Analysis of the afferent limb of the vesicovascular reflex using neurotoxins, resiniferatoxin and capsaicin

Nerve growth factor-dependent hyperexcitability of capsaicin-sensitive bladder afferent neurones in mice with spinal cord injury

NEW FINDINGS

What is the central question of this study? Nerve growth factor (NGF) is reportedly a mediator inducing urinary bladder dysfunction. Is NGF directly involved in hyperexcitability of capsaicin-sensitive C-fibre bladder afferent pathways after spinal cord injury (SCI)? What is the main finding and its importance? Neutralization of NGF by anti-NGF antibody treatment reversed the SCI-induced increase in the number of action potentials and the reduction in spike thresholds and A-type K⁺ current density in mouse capsaicin-sensitive bladder afferent neurones. Thus, NGF plays an important and direct role in hyperexcitability of capsaicin-sensitive C-fibre bladder afferent neurones attributable to the reduction in A-type K⁺ channel activity in SCI.

ABSTRACT

Nerve growth factor (NGF) has been implicated as an important mediator in the induction of C-fibre bladder afferent hyperexcitability, which contributes to the emergence of neurogenic lower urinary tract dysfunction after spinal cord injury (SCI). In this study, we determined whether NGF immunoneutralization using an anti-NGF antibody (NGF-Ab) normalizes the SCI-induced changes in electrophysiological properties of capsaicin-sensitive C-fibre bladder afferent neurones in female C57BL/6 mice. The spinal cord was transected at the Th8/Th9 level. Two weeks later, continuous administration of NGF-Ab (10 μg kg^-1  h^-1 , s.c. for 2 weeks) was started. Bladder afferent neurones were labelled with Fast-Blue (FB), a fluorescent retrograde tracer, injected into the bladder wall 3 weeks after SCI. Four weeks after SCI, freshly dissociated L6-S1 dorsal root ganglion neurones were prepared. Whole-cell patch-clamp recordings were then performed in FB-labelled neurones. After recording action potentials or voltage-gated K⁺ currents, the sensitivity of each neurone to capsaicin was evaluated. In capsaicin-sensitive FB-labelled neurones, SCI significantly reduced the spike threshold and increased the number of action potentials during membrane depolarization for 800 ms. These SCI-induced changes were reversed by NGF-Ab. Densities of slow-decaying A-type K⁺ (K_A ) and sustained delayed rectifier-type K⁺ currents were significantly reduced by SCI. The NGF-Ab treatment reversed the SCI-induced reduction in the K_A current density. These results indicate that NGF plays an important role in hyperexcitability of mouse capsaicin-sensitive C-fibre bladder afferent neurones attributable to a reduction in K_A channel activity. Thus, NGF-targeting therapies could be effective for treatment of afferent hyperexcitability and neurogenic lower urinary tract dysfunction after SCI.

OAB without an overactive bladder in the acute prostaglandin E2 rat model

Intravesical prostaglandin E2 (PGE2) was previously used to induce overactive bladder (OAB) symptoms, as it reduces bladder capacity in rats and causes a "strong urgency sensation" in healthy women. However, the mechanism by which this occurs is unclear. To clarify how PGE2 reduces bladder capacity, 100 µM PGE2 was administered intravesically during open, single-fill cystometry with simultaneous measurement of sphincter EMG in the urethane-anesthetized female Wistar rat. PGE2 was also applied to the urethra or bladder selectively by use of a ligature at the bladder neck before (urethra) or during (bladder) closed-outlet, single-fill cystometry. Additional tests of urethral perfusion with PGE2 were made. PGE2 decreased bladder capacity, increased voiding efficiency, and increased sphincter EMG during open cystometry compared with saline controls. The number of nonvoiding contractions did not change with PGE2; however, bladder compliance decreased. During closed-outlet cystometry, PGE2 applied only to the bladder or the urethra did not decrease bladder capacity. Urethral infusion of PGE2 decreased urethral perfusion pressure. Taken together, these results suggest that intravesical PGE2 may decrease bladder capacity by targeting afferents in the proximal urethra. This may occur through urethral relaxation and decreased bladder compliance, both of which may increase activation of proximal urethra afferents from distension of the proximal urethra. This hypothesis stands in contrast to many hypotheses of urgency that focus on bladder dysfunction as the primary cause of OAB symptoms. Targeting the urethra, particularly urethral smooth muscle, may be a promising avenue for the design of drugs and devices to treat OAB.

Comparison of Autonomic Reactions during Urodynamic Examination in Patients with Spinal Cord Injuries and Able-Bodied Subjects

BACKGROUND/PURPOSE

This study compares heart rate variability (HRV) and systolic blood pressure (SBP) changes of spinal cord injury (SCI) patients during urodynamic study (UDS) with able-bodied controls.

METHODS

Twenty four complete suprasacral SCI patients (12 tetraplegia and 12 paraplegia) and 12 age-matched able-bodied volunteers received BP and HRV evaluation throughout urodynamic examination. We chose seven time points during the examinations: resting, Foley catheter insertion, start of infusion, and infused volume reaching 1/4, 2/4, 3/4 and 4/4 of maximal capacity. At each time point, electrocardiogram with a duration of 5 min was used for power spectral density analysis of HRV.

RESULTS

Only control subjects displayed significant elevation of SBP during Foley catheter insertion compared to resting values. Both control and tetraplegic groups experienced significant elevation of SBP at maximal bladder capacity compared to resting values. Tetraplegic values were also significantly greater than the other two groups. Control subjects displayed significant elevation of low frequency/high frequency (LF/HF) ratios during Foley catheter insertion and when approaching maximum bladder capacity. These findings were not seen in the paraplegic and tetraplegic groups. However, subgroup analysis of tetraplegic subjects with SBP elevation >50 mmHg demonstrated a similar LF/HF response to the able-bodied controls.

CONCLUSION

Tetraplegic patients experienced BP elevation but did not experience significant changes in HRV during bladder distension. This finding may imply that different neurological pathways contribute to AD reaction and HRV changes during bladder distension. However, profound AD during UDS in tetraplegic patients was associated with corresponding changes in HRV. Whether HRV monitoring would be beneficial in SCI patients presenting with significant AD, it needs further studies to elucidate.

Autonomic response during bladder hydrodistention reflects the severity of symptoms in patients with bladder pain syndrome/interstitial cystitis

AIMS

To evaluate the correlation between symptom severity of bladder pain syndrome/interstitial cystitis (BPS/IC) and autonomic nervous system activity, we examined autonomic responses during bladder hydrodistention.

METHODS

Medical records were collected from a prospective database for patients who underwent bladder hydrodistention with a fixed protocol from March 2012 to December 2013. A total of 40 patients (16 males, 24 females) were included for the analysis. Hydrodistention was performed under general anesthesia (31 patients), spinal anesthesia (six patients), and both types of anesthesia (three patients) at different times. Twenty-five patients who underwent holmium laser enucleation of the prostate served as controls. Pulse rate (PR), systolic (SBP), and diastolic blood pressure (BP) were measured pre-hydrodistention, during hydrodistention, and after drainage.

RESULTS

The spinal anesthesia and control groups exhibited little change in BP and PR during hydrodistention, while a significant increase was demonstrated in the general anesthesia group (e.g., ΔSBP 4.89 ± 4.80, 10.40 ± 19.03, and 56.26 ± 30.38 mm Hg, respectively, P < 0.001). Under general anesthesia, autonomic response during hydrodistention was more prominent in patients with preoperative visual analogue scale (VAS) pain score ≥7, Hunner's lesion, and glomerulation grade 4. Preoperative maximal cystometric capacity negatively correlated with changes in SBP during hydrodistention (R²  = 0.294, P = 0.009), while VAS score and interstitial cystitis problem index demonstrated a positive correlation with the changes (R²  = 0.208, P = 0.012; R²  = 0.173, P = 0.015).

CONCLUSIONS

Under general anesthesia, exaggerated autonomic responses to bladder hydrodistention were demonstrated in BPS/IC patients, which reflected the severity of symptoms. These results support the hypothesis of altered activity of autonomic system in BPS/IC. Neurourol. Urodynam. 36:677-682, 2017. © 2016 Wiley Periodicals, Inc.

Mechanisms inducing autonomic dysreflexia during urinary bladder distention in rats with spinal cord injury

OBJECTIVES

This study investigated the mechanisms inducing autonomic dysreflexia due to enhanced bladder-to-vascular reflexes in rats with spinal cord injury (SCI).

METHODS

SCI was produced by the transection of the Th4-5 spinal cord in female Sprague-Dawley rats. At 4 weeks after SCI, changes in blood pressure during graded increases in intravesical pressure (20-60 cm H₂O) were measured in spinal-intact (SI) and SCI rats under urethane anesthesia. In five animals, effects of C-fiber desensitization induced by intravesical application of resiniferatoxin (RTX), a TRPV1 agonist, on the bladder-to-vascular reflex were also examined. Nerve growth factor (NGF) levels of mucosa and detrusor muscle layers of the bladder were measured by enzyme-linked immunosorbent assay. The expression levels of TRPV1 and TRPA1 channels were also examined in laser captured bladder afferent neurons obtained from L6 DRG, which were labeled by DiI injected into the bladder wall.

RESULTS

In SI and SCI rats, systemic arterial blood pressure was increased in a pressure-dependent manner during increases in the intravesical pressure, with significantly higher blood pressure elevation at the intravesical pressure of 20 cm H₂O in SCI rats vs SI rats. The arterial blood pressure responses to bladder distention were significantly reduced by RTX-induced desensitization of C-fiber bladder afferent pathways. SCI rats had higher NGF protein levels in the bladder and higher TRPV1 and TRPA1 mRNA levels in bladder afferent neurons compared with SI rats.

CONCLUSIONS

The bladder-to-vascular reflex induced by TRPV1-expressing C-fiber afferents during bladder distention is enhanced after SCI in association with increased expression of NGF in the bladder and TRP channels in bladder afferent neurons.

Somatic modulation of spinal reflex bladder activity mediated by nociceptive bladder afferent nerve fibers in cats

The goal of the present study was to determine if supraspinal pathways are necessary for inhibition of bladder reflex activity induced by activation of somatic afferents in the pudendal or tibial nerve. Cats anesthetized with α-chloralose were studied after acute spinal cord transection at the thoracic T9/T10 level. Dilute (0.25%) acetic acid was used to irritate the bladder, activate nociceptive afferent C-fibers, and trigger spinal reflex bladder contractions (amplitude: 19.3 ± 2.9 cmH2O). Hexamethonium (a ganglionic blocker, intravenously) significantly (P < 0.01) reduced the amplitude of the reflex bladder contractions to 8.5 ± 1.9 cmH2O. Injection of lidocaine (2%, 1-2 ml) into the sacral spinal cord or transection of the sacral spinal roots and spinal cord further reduced the contraction amplitude to 4.2 ± 1.3 cmH2O. Pudendal nerve stimulation (PNS) at frequencies of 0.5-5 Hz and 40 Hz but not at 10-20 Hz inhibited reflex bladder contractions, whereas tibial nerve stimulation (TNS) failed to inhibit bladder contractions at all tested frequencies (0.5-40 Hz). These results indicate that PNS inhibition of nociceptive afferent C-fiber-mediated spinal reflex bladder contractions can occur at the spinal level in the absence of supraspinal pathways, but TNS inhibition requires supraspinal pathways. In addition, this study shows, for the first time, that after acute spinal cord transection reflex bladder contractions can be triggered by activating nociceptive bladder afferent C-fibers using acetic acid irritation. Understanding the sites of action for PNS or TNS inhibition is important for the clinical application of pudendal or tibial neuromodulation to treat bladder dysfunctions.

Assessment of bladder sensation in mice with a novel device

OBJECTIVE

To develop and test the efficacy of an implantable bladder electrode device that can be used with the Neurometer electrodiagnostic stimulator to assess fiber-specific afferent bladder sensation in the mouse.

METHODS

We constructed a ball-tipped platinum electrode and surgically implanted it into the mouse bladder. The Neurometer was connected to the electrode to apply selective nerve fiber stimuli (250 Hz for Aδ fibers and 5 Hz for C fibers) of increasing intensities to the bladder mucosa in the mouse to determine bladder sensory threshold (BST) values. Using 58 female C57BL/6J mice, we measured the temporal and interobserver consistency of BST measurements, the effects of intravesical administration of lidocaine and resiniferatoxin on the BST, and the effects of our device on voiding behavior and bladder mucosal integrity.

RESULTS

BST values at 250 and 5 Hz did not vary significantly when measured 2, 4, and 6 days after device implantation, or when obtained by 2 blinded independent observers. Intravesical lidocaine yielded a transient increase in BST values at both 250 Hz and 5 Hz, whereas resiniferatoxin yielded a significant increase only at the 5 Hz stimulus frequency after 24 hours. Moderately increased micturition frequency and decreased volume per void were observed 4 and 6 days after device implantation. Histology revealed mild inflammatory changes in the area of the bladder adjacent to the implanted BST device.

CONCLUSION

Assessment of neuroselective bladder sensation in mice is feasible with our device, which provides reproducible BST values for autonomic bladder afferent nerve fibers.

Inhibitory effect of somatostatin receptor subtype-4 agonist NNC 26-9100 on micturition reflex in rats

OBJECTIVE

To investigate the effects of activation of somatostatin subtype 4 (SST4) on the micturition reflex in rats.

METHODS

Continuous cystometrograms (0.04 mL/min infusion rate) were performed in female Sprague-Dawley rats (242-265 g) under urethane anesthesia. After stable micturition cycles were established, a selective SST4 receptor agonist, NNC 26-9100, was administered intravenously in normal rats or rats pretreated with capsaicin 4 days before the experiments. The micturition parameters were recorded and compared before and after drug administration.

RESULTS

Intravenous administration of NNC 26-9100 (10-300 μg/kg) significantly increased the intercontraction interval in a dose-dependent fashion. Intravenous administration of NNC 26-9100 (10-300 μg/kg) also significantly increased the pressure threshold in a dose-dependent fashion. No significant changes were seen in the baseline pressure, maximum voiding pressure, or postvoid residual urine volume. However, NNC 26-9100-induced increases in the intercontraction intervals and pressure threshold were not seen in rats with C-fiber desensitization induced by capsaicin pretreatment.

CONCLUSION

These results indicate that in urethane-anesthetized rats, activation of the SST4 receptor can inhibit the micturition reflex by suppression of capsaicin-sensitive C-fiber afferent pathways. Thus, the SST4 receptor could be a potential target for the treatment of C-fiber afferent-mediated bladder dysfunction.

Strain-dependent urethral response

AIMS

The Sprague-Dawley (SD) rat, an out-bred, all-purpose strain, has served well for lower urinary tract research. However, to test new cellular therapies for conditions such as stress urinary incontinence, an in-bred rat strain with immune tolerance, such as the Lewis rat, may be more useful. The objective of this study was to reveal any differences in lower urinary tract continence mechanisms between the Lewis and SD rat.

METHODS

The contribution of (1) the striated and smooth muscle to the mechanical and functional properties of the urethra in vitro, and (2) the striated sphincter to leak point pressure (LPP) and reflex continence mechanisms in vivo were assessed in normal (control) Lewis and SD rats and in a model of stress urinary incontinence produced by bilateral pudendal nerve transection.

RESULTS

Control, Lewis rats had significantly lower LPP, significantly less fast-twitch skeletal muscle and relied less on the striated sphincter for continence than control, SD rats, as indicated by the failure of neuromuscular blockade with alpha-bungarotoxin to reduce LPP. Nerve transection significantly decreased LPP in the SD rat, but not in the Lewis rat. Although the Lewis urethra contained more smooth muscle than the SD rat, it was less active in vitro as indicated by a low urethral baseline pressure and lack of response to phenylephrine.

CONCLUSIONS

We have observed distinct differences in functional and mechanical properties of the SD and Lewis urethra and have shown that the Lewis rat may not be suitable as a chronic model of SUI via nerve transection.

Effect of ovariectomy on external urethral sphincter activity in anesthetized female rats

PURPOSE

The postmenopausal hypoestrogen condition is associated with various lower urinary tract dysfunctions, including frequency, urgency, stress urinary incontinence and recurrent urinary infection. We determined whether hypoestrogen induced lower urinary tract dysfunction after ovariectomy is also associated with an alteration in external urethral sphincter activity.

MATERIALS AND METHODS

Bilateral ovariectomy was performed in female Sprague-Dawley® rats and sham operated rats served as controls. Transvesical cystometry and external urethral sphincter electromyogram activity were monitored 4, 6 and 12 weeks after sham operation or bilateral ovariectomy and at 6 weeks in bilaterally ovariectomized rats treated with estrogen.

RESULTS

The micturition reflex was elicited in sham operated and bilaterally ovariectomized, urethane anesthetized animals. Post-void residual urine increased and voiding efficiency decreased in rats with 4 to 12 weeks of bilateral ovariectomy. The silent period of external urethral sphincter electromyogram activity was shortened significantly and progressively at increased times after bilateral ovariectomy. These effects were prevented by estradiol treatment.

CONCLUSIONS

As evidenced by shortening of the external urethral sphincter electromyogram silent period in ovariectomized rats, the disruption of coordination between the external urethral sphincter and the detrusor muscle could decrease urine outflow and in turn voiding efficiency. Estrogen replacement reverses these changes, suggesting that the central pathways responsible for detrusor-sphincter coordination are modulated by gonadal hormones.

Neuropeptides in lower urinary tract function

Numerous neuropeptide/receptor systems including vasoactive intestinal polypeptide, pituitary adenylate cyclase-activating polypeptide, calcitonin gene-related peptide, substance P, neurokinin A, bradykinin, and endothelin-1 are expressed in the lower urinary tract (LUT) in both neural and nonneural (e.g., urothelium) components. LUT neuropeptide immunoreactivity is present in afferent and autonomic efferent neurons innervating the bladder and urethra and in the urothelium of the urinary bladder. Neuropeptides have tissue-specific distributions and functions in the LUT and exhibit neuroplastic changes in expression and function with LUT dysfunction following neural injury, inflammation, and disease. LUT dysfunction with abnormal voiding, including urinary urgency, increased voiding frequency, nocturia, urinary incontinence, and pain, may reflect a change in the balance of neuropeptides in bladder reflex pathways. LUT neuropeptide/receptor systems may represent potential targets for therapeutic intervention.

Effects of CL316,243, a beta 3-adrenoceptor agonist, and intravesical prostaglandin E2 on the primary bladder afferent activity of the rat

AIMS

It has been suggested that beta(3)-adrenoceptor (beta(3)-AR) agonists affect not only the efferent but also the afferent pathways innervating the bladder. In addition, prostaglandin E(2) (PGE(2)) causes bladder hyperactivity in conscious rats. We investigated the direct effects of a beta(3)-AR agonist (CL316,243; CL) and PGE(2) on single fiber activities of the primary bladder afferent nerves.

METHODS

Female Sprague-Dawley rats were used. Under urethane anesthesia, a single nerve fiber primarily originating from the bladder was identified by electrical stimulation of the left pelvic nerve and by bladder distention, and was divided by conduction velocity (2.5 m/sec) as A delta-fiber or C-fiber. The afferent activity measurements with constant bladder filling were repeated three times and the third measurement served as the base-line observation. Then, CL (10 microg/kg) or its vehicle was administrated intravenously. Thereafter, 10(-4) M of PGE(2) or saline was instilled intravesically and another three cycles recorded.

RESULTS

Forty-three single afferent fibers (A delta-fibers: n = 20, C-fibers: n = 23) were isolated from 34 rats. Intravenous administration of CL, but not vehicle, significantly decreased A delta-fiber, but not C-fiber, activities in response to bladder filling with saline. Intravesical instillation of PGE(2) significantly increased C-fiber activities, but not A delta-fiber activities. The PGE(2)-induced increase in C-fiber activities was inhibited by pretreatment with CL.

CONCLUSIONS

The present results clearly demonstrate that the beta(3)-AR agonist, CL316,243, can inhibit the mechanosensitive A delta-fibers, but not the C-fibers, of the primary bladder afferents of the rat. In addition, the beta(3)-AR agonist can inhibit PGE(2)-induced C-fiber hyperactivity.

In-chern-hau-tang and genipin reduces acute urinary bladder distension evoked sympathetic activation-induced hepatic dysfunction in rats

Increased norepinephrine production by acute urine retention (AUR) induced sympathetic activation may contribute to acute liver injury (ALI) via the action of hepatic vasoconstriction and increased reactive oxygen species (ROS) production. We evaluated whether In-Chern-Hau-Tang, a hepatoprotective herb medicine, and its major ingredient genipin, may ameliorate norepinephrine-induced liver injury in the rat. We determined the effects of In-Chern-Hau-Tang and genipin on norepinephrine-induced oxidative stress in the Kupffer and endothelial cells and AUR-induced ALI in the rat via a chemiluminescence analyzer, physiologic and biochemical determination and western blot. The results of in vitro study showed that genipin with efficient H(2)O(2) and HOCl scavenging activities decreased norepinephrine-enhanced ROS production in the Kupffer cell and endothelial cell cultures. AUR activated hepatic sympathetic nervous activity lead to a hepatic hypoxia/hypoperfusion, and a reduction in bile flow. AUR increased intercellular adhesion molecular 1 (ICAM-1) protein expression, and hepatic ROS production from the activated leukocyte NADPH oxidase activity subsequently leading to plasma aspartate aminotransferase (AST) elevation. Hepatic sympathetic denervation, or oral pretreatment of In-Chern-Hau-Tang or genipin for 1 week ameliorated the level in AUR-induced hepatic hypoxia/hypoperfusion, and bile stasis. Hepatic denervation, In-Chern-Hau-Yang and genipin inhibited AUR-enhanced hepatic ICAM-1 expression, hepatic ROS production, leukocyte NADPH oxidase activity and plasma AST activity. In conclusion, In-Chern-Hau-Tang along with its active component, genipin, can ameliorate AUR-induced ALI via the alleviation of oxidative stress possibly by the inhibition of sympathetic induced hypoxia/hypoperfusion and leukocyte NADPH oxidase activity.

Changes in afferent activity after spinal cord injury

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Brain switch for reflex micturition control detected by FMRI in rats

The functions of the lower urinary tract are controlled by complex pathways in the brain that act like switching circuits to voluntarily or reflexly shift the activity of various pelvic organs (bladder, urethra, urethral sphincter, and pelvic floor muscles) from urine storage to micturition. In this study, functional magnetic resonance imaging (fMRI) was used to visualize the brain switching circuits controlling reflex micturition in anesthetized rats. The fMRI images confirmed the hypothesis based on previous neuroanatomical and neurophysiological studies that the brain stem switch for reflex micturition control involves both the periaqueductal gray (PAG) and the pontine micturition center (PMC). During storage, the PAG was activated by afferent input from the urinary bladder while the PMC was inactive. When bladder volume increased to the micturition threshold, the switch from storage to micturition was associated with PMC activation and enhanced PAG activity. A complex brain network that may regulate the brain stem micturition switch and control storage and voiding was also identified. Storage was accompanied by activation of the motor cortex, somatosensory cortex, cingulate cortex, retrosplenial cortex, thalamus, putamen, insula, and septal nucleus. On the other hand, micturition was associated with: 1) increased activity of the motor cortex, thalamus, and putamen; 2) a shift in the locus of activity in the cingulate and insula; and 3) the emergence of activity in the hypothalamus, substantia nigra, globus pallidus, hippocampus, and inferior colliculus. Understanding brain control of reflex micturition is important for elucidating the mechanisms underlying neurogenic bladder dysfunctions including frequency, urgency, and incontinence.

Bladder hyperactivity and increased excitability of bladder afferent neurons associated with reduced expression of Kv1.4 alpha-subunit in rats with cystitis

Hyperexcitability of C-fiber bladder afferent pathways has been proposed to contribute to urinary frequency and bladder pain in chronic bladder inflammation including interstitial cystitis. However, the detailed mechanisms inducing afferent hyperexcitability after bladder inflammation are not fully understood. Thus, we investigated changes in the properties of bladder afferent neurons in rats with bladder inflammation induced by intravesical application of hydrochloric acid. Eight days after the treatment, bladder function and bladder sensation were analyzed using cystometry and an electrodiagnostic device of sensory function (Neurometer), respectively. Whole cell patch-clamp recordings and immunohistochemical staining were also performed in dissociated bladder afferent neurons identified by a retrograde tracing dye, Fast Blue, injected into the bladder wall. Cystitis rats showed urinary frequency that was inhibited by pretreatment with capsaicin and bladder hyperalgesia mediated by C-fibers. Capsaicin-sensitive bladder afferent neurons from sham rats exhibited high thresholds for spike activation and a phasic firing pattern, whereas those from cystitis rats showed lower thresholds for spike activation and a tonic firing pattern. Transient A-type K(+) current density in capsaicin-sensitive bladder afferent neurons was significantly smaller in cystitis rats than in sham rats, although sustained delayed-rectifier K(+) current density was not altered after cystitis. The expression of voltage-gated K(+) Kv1.4 alpha-subunits, which can form A-type K(+) channels, was reduced in bladder afferent neurons from cystitis rats. These data suggest that bladder inflammation increases bladder afferent neuron excitability by decreasing expression of Kv1.4 alpha-subunits. Similar changes in capsaicin-sensitive C-fiber afferent terminals may contribute to bladder hyperactivity and hyperalgesia due to acid-induced bladder inflammation.

Herpes simplex virus vector-mediated gene delivery for the treatment of lower urinary tract pain

Interstitial cystitis (IC)/painful bladder syndrome (PBS) is a painful debilitating chronic visceral pain disorder of unknown etiology that affects an estimated 1 million people in the United States alone. It is characterized by inflammation of the bladder that results in chronic pelvic pain associated with bladder symptoms of urinary frequency and urgency. Regardless of the etiology, IC/PBS involves either increased and/or abnormal activity in afferent nociceptive sensory neurons. Pain-related symptoms in patients with IC/PBS are often very difficult to treat. Both medical and surgical therapies have had limited clinical utility in this debilitating disease and numerous drug treatments, such as heparin, dimethylsulfoxide and amitriptyline, have proven to be palliative at best, and in some IC/PBS patients provide no relief whatsoever. Although opiate narcotics have been employed to help alleviate IC/PBS pain, this strategy is fraught with problems as systemic narcotic administration causes multiple unwanted side effects including mental status change and constipation. Moreover, chronic systemic narcotic use leads to dependency and need for dose escalation due to tolerance; therefore, new therapies are desperately needed to treat refractory IC/PBS. This has led our group to develop a gene therapy strategy that could potentially alleviate chronic pelvic pain using the herpes simplex virus-directed delivery of analgesic proteins to the bladder.

Herpes simplex virus vector-mediated delivery of neurturin rescues erectile dysfunction of cavernous nerve injury

Neurturin (NTN), a member of glial cell line-derived neurotrophic factor (GDNF) family, is known as an important neurotrophic factor for penis-projecting neurons. We recently demonstrated significant protection from erectile dysfunction (ED) following a replication-defective herpes simplex virus (HSV) vector-mediated GDNF delivery to the injured cavernous nerve. Herein, we applied HSV vector-mediated delivery of NTN to this ED model. Rat cavernous nerve was injured bilaterally using a clamp and dry ice. For HSV-treated groups, 20 microl of vector stock was administered directly to the damaged nerve. Delivery of an HSV vector expressing both green fluorescent protein and lacZ (HSV-LacZ) was used as a control. Intracavernous pressure along with systemic arterial pressure (ICP/AP) was measured 2 and 4 weeks after the nerve injury. Fluorogold (FG) was injected into the penile crus 7 days before being killed to assess neuronal survival. Four weeks after nerve injury, rats treated with HSV-NTN exhibited significantly higher ICP/AP compared with untreated or control vector-treated groups. The HSV-NTN group had more FG-positive major pelvic ganglion neurons than the control group following injury. HSV vector-mediated delivery of NTN could be a viable approach for the improvement of ED following cavernous nerve injury.

Efficacy of a novel device for assessment of autonomic sensory function in the rat bladder

PURPOSE

We developed and tested the efficacy of an implantable bladder device which, when combined with the Neurometer, can be used to assess fiber specific afferent bladder sensation in the rat.

MATERIALS AND METHODS

We developed an implantable bladder device that applies selective nerve fiber stimuli (250 Hz for small myelinated Adelta fibers and 5 Hz for unmyelinated C fibers) to the bladder mucosa in the rat to determine bladder sensory perception threshold values. We performed 3 experiments in 55 female Sprague-Dawley rats to examine the effects of our device on voiding habits, assess the interobserver reliability of the sensory perception threshold and determine the effects of intravesical administration of resiniferatoxin (Sigma) and lidocaine on the sensory perception threshold.

RESULTS

Sensory perception threshold values obtained by 2 blinded, independent observers were not different from each other (p = 0.41). Sensory perception threshold values obtained at the 2 stimulation frequencies remained constant for at least 3 weeks after device implantation. A significant increase in sensory perception threshold values after resiniferatoxin instillation was noted at a stimulus frequency of 5 Hz (p = 0.02), whereas intravesical lidocaine led to an immediate increase in the sensory perception threshold at 250 and 5 Hz. Device implantation led to an early decreased voided volume and increased frequency of voids, although these parameters returned to normal after 4 days.

CONCLUSIONS

Assessment of bladder afferent sensation with our newly developed device is feasible in rats. It provides sensory perception thresholds that appear to be fiber-type selective for autonomic bladder afferent nerves.

Inhibitory roles of peripheral nitrergic mechanisms in capsaicin-induced detrusor overactivity in the rat

OBJECTIVES

To investigate the peripheral role of nitric oxide (NO) in capsaicin-induced detrusor overactivity (DO), as exogenously applied vanilloids can evoke NO release in urothelial cells but its functional role has not yet been reported.

MATERIALS AND METHODS

The effects of N(G)-nitro-l-arginine methyl ester (L-NAME), an inhibitor of NO synthase (NOS), on bladder activity during intravesical capsaicin (30 microm) instillation were examined by using continuous infusion cystometry in urethane-anaesthetized rats. L-NAME was administered intravenously (i.v., 20 mg/kg), intrathecally (i.t., 270 microg/rat), intracerebroventricularly (i.c.v., 270 microg/rat) or intravesically (10 mg/mL) before or during capsaicin instillation.

RESULTS

During cystometry with intravesical saline infusion, L-NAME injected i.v., i.t. and i.c.v., but not intravesically, significantly increased the intercontraction intervals (ICI) and L-NAME injected i.v., but not i.t., i.c.v. or intravesically, increased the maximum voiding pressure (MVP) without affecting the baseline pressure. Capsaicin instillation induced DO evidenced by a significant reduction in the ICI. L-NAME administered i.v. further decreased the ICI and increased the MVP and the baseline pressure during capsaicin instillation. Co-intravesical application of capsaicin and L-NAME also similarly enhanced capsaicin-induced DO. However, L-NAME injected i.t. or i.c.v. had no effect on capsaicin-induced DO. The excitatory effects of i.v and intravesical L-NAME on the ICI, MVP and baseline pressure during capsaicin infusion were significantly suppressed by desensitization of C-fibre afferent pathways by capsaicin pretreatment (125 mg/kg s.c., 4 days before cystometry).

CONCLUSION

These results indicate that locally released NO can suppress DO induced by capsaicin-mediated C-fibre activation and that central NO pathways are not involved in capsaicin-induced DO.

Activation of urothelial transient receptor potential vanilloid 4 by 4alpha-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.

Herpes simplex virus vector-mediated delivery of glial cell line-derived neurotrophic factor rescues erectile dysfunction following cavernous nerve injury

Erectile dysfunction (ED) is frequently associated with injury to the cavernous nerve sustained during pelvic surgery. Functional recovery from cavernous nerve injury is generally incomplete and occurs over an extended time frame. We employed a therapeutic gene transfer approach with herpes simplex virus (HSV) vector expressing glial cell line-derived neurotrophic factor (GDNF). Rat cavernous nerve was injured bilaterally using a clamp and dry ice. For HSV-treated groups, 20 microl of purified vector stock was administered directly to and around the damaged nerve. Delivery of an HSV vector expressing both green fluorescent protein (GFP) and lacZ (HSV-LacZ) was used as a control. Intracavernous pressure along with systemic arterial pressure (ICP/AP) was measured 2 and 4 weeks after the nerve injury. Fluorogold (FG) was injected into the penile crus 7 days before killing to assess nerve survival. Approximately 60% of major pelvic ganglion (MPG) cells were GFP positive after viral administration. At 4 weeks after nerve injury, rats treated with HSV-GDNF exhibited significant recovery of ICP/AP compared with control vector or untreated groups. The HSV-GDNF group also yielded more FG-positive MPG cells than the control vector group. HSV vector-mediated delivery of GDNF presents a viable approach for the treatment of ED following cavernous nerve injury.

Suppression of detrusor overactivity in rats with bladder outlet obstruction by a type 4 phosphodiesterase inhibitor

OBJECTIVE

To investigate the effects of a selective type 4 cyclic nucleotide phosphodiesterase (PDE4) inhibitor, IC486051, on bladder activity in normal rats and those with and bladder outlet obstruction (BOO), as inhibition of PDE4 leads to elevation of intracellular cAMP levels and relaxation of smooth muscle.

MATERIALS AND METHODS

BOO was induced in female Sprague-Dawley rats by tying a silk ligature around the urethra. At 4 or 6 weeks after inducing BOO, conscious rats were assessed by cystometry with the urethral ligature intact. In unobstructed rats, blood pressure was also measured.

RESULTS

In unobstructed rats, IC486051 (0.1 mg/kg intravenously) produced no significant changes in cystometric variables, while at a dose of 0.5 mg/kg maximum voiding pressure was reduced by 34%. At both doses, there was a small, transient increase in blood pressure. In both 4- and 6-week BOO rats IC486051 dose-dependently decreased the number and amplitude of non-voiding bladder contractions by up to 80%, relative to pre-treatment values. At doses of 0.1 and 0.5 mg/kg IC486051 had no significant effect on voiding variables. In the 4-week BOO rats, a dose of 1.0 mg/kg decreased bladder capacity, voided volume and residual volume by 21%, 32% and 18%, respectively. In 6-week BOO rats, a dose of 1.0 mg/kg decreased maximal voiding pressure by 17% and pressure threshold for voiding by 28%. In both groups of rats with BOO, voiding efficiency was unchanged.

CONCLUSIONS

A selective PDE4 inhibitor can effectively suppress detrusor overactivity in rats with BOO, at doses that have no effect on voiding bladder contractions. Thus, selective PDE4 inhibitors should be considered for the treatment of overactive bladder in patients with BOO.

The Immediate Effect of Castration on Female Rabbit Bladder Blood Flow and Tissue Oxygenation

BACKGROUND

The female urinary bladder is a target organ for estrogen. Reductions in circulating estrogen have been associated with urothelial and vaginal atrophy and bladder disorders including incontinence and increased incidence of bladder infections. We determined the effect of short-term ovariectomy on sex hormones, bladder blood flow, and tissue oxygenation in the rabbit model.

MATERIALS AND METHODS

Female New Zealand White rabbits were ovariectomized and evaluated on 1, 3, and 7 days after ovariectomy. Tissue oxygenation (pO2) and blood flow were measured with oxylab system of real time measurements. Serum estrogen and progesterone were determined at sacrifice. Tissue hypoxia was localized histologically using Hypoxyprobe-1 immunohistochemistry.

RESULTS

Short-term ovariectomy caused rapid decreases in serum estrogen and progesterone, significant decreases in urothelial oxygenation and blood flow. No significant decreases in blood flow or oxygenation were noted for the detrusor smooth muscle. Immunohistochemistry confirmed the presence of urothelial hypoxia at all times after ovariectomy. Bladder muscle did not demonstrate significant levels of hypoxia.

CONCLUSION

The bladder urothelium is extremely sensitive to short-term ovariectomy, with significant urothelial hypoxia seen by post-ovariectomy day 1. Urothelial hypoxia may play a significant role in pelvic pain syndromes, incontinence, and increased susceptibility to bladder infection.

Gene gun particle encoding preproenkephalin cDNA produces analgesia against capsaicin-induced bladder pain in rats

OBJECTIVES

To evaluate the efficacy of gene therapy using a gene gun or direct injection for the transfer of human preproenkephalin (PPE) plasmid cDNA using a capsaicin-induced bladder pain model in rats. Opioid peptides play an essential role in the modulation of micturition reflex and control of inflammatory pain. PPE is one such precursor molecule.

METHODS

Human PPE cDNA was cloned into a modified pCMV plasmid and delivered into the bladder wall of adult female rats by direct injection or gene gun. At 4 and 7 days after gene therapy, continuous cystometrograms were performed under urethane anesthesia by filling the bladder (0.08 mL/min) with saline, followed by 15 muM capsaicin. Immunohistochemical staining was used to detect enkephalins in the bladder after PPE cDNA transfer.

RESULTS

The intercontraction interval was decreased after intravesical instillation of capsaicin (65.0% and 63.1% decrease) in the control group or direct PPE gene injection group, respectively. However, the gene gun-treated group showed a significantly reduced response to capsaicin instillation at day 4 and day 7 (intercontraction interval 16.2% and 42.8% decrease, respectively). This analgesic effect was reversed by intravenous naloxone, an opioid antagonist (5 mg/kg). Increased enkephalin immunoreactivity in the bladder was observed in the gene gun-treated group at day 4, which was reduced at day 7.

CONCLUSIONS

The PPE gene can be effectively transferred and suppress the nociceptive response in the bladder using the gene gun method. These results support potential clinical application of PPE gene gun delivery system for the treatment of bladder pain and other types of visceral pain.

Sympathetic vesicovascular reflex induced by acute urinary retention evokes proinflammatory and proapoptotic injury in rat liver

Increased hepatic sympathetic activity affects hepatic metabolism and hemodynamics and subsequently causes acute hepatic injury. We examined whether the vesicovascular reflex evoked by bladder overdistension could affect hepatic function, specifically reactive oxygen species (ROS)-induced inflammation and apoptosis, through activation of the hepatic sympathetic nerve. We evaluated the hepatic hemodynamics, hepatic sympathetic nervous activities, and cystometrograms in anesthetized rats subjected to acute urinary retention. We used a chemiluminescence method, an in situ nitro blue tetrazolium perfusion technique, and a DNA fragmentation/apoptosis-related protein assay to demonstrate de novo and colocalize superoxide production and apoptosis formation in rat liver. Acute urinary retention increased the hepatic sympathetic-dependent vesicovascular reflex, which caused hepatic vasoconstriction/hypoxia and increased superoxide anion production from the periportal Kupffer cells and hepatocytes, which were aggravated by the increase in volume and duration of urinary retention. The ROS-enhanced proinflammatory NF-κB, activator protein-1, and ICAM-1 expression also promoted proapoptotic mechanisms, including increases in the Bax/Bcl-2 ratio, CPP32 expression, poly-(ADP-ribose)-polymerase cleavages, and DNA fragmentation and apoptotic cells in the liver. The proinflammatory and proapoptotic mechanisms were significantly attenuated in rats treated with hepatic sympathetic nerve denervation or catechin (antioxidant) supplement. In conclusion, our results suggest that acute urine retention enhances hepatic sympathetic activity, which causes hepatic vasoconstriction and evokes proinflammatory and proapoptotic oxidative injury in the rat liver. Reduction of the hepatic sympathetic tone or antioxidant supplement significantly attenuates these injuries.

Elimination of rat spinal neurons expressing neurokinin 1 receptors reduces bladder overactivity and spinal c-fos expression induced by bladder irritation

Substance P (SP) binding to neurokinin 1 receptors (NK1R) in the spinal cord reportedly plays an important role in the micturition reflex as well as in nociceptive responses. We therefore investigated the effect of ablation of NK1R-expressing neurons in the spinal cord using saporin, a ribosome-inactivating protein, conjugated with [Sar9, Met (O2)11]SP, a specific ligand of NK1R (SSP-saporin), on the micturition reflex in rats. In female Sprague-Dawley rats, SSP-saporin (1.0 or 1.5 microM) or saporin (1.5 microM) only was injected through an intrathecal catheter implanted at the L6-S1 level of the spinal cord. Three weeks after intrathecal administration of SSP-saporin, NK1R immunoreactivity in lamina I of the spinal cord was significantly reduced, but cystometric parameters in awake rats were not altered. Instillation of capsaicin (15 microM) into the bladder of normal rats induced bladder overactivity. This response to capsaicin was significantly suppressed in SSP-saporin-treated animals. SSP-saporin treatment also decreased c-fos expression in the dorsal horn of the spinal cord induced by instillation of capsaicin into the bladder. These data indicate that NK1R-expressing neurons in the superficial layer of the dorsal horn play an important role in transmission of nociceptive afferent information from the bladder to induce bladder overactivity and spinal c-fos expression elicited by bladder irritation. Toxin-induced damage of NK1R-expressing neurons in the lumbosacral spinal cord may provide an effective modality for treating overactivity and/or nociceptive responses in the bladder without affecting normal micturition.

Effects of isolectin B4-conjugated saporin, a targeting cytotoxin, on bladder overactivity induced by bladder irritation

In order to clarify the functional role of the isolectin B4 (IB4)-binding afferent pathway in the micturition reflex, we investigated the effects on bladder activity of intrathecal application of the IB4-saporin conjugate, a targeting cytotoxin that destroys neurons binding IB4. In rats, IB4-saporin (2.5 micro m) or vehicle was administered through an intrathecal catheter implanted at the level of the L6-S1 spinal cord. Three weeks after IB4-saporin administration, cystometry in conscious animals revealed a reduction in bladder overactive responses induced by intravesical capsaicin or ATP infusion without affecting normal voiding function. In histochemical studies, double staining for IB4 and saporin was detected in L6 dorsal root ganglia (DRG) neurons 2 days after the treatment. Three weeks after the treatment, the area in lamina II of the L6 spinal cord stained with IB4 was significantly reduced compared with the area stained in control rats. The staining in the L1 spinal cord was not affected. The percentage of neurons in the L6 DRG intensely labeled with IB4 was also reduced in IB4-saporin-treated rats. These results indicate that intrathecal treatment with the IB4-saporin conjugate at the level of L6-S1 spinal cord, which reduces IB4 afferent nerve terminal staining in lamina II of the L6 spinal cord as well as the number of IB4-binding neurons in L6 DRG, suppressed bladder overactivity induced by bladder irritation without affecting normal micturition. Thus targeting IB4-binding, non-peptidergic afferent pathways sensitive to capsaicin and adenosine 5'-triphosphate may be an effective treatment for overactivity and/or pain responses in the bladder.

Treatment of interstitial cystitis

Although the symptoms of interstitial cystitis (IC)--a debilitating, chronic disease characterized by urinary urgency and frequency, and bladder and pelvic pain on bladder filling--are easily confused with those of urinary tract infections, there is an absence of an underlying infection, and antibiotic therapy is of no therapeutic benefit. Severe cases of this disorder, which affects mainly women, can have a great negative impact on the quality of life of patients because of extreme urinary frequency. The diagnosis of IC is difficult and should be based on patient history, physical examination, and cystoscopy. A large number of pharmacologic treatments have been used to treat this condition with limited success, including pentosan polysulfate, heparin, antihistamines, tricyclic antidepressants, intravesical dimethyl sulfoxide, and bacille Calmette-Guérin. Among the potentially effective new treatment modalities currently under investigation are suplatast tosilate, resiniferatoxin, botulinum toxin, and gene therapy to modulate the pain response. As knowledge of the pathogenesis of IC increases through intensified research, the ability to provide effective treatment to patients with this disease will improve.

Suppression of detrusor-sphincter dyssynergia by immunoneutralization of nerve growth factor in lumbosacral spinal cord in spinal cord injured rats

PURPOSE

We investigated the effects of intrathecal application of nerve growth factor (NGF) antibodies (NGF-Abs) and desensitization of C-fiber afferent pathways by capsaicin treatment on detrusor-sphincter dyssynergia (DSD) after spinal cord injury (SCI).

MATERIALS AND METHODS

In adult female rats SCI was induced by complete transection of the spinal cord at Th8 to 9. Ten days after spinalization vehicle or NGF-Ab (10 microg daily) was continuously administered at the level of the L6-S1 spinal cord through an implanted intrathecal catheter connected to an osmotic pump for 2 weeks. Another group of spinalized rats was treated with capsaicin (125 mg/kg subcutaneously) 3 weeks after spinalization and 5 days before experiments. Simultaneous recordings of intravesical pressure and urethral perfusion pressure were then performed. NGF levels in the L6 spinal cord were measured in vehicle or NGF-Ab treated spinalized rats using enzyme-linked immunosorbent assay.

RESULTS

DSD was observed in all vehicle treated spinalized rats. The average urethral pressure increase at the peak bladder contraction was significantly lower by 84% and 78% in NGF-Ab and capsaicin treated spinalized rats, respectively, than in vehicle treated rats. After NGF-Ab treatment NGF levels were significantly decreased by 38% in the L6 spinal cord compared with vehicle treated spinalized rats, in which NGF levels in the L6 spinal cord were 7 times higher than in spinal intact rats.

CONCLUSIONS

Increased levels of NGF in the spinal cord could contribute to the emergence of DSD that is at least in part mediated by C-fiber bladder afferents after SCI. Thus suppression of NGF levels in afferent pathways could be useful for treating DSD following SCI.

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.