Diabetic plasticity of non-adrenergic non-cholinergic and P2X-mediated rat bladder contractions

We investigated the plasticity effects of diabetes mellitus and diuresis on the non-adrenergic non-cholinergic (NANC) and purinergic (P2X-type) contractile responses in longitudinal rat bladder strips. Female Sprague-Dawley rats received streptozotocin to induce diabetes, or sucrose in water to induce diuresis as a control condition for polyuria. Experiments were carried out at four weeks after treatments, using bladders from non-treated rats as control. Urinary bladder strips were electrically stimulated throughout the experiments to generate neurally evoked contractions (NEC). In all cases, P2X-mediated purinergic contractions were evaluated at the beginning and end of the stimulations with α,β-methylene-adenosine triphosphate (α,βMeATP). The NANC responses were assessed by using two independent protocols. First, cholinergic receptors were activated with carbachol (CCh), followed by inhibition of the muscarinic component with atropine. In the second protocol, the application order for CCh and atropine was reversed. The NANC response, unmasked with the application of atropine, and the P2X purinergic contractions were analyzed. NANC contractions in diabetic bladder strips are more resistant to the desensitizing effects caused by activation of cholinergic receptors. In early stages of experimental diabetes, NANC responses in diabetic strips are less sensitive to functional inhibition mediated by the cholinergic activation. However, P2X-mediated purinergic contractions are more sensitive to desensitization in diabetic or diuretic bladders. For instance preventing muscarinic receptor activation with atropine does not counteract the desensitization of purinergic contractions in either diabetic or diuretic strips. We suggest that diabetes may induce a plasticity of the NANC and P2X-mediated bladder contractile responses. The first one may be associated with diabetic neuropathic damage to bladder nerves, while impaired P2X purinergic contractions might be associated with detrusor hypertrophy observed in diabetic and diuretic strips.

Modulation of bladder afferent signals in normal and spinal cord-injured rats by purinergic P2X3 and P2X2/3 receptors

OBJECTIVE

To evaluate the role of bladder sensory purinergic P2X3 and P2X2/3 receptors on modulating the activity of lumbosacral neurones and urinary bladder contractions in vivo in normal or spinal cord-injured (SCI) rats with neurogenic bladder overactivity.

MATERIALS AND METHODS

SCI was induced in female rats by complete transection at T8-T9 and experiments were performed 4 weeks later, when bladder overactivity developed. Non-transected rats were used as controls (normal rats). Neural activity was recorded in the dorsal horn of the spinal cord and field potentials were acquired in response to intravesical pressure steps via a suprapubic catheter. Field potentials were recorded under control conditions, after stimulation of bladder mucosal purinergic receptors with intravesical ATP (1 mm), and after intravenous injection of the P2X3/P2X2/3 antagonist AF-353 (10 mg/kg and 20 mg/kg). Cystometry was performed in urethane-anaesthetised rats intravesically infused with saline. AF-353 (10 mg/kg) was systemically applied after baseline recordings; the rats also received a second dose of AF-353 (20 mg/kg). Changes in the frequency of voiding (VC) and non-voiding (NVC) contractions were evaluated.

RESULTS

SCI rats had significantly higher frequencies for field potentials and NVC than NL rats. Intravesical ATP increased field potential frequency in control but not SCI rats, while systemic AF-353 significantly reduced this parameter in both groups. AF-353 also reduced the inter-contractile interval in control but not in SCI rats; however, the frequency of NVC in SCI rats was significantly reduced.

CONCLUSION

The P2X3/P2X2/3 receptors on bladder afferent nerves positively regulate sensory activity and NVCs in overactive bladders.

Central inhibitory effect of intravesically applied botulinum toxin A in chronic spinal cord injury

AIMS

We evaluated a putative central inhibitory effect of intravesical botulinum toxin A (BoNT-A) on the activity of lumbosacral spinal neurons in a chronic spinal cord injury (SCI) model of bladder overactivity.

METHODS

Female Sprague-Dawley rats underwent T8 spinal cord transection. Four weeks later, once overactive neuropathic detrusor pathways had developed, the animals underwent intravesical instillation with either saline (1 ml) or BoNT-A (Botox®, 20 U/1 ml) for 1 hr. Two days later, the rats then completed a cystometric evaluation prior to spinal cord harvest. Sections from the L4-S1 spinal cord segments were examined for the total number of c-fos immunoreactive cells.

RESULTS

Comparison of the saline and BoNT-A treated groups showed a significant decrease in L6 (i.e., 67%, P < 0.001) and S1 (i.e., 47%, P < 0.01) c-fos expression (43%) in BoNT-A treated rats compared to saline controls. Cystometrogram studies revealed that the frequency of non-voiding bladder contractions was reduced by 73% (P < 0.05) in BoNT-A compared to saline treated rats. No change in the frequency of voiding bladder contractions or amplitude of bladder contraction was observed between the saline and BoNT-A treated groups.

CONCLUSION

In a SCI model of bladder overactivity, intravesical BoNT-A significantly inhibits the response of bladder afferent activated lumbosacral neurons without significantly impairing efferent bladder function.

Overactive and underactive bladder dysfunction is reflected by alterations in urothelial ATP and NO release

ATP and NO are released from the urothelium in the bladder. Detrusor overactivity (DO) following spinal cord injury results in higher ATP and lower NO release from the bladder urothelium. Our aim was to study the relationship between ATP and NO release in (1) early diabetic bladders, an overactive bladder model; and (2) "diuretic" bladders, an underactive bladder model. To induce diabetes mellitus female rats received 65mg/kg streptozocin (i.v.). To induce chronic diuresis rats were fed with 5% sucrose. At 28 days, in vivo open cystometry was performed. Bladder wash was collected to analyze the amount of ATP and NO released into the bladder lumen. For in vitro analysis of ATP and NO release, a Ussing chamber was utilized and hypoosmotic Krebs was perfused on the urothelial side of the chamber. ATP was analyzed with luminometry or HPLC-fluorometry while NO was measured with a Sievers NO-analyzer. In vivo ATP release was increased in diabetic bladders and unchanged in diuretic bladders. In vitro release from the urothelium followed the same pattern. NO release was unchanged both in vitro and in vivo in overactive bladders whereas it was enhanced in underactive bladders. We found that the ratio of ATP/NO, representing sensory transmission in the bladder, was high in overactive and low in underactive bladder dysfunction. In summary, ATP release has a positive correlation while NO release has a negative correlation with the bladder contraction frequency. The urinary ATP/NO ratio may be a clinically relevant biomarker to characterize the extent of bladder dysfunction.

Removal of urothelium affects bladder contractility and release of ATP but not release of NO in rat urinary bladder

Background

The objective of our work was to investigate both the contractile function and the release of ATP and NO from strips of bladder tissue after removal of the urothelium.

Methods

The method of removal was a gentle swabbing motion rather than a sharp surgical cutting to separate the urothelium from the smooth muscle. The contractile response and ATP and NO release were measured in intact as well as on swabbed preparations. The removal of the urothelial layer was affirmed microscopically.

Results

After the swabbing, the smaller contractions were evoked by electrical as well as by chemical stimulation (50 μM carbachol or 50 μM α, β meATP). Electrical stimulation, carbachol and substance P (5 μM) evoked lower release of ATP in the swabbed strips than in intact strips. Although release of NO evoked by electrical stimulation or substance P was not changed, release of NO evoked by carbachol was significantly less in the swabbed preparations.

Conclusion

Since swabbing removes only the urothelium, the presence of the suburothelial layer may explain the difference between our findings and those of others who found an increase in contractility. Evoked release of ATP is reduced in swabbed strips, indicating that ATP derives solely from the urothelium. On the other hand, electrical stimulation and substance P evoke identical degrees of NO release in both intact and swabbed preparations, suggesting that NO can be released from the suburothelium. Conversely, carbachol-induced release of NO is lower in swabbed strips, implying that the cholinergic receptors (muscarinic or nicotinic) are located in the upper layer of the urothelium.

Activation of cholinergic receptors blocks non-adrenergic non-cholinergic contractions in the rat urinary bladder

In the present study, the plasticity of the non-adrenergic non-cholinergic (NANC) response was investigated. Isolated rat bladder strips were electrically stimulated and the evoked contractions were isometrically recorded. The NANC part of the contractions were unmasked by applying 500 nM 4-DAMP, a potent muscarinic antagonist. Treatment of the bladder strips with 10 microM carbachol (a cholinergic agonist) increased the muscle tone but did not alter the neurally evoked contractions. However, carbachol decreased: (1) the NANC response from 74.6% to 33.3% of control and (2) the purinergic contractile response to alpha,beta-methylene ATP (alpha,beta-mATP) (10 microM) from 97.0% to 43.4% (p<0.05). Treatment with the cholinesterase inhibitor eserine (10 microM) also significantly decreased the NANC response to 21.1% (p<0.0001). The purinergic receptor antagonist suramin (100 microM) did not affect the neurally evoked contractions, however; subsequent addition of 4-DAMP decreased the contractions to 31%. Activation of the smooth muscle cholinergic receptors (with carbachol or eserine) and purinergic receptors (with alpha,beta-mATP) decreased the NANC contractions and the direct contractile response to alpha,beta-mATP. When the electrically evoked contractions were facilitated by the L-type Ca2+ channel activator, Bay-K 8644 the subsequent application of 4-DAMP did not unmask inhibited NANC contractions. We conclude that activation of muscarinic receptors by cholinergic agonist, carbachol or by endogenous acetylcholine (ACh) induce a cascade of events that leads to diminished purinergic response and consequently an inhibition of the bladder NANC response.

Botulinum toxin type A normalizes alterations in urothelial ATP and NO release induced by chronic spinal cord injury

The purpose of this paper was to simultaneously examine changes in urothelial ATP and NO release in normal and spinal cord injured animals as well as in spinal cord injured animals treated with botulinum toxin type A (BoNT-A). Furthermore we correlated changes in transmitter release with functional changes in bladder contraction frequency, and determined the effects of BoNT-A on bladder efferent nerve function. Normal and spinal cord injured rat bladders were injected on day 0 with either vehicle (saline containing bovine serum albumin) or BoNT-A. On day 2, in vitro neurotransmitter release and bladder strip contractility studies as well as in vivo cystometrographic studies were conducted. Resting ATP release was significantly enhanced following spinal cord injury (i.e. 57% increase, p<0.05) and was unaffected by BoNT-A treatment. SCI increased hypoosmotic evoked urothelial ATP release by 377% (p<0.05). BoNT-A treatment reduced evoked ATP release in SCI bladders by 83% (p<0.05). In contrast, hypoosmotic stimulation induced NO release was significantly inhibited following SCI (i.e. 50%, p<0.05) but recovered in SCI rats treated with BoNT-A (i.e. 195% increase in NO release in SCI-BTX-treated rats compared to SCI controls, p<0.01). Changes in urothelial transmitter release coincided with a significant decrease in non-voiding bladder contraction frequency (i.e. 71%, p<0.05) in SCI-BTX rats compared to SCI rats. While no difference was measured between neurally evoked contractile amplitude between SCI and SCI-BTX animals, atropine (1 microM) inhibited contractile amplitude to a greater extent (i.e. 76%, p<0.05) in the SCI-BTX group compared to the SCI group. We hypothesize that alterations in the ratio of excitatory (i.e. ATP) and inhibitory (i.e. NO) urothelial transmitters promote bladder hyperactivity in rat bladders following SCI that can be reversed, to a large extent, by treatment with BoNT-A.

Comparison of cystometric methods in female rats

AIMS

Rat cystometry is a common model used to investigate urinary storage and voiding function. The effect of cystometric instrumentation in rat studies might be a source of deviation from normal physiologic responses. We hypothesized that transurethral catheterization would produce obstruction-related changes, and that suprapubic catheterization would limit volume-related functions as well as disrupt normal urothelial sensory function. We investigated the influence of transurethral and suprapubic catheterization on storage and voiding in the rat model.

METHODS

Three groups of female SD rats 250-300 g under urethane anesthesia were studied. Cystometric and pseudoaffective responses to physiologic voiding with and without suprapubic catheter placement, and cystometry via suprapubic and transurethral catheterization were studied.

RESULTS

In free-voiding animals, per-void volume was 1.8 +/- 0.2 ml with an average flow rate of 0.18 ml/sec, and intercontraction interval (ICI) 60 min. Suprapubic catheterization decreased the ICI and per-void volume consistent with capacity reduction. Suprapubic cystometry did not significantly alter parameters compared to voiding except for a shortened ICI. Bladder pressures and somatic responses were increased, and urine flow impaired by transurethral cystometry. Terazosin did not significantly improve voiding parameters.

CONCLUSIONS

Other than volume-related parameter changes probably related to surgical compromise of bladder capacity, suprapubic catheterization does not alter the cystometric and physiologic responses to voiding when compared to normal, uninstrumented voiding. Transurethral cystometry appears to be obstructive and may activate nociceptive reflexes. For this reason, whenever possible, urodynamic testing using the rat model should employ suprapubic catheterization.

The role of the prostacyclin receptor antagonist RO3244019 in treating neurogenic detrusor overactivity after spinal cord injury in rats

OBJECTIVE

To determine the effects of the prostacyclin receptor (IP) antagonist RO3244019 on neurogenic detrusor overactivity (NDO) in spinal cord-injured (SCI) neurogenic bladder of the rat.

MATERIALS AND METHODS

Female Sprague-Dawley rats with SCI were divided into four treatment groups of eight each: vehicle (200 mm Tris base), indomethacin (3 mg/kg), RO3244019 (at 1 and 5 mg/kg). The conscious rats were assessed by cystometry, by slowly infusing the bladder with physiological normal saline at 0.04 mL/min. After 1 h of cystometry one of the four compounds was administered intravenously to the rats and changes in cystometrogram tracings recorded. Seven voiding variables were calculated before and after administering each compound: the intercontractile interval (ICI) for all contractions, voiding ICI, amplitude of all contractions, amplitude of voiding contractions, time to first void (TFV), voided volumes (VVs), and first VV. Data were analysed using a paired t-test for each of the experiments.

RESULTS

At 1 mg/kg, the RO compound was associated with a statistically significant difference in the voiding ICI and VVs (both P < 0.05). The mean (sd) voiding ICI increased from 621 (140) to 889 (119) s (43% increase) and the VVs from 0.53 (0.13) to 0.72 (0.09) mL (36% increase). However, there was no statistically significant difference in the TFV or the first VVs. Increasing the dose to 5 mg/kg was more effective in improving the voiding ICI and the VVs (both P < 0.01). The voiding ICI increased from 716 (130) to 1346 (159) s (88% increase) and the VVs from 0.60 (0.11) to 1.05 (0.12) mL (75% increase). In addition, the higher dose had a statistically significant difference in the TFV (P < 0.05). There was more than a four-fold increase in the TFV, from 807 (138) to 3239 (883) s. At 5 mg/kg, the difference in the first VV before and after administering the compound was also almost statistically significant (P = 0.057); the first VV increased from 0.56 (0.14) to 1.01 (0.21) mL. There were no statistically significant differences in the amplitude of contractions or the ICI for all contractions for either of the dosages. Indomethacin at 3 mg/kg was the most effective compound for improving all of the voiding variables and was the only one to show a significant difference in the first VV. However, the IP antagonist at 5 mg/kg was almost as effective as indomethacin when comparing other variables, e.g. the voiding ICI and the VV. There was no statistically significant difference in any of the seven voiding variables before and after administering the vehicle.

CONCLUSION

The IP antagonist RO3244019 was effective in treating NDO in SCI bladders. While RO3244019 at 1 mg/kg significantly increased the voiding ICI and VVs, 5 mg/kg appeared to be more effective, suggesting a dose-dependent effect of the drug. The RO compound at 5 mg/kg was almost as effective as indomethacin in improving all of the voiding variables.

Using Caveolin-1 Knockout Mouse to Study Impaired Detrusor Contractility and Disrupted Muscarinic Activity in the Aging Bladder

OBJECTIVES

The caveolin-1 knockout mouse has been proposed as an animal model to study impaired bladder contractility and detrusor overactivity. This study investigated the effects of aging on detrusor contraction in wild type and caveolin-1 knockout mice.

METHODS

Young (3-month-old) and old (1-year-old) male caveolin-1 knockout mice and their age-matched male wild type littermates (controls) were used. Longitudinal bladder strips were stimulated electrically (20 Hz) and pharmacologically using 1 to 10 microM carbachol (a nonsubtype selective cholinergic receptor agonist), 10 microM alpha,beta-methylene adenosine triphosphate (a purinergic receptor agonist), and 100 mM potassium (a depolarizing agent). Isometric bladder strip contractions were compared between the young wild type and knockout groups and between the old wild type and knockout groups.

RESULTS

The bladder strips from the 1-year-old knockout mice exhibited a 40% to 42% decrease in electrical neural contractions and carbachol-evoked contractions compared with the 1-year-old wild type controls (P <0.05). Even though the bladder strips from the 3-month-old knockout mice demonstrated a smaller decrease (29% to 32%) in electrical neural contractions and carbachol-evoked contractions compared with their age-matched controls, the trend did not reach statistical significance (P >0.05). The postjunctional cholinergic pathway was specifically disrupted in caveolin-1 knockout animals because no difference was found in contractility between the knockout and wild type mice (young or old) when the bladders were stimulated by alpha,beta-methylene adenosine triphosphate or potassium. The differences in cholinergic contractility between the knockout and wild type mice became significantly greater as the animals aged from 3 months old (young bladders) to 1 year old (aged bladders).

CONCLUSIONS

The male caveolin-1 knockout mouse provides a much-needed animal model for the study of impaired detrusor contractility in the aging bladder.

Receptor activated bladder and spinal ATP release in neurally intact and chronic spinal cord injured rats

Neurally intact (NI) rats and chronic spinal cord injured (SCI) rats were studied to determine how activation of mechanosensory or cholinergic receptors in the bladder urothelium evokes ATP release from afferent terminals in the bladder as well as in the spinal cord. Spinal cord transection was performed at the T(9)-T(10) level 2-3 weeks prior to the experiment and a microdialysis fiber was inserted in the L(6)-S(1) lumbosacral spinal cord one day before the experiments. Mechanically evoked (i.e. 10 cm/W bladder pressure) ATP release into the bladder lumen was approximately 6.5-fold higher in SCI compared to NI rats (p<0.05). Intravesical carbachol (CCh) induced a significantly greater release of ATP in the bladder from SCI as compared to NI rats (3424.32+/-1255.57 pmol/ml versus 613.74+/-470.44 pmol/ml, respectively, p<0.05). However, ATP release in NI or SCI rats to intravesical CCh was not affected by the muscarinic antagonist atropine (Atr). Spinal release of ATP to bladder stimulation with 10 cm/W pressure was five-fold higher in SCI compared to NI rats (p<0.05). CCh also induced a significantly greater release of spinal ATP in SCI rats compared to controls (4.3+/-0.9 pmol versus 0.90+/-0.15 pmol, p<0.05). Surprisingly, the percent inhibitory effect of Atr on CCh-induced ATP release was less pronounced in SCI as compared to NI rats (49% versus 89%, respectively). SCI induces a dramatic increase in intravesical pressure and cholinergic receptor evoked bladder and spinal ATP release. Muscarinic receptors do not mediate intravesical CCh-induced ATP release into the bladder lumen in NI or SCI rats. In NI rats sensory muscarinic receptors are the predominant mechanism by which CCh induces ATP release from primary afferents within the lumbosacral spinal cord. Following SCI, however, nicotinic or purinergic receptor mechanisms become active, as evidenced by the fact that Atr was only partially effective in inhibiting CCh-induced spinal ATP release.

In vivo effects of botulinum toxin A on visceral sensory function in chronic spinal cord-injured rats

OBJECTIVES

To analyze the in vivo effects of botulinum toxin type A (BTX-A) on visceral sensory function in chronic spinal cord-injured (SCI) rats.

METHODS

One group of rats underwent spinal cord transection at the T8-T9 level (SCI) and the other group was left untreated. In 21 days, baseline open cystometrography (CMG) was performed. The rats were then treated intravesically with either 1 mL of 1% protamine sulfate (PS) to increase urothelial permeability or saline, followed by either 1 mL of BTX-A (20 U) or saline. CMG was repeated 48 hours after instillation, and any changes in the bladder contraction frequency and amplitude were evaluated.

RESULTS

After the instillation of PS and BTX-A or BTX-A alone, the bladder contraction frequency was significantly decreased in the SCI rats compared with the control rats (P < 0.05); no change was seen in the contraction amplitude. When normal rats were given intravesical PS and/or BTX-A, or SCI animals were treated with PS alone, neither the frequency nor the amplitude of the contractions was affected. Also, no significant differences were found in the bladder contraction frequency or amplitude of contractions in any animal treated with instillation of saline alone.

CONCLUSIONS

Intravesical BTX-A inhibits bladder sensory mechanisms by reducing the frequency of bladder contractions in an SCI rat model. Furthermore, our results suggest that intravesically applied BTX-A does not penetrate to the smooth muscle layer even after PS disruption of the bladder urothelium. These findings may have important clinical applications in treating overactive bladders after SCI.

Enhanced ATP release from rat bladder urothelium during chronic bladder inflammation: Effect of botulinum toxin A

The effects of mechanoreceptor stimulation and subsequent ATP release in cyclophosphamide evoked chronic bladder inflammation was examined to demonstrate: (1) whether inflammation modulates ATP release from bladder urothelium and (2) whether intravesical botulinum toxin A administration inhibits urothelial ATP release, a measure of sensory nerve activation. ATP release was measured from rat bladders in a Ussing chamber, an apparatus that allows one to separately measure resting and mechanoreceptor evoked (e.g. hypoosmotic stimulation) ATP release from urothelial and serosal sides of the bladder. Cystometry was utilized to correlate changes in ATP release with alterations in the frequency of voiding and non-voiding bladder contractions, in vivo measures of bladder afferent activity. The resting urothelial release of ATP was not significantly affected by either cyclophosphamide or botulinum toxin A treatment. However, evoked ATP release following hypoosmotic stimulation was significantly increased (i.e. 94%) in chronic cyclophosphamide treated bladder urothelium compared to control bladders. In addition, botulinum toxin A treatment significantly reduced hypoosmotic shock induced ATP release in cyclophosphamide treated animals by 69%. Cystometry revealed that cyclophosphamide and botulinum toxin A treatments altered non-voiding (i.e. cyclophosphamide increased, botulinum toxin A decreased) but not voiding contraction frequency suggesting that alterations in urothelial ATP release selectively diminished underlying bladder C-fiber nerve activity. Finally, intravesical instillation of botulinum toxin A did not affect ATP release from the serosal side implying that its effects were confined to the urothelial side of the bladder preparation.

Age-dependence of the spontaneous activity of the rat urinary bladder

Abnormal mechanical function of the bladder is manifested in a number of ways including higher frequency of involuntary detrusor contractions associated with reduced compliance of the bladder that is responsible for an increase in intraluminal pressure during filling. There are basically two ways to approach experimentally these problems: (1) by studying the neural control of the lower urinary tract function, and (2) by measuring the properties of smooth muscle cells in the bladder wall. Studies on smooth muscle function often do not take the origin of smooth muscle cells into account i.e., whether they were harvested from normal or overactive bladders. Although, this simplistic view may be beneficial to understanding the generation of the spontaneous activity of the bladder, however, it does not sufficiently explain the cell-to-cell propagation of the spontaneous smooth muscle activity. The spontaneous activity of smooth muscle is an important factor that works against the bladder compliance in the filling phase, and may inversely affect the neurally evoked response during micturition. The intensity of spontaneous activity is the age-dependent; it is high in neonatal bladders it is small or almost non-existent in adults and reemerges in older bladders. This review focuses on these age-dependent alterations of spontaneous bladder contractions and describes the possible mechanisms which may have important role in regulating the spontaneous contractions using the rat as an animal model.

Inhibitory effect of intravesically applied botulinum toxin A in chronic bladder inflammation

PURPOSE

We evaluated a putative inhibitory effect of intravesical botulinum toxin A (BTX-A) on afferent pathways in conditions of chronic bladder inflammation.

MATERIALS AND METHODS

Female Sprague-Dawley rats were divided into 4 groups, namely group 1-saline treated, group 2-BTX-A treated, group 3-cyclophosphamide (CYP) treated and group 4-BTX-A and CYP treated. At the beginning of the treatment period all animals received intravesical protamine sulfate (1%), followed by intravesical BTX-A or saline. Subsequently CYP or saline was injected intraperitoneally every 3 days for 10 days. The rats then underwent cystometrogram evaluation prior to spinal cord harvest. Sections from the L6 and S1 spinal cord segments were examined for the total number of Fos immunoreactive cells.

RESULTS

Comparisons of the L6 and S1 sections showed a significant difference among groups (p <0.05). CYP treated animals had a significant increase in L6 and S1 (78% and 107%, respectively) c-fos expression compared with saline controls (p <0.001). Comparison of the CYP and BTX-A/CYP groups showed a significant decrease in L6 and S1 in c-fos expression (50% and 52%, respectively) in the BTX-A/CYP treated group (p <0.001). No significant difference was present between the saline and BTX-A alone groups. Cystometrogram studies revealed that the nonvoiding intercontractile interval increased by more than 10-fold in BTX-A/CYP treated animals compared with CYP treated rats (p <0.01).

CONCLUSIONS

In a CYP model of chronic bladder inflammation intravesical BTX-A significantly inhibits the afferent neural response without impairing efferent bladder function.

A case for botulinum toxin-A in idiopathic bladder overactivity

Botulinum toxin (BTX) has been shown to be an effective agent in suppressing detrusor overactivity due to neurogenic causes. Similar to results obtained with traditional agents to treat bladder overactivity (ie, antimuscarinic medications), the use of BTX has been extended to patients with idiopathic detrusor overactivity. This article briefly reviews the use of BTX to treat disorders of detrusor overactivity and, based on early clinical and laboratory results, establishes the case for its use as a therapeutic modality to treat idiopathic detrusor overactivity.

Loss of caveolin-1 expression is associated with disruption of muscarinic cholinergic activities in the urinary bladder

Caveolin-1 (Cav1), a structural protein of caveolae, plays cell- and context-dependent roles in signal transduction pathway regulation. We have generated a knockout mouse homozygous for a null mutation of the Cav1 gene. Cav1 knockout mice exhibited impaired urinary bladder contractions in vivo during cystometry. Contractions of male bladder strips were evoked with electric and pharmacologic stimulation (5-40 Hz, 1-10 microM carbachol, 10 mM alpha,beta-methylene ATP, 100 mM KCl). Acetylcholine (ACh) and norepinephrine (NE) release from bladder strips were measured with a radiochemical method by incubating the strips with 14C-choline and 3H-NE prior to electric stimulation, whereas ATP release was measured using the luciferin-luciferase assay with a luminometer. A 60-75% decline in contractility was observed when Cav1 knockout muscle strips were stimulated with electric current or carbachol, compared to wildtype muscle strips. No difference in contractility was noted when contractions were evoked either by the purinergic agonist alpha,beta-methylene ATP, or by extracellular potassium. To investigate the relative contribution of non-cholinergic activity to bladder contractility, the amplitude of the electric stimulation-evoked contractions was compared in the presence of the muscarinic antagonist atropine (1 microM). While the non-muscarinic (purinergic) response was unaltered, muscarinic cholinergic response was principally disrupted in Cav1 knockout mice. The loss of Cav1 gene expression was also associated with a 70% reduction in ACh release. NE and ATP release was not altered. It is concluded that the loss of caveolin-1 is associated with disruption of M3 muscarinic cholinergic activity in the bladder. Both pre-junctional (acetylcholine neurotransmitter release from neuromuscular junctions) and post-junctional (M3 receptor-mediated signal transduction in bladder smooth muscles) mechanisms are disrupted, resulting in impaired bladder contraction.

Botulinum toxin A inhibits ATP release from bladder urothelium after chronic spinal cord injury

The effects of mechanoreceptor stimulation and subsequent ATP release in spinal cord injured and normal bladders was examined to demonstrate if spinal cord injury (SCI) modulates the basal or evoked release of ATP from bladder urothelium and whether intravesical botulinum toxin A (BTX-A) administration inhibits urothelial ATP release, a measure of sensory nerve activation. A Ussing chamber was used to isolate and separately measure resting and mechanoreceptor evoked (e.g. hypoosmotic stimulation) ATP release from urothelial and serosal sides of the bladder. Following spinal cord injury, resting urothelial release of ATP was ninefold higher than that of normal rats. Botulinum toxin A instillation did not significantly affect the resting release of ATP after spinal cord injury. Evoked ATP release following hypoosmotic stimulation was significantly higher in chronic spinal cord injured compared to normal rat bladders. However, botulinum toxin A treatment markedly reduced ATP release in spinal cord injured bladders by 53% suggesting that ATP release by mechanoreceptor stimulation, as opposed to basal release, occurs by exocytotic mechanisms. In contrast, there was no significant difference in basal or evoked ATP release from bladder serosa following spinal cord injury. Moreover, intravesical instillation of botulinum toxin A did not affect ATP release from the serosal side after spinal cord injury, suggesting that its effects were confined to the urothelial side of the bladder preparation. In summary: (1) increased release of ATP from the urothelium of spinal cord injured bladders may contribute to the development of bladder hyperactivity and, (2) mechanoreceptor stimulated vesicular ATP release, as opposed to basal non-vesicular release of ATP, is significantly inhibited in spinal cord injured bladders by intravesical instillation of botulinum toxin A. These results may have important relevance in our understanding of the mechanisms underlying plasticity of bladder afferent pathways following SCI.

Botulinum toxin in urology: evaluation using an evidence-based medicine approach

Clinical reports documenting the beneficial effects of botulinum toxin (BTX) to treat various lower urinary tract disorders of muscle spasticity (e.g. detrusor hyperreflexia, detrusor sphincter dyssynergia) have led to its expanded application in non-neurogenic conditions such as idiopathic detrusor overactivity, detrusor underactivity and benign prostatic hyperplasia (BPH). As greater numbers of investigators report their results utilizing this agent, it becomes more important that clinicians are able to synthesize and describe the findings of current clinical studies in a meaningful way. Evidence-based medicine is a platform on which investigations concerning a particular topic can be evaluated for their levels of scientific evidence, so that rational clinical recommendations can be formulated. This review article applies evidence-based practices to the use of BTX in common urologic conditions. Appreciating the benefits as well as limitations of currently available studies will hopefully drive the development of well-controlled, randomized studies of BTX, particularly in highly prevalent conditions such as idiopathic detrusor overactivity and BPH.

Botulinum toxin a has antinociceptive effects in treating interstitial cystitis

OBJECTIVES

To present clinical evidence with botulinum toxin A (BTX-A) suggesting an antinociceptive role in patients with interstitial cystitis (IC). Intriguing evidence in a somatic pain model has suggested that BTX-A injection may have an antinociceptive effect on both acute and chronic (inflammatory) pain.

METHODS

Thirteen female patients (6 in the United States and 7 in Poland) with IC according to the criteria of the National Institute of Diabetes, Digestive and Kidney Disease were included. Under short general anesthesia or sedation, 100 to 200 U of Dysport (Polish patients) or Botox (U.S. patients) was injected through a cystoscope into 20 to 30 sites submucosally in the trigone and floor of the bladder. Patients were evaluated with the O'Leary-Sant validated IC questionnaire or with voiding charts and a visual analog pain scale 1 month postoperatively and at subsequent 3-month intervals. The Polish patients also underwent pretreatment and post-treatment urodynamic evaluations.

RESULTS

Overall, 9 (69%) of 13 patients noted subjective improvement after BTX-A treatment. The Interstitial Cystitis Symptom Index and Interstitial Cystitis Problem Index mean scores improved by 71% and 69%, respectively (P <0.05). Daytime frequency, nocturia, and pain by visual analog scale decreased by 44%, 45%, and 79%, respectively (P <0.01). The first desire to void and maximal cystometric capacity increased by 58% and 57%, respectively (P <0.01).

CONCLUSIONS

Our results suggest that BTX-A has an antinociceptive effect on bladder afferent pathways in patients with IC, producing both symptomatic and functional (ie, urodynamic) improvements.

Effect of experimental diabetes on cholinergic, purinergic and peptidergic motor responses of the isolated rat bladder to electrical field stimulation or capsaicin

An attempt has been made to pharmacologically isolate cholinergic, P(2) purinoceptor-mediated and peptidergic (capsaicin-sensitive, tachykinin-mediated) contraction of the guanethidine-treated rat bladder detrusor preparation, in vitro. The effect of experimental diabetes was assessed on these types of contraction. Responses were evoked by electrical field stimulation (single shocks or 1 Hz for 30 s or 10 Hz for 40 s). Single shocks and 1-Hz stimulation were applied in the presence of (a). atropine (1 microM) or (b). P(2) purinoceptor antagonists (50 microM pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid) [PPADS] plus 100 microM suramin. Long-term electrical field stimulation (10 Hz for 40 s) (c). was applied with both atropine and the P(2) purinoceptor antagonists present in the organ bath. The effects of capsaicin (d). and ATP (e). were also studied. Three groups of experimental animals were used: streptozotocin-treated (50 mg.kg(-1) i.p., 8 weeks before the experiment), parallel solvent-treated and untreated rats. (a). Responses to electrical field stimulation in the presence of atropine were reduced by half by PPADS plus suramin, but were resistant to capsaicin tachyphylaxis. They were enhanced in preparations taken from diabetic rats. (b). Contractions to electrical field stimulation in the presence of PPADS plus suramin were reduced by 2/3 by atropine, but were left unchanged by capsaicin or diabetes. (c). Contractions to long-term stimulation had a quick and a sustained phase. Especially the latter was inhibited by capsaicin tachypyhlaxis; it was also strongly reduced in preparations taken from diabetic rats. (d). Contractions to capsaicin (30 nM and 1 microM) were resistant to tetrodotoxin, strongly reduced by a combination of tachykinin NK(1) and NK(2) receptor antagonists, and slightly reduced in preparations from diabetic animals. Capsaicin (1 microM) had no acute inhibitory action on cholinergic or purinergic responses, nor did it cause relaxation in precontracted preparations treated with tachykinin receptor antagonists. (e) ATP-induced contractions were strongly reduced by PPADS plus suramin (50 plus 100 microM) and to a similar degree by 100 plus 200 microM, respectively. It is concluded that experimental diabetes selectively impairs peptidergic, capsaicin-sensitive responses (especially those that involve impulse conduction) in the rat detrusor preparation. The contractile response to electrical field stimulation that remains after atropine plus the P(2) purinoceptor antagonists has a yet unknown transmitter background.

Developmental changes in spontaneous smooth muscle activity in the neonatal rat urinary bladder

Changes in spontaneous activity of the urinary bladder during postnatal development were examined in muscle strips from the base and dome of bladders from 1- to 5-wk-old rats. Activity was analyzed using fast Fourier transformation (FFT), nonlinear cross prediction, and the Shannon entropy test. Spontaneous activity was not detected in strips from 1- to 5-day-old rats but was observed in 50% of strips from 6- to 7-day-old rats and was prominent in strips from 2-wk-old animals. FFT analysis revealed one peak in activity, which was significantly faster in the bladder base (0.21 +/- 0.03 Hz) than in the dome (0.08 +/- 0.01 Hz). A second peak at approximately 0.5 Hz was detected at 3-5 wk of age. Atropine but not tetrodotoxin decreased the amplitude of spontaneous contractions, whereas carbachol, a muscarinic agonist, unmasked or stimulated spontaneous activity. These data suggest that slow rhythmic activity observed previously in neonatal whole bladders is generated by pacemaker cells in the bladder base or dome. The emergence of faster activity in bladders from older animals may reflect the development of multiple pacemaker sites, which would reduce coordination within the bladder wall and improve storage function in the mature bladder.

Effect of stimulation intensity and botulinum toxin isoform on rat bladder strip contractions

The present experiments compared the inhibitory effects of botulinum toxin A (BoNT-A) and botulinum toxin D (BoNT-D) on neurally evoked contractions of rat bladder strips. We examined the effect of fatigue (trains of 100 shocks at 20Hz every 20s for 10min) followed by non-fatigue stimulation (trains of 100 shocks at 20Hz every 100s for 20min) on the onset of effect and potency of the two toxins. For non-fatigue experiments, strips were untreated (n=4); or incubated with 1.36nM BoNT-A (n=4). During fatigue experiments, strips were untreated (n=5); or treated with either 1.36nM BoNT-A (n=6) or 0.8nM BoNT-D (n=6). In non-fatigue experiments, BoNT-A produced significant decreases in contractile area after 1h of stimulation compared to untreated strips (P<0.05). After three series of fatigue stimulation, differences in recovery amplitude and area between untreated versus BoNT-A, and untreated versus BoNT-D bladder strips, were statistically significant (P<0.05). The onset of inhibitory effect was quicker in BoNT-D-treated strips, as a significant reduction (P<0.05) in recovery of contractile area was observed after 1h of stimulation compared to both untreated and BoNT-A-treated preparations. In addition, treated (BoNT-A and BoNT-D) and untreated bladder strips responded similarly to atropine, suggesting that the effects of BoNT result from inhibition of both acetylcholine and ATP release. Our results demonstrate that BoNT-D may be a more effective agent to inhibit transmitter release from autonomic nerves of the rat lower urinary tract. Moreover, in our hands, non-fatigue stimulation is as effective as fatigue stimulation in inhibiting bladder strip contractions.

Change in muscarinic modulation of transmitter release in the rat urinary bladder after spinal cord injury

Muscarinic facilitation of 14C-ACh release from post-ganglionic parasympathetic nerve terminals was studied in bladder strips prepared from spinal intact (SI) and spinal cord transected (SCT) rats. The spinal cord was transected at the lower thoracic spinal segments 3 weeks prior to the experiments. Using non-facilitatory stimulation (2 Hz) the release of ACh in spinal intact rats did not change in the presence of a non-specific muscarinic antagonist, atropine (100 nM), an M(1) specific antagonist (pirenzepine, 50 nM) or an M(1)-M(3) specific antagonist (4-DAMP, 5 nM). However, during a facilitatory stimulation paradigm (10 Hz or 40 Hz, 100 shocks) atropine and pirenzepine, but not 4-DAMP inhibited the release of ACh in bladders from spinal intact rats, indicating an M(1) receptor-mediated facilitation. In spinal cord transected rats, 2 Hz stimulation-induced release was significantly inhibited by atropine or 4-DAMP but not by pirenzepine indicating that a pre-junctional facilitatory mechanism mediated via M(3) muscarinic receptors could be induced by a non-facilitatory stimulation paradigm after spinal injury. In bladders of spinal cord transected rats, 10 Hz stimulation-evoked release of ACh was also inhibited by atropine and 4-DAMP (5 nM) but not by pirenzepine (50 nM). These results indicate that pre-junctional muscarinic receptors at cholinergic nerve endings in the bladder change after chronic spinal cord injury. It appears that low affinity M(1) muscarinic receptors are replaced by high affinity M(3) receptors. This change in modulation of ACh release may partly explain the bladder hyperactivity after chronic spinal cord injury.

Effect of botulinum toxin A on the autonomic nervous system of the rat lower urinary tract

PURPOSE

The magnitude and duration of the effects of botulinum toxin A on acetylcholine (ACh) and norepinephrine release from the bladder and urethra of rats were measured using a radiochemical method.

MATERIALS AND METHODS

Saline (sham treatment) or botulinum toxin A was injected into the bladder (50 microl.) or urethra (30 microl.) in separate groups of animals. The release of 3H-norepinephrine or 14C-choline was measured at 2 time points after injection (5 or 30 days).

RESULTS

The fractional release of ACh in botulinum toxin A treated animals was significantly inhibited at higher frequencies of electrical field stimulation (20 Hz.) but not at lower frequencies (2 Hz.) 5 days after injection. However, ACh release recovered to sham injected values 30 days after toxin injection. No significant differences in the fractional release of norepinephrine from sham injected or botulinum toxin A bladders were observed. In contrast, norepinephrine release from the urethra was inhibited by botulinum toxin A for at least 30 days after injection. Similar to its effect on transmitter release in the bladder, botulinum toxin A inhibited norepinephrine release in the urethra at high (20 Hz.) but not at low (4 Hz.) electrical stimulation frequencies.

CONCLUSIONS

These data indicate that the clinical effects of botulinum toxin A on the lower urinary tract may vary depending on the site of injection and level of nerve activity.

Botulinum toxin treatment of urethral and bladder dysfunction

Botulinum toxin (BTX) is the most lethal naturally occurring toxin known to mankind. Injection of BTX into the urethral sphincter or bladder is an effective treatment for lower urinary tract dysfunction. We reviewed the literature on the mechanisms of action and clinical efficacy of BTX treatment in urologic diseases, with a focus on lower urinary tract dysfunction. Injection of BTX is safe and effective in the treatment of detrusor-sphincter dyssynergia, non-neurogenic pelvic floor spasticity, and refractory overactive bladder. Urodynamic assessment after sphincter injection with BTX reveals a decrease of bladder voiding pressure, urethral pressure profile, and post-void residual urine. An increase of the functional bladder capacity and a decrease of the bladder voiding pressure can be seen after bladder injection with BTX. Clinical improvement was found in a moderate percentage of treated patients in most reported series and lasted for 3 to 14 months without significant adverse effects. In addition, BTX-A treatment inhibits afferent-nerve-mediated bladder contraction. This analgesic effect may expand the application of BTX in the localized genitourinary tract pain syndrome, such as interstitial cystitis and prostatodynia. In conclusion, application of BTX is a promising treatment for lower urinary tract dysfunction with profound basic and clinical implications.

Botulinum toxin treatment of urethral and bladder dysfunction

Tremendous excitement has been generated by the use of botulinum toxin for the treatment of various types of urethral and bladder dysfunction over the past several years. Botulinum toxin is the most lethal naturally occurring toxin known to mankind. Why, then, would an urologist want to use this agent to poison the bladder or urethral sphincter? In this review article we will examine the mechanisms underlying the effects of botulinum toxin treatment. We will discuss the current use of this agent within the urologic community and will provide perspectives on future targets of botulinum toxin.

Muscle-derived cell-mediated ex vivo gene therapy for urological dysfunction

We have tested the feasibility of muscle-based gene therapy and tissue engineering for urological dysfunction using highly purified muscle-derived cells (MDC) that display stem cell characteristics. We then explored the potential use of these MDC as an alternative therapy for the treatment of impaired detrusor contractility. The MDC were genetically engineered to express the gene encoding beta-galactosidase and injected into the bladder walls of SCID mice. The injected bladders were harvested at various time-points after injection and assayed for beta-galactosidase activity; the presence of myofibers within the injected tissue was determined by detection of fast myosin heavy chain isoform (MyHCs). We have demonstrated that the injected MDC are capable of not only surviving in the lower urinary tract, but also improving the contractility of the bladder following an induced injury. Two potential mechanisms can be used to explain this finding. First, we have observed that some of the beta-galactosidase-expressing cells expressed alpha-smooth muscle actin, suggesting a differentiation into smooth muscle. Second, a stain for acetylcholine receptors (AChRs), which identifies the location of neuromuscular junctions, revealed that the myofibers derived from the doner cells became innervated into the bladder as early as 2 weeks after injection. These results suggest that gene therapy and tissue engineering based on MDC potentially can be used for urological dysfunction.

Botulinum toxin treatment of urethral and bladder dysfunction

There has been tremendous excitement with the use of botulinum toxin for the treatment of various urethral and bladder dysfunction over the past several years. Botulinum toxin is the most lethal naturally occurring toxin known to humankind. Why, then, would an urologist want to use this agent to poison the bladder or urethral sphincter? In this article, we will review the mechanisms underlying the effects of botulinum toxin treatment. We will discuss the current usage of this agent within the urologic community and will provide perspectives on future targets of botulinum toxin.

Botulinum toxin urethral sphincter injection resolves urinary retention after pubovaginal sling operation

The management of prolonged urinary retention following pubovaginal sling surgery typically involves transvaginal urethrolysis for anatomical urethral obstruction. Brubaker [1] recently reported on urethral sphincter abnormalities as a cause of postoperative urinary retention following either Burch suspension or pubovaginal sling procedure. We report a case of functional urethral obstruction and detrusor acontractility following pubovaginal sling surgery that was successfully treated by botulinum A toxin urethral sphincter injection.