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

Circadian Rhythms Fluctuate the Treatment Effects of Intravesical Treatments on Rat Urinary Frequency Models

Objectives

It is still not clear how the intravesical instillation of drugs affects rat urinary frequency. This study aimed to examine the dynamics of intravesical treatments' treatment effect on rat urinary frequency models by real-time and extended monitoring using a novel continuous urination monitoring system.

Methods

Nine eleven-week-old female Wistar rats were divided into three groups to receive intravesical instillation of 0.1% acetic acid (AA), 1.0% AA, or phosphate-buffered saline (PBS). Thirty minutes later, these drugs were voided, and rats were moved to a continuous urination monitoring system, UM-100. UM-100 monitored rat urination quantitatively and continuously for 24 hours. Rats were then euthanized, and histopathologic examinations using a damage score validated the severity of bladder inflammation. We used nine additional rats to determine the treatment effect of various drugs against the urinary frequency. These rats were also treated with 1.0% AA in the same way and divided into three groups (n = 3 each) to receive intravesical instillation of lidocaine, silver nitrate (AgNO3), or dimethyl sulfoxide (DMSO), respectively. Thirty minutes later, rats were catheterized again and moved to the UM-100, and their voiding was monitored for 24 hours.

Results

Intravesical instillation of AA increased the urinary frequency and decreased the mean voided volume (VV) in a concentration-dependent manner, with statistical significance at a concentration of 1.0% (urinary frequency; p=0.0007, mean VV; p=0.0032, respectively) compared with PBS. Histopathological analysis of these models demonstrated a significantly higher damage score of bladder mucosa in both 0.1% AA and 1.0% AA compared with PBS, with the severity in concordance with the clinical severity of urinary frequency (0.1% AA: p < 0.0001, 1.0% AA: p < 0.0001). Moreover, intravesical instillation of lidocaine, AgNO3, and DMSO decreased the urinary frequency. Continuous monitoring with UM-100 also demonstrated that the treatment effect of these intravesically instilled drugs occurred only at night.

Conclusions

The extended monitoring of rat urination by UM-100 revealed a significant fluctuation in the treatment effect of intravesically instilled drugs between day and night. These findings may help establish novel therapies for urinary frequency.

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.

Antidiuretic effect of antimuscarinic agents in rat model depends on C-fibre afferent nerves in the bladder

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Antichollnergic agents are anticipated to diminish storage symptoms, as well as nocturia. Nevertheless, the effect of this treatment on polyuria related to nocturia is not clear. By subgroup analysis of the data set from a phase III clinical trial of antimuscarinic agent for OAB patients in Japan, imidafenacin was found to improve nocturia with a reduction in nocturnal polyuria. This study adds the effects and underlying mechanism of antimuscarinic agents decreasing urine production through inhibition of C-fibre in the bladder of water-leaded rats.

OBJECTIVE

To evaluate the effects and underlying mechanisms of antimuscarinic agents used to decrease in urine production in water-loaded rats.

SUBJECTS AND METHODS

Urine production was measured using a cystostomy catheter in female Sprague-Dawley rats every 2 h. The effect of the antimuscarinic agents atropine, tolterodine and imidafenacin on urine production was investigated under water-loaded conditions, which were induced by i.p. injection of 15 mL saline. Blood samples were collected to determine the levels of antidiuretic hormone (ADH), aldosterone (ALD), atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) before, and 2 and 8 h after, antimuscarinic agent administration. To induce desensitization of C-fibre afferent nerves, resiniferatoxin (RTX)was injected s.c. or intravesically 2 days before experiments.

RESULTS

Urine production increased and reached its maximum 2 h after 15 mL saline injection. Imidafenacin and tolterodine decreased urine production in water-loaded rats, but ADH, ALD, ANP and BNP levels were not different between imidafenacin-treated and vehicle-treated rats. The inhibitory effect on urine production was not found in RTX-treated rats. Atropine did not reduce urine production.

CONCLUSION

These results suggest that antimuscarinic agents decrease urine volume through C-fibres in the bladder; thus, antimuscarinics with inhibitory effects on C-fibres could be beneficial for nocturia with nocturnal polyuria.

Efficacy of neuroselective and site-specific nociceptive stimuli of rat bladder

OBJECTIVE

To evaluate the organ specificity of sine wave electrical stimulation of the bladder through assessment of the expression of Fos-immunoreactive (IR) cells in rat spinal cord regions.

METHODS

A total of 37 female Sprague-Dawley rats were divided into 8 groups: sham stimulation; 5, 250, and 2000 Hz stimulation with 1.5- or 2.0-mA intensity; and a group instilled with capsaicin in the bladder. Using a recently developed bladder sensory threshold device, sine wave electrical stimulation was applied for 90 minutes to the rat bladder. The spinal cord was harvested after the rats were killed. The Fos-IR cells in the spinal regions of the medial dorsal horn, lateral dorsal horn, dorsal commissure, and sacral parasympathetic nucleus were measured. The distributions of the Fos-IR neurons were compared.

RESULTS

The maximal expression of Fos-IR cells, induced by 250- and 5-Hz stimulation of the bladder, was found at L6 of the spinal cord and was significantly greater than that in the control group (P<.01). Stimulation with 2000 Hz did not induce any Fos-IR cells. Fos-IR neurons were predominantly seen in the sacral parasympathetic nucleus region in response to 250-Hz stimulation and in the dorsal commissure region in response to 5-Hz stimulation. The number of positive neurons was similar to the number caused by capsaicin instillation.

CONCLUSION

Frequency-specific sine wave electrical stimulation of the rat bladder induced the expression of Fos-IR cells in a neuroselective manner. The bladder sensory threshold device could be used for exploration of the pathophysiology of diseases with disturbances of the afferent pathway of the bladder.

Autoimmunity to uroplakin II causes cystitis in mice: a novel model of interstitial cystitis

BACKGROUND

The pathophysiology of interstitial cystitis (IC) is unknown. Deficits in urothelial cell layers and autoimmune mechanisms may play a role.

OBJECTIVE

To examine whether immunization of mice with recombinant mouse uroplakin II (rmUPK2), a bladder-specific protein, would provoke an autoimmune response sufficient to create an IC phenotype.

DESIGN, SETTING, AND PARTICIPANTS

RmUPK2 complementary DNA was generated, transferred into a bacterial expression vector, and the generated protein was purified. Eight-week-old SWXJ female mice were immunized with rmUPK2 protein via subcutaneous injection of 200μg of rmUPK2 protein in 200μl of an emulsion.

MEASUREMENTS

Mice were euthanized 5 wk after immunization. Axillary and inguinal lymph node cells were tested for antigen-specific responsiveness and cytokine production, serum isotype antibody titers against rmUPK2 were determined, and gene expression of inflammatory mediators was measured in the bladder and other organs. For functional analysis, mice were placed in urodynamic chambers for 24-h micturition frequency and total voided urine measurements.

RESULTS AND LIMITATIONS

Immunization with rmUPK2 resulted in T-cell infiltration of the bladder urothelium and increased rmUPK2-specific serum antibody responses in the experimental autoimmune cystitis (EAC) mice models compared with controls. The ratio of bladder to body weight was increased in EAC mice. Quantitative reverse transcriptase polymerase chain reaction analysis showed elevated gene expression of tumor necrosis factor α, interferon γ, interleukin (IL)-17A, and IL-1β in bladder urothelium but not in other organs. Evaluation of 24-h micturition habits of EAC mice showed significantly increased urinary frequency (p<0.02) and significantly decreased urine output per void (p<0.021) when compared with control mice.

CONCLUSIONS

Our study showed that a bladder-specific autoimmune response sufficient to induce inflammation and EAC occurs in mice following immunization with rmUPK2. EAC mice displayed significant evidence of urinary frequency and decreased urine output per void. Further phenotype characterization of EAC mice should include evidence for pain and/or afferent hypersensitivity, and evidence of urothelial cell layer damage.

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.

Lower urinary tract phenotype of experimental autoimmune cystitis in mouse: a potential animal model for interstitial cystitis

OBJECTIVE

To examine bladder function in a newly developed experimental autoimmune cystitis (EAC) model in female SWXJ strain mice, as a potential animal model for interstitial cystitis (IC).

MATERIALS AND METHODS

In all, 20 SWXJ female mice were divided into two groups: an EAC group immunized with mouse bladder homogenate in complete Freund's adjuvant (CFA) and a control group immunized with CFA alone. At 4 months after injection, the bladder function of some mice (six) was studied with 24-h micturition habits using metabolic cages and conscious cystometrography (CMG). The bladder and lung were harvested for histological examination and to assess interferon-gamma (IFN-gamma) mRNA expression.

RESULTS

Histology examination showed obviously thickened lamina propria, infiltration of lymphocytes, giant cells, and increased mast cells in the detrusor muscle of the EAC mice. The lungs of EAC mice showed normal histology. The IFN-gamma mRNA expression increased significantly in the bladder, but not in the lung of the EAC mice. The 24-h micturition habits measurements showed increased frequency of urination in the EAC mice compared with the controls. Similarly, CMG showed decreased intercontraction intervals and voided volumes per micturition in the EAC mice compared with the controls. However, there were no significant differences in peak voiding pressure or total voiding volume between the EAC and control mice.

CONCLUSIONS

Our murine EAC model has comparable functional and histological alterations to those seen in human IC, and may provide a useful model for the study of the pathogenesis and treatment of IC.