Vanilloid receptor and detrusor instability

Molecular Influence of Resiniferatoxin on the Urinary Bladder Wall Based on Differential Gene Expression Profiling

Resiniferatoxin (RTX) is a potent capsaicin analog used as a drug for experimental therapy to treat neurogenic disorders associated with enhanced nociceptive transmission, including lower urinary tract symptoms. The present study, for the first time, investigated the transcriptomic profile of control and RTX-treated porcine urinary bladder walls. We applied multistep bioinformatics and discovered 129 differentially expressed genes (DEGs): 54 upregulated and 75 downregulated. Metabolic pathways analysis revealed five significant Kyoto Encyclopedia of Genes and Genomes (KEGG) items ('folate biosynthesis', 'metabolic pathways', 'sulfur relay system', 'sulfur metabolism' and 'serotonergic synapse') that were altered after RTX intravesical administration. A thorough analysis of the detected DEGs indicated that RTX treatment influenced the signaling pathways regulating nerve growth, myelination, axon specification, and elongation. Many of the revealed DEGs are involved in the nerve degeneration process; however, some of them were implicated in the initiation of neuroprotective mechanisms. Interestingly, RTX intravesical installation was followed by changes in the expression of genes involved in synaptic plasticity and neuromodulation, including 5-HT, H2S, glutamate, and GABA transmission. The obtained results suggest that the toxin may exert a therapeutic, antinociceptive effect not only by acting on TRPV1 receptors.

Intravesical vanilloids for treating neurogenic lower urinary tract dysfunction in patients with multiple sclerosis: A systematic review and meta-analysis. A report from the Neuro-Urology Promotion Committee of the International Continence Society (ICS)

AIMS

To systematically assess all available evidence on efficacy and safety of vanilloids for treating neurogenic lower urinary tract dysfunction (NLUTD) in patients with multiple sclerosis (MS).

METHODS

This systematic review and meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Studies were identified by electronic search of Cochrane register, Embase, Medline, Scopus, (last search January 8, 2016).

RESULTS

After screening of 7848 abstracts, 4 randomized controlled trials (RCTs) and 3 prospective cohort studies were included. Pooled data from three RCTs evaluating intravesical capsaicin showed the standardized mean difference to be -2.16 (95% confidence interval [CI] -2.87 to -1.45) in incontinence episodes per 24 h and -0.54 (95%CI -1.03 to -0.05) in voids per 24 h. There was no statistically significant effect on maximum cystometric capacity and maximum storage detrusor pressure. Overall, adverse events were reported by >50% of the patients, most commonly were pelvic pain, facial flush, worsening of incontinence, autonomic dysreflexia, urinary tract infection and haematuria. Risk of bias and confounding was relevant in both RCTs and non-RCTs.

CONCLUSIONS

Preliminary data suggest that intravesical vanilloids might be effective for treating NLUTD in patients with MS. However, the safety profile seems unfavorable, the overall quality of evidence is low and no licensed substance is currently available warranting well-designed, adequately sampled and properly powered RCTs.

Increased vanilloid receptor VR1 innervation in vulvodynia

Vulvodynia is characterised by painful burning sensation, allodynia and hyperalgesia in the region of the vulval vestibulus. While in many patients the cause of vulvodynia remains uncertain, we and others have previously shown increased intraepithelial and papillary innervation in vulvodynia. The vanilloid receptor VR1 (TRPV1) is expressed by nociceptors, and is triggered by capsaicin, noxious heat, protons, and chemicals produced during inflammation. In the present study we show increased papillary VR1 fibres by immunostaining and image analysis in vulvodynia tissues compared to controls (p<0.002). VR1 expression was found to be significantly increased when the percentage area immunostained was expressed as a ratio of VR1 to PGP 9.5, a pan-neuronal marker (P=0.01). VR1-positive fine epidermal fibres also appeared to be increased in vulvodynia tissues, by inspection. Fibres immunoreactive to the voltage-gated sodium channel SNS1/PN3 (Nav1.8), also expressed by nociceptors, were relatively scarce in both vulvodynia and control tissues. We hypothesize that increased expression of VR1 by nociceptors could mediate some of the symptoms in vulvodynia, for which systemic or topical specific VR1 antagonists may provide novel treatment.

TRPV1, NK1 receptor and substance P immunoreactivity and gene expression in the rat lumbosacral spinal cord and urinary bladder after systemic, low dose vanilloid administration

Transient receptor potential vanilloid 1 (TRPV1), neurokinin 1 (NK1) receptor and substance P (SP) immunoreactivity (-ir) and mRNA in the rat lumbosacral spinal cord and urinary bladder were measured 24h after s.c. injection of the vanilloids, capsaicin (50mg/kg) and resiniferatoxin (RTX, 100μg/kg), or vehicle (10% ethanol/10% Tween 80/saline). In the spinal cord, capsaicin significantly reduced TRPV1 and SP-ir (40-45%) in laminae I/II compared to controls, while RTX produced decreases of ~35%. NK1-ir in the spinal cord was unaffected by both vanilloid treatments. In the bladder, SP-ir was reduced in urothelial cells of some capsaicin- and RTX-treated rats, while SP-ir in the suburothelium and muscularis was significantly reduced by RTX. A significant increase in NK1-ir was observed in the urothelium and muscularis after capsaicin administration. Capsaicin significantly increased SP mRNA in the spinal cord, and TRPV1 and SP mRNA in the bladder, whereas RTX increased TRPV1, SP and NK1 mRNA in the spinal cord, and TRPV1 and SP mRNA in the bladder. These data suggest that stimulation of TRPV1 by low dose vanilloid administration can rapidly (within 24h) alter both transcription and translation of TRPV1 channels, SP and NK1 receptors in the rat urinary bladder and spinal cord.

Effects of intravesical instillation of ATP on rat bladder primary afferent activity and its relationship with capsaicin-sensitivity

AIMS

Previous studies have suggested that ATP has a role in mechano-afferent transduction, at least partly mediated by nerves other than capsaicin (Cap)-sensitive nerves. We investigated the direct effect of ATP on single fiber activity (SFA) of the primary bladder afferent nerves and its relationship with Cap-sensitivity.

METHODS

Female Sprague-Dawley rats were used. On the basis of conduction velocities, SFA was grouped as Aδ- or C-fibers. First, SFA and intravesical pressure were measured during filling as the baseline. Then, Cap (10(-5) M) was instilled intravesically and the SFA response was monitored. To desensitize Cap-sensitive nerves, resiniferatoxin (RTX) (10(-6) M) was administered intravesically, and then Cap was again administered to confirm the desensitization effect. Thereafter, ATP (10(-3) M) or its vehicle was instilled intravesically and another filling cycles recorded.

RESULTS

Thirty-two single afferent fibers were discriminated. Aδ-fibers did not respond to intravesical instillation of Cap, RTX or ATP. Based on Cap-sensitivity, C-fibers could be divided into two subtypes: Cap-sensitive (n=8) and Cap-insensitive (n=16). In the Cap-sensitive C-fibers, the response to bladder filling mostly disappeared after RTX desensitization, no matter if the bladder was filled with vehicle or ATP. On the other hand, in the Cap-insensitive C-fibers, even after RTX-treatment, the response was preserved and more enhanced when the bladder was filled with ATP compared to vehicle.

CONCLUSIONS

Mechanosensitive bladder afferents can be classified as (1) Aδ-fibers, (2) Cap-insensitive, and (3) Cap-sensitive C-fibers. The activation of the bladder afferents induced by intravesical application of ATP is mediated mainly through Cap-insensitive C-fibers.

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.

Chapitre C-l A - Traitement pharmacologique de l’hyperactivité détrusorienne neurologique : per os, en patch, en instillation endo-vésicale

Functional rehabilitation of neurourological patients always starts with patient education, retraining, and occupational therapy, possibly completed by medical treatments. In the light of a systematic review of the literature, the authors describe the various treatments that can be used orally and by intravesical instillation in these patients. They also describe treatments such as desmopressin or agents that increase sphincter pressure, which can sometimes be very useful to obtain stable clinical results that are satisfactory for the patient.

Transient receptor potential vanilloid subfamily 1 is essential for the generation of noxious bladder input and bladder overactivity in cystitis

PURPOSE

We evaluated the role of transient receptor potential vanilloid subfamily 1 for the generation of noxious bladder input and bladder overactivity associated with cystitis.

MATERIALS AND METHODS

Spinal c-fos expression triggered by innocuous bladder distention (10 cm water) was studied in sham and lipopolysaccharide inflamed transient receptor potential vanilloid subfamily 1 +/+ and -/- mice. Bladder reflex activity was studied using urethane anesthesia in sham and lipopolysaccharide inflamed transient receptor potential vanilloid subfamily 1 +/+ and -/- mice.

RESULTS

Inflammatory changes in the bladder of transient receptor potential vanilloid subfamily 1 +/+ and -/- mice were identical. Bladder distention in sham inflamed +/+ mice induced a mean +/- SD of 4 +/- 2 Fos cells per section. Bladder distention after lipopolysaccharide inflammation increased Fos cells to 34 +/- 5 (p <0.001). The number of Fos cells after bladder distention in sham and lipopolysaccharide inflamed -/- mice was similar (2 +/- 1 and 2 +/- 1, respectively, p >0.05). During saline infusion of sham inflamed bladders in +/+ mice 0.46 +/- 0.14 contractions per minute were documented. In lipopolysaccharide inflamed +/+ mice that frequency was increased to 1.13 +/- 0.12 contractions per minute (p <0.001). In sham and lipopolysaccharide inflamed -/- mice bladder frequency was similar (0.47 +/- 0.08 and 0.61 +/- 0.10, respectively, p >0.05).

CONCLUSIONS

Our data demonstrate that transient receptor potential vanilloid subfamily 1 is essential for the generation of noxious bladder input and bladder overactivity associated with cystitis.

Recent advances in intravesical drug/gene delivery

Targeting of drugs administered systemically relies on the higher affinity of ligands for specific receptors to obtain selectivity in drug response. However, achieving the same goal inside the bladder is much easier with an intelligent pharmaceutical approach that restricts drug effects by exploiting the pelvic anatomical architecture of the human body. This regional therapy involves placement of drugs directly into the bladder through a urethral catheter. It is obvious that drug administration by this route holds advantage in chemotherapy of superficial bladder cancer, and it has now become the most widely used treatment modality for this ailment. In recent years, the intravesical route has also been exploited either as an adjunct to an oral regimen or as a second-line treatment for neurogenic bladder. (Lamm, D. L.; Griffith, J. G. Semin. Urol. 1992, 10, 39-44. Igawa, Y.; Satoh, T.; Mizusawa, H.; Seki, S.; Kato, H.; Ishizuka, O.; Nishizawa, O. BJU Int. 2003, 91, 637-641.) Instillation of DNA via this route using different vectors has been able to restrict the transgene expression in organs other than bladder. The present review article will discuss the shortcomings of the current options available for intravesical drug delivery (IDD) and lay a perspective for future developments in this field.

Urodynamic effect of intravesical resiniferatoxin in patients with neurogenic detrusor overactivity of spinal origin: results of a double-blind randomized placebo-controlled trial

OBJECTIVES

To access by a placebo-controlled randomized clinical trial the effect of intravesical resiniferatoxin on the urodynamic parameters of patients with neurogenic detrusor overactivity (NDO) of spinal origin.

METHODS

Twenty eight patients with spinal NDO were randomised to receive intravesically 50 nM resiniferatoxin dissolved in 10% ethanol in saline (RTX group) or only the vehicle solution (placebo group). Filling cystometries were obtained in each patient at 1 month and 1 week before and at 1 and 3 months after treatment. In a visual analog scale patients were asked to estimate the discomfort induced by treatment. Patients were also persuaded to fill a micturition chart during the 3 days preceding each cystometry.

RESULTS

The RTX and placebo groups were homogeneous in what respects the volume to first involuntary detrusor contraction (FDC, 143+/-95 ml and 115+/-58 ml, respectively, p=0.3) and maximal cystometric capacity (MCC, 189+/-99 ml and 198+/-111 ml, respectively, p=0.8). At the end of the study, mean FDC and MCC in the RTX group, 184+/-93 ml and 314+/-135 ml, respectively were significantly higher than in the placebo group, 115+/-61 ml (p=0.03) and 204+/-92 ml (p=0.02). In the visual analogue scale discomfort caused by treatment was similar. Only 10 patients in the RTX group and 6 patients in the placebo group completed adequately the micturition chart. Mean frequency and urinary incontinence decreased significantly only in the RTX group.

CONCLUSIONS

Intravesical RTX is effective in increasing bladder capacity in spinal NDO patients. Such increment might contribute to decrease urinary frequency and incontinence of these patients.

Therapy Insight: bladder dysfunction associated with multiple sclerosis

Bladder dysfunction is a common problem for patients with multiple sclerosis. The severity of symptoms often correlate with the degree of spinal cord involvement and, hence, the patient's general level of disability. The emphasis of management is now mainly medical and is increasingly offered by nonurologists. Treatments can be highly effective, relieving patients of what are otherwise very troublesome symptoms that would compound their neurological disability. This article gives an overview of the neural control of the bladder, followed by an explanation of the pathophysiology of detrusor overactivity secondary to neurological disease. A review of methods available for treating bladder dysfunction in multiple sclerosis then follows. The treatment options for this disorder are largely medical and include established first-line measures such as anticholinergics, clean intermittent self-catheterization and the use of desmopressin, as well as potential second-line agents, such as cannabinoids, intravesical vanilloids and intradetrusor botulinum neurotoxin type A. The diminishing role of surgical intervention is also discussed.

Intravesikale Therapie der überaktiven Blase

INTRODUCTION

Despite recent advances in the field of anticholinergic drugs, lack of efficiency and side effects are still the main reasons for discontinuation of treatment. The introduction of botulinum A toxin was a milestone in the treatment of detrusor overactivity. The treatment, however, is invasive, the duration of the treatment effects is limited, and long-term results are not yet available. The following addresses therapeutic alternatives to local treatment of overactive bladder.

MATERIALS AND METHODS

A total of 52 patients received intravesical oxybutynin. In 16 patients, capsaicin was instilled in the bladder and 28 patients were treated with EMDA.

RESULTS

Intravesical oxybutynin was successful in 86%; the success rate of capsaicin instillation was 47%. EMDA was successful in 78%. Two transient ischemic attacks following EMDA were observed as significant side effects.

CONCLUSION

Besides botulinum A toxin, several effective treatment options are available for patients with detrusor overactivity refractory to oral anticholinergic treatment. Therefore, in each individual patient, possible risks and complications of the different treatment options should be considered thoroughly to find the optimal method in each case.

The Distribution of Sensory Fibers Immunoreactive for the TRPV1 (Capsaicin) Receptor in the Human Prostate

OBJECTIVES

To determine the distribution of sensory fibers immunoreactive to the pain receptor TRPV1 in the human prostate.

METHODS

Eight prostates were harvested from cadaver transplant donors and immediately immersion fixed. Longitudinal and transverse 20 microm sections were cut on a cryostat and immunoreacted with two anti-human TPRV1 antibodies.

RESULTS

TRPV1-immunoreactive nerve fibers were distributed throughout the prostatic urethral mucosa, verumontanum, ejaculatory ducts and periurethral prostatic acini. In the urethral mucosa, TRPV1-immunoreactive fibers penetrated the epithelial layer up to its surface. In the transitional and peripheral zones of the gland no TRPV1-immunoreactive nerve fibers were detected.

CONCLUSIONS

The existence of a rich TRPV1 sensory innervation in the human prostate may open new therapeutic perspectives for the treatment of pain in patients with chronic prostatitis (Chronic Pelvic Pain Syndrome).

ROLE OF C AFFERENT FIBERS AND MONITORING OF INTRAVESICAL RESINIFERATOXIN THERAPY FOR PATIENTS WITH IDIOPATHIC DETRUSOR OVERACTIVITY

PURPOSE

Resiniferatoxin (RTX) is a specific C fiber neurotoxin which produces desensitization. In this study we performed intravesical RTX therapy in patients with idiopathic detrusor overactivity. In addition we measured the current perception threshold of C and A delta fibers before and after treatment to evaluate clinical significance.

MATERIALS AND METHODS

The protocol involved an RTX solution (100 ml of 50 nM) instilled in the bladder for 30 minutes. Four men and 6 women 59 to 75 years old were treated. Effects on bladder function were evaluated before and 30 days after treatment by cystometry and Neurometer (Neurotron, Inc., Baltimore, Maryland). Subjective and objective measures included bladder diaries and quality of life before treatment, and 7, 30 and 90 days subsequently.

RESULTS

Of the 10 patients 5 noted improvement and 2 of them became dry. The other 5 patients were considered to have stationary symptoms. Mean maximal cystometric capacity +/- SD increased from 229 +/- 108 ml at baseline to 271 +/- 99.5 ml at 30 days (p = 0.04). The mean number of daily episodes of urinary incontinence decreased from 3.5 +/- 2.2 to 2.0 +/- 1.6 (p = 0.008) at 7 days, to 1.9 +/- 1.6 (p = 0.018) at 30 days and to 2.5 +/- 1.7 (p = 0.018) at 90 days. Mean current perception threshold values of C and A delta fibers did not change significantly, from 46.9 +/- 35.2 to 56.4 +/- 32.1 (p = 0.161) and from 66.9 +/- 31.7 to 66.4 +/- 25.2 (p = 0.952), respectively. However, values of C fibers increased in all patients who showed improvement from 46.2 +/- 33.2 to 64.0 +/- 36.8 (p = 0.043).

CONCLUSIONS

Intravesical RTX improved bladder capacity and leak episodes in patients with idiopathic detrusor overactivity. Intravesical RTX is a promising treatment for this condition.

Intravesical resiniferatoxin decreases spinal c-fos expression and increases bladder volume to reflex micturition in rats with chronic inflamed urinary bladders

OBJECTIVE

To evaluate the effect of intravesical resiniferatoxin on spinal c-fos expression and bladder volume at reflex micturition in rats with chronic urinary bladder inflammation.

MATERIALS AND METHODS

Of three groups of female Wistar rats, group 1 received cyclophosphamide (75 mg/kg body weight) intraperitoneally every third day (cyclophosphamide is an antitumoral agent that induces bladder inflammation after urinary excretion of its metabolite, acrolein); group 2 comprised sham-inflamed rats that received saline instead of cyclophosphamide, and group 3 received cyclophosphamide, as group 1, every third day but plus 10 nmol/L resiniferatoxin intravesically, through a urethral catheter, at 7 days. At 8 days, under urethane anaesthesia, a needle was inserted in the bladder dome and saline infused at 6 mL/h for 2 h. Finally the animals were perfusion-fixed through the ascending aorta with 4% paraformaldehyde. Transverse sections cut from L6 spinal cord segments were immunoreacted for Fos protein and positive cells in the dorsal horn counted. In a further set of equal groups the bladders were prepared in the same way under urethane anaesthesia and after 30-min of stabilization, saline was infused at 6 mL/h and the volume evoking reflex micturition determined.

RESULTS

The mean (SD) number of positive c-fos cells per spinal cord section was 85 (21), 42 (9) (P = 0.002) and 55 (10) in groups 1 to 3, respectively; the values for group 2 and 3 were similar (P = 0.22) and statistically less than that of group 1 (P = 0.02). Reflex micturition occurred at, respectively, 0.26 (0.09), 0.49 (0.18) and 0.52 (0.11) mL, being similar in group 2 and 3 (P = 0.74) but lower in group 1 (P = 0.003).

CONCLUSION

Intravesical resiniferatoxin decreases c-fos expression and increases bladder capacity in chronically inflamed rat bladders. These findings suggest that desensitizing the vanilloid receptor type 1 by intravesical resiniferatoxin is relevant to the treatment of pain and voiding frequency in patients with chronic inflammatory bladder conditions.

New pharmacologic targets for the treatment of the overactive bladder: an update

Although currently available antimuscarinic agents are the standard of care for overactive bladder (OAB), they are limited by certain side effects, particularly dry mouth and constipation. Research aimed at discovering new therapies for OAB has resulted in the identification of some promising drugs. Investigations of pharmacologic targets in the central nervous system (CNS) have yielded encouraging results with several agents, including tramadol and gabapentin. Further investigation may show that drugs acting at serotonergic and noradrenergic CNS sites are clinically useful as therapies for OAB. Some peripherally acting drugs, such as resiniferatoxin and botulinum toxin, have already been proved to be of clinical value. However, development of other agents that block afferent or efferent nerve impulses in the bladder through activity at vanilloid, purinergic, or opioid-like receptor sites may result in clinically useful drugs.

Intravesical capsaicin versus resiniferatoxin for the treatment of detrusor hyperreflexia in spinal cord injured patients: a double-blind, randomized, controlled study

PURPOSE

Chemical defunctionalization of C-fiber bladder afferents with intravesical vanilloids such as capsaicin (CAP) or resiniferatoxin (RTX) improves detrusor hyperreflexia in humans and animals. The little existing data comparing the efficacy and tolerance of these 2 vanilloid agents seem to favor RTX in 10% alcohol over CAP, which is usually diluted in 30% alcohol. We compared the efficacy and tolerability of the 2 vanilloid agonists in what to our knowledge is the first randomized, controlled study comparing nonalcohol CAP vs RTX in 10% alcohol in neurogenic patients with detrusor hyperreflexia.

MATERIALS AND METHODS

This single center, randomized, double-blind, parallel groups study included 39 spinal cord injured adults with detrusor hyperreflexia. On day 0 patients were randomized to receive 1, 100 ml intravesical instillation of 100 nMol/l RTX diluted in 10% ethanol or 1 mmol/l CAP diluted in glucidic solvent. Efficacy (voiding chart and cystomanometry) and tolerability were evaluated during a 3-month followup.

RESULTS

On day 30 clinical and urodynamical improvement was found in 78% and 83% of patients with CAP vs 80% and 60% with RTX, respectively, without a significant difference between the 2 treated groups. The benefit remained in two-thirds of the 2 groups on day 90. There were no significant differences in regard to the incidence, nature or duration of side effects in CAP vs RTX treated patients.

CONCLUSIONS

Our results strongly argue for the importance of accounting for the role of vanilloid solute when interpreting the efficacy and tolerance of vesical vanilloid instillation in detrusor hyperreflexia cases. They suggest that a glucidic solute is a valuable solvent for vanilloid instillation.

Urodynamic and Immunohistochemical Evaluation of Intravesical Capsaicin Delivery Using Thermosensitive Hydrogel and Liposomes

PURPOSE

Aqueous insolubility of the vanilloids such as capsaicin is a major disincentive in their intravesical therapy of detrusor hyperreflexia. We sought to overcome the delivery of this hydrophobic neurotoxin by entrapping it in a lipid bilayer of positively charged multilamellar lipid vesicles (liposomes) or in a hydrophobic polymer matrix of thermosensitive hydrogel.

MATERIALS AND METHODS

Liposomes, hydrogel and 30% ethanol/normal saline were prepared with or without 1 mM capsaicin (0.5 ml) and administered intravesically for 30 minutes to 7 groups of age matched, normal female adult Sprague-Dawley rats under halothane anesthesia. At 48 hours after intravesical instillation cystometric studies were performed using urethane anesthesia (0.04 ml per minute). The animals were subsequently sacrificed and whole bladders were harvested for histology and immunohistochemistry.

RESULTS

In normal urethane anaesthetized rats capsaicin in 30% ethanol and liposomes completely blocked micturition reflexes. Capsaicin in hydrogel did not completely block the micturition reflex but it significantly decreased bladder contraction frequency compared with vehicle controls. The results of cystometry with capsaicin in liposomes and capsaicin in 30% ethanol correlated with a significant decrease in calcitonin gene-related peptide staining of afferent nerves in the bladder wall. Photographs taken after hematoxylin and eosin staining of the bladder treated with liposomes and hydrogel in the absence of capsaicin did not reveal any adverse histological changes. There were significant histological changes in bladders treated with 30% ethanol alone.

CONCLUSIONS

In comparison with 30% ethanol liposomes are a superior vehicle for the intravesical administration of capsaicin, producing comparable efficacy with less tissue damage. Hydrogel can also serve as safe alternative option for capsaicin delivery.

The perspective of a neurologist on treatment-related research in fecal and urinary incontinence

Afferent innervation is important in sensing the degree of bladder fullness and in forming the input limb to involuntary detrusor contractions in neurogenic and probably also non-neurogenic detrusor overactivity. It is likely that homologous mechanisms are involved in control of the bowel. Accumulating evidence now suggests that in conditions of bladder hypersensitivity as well as non-neurogenic detrusor overactivity, there is up-regulation of unmyelinated nerve fibers expressing both the vanilloid receptor and purinergic receptors. The development of a selective neurotoxin that could successfully "deafferent" the bladder would have major therapeutic consequences. Women who respond best to neuromodulation through sacral nerve stimulation are those with a primary disorder of sphincter relaxation and a very large capacity without sensations of urgency or a hyperactive sphincter. For these women, neuromodulation may counteract the inhibitory effects of overactive sphincter afferents on the detrusor, and determination of the central nervous system level at which this response occurs may provide an explanation for the paradoxical finding that both urge incontinence and urinary retention are responsive to this intervention. Experimental evidence suggests that the "procontinence" reaction consists of an inhibitory effect on the detrusor and presumably the lower rectum resulting from contraction of the pelvic floor and the anal or urethral sphincter. Development of methods of enhancing the inhibitory reflex effect could lead to improved voluntary control of micturition and defecation for patients with neurogenic bladder overactivity or spinal cord lesions.

Insulin induces cobalt uptake in a subpopulation of rat cultured primary sensory neurons

Previous findings show that both the vanilloid receptor 1 and the insulin receptor are expressed on small primary sensory neurons. As insulin evokes activity in second messengers which could induce opening of the vanilloid receptor 1, we examined, by using the cobalt-uptake technique, whether or not insulin can activate cultured rat primary sensory neurons through activating the vanilloid receptor 1. Capsaicin (50, 100 and 500 nm) induced concentration-dependent labelling in primary sensory neurons. Preincubation of cells in insulin (10 micromoles) for 10 min followed by a 2-min wash did not produce significant change in the capsaicin-induced labelling. Coapplication of insulin (10 micromoles) with capsaicin, however, potentiated the 50 and 100 nm capsaicin-evoked staining. Insulin itself also produced cobalt labelling in a concentration-dependent manner. The size-frequency distributions of neurons showing capsaicin- or insulin-induced cobalt accumulation were similar. The insulin-induced cobalt labelling was significantly reduced by the tyrosine kinase inhibitor, tyrphostin AG1024, the vanilloid receptor 1 antagonists, ruthenium red and capsazepine, the protein kinase inhibitor, staurosporine and the phospholipase C inhibitor neomycin. Double immunostaining of cultured primary sensory neurons and sections from dorsal root ganglia revealed that about one-third of the cells coexpress the insulin receptor and vanilloid receptor 1. These findings suggest that insulin activates a subpopulation of primary sensory neurons, probably through phosphorylation- and/or phosphatidylinositol(4,5)biphosphate hydrolysis-evoked activation of the vanilloid receptor 1. Although the insulin-induced activation of vanilloid receptor 1 seems to be a short-lived effect in vitro, in vivo it might play a role in the development of burning pain sensation in hyperinsulinism.

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.