preparation, three of five tension, four of 21 mucosal and two of eight tension/mucosal receptors responded to topical application of 1mM capsaicin. Occurrence of responses was therefore unrelated to location of endings and isolation of tissue. Responsiveness was also unrelated to conduction velocity. Capsaicin caused desensitization of responses to further capsaicin application in 37% of afferents. It additionally caused cross-desensitization to mechanical stimuli, which was also seen in afferents that did not respond directly to capsaicin. In conclusion, capsaicin acutely activates all subtypes of gut vagal afferents in vivo and in vitro, although responsiveness is restricted to 30% of fibres and follows no specific pattern. Acute desensitization may be induced with or without a response.

Experimental study of the effect of capsaicin on the urinary bladder function in rats

In order to investigate the effect of capsaicin (CAP) on the urinary bladder function, an in vivo whole bladder study was undertaken in 25 adult healthy Wistar rats. CAP of various concentrations was instilled into the urinary bladder, and intravesical pressure, detrusor contraction and micturition status were recorded; then the trigone of the bladder was cut off and prepared for peroxidase-antiperoxidase (PAP) immunohistochemical investigation. The changes on the distribution of Substance P (SP) in control and experimental groups were compared. The results showed that the intravesical application of CAP caused a significant change in the urinary bladder function. At a low concentration of CAP there was a slight increase of maximal detrusor pressure, but at a high concentration of CAP the maximal intravesical pressure was significantly decreased and associated with urinary retention and urinary incontinence. PAP sustaining had shown a depletion of SP in CAP-treated urinary bladder in rats, and this depletion was more significant at high concentrations of CAP. Because this depletion could block C-fiber transmission, detrusor function entered, from primary excitation phase, a late inhibitory phase. This suggests that a local application of CAP into urinary bladder could be used in the treatment of neurogenic bladder (detrusor hyperreflexia) to relieve frequency, urgency, incontinence and improve renal function.

The bladder cooling reflex and the use of cooling as stimulus to the lower urinary tract

PURPOSE

We review the physiology of bladder cooling response in experimental animals and humans, and present its clinical usefulness.

MATERIALS AND METHODS

We describe experimental studies of the bladder cooling response, and more recent clinical retrospective and prospective studies of the bladder cooling test in adults and children.

RESULTS

Studies indicate the existence of a segmental spinal bladder cooling reflex that originates from specific cold receptors in the bladder and urethral walls supplied by unmyelinated C-afferents. The reflex is positive in neurologically normal infants and children until about age 4 years. It becomes negative with further maturation of the nervous system but may be unmasked by pathological processes that disturb the descending neuronal control of normal voiding. A positive test in a patient with an overactive bladder requires further neurourological evaluation.

CONCLUSIONS

The bladder cooling response originates from cold receptors within the walls of the lower urinary tract. The cooling response represents a neonatal reflex that may be unmasked by central neuropathology, analogous to the appearance of the Basbinki sign in pyramidal tract lesions. The bladder cooling test is a simple and valuable tool to support the diagnosis of neurourological disorders.

Interstitial cystitis: update on etiologies and therapeutic options

Interstitial cystitis (IC) is a syndrome of pelvic and/or perineal pain, urinary urgency, and frequency. It is now agreed that IC is a multifactorial syndrome, not a single condition. A variety of etiologies for IC have been proposed, but none has been definitively proven. Since the etiologies for IC remain unknown, the current treatments are empiric. This article will review the major theories of etiology for IC and discuss the current treatment options with relevance to the proposed etiologies. No single treatment is effective for all IC patients. Therefore, the approach is to try different treatments, alone or in combination, until symptom relief is satisfactory. In some cases, none of the empiric IC treatments are successful. These patients require adjunctive pain management, and a small minority of IC patients resort to surgery if all other options fail.

A non-pungent triprenyl phenol of fungal origin, scutigeral, stimulates rat dorsal root ganglion neurons via interaction at vanilloid receptors

1. A [3H]-resiniferatoxin (RTX) binding assay utilizing rat spinal cord membranes was employed to identify novel vanilloids in a collection of natural products of fungal origin. Of the five active compounds found (scutigeral, acetyl-scutigeral, ovinal, neogrifolin, and methyl-neogrifolin), scutigeral (Ki=19 microM), isolated from the edible mushroom Albatrellus ovinus, was selected for further characterization. 2. Scutigeral induced a dose-dependent 45Ca uptake by rat dorsal root ganglion neurons with an EC50 of 1.6 microM, which was fully inhibited by the competitive vanilloid receptor antagonist capsazepine (IC50=5.2 microM). 3. [3H]-RTX binding isotherms were shifted by scutigeral (10-80 microM) in a competitive manner. The Schild plot of the data had a slope of 0.8 and gave an apparent Kd estimate for scutigeral of 32 microM. 4. Although in the above assays scutigeral mimicked capsaicin, it was not pungent on the human tongue up to a dose of 100 nmol per tongue, nor did it provoke protective wiping movements in the rat (up to 100 microM) upon intraocular instillation. 5. In accord with being non-pungent, scutigeral (5 microM) did not elicit a measurable inward current in isolated rat dorsal root ganglion neurons under voltage-clamp conditions. It did, however, reduce the proportion of neurons (from 61 to 15%) that responded to a subsequent capsaicin (1 microM) challenge. In these neurons, scutigeral both delayed (from 27 to 72 s) and diminished (from 5.0 to 1.9 nA) the maximal current evoked by capsaicin. 6. In conclusion, scutigeral and its congeners form a new chemical class of vanilloids, the triprenyl phenols. Scutigeral promises to be a novel chemical lead for the development of orally active, non-pungent vanilloids.

Desensitization of bladder sensory fibers by intravesical capsaicin or capsaicin analogs. A new strategy for treatment of urge incontinence in patients with spinal detrusor hyperreflexia or bladder hypersensitivity disorders

Recent experimental studies have identified a category of unmyelinated type C bladder afferent fibers in the pelvic nerves which are extremely sensitive to capsaicin. Sensory input conveyed by these fibers triggers a spinal reflex which, in chronic spinalized animals, facilitates and controls micturition. In addition, bladder C fibers were also shown to have a role in bladder pain perception. In humans capsaicin-sensitive afferent fibers also innervate the bladder and contribute to the reflexogenic control of the detrusor muscle and to bladder pain perception. Desensitization of such fibers by intravesical administration of capsaicin, presumably by blocking sensory transmission, has been shown to reduce involuntary micturition and to increase bladder capacity in patients with detrusor hyperreflexia of spinal origin, and to reduce the intensity of bladder pain in patients with bladder hypersensitivity. Very recently, resiniferatoxin, an ultrapotent capsaicin analog, was shown to have a similar clinical effect in this subset of patients. However, unlike capsaicin, resiniferatoxin did not evoke acute irritative urinary symptoms during bladder instillation.

Interstitial cystitis: a neuroimmunoendocrine disorder

Interstitial cystitis (IC) is a sterile bladder condition occurring primarily in females. It is characterized by frequency, nocturia, and suprapubic pain. IC symptoms are exacerbated during ovulation and under stress, thus implicating neurohormonal processes. The most prevalent theories to explain the pathophysiology of IC appear to be altered bladder lining and increased number of activated bladder mast cells. A defective bladder glycosaminoglycan (GAG) layer could allow penetration of allergic triggers, as well as chemicals, food preservatives, drugs, toxins, and adherent bacteria, all of which can activate bladder mast cells. Vasoactive, nociceptive, and proinflammatory molecules released can lead to immune cell infiltration and can sensitize neurons to secrete neurotransmitters or neuropeptides that can further activate mast cells. Mast cell-derived proteases can directly cause tissue damage, and it is noteworthy that urine tryptase is elevated in IC. Bladder mast cells are located close to neuronal processes, which are increased in IC, and they can be activated in situ by acetylcholine (ACh) and substance P (SP). Such activation is augmented by estradiol, which acquires significance in view of the fact that human bladder mast cells express estrogen receptors, but few progesterone receptors, which may explain the worsening of IC symptoms during ovulation. Finally, acute psychological stress in rats leads to mast cell activation that can be reduced by depletion of SP or neutralization of peripheral immune corticotropin-releasing hormone (CRH). These findings suggest that IC could be a syndrome with neural, immune, and endocrine components, in which activated mast cells play a central role.

Urodynamic effects of intravesical resiniferatoxin in humans: preliminary results in stable and unstable detrusor

PURPOSE

Resiniferatoxin, a substance isolated from some species of euphorbia, a cactus-like plant, presents pharmacological effects similar to those of capsaicin. We studied the urodynamic effects of intravesical resiniferatoxin* in normal subjects and patients with unstable detrusor contraction to provide insight into the action mechanism of the molecule on sensory neurons and possible future pharmacological and clinical use.

MATERIALS AND METHODS

A total of 15 subjects with normal (8 patients) or unstable detrusor muscle (1 with detrusor instability and 6 with detrusor hyperreflexia) underwent urodynamic assessment during and after intravesical instillation of resiniferatoxin. Volume required to elicit the first desire to void, maximum bladder capacity and maximum bladder pressure were recorded during instillation of resiniferatoxin at a flow rate of 20 ml. per minute (normal subjects) or 15 minutes after instillation of 30 cc of a saline solution containing 10(-8) M. of resiniferatoxin and kept for 30 minutes in patients with unstable detrusor. The experiment was examined by the analysis of variance for repeated measures and post hoc comparisons were performed by Tukey-Kramer procedure. A p value <0.05 was accepted as significant.

RESULTS

Resiniferatoxin did not decrease the volume required to elicit the first desire to void and did not produce warm or burning sensations at the suprapubic/urethral level during infusion in subjects with normal detrusor function. In patients with bladder hyperactivity mean bladder capacity increased from 175.28 ml. plus or minus standard deviation 36.05 to 280.85 ml. plus or minus standard deviation 93.33 (p <0.01) immediately after treatment, and no significant modification of bladder pressure was recorded. Four weeks after treatment, bladder capacity remained increased in 2 patients but mean capacity did not increase significantly from 175.28 ml. plus or minus standard deviation 36.053 to 216.71 plus or minus standard deviation 86.91. The 2 patients with stable increase of bladder capacity reported significant clinical improvement of frequency, nocturia and incontinence 4 weeks later.

CONCLUSIONS

Our results suggest that in humans there may be substantial differences in urodynamic effects between resiniferatoxin and capsaicin when the drugs are instilled into the bladder. Further studies, in vitro and in vivo, are necessary to define the pharmacological and clinical effects of resiniferatoxin. Because resiniferatoxin did not produce warm or burning sensations at the suprapubic/urethral level during infusion and seems to have rapid desensitization, it could be an interesting alternative to intravesical capsaicin in the treatment of select cases of bladder hyperactivity.

Intravesical capsaicin as a treatment for refractory detrusor hyperreflexia: a dual center study with long-term followup

PURPOSE

We described the long-term outcome of intravesical capsaicin instillations in patients with urinary incontinence and compared its efficacy in 2 similar populations of patients with multiple sclerosis in a dual center study.

MATERIALS AND METHODS

During 5 years 79 patients with intractable urinary incontinence have been treated with intravesical capsaicin. The majority of patients had spinal cord disease due to multiple sclerosis but 4 were neurologically normal. Cystometry was performed before and 4 to 6 weeks after intravesical instillation of 1 to 2 mmol./l. of capsaicin in 30% ethanol in saline. Instillations of vehicle (30% ethanol in saline) alone were carried out in 5 patients.

RESULTS

In patients with phasic detrusor hyperreflexia complete continence was achieved in 44%, satisfactory improvement occurred in 36% and treatment failed in 20%. Clinical benefit from a single instillation lasted 3 to 6 months and was repeated in some patients with similar improvement. Capsaicin was ineffective in patients with poor bladder compliance and in neurologically normal patients with sensory urgency and detrusor instability. There was no clinical or urodynamic improvement in patients treated with vehicle alone. There have been no long-term complications.

CONCLUSIONS

Our study shows that repeated instillations of intravesical capsaicin are effective in treatment of patients with detrusor hyperreflexia due to spinal cord disease and that effectiveness of the treatment persists at least 3 to 5 years.

Vanilloid receptors: new insights enhance potential as a therapeutic target

Compounds related to capsaicin and its ultrapotent analog, resiniferatoxin (RTX), collectively referred to as vanilloids, interact at a specific membrane recognition site (vanilloid receptor), expressed almost exclusively by primary sensory neurons involved in nociception and neurogenic inflammation. Desensitization to vanilloids is a promising therapeutic approach to mitigate neuropathic pain and pathological conditions (e.g. vasomotor rhinitis) in which neuropeptides released from primary sensory neurons play a major role. Capsaicin-containing preparations are already commercially available for these purposes. The use of capsaicin, however, is severely limited by its irritancy, and the synthesis of novel vanilloids with an improved pungency/desensitization ratio is an on-going objective. This review highlights the emerging evidence that the vanilloid receptor is not a single receptor but a family of receptors, and that these receptors recognize not simply RTX and capsaicin structural analogs but are broader in their ligand-binding selectivity. We further focus on ligand-induced messenger plasticity, a recently discovered mechanism underlying the analgesic actions of vanilloids. Lastly, we give a brief overview of the current clinical uses of vanilloids and their future therapeutic potential. The possibility is raised that vanilloid receptor subtype-specific drugs may be synthesized, devoid of the undesirable side-effects of capsaicin.

Desensitization follows excitation of bladder primary afferents by intravesical capsaicin, as shown by c-fos activation in the rat spinal cord

Activation of the protooncogene c-fos at spinal cord segments T12-L2 and L5-S1 was used to study the effects of topical administration of capsaicin on bladder primary afferents coursing in the hypogastric (HGN) or pelvic (PN) nerves of adult rats. Two hours after capsaicin instillation in the bladder numerous Fos cells occurred in lamina I at T12-L2 and in lamina I, intermediolateral gray matter (ILG) and dorsal commissure (DCM) at L5-S1. Twenty-four hours later, the Fos immunoreaction had disappeared from the spinal cord. At this time, instillation of 1% acetic acid into the bladder of capsaicin-treated rats induced considerably fewer Fos cells than in animals that had been instilled only with the vehicle solution for capsaicin. The difference in the average number of Fos cells was statistically significant in lamina I, ILG and DCM at L5-S1 but not in lamina I at T12-L2. Thus, intravesical capsaicin at the doses used excites bladder primary afferents coursing in the HGN and PN, but only desensitizes those coursing in the PN. It is suggested that this may depend on the differential occurrence of capsaicin receptors in the two nerves.

Vesical-renal reflex: diuresis and natriuresis activated by intravesical capsaicin

In the last years the role of capsaicin sensitive innervation, in the activation of the micturition reflex, has been reported in many papers. In our experience, upon the intravesical administration of capsaicin in humans, we noticed an increase of diuresis. No interaction is known about the sensory innervation of the bladder and renal function, so we studied the possibility of the existence of a vesical-renal reflex arc. Twenty-one patients (9 men and 12 women) were randomised to receive intravesical infusion of saline solution containing 10 microM capsaicin. Urine output, glomerular renal filtrate (GRF) and effective plasma renal flow (EPRF), measured by Technetium-99m diethylenetetramine-penta-acetic acid (DTPA) renal scintigraphy, were recorded over twenty minutes before and after the intravesical administration of capsaicin. Urine density, [Na+] and [K+] concentration, and prostaglandin E2 excretion were also determined before and after intravesical administration of capsaicin or vehicle. Installation of saline solution containing 10 microM capsaicin produced a significant increase of mean urine output, an increase of GRF, of EPRF and of [Na+] and [K+] urine concentration. An increase, not statistically significant, was observed of PgE2 excretion. None of the patients treated with vehicle showed any modification of parameters examined. The present findings demonstrate a hitherto unrecognized effect: increased diuresis following selective chemical stimulation of bladder efferents with capsaicin. The renal diuretic response to intravesical capsaicin represents a working hypothesis about the possible involvement of a vesical-renal reflex arc organized at spinal or supraspinal level.

Intraurethrally infused capsaicin induces penile erection in humans

Capsaicin-sensitive primary afferents widely innervate the genitourinary tract and play an important role in the integration of various mechanisms which activate reflexes leading to penile erection. We investigated the effect of intraurethral capsaicin infusion in psychogenically impotent men. The 20 patients were prospectively randomized to four groups, each of five men. Group A received intraurethral infusion of saline solution, group B intraurethral capsaicin (10(-5) M), group C intracavernosal papaverine hydrochloride (8 mg) plus intraurethral saline infusion, and group D intracavernosal papaverine hydrochloride (8 mg) plus intraurethral capsaicin (10(-5) M). The penile response was recorded real-time. Intraurethral capsaicin induced penile erection, as did the papaverine injection, while saline infusion was without effect. The erectile response to intraurethral infusion of capsaicin is suggested to involve activation of a urethra-corpora cavernosa reflex arc. Further studies are necessary to clarify if this arc is integrated at central nervous system level or is locally triggered, and if it may have pathophysiologic implications.