Unmasking of a neonatal somatovesical reflex in adult cats by the serotonin autoreceptor agonist 5-methoxy-N,N-dimethyltryptamine

Model-based analysis of the acute effects of transcutaneous magnetic spinal cord stimulation on micturition after spinal cord injury in humans

AIM

After spinal cord injuries (SCIs), patients may develop either detrusor-sphincter dyssynergia (DSD) or urinary incontinence, depending on the level of the spinal injury. DSD and incontinence reflect the loss of coordinated neural control among the detrusor muscle, which increases bladder pressure to facilitate urination, and urethral sphincters and pelvic floor muscles, which control the bladder outlet to restrict or permit bladder emptying. Transcutaneous magnetic stimulation (TMS) applied to the spinal cord after SCI reduced DSD and incontinence. We defined, within a mathematical model, the minimum neuronal elements necessary to replicate neurogenic dysfunction of the bladder after a SCI and incorporated into this model the minimum additional neurophysiological features sufficient to replicate the improvements in bladder function associated with lumbar TMS of the spine in patients with SCI.

METHODS

We created a computational model of the neural circuit of micturition based on Hodgkin-Huxley equations that replicated normal bladder function. We added interneurons and increased network complexity to reproduce dysfunctional micturition after SCI, and we increased the density and complexity of interactions of both inhibitory and excitatory lumbar spinal interneurons responsive to TMS to provide a more diverse set of spinal responses to intrinsic and extrinsic activation of spinal interneurons that remains after SCI.

RESULTS

The model reproduced the re-emergence of a spinal voiding reflex after SCI. When we investigated the effect of monophasic and biphasic TMS at two frequencies applied at or below T10, the model replicated the improved coordination between detrusor and external urethral sphincter activity that has been observed clinically: low-frequency TMS (1 Hz) within the model normalized control of voiding after SCI, whereas high-frequency TMS (30 Hz) enhanced urine storage.

CONCLUSION

Neuroplasticity and increased complexity of interactions among lumbar interneurons, beyond what is necessary to simulate normal bladder function, must be present in order to replicate the effects of SCI on control of micturition, and both neuronal and network modifications of lumbar interneurons are essential to understand the mechanisms whereby TMS reduced bladder dysfunction after SCI.

TAS-303, a Novel Selective Norepinephrine Reuptake Inhibitor that Increases Urethral Pressure in Rats, Indicating Its Potential as a Therapeutic Agent for Stress Urinary Incontinence

Stress urinary incontinence (SUI) is characterized by involuntary leakage associated with exertion, effort, sneezing, coughing, or lifting. Duloxetine, a serotonin norepinephrine reuptake inhibitor, is approved for the treatment of patients with SUI in some European countries, but not in the United States. There is currently no globally approved pharmacological drug for the treatment of patients with SUI. Therefore, a new pharmacological treatment option is required. TAS-303 [4-piperidinyl 2,2-diphenyl-2-(propoxy-1,1,2,2,3,3,3-day7 )acetate hydrochloride] is a novel small-molecule selective norepinephrine reuptake inhibitor that displays significant norepinephrine transporter (NET) inhibitory activity toward the serotonin or dopamine transporters. In this report, we describe the pharmacological properties of TAS-303 and its effects on urethral function, using preclinical in vitro and in vivo studies. Radioligand-binding studies showed that TAS-303 selectively and potently inhibited [3H]norepinephrine binding to the human NET. Oral administration of TAS-303 (3 mg/kg) significantly increased norepinephrine levels in the plasma, whereas it did not significantly affect epinephrine, dopamine, and serotonin levels. TAS-303 (0.3, 1, and 3 mg/kg) dose-dependently increased basal urethral pressure in normal rats and leak point pressure in vaginal distention rats, exhibiting a maximal effect comparable to duloxetine. In the forced swimming test, TAS-303 (100 mg/kg) showed no significant effects on immobility time in rats, raising the possibility that this agent would have minimal central nervous system side effects at an effective dose for urethral function. These results demonstrate that TAS-303 has therapeutic potential for the treatment of patients with SUI.

Electrical stimulation for the treatment of lower urinary tract dysfunction after spinal cord injury

Electrical stimulation for bladder control is an alternative to traditional methods of treating neurogenic lower urinary tract dysfunction (NLUTD) resulting from spinal cord injury (SCI). In this review, we systematically discuss the neurophysiology of bladder dysfunction following SCI and the applications of electrical stimulation for bladder control following SCI, spanning from historic clinical approaches to recent pre-clinical studies that offer promising new strategies that may improve the feasibility and success of electrical stimulation therapy in patients with SCI. Electrical stimulation provides a unique opportunity to control bladder function by exploiting neural control mechanisms. Our understanding of the applications and limitations of electrical stimulation for bladder control has improved due to many pre-clinical studies performed in animals and translational clinical studies. Techniques that have emerged as possible opportunities to control bladder function include pudendal nerve stimulation and novel methods of stimulation, such as high frequency nerve block. Further development of novel applications of electrical stimulation will drive progress towards effective therapy for SCI. The optimal solution for restoration of bladder control may encompass a combination of efficient, targeted electrical stimulation, possibly at multiple locations, and pharmacological treatment to enhance symptom control.

Neural control of the lower urinary tract

This article summarizes anatomical, neurophysiological, pharmacological, and brain imaging studies in humans and animals that have provided insights into the neural circuitry and neurotransmitter mechanisms controlling the lower urinary tract. The functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain, spinal cord, and peripheral autonomic ganglia that coordinates the activity of smooth and striated muscles of the bladder and urethral outlet. The neural control of micturition is organized as a hierarchical system in which spinal storage mechanisms are in turn regulated by circuitry in the rostral brain stem that initiates reflex voiding. Input from the forebrain triggers voluntary voiding by modulating the brain stem circuitry. Many neural circuits controlling the lower urinary tract exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. The major component of the micturition switching circuit is a spinobulbospinal parasympathetic reflex pathway that has essential connections in the periaqueductal gray and pontine micturition center. A computer model of this circuit that mimics the switching functions of the bladder and urethra at the onset of micturition is described. Micturition occurs involuntarily in infants and young children until the age of 3 to 5 years, after which it is regulated voluntarily. Diseases or injuries of the nervous system in adults can cause the re-emergence of involuntary micturition, leading to urinary incontinence. Neuroplasticity underlying these developmental and pathological changes in voiding function is discussed.

Plasticity of urinary bladder reflexes evoked by stimulation of pudendal afferent nerves after chronic spinal cord injury in cats

Bladder reflexes evoked by stimulation of pudendal afferent nerves (PudA-to-Bladder reflex) were studied in normal and chronic spinal cord injured (SCI) adult cats to examine the reflex plasticity. Physiological activation of pudendal afferent nerves by tactile stimulation of the perigenital skin elicits an inhibitory PudA-to-Bladder reflex in normal cats, but activates an excitatory reflex in chronic SCI cats. However, in both normal and chronic SCI cats electrical stimulation applied to the perigenital skin or directly to the pudendal nerve induces either inhibitory or excitatory PudA-to-Bladder reflexes depending on stimulation frequency. An inhibitory response occurs at 3-10 Hz stimulation, but becomes excitatory at 20-30 Hz. The inhibitory reflex activated by electrical stimulation significantly (P<0.05) increases the bladder capacity to about 180% of control capacity in normal and chronic SCI cats. The excitatory reflex significantly (P<0.05) reduces bladder capacity to about 40% of control capacity in chronic SCI cats, but does not change bladder capacity in normal cats. Electrical stimulation of pudendal afferent nerves during slow bladder filling elicits a large amplitude bladder contraction comparable to the contraction induced by distension alone. A bladder volume about 60% of bladder capacity was required to elicit this excitatory reflex in normal cats; however, in chronic SCI cats a volume less than 20% of bladder capacity was sufficient to unmask an excitatory response. This study revealed the co-existence of both inhibitory and excitatory PudA-to-Bladder reflex pathways in cats before and after chronic SCI. However our data combined with published electrophysiological data strongly indicates that the spinal circuitry for both the excitatory and inhibitory PudA-to-Bladder reflexes undergoes a marked reorganization after SCI.

Multiple pudendal sensory pathways reflexly modulate bladder and urethral activity in patients with spinal cord injury

PURPOSE

Electrical stimulation of pudendal afferents can evoke reflex bladder contractions with relaxation of the external urethral sphincter in cats. This voiding reflex is mediated by pudendal sensory fibers innervating the penile and prostatic urethra that engage spinal and spinobulbospinal micturition pathways, respectively. However, clinical translation of this potential therapy in individuals with spinal cord injury is limited by the lack of evidence showing analogous reflex mechanisms in humans. We investigated excitatory pudendal-to-bladder reflexes in 7 individuals with chronic spinal cord injury.

MATERIALS AND METHODS

We recorded isovolumetric bladder pressure and perineal electromyogram in response to intraurethral electrical stimulation at varying amplitudes and frequencies.

RESULTS

Selective electrical stimulation of the proximal (29.7 ± 11.6 cm H(2)O) and distal urethral (23.3 ± 9.28 cm H(2)O) segments evoked sustained reflex bladder contractions in different subsets (3 each) of participants. In contrast, the corresponding reflex perineal electromyogram revealed a differential activation pattern between proximal and distal intraurethral stimulation (normalized electromyogram of 1.3 ± 0.2 and 0.3 ± 0.1, respectively, p <0.05).

CONCLUSIONS

To our knowledge we report the first clinical evidence of 2 independent excitatory pudendal-to-bladder reflex pathways, which in turn differentially modulate efferent pudendal output. Each reflex mechanism involves complex interaction of multiple sensory inputs and may provide a neural substrate to restore micturition after spinal cord injury.

Short- and long-term efficacy and safety of duloxetine in women with predominant stress urinary incontinence

OBJECTIVE

To evaluate short- and long-term safety and efficacy of duloxetine in women with predominant stress urinary incontinence (SUI).

RESEARCH DESIGN AND METHODS

The study was a 6-week, double-blind, randomised, parallel, placebo-controlled study followed by an uncontrolled open-label extension (OLE) run in 342 study centres in 16 European countries. Women with predominant SUI were randomly assigned to placebo (n = 1380) or duloxetine 40 mg twice daily (n = 1378) for 6 weeks. Completers of the acute phase were enrolled in the OLE, which had a minimum duration of 6 weeks and ended, based on the approval status of duloxetine in the participating country.

MAIN OUTCOME MEASURES

The primary outcome measure was the change in incontinence episode frequency (IEF) over 6 weeks. Secondary outcome measures were the long-term maintenance of effect on IEF and Patient Global Impression of Improvement (PGI-I), the short- and long-term impact on quality of life using the King's Health Questionnaire (KHQ), and the long-term safety of duloxetine.

RESULTS

After 6 weeks, the decrease in weekly IEF was significantly greater with duloxetine treatment compared to placebo (-50.0 vs. -29.9%; p < 0.001). The percentage of responders (defined as > or =50% decrease in IEF) was significantly higher with duloxetine treatment than with placebo (50.6 vs. 31.2%; p < 0.001). Duloxetine treatment was associated with improvements in weekly pad use (-31.4%), PGI-I ratings (63.6%), and KHQ score (-6.25) compared to placebo (-12.5%, 48.5% and -3.13, respectively, all p < 0.001). Treatment-emergent adverse events were significantly more common during duloxetine treatment (48.3%) than placebo (33.3%), (p < 0.001). Of the 2290 patients continuing into the OLE, 1165 (42.2%) completed the available duration, and 592 (21.5%) discontinued because of an adverse event (percentages relative to total randomised patients). Long-term efficacy in the OLE was assessed over a 72-week period and was maintained over that time. However, the results should be interpreted within the context that better responding patients are more likely to remain on duloxetine, while patients responding poorly are more likely to discontinue over time.

CONCLUSIONS

Duloxetine seems to be an efficacious treatment with an acceptable safety profile for women with SUI. Achieved improvement is maintained over the longer term in those women who remain on therapy.

Role of 5-HT1A receptors in control of lower urinary tract function in anesthetized rats

The role of 5-hydroxytryptamine (5-HT) 1A (5-HT1A) receptors in lower urinary tract function was examined in urethane-anesthetized female Sprague-Dawley rats. Bladder pressure and the external urethral sphincter electromyogram (EUS EMG) activity were recorded during continuous-infusion transvesical cystometrograms (TV-CMGs) to allow voiding and during transurethral-CMGs (TU-CMGs) which prevented voiding and allowed recording of isovolumetric bladder contractions. 8-Hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), a 5-HT1A receptor agonist, decreased volume threshold (VT) for initiating voiding and increased contraction amplitude (CA) during TU-CMGs but decreased CA during TV-CMGs. 8-OH-DPAT prolonged EUS bursting as well as the intrabursting silent periods (SP) during voiding. N-[2-[4-(2-methoxyphenyl)-1- piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamine trihydrochloride (WAY-100635), a 5-HT1A antagonist, increased VT, increased residual volume, markedly decreased voiding efficiency, decreased the amplitude of micturition contractions recorded under isovolumetric conditions, and decreased the SP of EUS bursting. These results indicate that activation of 5-HT1A receptors by endogenous 5-HT lowers the threshold for initiating reflex voiding and promotes voiding function by enhancing the duration of EUS relaxation, which should reduce urethral outlet resistance.

Activation and inhibition of the micturition reflex by penile afferents in the cat

Coordination of the urinary bladder and the external urethral sphincter is controlled by descending projections from the pons and is also subject to modulation by segmental afferents. We quantified the effects on the micturition reflex of sensory inputs from genital afferents traveling in the penile component of the somatic pudendal nerve by electrical stimulation of the dorsal nerve of the penis (DNP) in alpha-chloralose anesthetized male cats. Depending on the frequency of stimulation (range, 1-40 Hz), activation of penile afferents either inhibited contractions of the bladder and promoted urine storage or activated the bladder and produced micturition. Stimulation of the DNP at 5-10 Hz inhibited distension-evoked contractions and increased the maximum bladder capacity before incontinence. Conversely, stimulation at 33 and 40 Hz augmented distension-evoked contractions. When the bladder was filled above a threshold volume (70% of the volume necessary for distension-evoked contractions), stimulation at 20-40 Hz activated de novo the micturition reflex and elicited detrusor contractions that increased voiding efficiency compared with distension-evoked voiding. Electrical stimulation of the DNP with a cuff electrode or percutaneous wire electrode produced similar results. The ability to evoke detrusor contractions by activation of the DNP was preserved following acute spinal cord transection. These results demonstrate a clear role of genital afferents in modulating the micturition reflex and suggest the DNP as a potential target for functional restoration of bladder control using electrical stimulation.

Bladder activation by selective stimulation of pudendal nerve afferents in the cat

Bladder contractions evoked by pudendal nerve stimulation in both spinal intact and spinal transected cats support the possibility of restoring urinary function in persons with chronic spinal cord injury (SCI). However, electrically evoked bladder responses in persons with SCI were limited to transient contractions at relatively low pressures. This prompted the present study, which presents a detailed quantification of the responses evoked by selective stimulation of individual branches of the pudendal nerve at different stimulation frequencies. In spinal intact cats anesthetized with alpha-chloralose, selective frequency-dependent electrical activation of the sensory (2 Hz<or=f<or=50 Hz), cranial sensory (f<or=5 Hz), dorsal genital (f>or=20 Hz) and rectal perineal (f<or=10 Hz) branches of the pudendal nerve evoked sustained bladder contractions dependent on the stimulation frequency. Contractions evoked by selective electrical stimulation resulted in significant increases in voiding efficiency compared to bladder emptying by distension-evoked contractions (p(ANOVA)<0.05). Acute spinal transection abolished reflex bladder contractions evoked by low frequency stimulation of the cranial sensory or rectal perineal branches, whereas contractions evoked by high frequency stimulation of the dorsal genital branch remained intact. This study presents evidence for two distinct micturition pathways (spino-bulbo-spinal vs. spinal reflexes) activated by selective afferent pudendal nerve stimulation, the latter of which may be applied to restore bladder function in persons with SCI.

Voiding reflex in chronic spinal cord injured cats induced by stimulating and blocking pudendal nerves

AIMS

To induce efficient voiding in chronic spinal cord injured (SCI) cats.

METHODS

Voiding reflexes induced by bladder distension or by electrical stimulation and block of pudendal nerves were investigated in chronic SCI cats under alpha-chloralose anesthesia.

RESULTS

The voiding efficiency in chronic SCI cats induced by bladder distension was very poor compared to that in spinal intact cats (7.3 +/- 0.9% vs. 93.6 +/- 2.0%, P < 0.05). In chronic SCI cats continuous stimulation of the pudendal nerve on one side at 20 Hz induced large amplitude bladder contractions, but failed to induce voiding. However, continuous pudendal nerve stimulation (20 Hz) combined with high-frequency (10 kHz) distal blockade of the ipsilateral pudendal nerve elicited efficient (73.2 +/- 10.7%) voiding. Blocking the pudendal nerves bilaterally produced voiding efficiency (82.5 +/- 4.8%) comparable to the efficiency during voidings induced by bladder distension in spinal intact cats, indicating that the external urethral sphincter (EUS) contraction was caused not only by direct activation of the pudendal efferent fibers, but also by spinal reflex activation of the EUS through the contralateral pudendal nerve. The maximal bladder pressure and average flow rate induced by stimulation and bilateral pudendal nerve block in chronic SCI cats were also comparable to those in spinal intact cats.

CONCLUSIONS

This study shows that after the spinal cord is chronically isolated from the pontine micturition center, bladder distension evokes a transient, inefficient voiding reflex, whereas stimulation of somatic afferent fibers evokes a strong, long duration, spinal bladder reflex that elicits efficient voiding when combined with blockade of somatic efferent fibers in the pudendal nerves.

Duloxetine versus placebo for the treatment of women with stress predominant urinary incontinence in Taiwan: a double-blind, randomized, placebo-controlled trial

BACKGROUND

This manuscript compares the efficacy and safety of duloxetine with placebo in Taiwanese women with SUI.

METHODS

Taiwanese women with SUI were were randomly assigned to placebo (n = 61) or duloxetine 80 mg/day (n = 60) in this double-blind, 8-week, placebo-controlled study. Outcome variables included: incontinence episode frequency (IEF), Incontinence Quality of Life questionnaire (I-QOL) scores, and Patient Global Impression of Improvement rating (PGI-I).

RESULTS

Decrease in IEF was significantly greater in duloxetine-treated than placebo-treated women (69.98% vs 42.56%, P < .001). No treatment differences in I-QOL scores were significant. There were significant differences in PGI-I rating. Treatment-emergent adverse events (TEAEs) were experienced by more duloxetine-treated than placebo-treated women (80.0% vs 44.3%; P < .001). Discontinuations due to adverse events were significantly greater for duloxetine-treated than placebo-treated women (26.7% vs 6.6%; P = .003).

CONCLUSION

Data provide evidence for the safety and efficacy of duloxetine for the treatment for Taiwanese women with SUI.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00475358.

The role of central 5-hydroxytryptamine (5-HT, serotonin) receptors in the control of micturition

At present the most investigated 5-HT receptor that has been shown to play a role in the control of micturition is the 5-HT(1A) receptor followed by 5-HT(7), 5-HT(2) and 5-HT(3) receptors. Most experiments focus on the control these receptors have on the parasympathetic outflow to the bladder and the somatic outflow to the external urethral sphincter (EUS) in the rat. Furthermore, 5-HT(1A) and 5-HT(7) receptors have been identified as having an excitatory physiological role in the control of bladder function. 5-HT(1A) receptors act, at least in the rat, at both a spinal (probably a heteroreceptor) and supraspinal (probably an autoreceptor) level, while 5-HT(7) receptors only act at a supraspinal level. Additionally, in the rat, 5-HT administered at a spinal or supraspinal site has an excitatory action, although earlier experiments have shown that activating 5-HT-containing brain areas causes inhibition of the bladder. Recent experiments have also indicated that blockade of the 5-HT(1A) receptor pathway shows rapid tolerance. However, no data exist for the development of tolerance for the 5-HT(7) receptor pathway. Neither receptor seems to play a role in the control of the urethra. Regarding 5-HT(2) receptors, activation of this receptor subtype inhibits micturition, and this inhibitory action may occur at a spinal, supraspinal or both levels. Although no physiological role for 5-HT(2C) receptors can yet be identified, 5-HT(2C) receptors have been implicated in the proposed supraspinal tonically active 5-HT(1A) autoreceptor (negative feedback) pathway. This proposition reconciles the data that central 5-HT-containing pathways are inhibitory to micturition, while 5-HT(1A) receptors, although inhibitory to adenylyl cyclase, have an excitatory function. This is because activation of 5-HT(1A) autoreceptors reduces the release of 5-HT thus reducing the activation of the 5-HT(2C) receptors, which are inhibitory in the control of micturition (disinhibition). Furthermore, 5-HT(2A) receptors in the rat and 5-HT(2C) receptors in the guinea pig cause activation of the EUS. In this respect, 5-ht(5A) receptors have also been identified in Onuf's nucleus, the site of somatic motoneurones controlling this sphincter. In the cat there is very little evidence to indicate that 5-HT receptors are involved in micturition except under pathological conditions in which activation of 5-HT(1A) receptors causes inhibition of micturition. Interestingly, under such conditions 5-HT(1A) receptors cause excitation of the EUS. Nevertheless, spinal 5HT(3) receptors have been implicated in the physiological control of micturition in the cat, but not yet in the rat. Overall, the data support the view that 5-HT receptors are important in the control of micturition. However, many more studies are required to fully understand these roles and why there are such species differences.

Roles of glutamatergic and serotonergic mechanisms in reflex control of the external urethral sphincter in urethane-anesthetized female rats

This study was conducted to examine reflex mechanisms that mediate urinary bladder and external urethral sphincter (EUS) coordination in urethane-anesthetized female Sprague-Dawley rats. We investigated the properties of EUS reflexes elicited by electrical stimulation of pelvic nerve afferent axons (pelvic-EUS reflex). The changes in the reflexes induced by bladder distension and administration of agonists or antagonists for glutamatergic or serotonergic receptors were examined. The reflexes consisted of an early response (ER, 18- to 22-ms latency) and a late, long-duration (>100-ms latency) response (LR), which consisted of bursts of activity at 20- to 160-ms interburst intervals. In a few experiments, a reflex with an intermediate (40- to 70-ms) latency was also identified. With the bladder empty, the ER, but not the LR, was detected in the majority of experiments. The LR was markedly enhanced when the bladder was distended. The ER remained, but the LR was abolished, after spinal cord transection at T8-T9. The ER and LR were significantly decreased 75 and 35%, respectively, by the N-methyl-D-aspartate receptor antagonist MK-801 (0.3 mg/kg iv), but only decreased 18 and 14%, respectively, by the alpha-amino-5-methylisoxazole-4-propionate receptor antagonist LY-215490 (3 mg/kg iv). The serotonin (5-HT1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (1 mg/kg iv) enhanced spontaneous EUS activity and the pelvic-EUS reflex. WAY-100635 (0.1-1 mg/kg iv), a 5-HT1A antagonist, reversed the effect of 8-hydroxy-2-(di-n-propylamino)-tetralin and suppressed EUS activity and the pelvic-EUS reflex. These results indicate that glutamatergic and serotonergic mechanisms are important in the reflex pathways underlying bladder- sphincter coordination in rats.

Mechanisms underlying the recovery of lower urinary tract function following spinal cord injury

The lower urinary tract has two main functions, the storage and periodic expulsion of urine, which are regulated by a complex neural control system in the brain and lumbosacral spinal cord. This neural system coordinates the activity of two functional units in the lower urinary tract: (1) a reservoir (the urinary bladder) and (2) an outlet (consisting of bladder neck, urethra and striated muscles of the pelvic floor). During urine storage the outlet is closed and the bladder is quiescent, thereby maintaining a low intravesical pressure over a wide range of bladder volumes. During micturition the outlet relaxes and the bladder contracts to promote the release of urine. This reciprocal relationship between bladder and outlet is generated by visceral reflex circuits, some of which are under voluntary control. Experimental studies in animals indicate that the micturition reflex is mediated by a spinobulbospinal pathway passing through a coordination center (the pontine micturition center) located in the rostral brainstem. This reflex pathway is in turn modulated by higher centers in the cerebral cortex that are presumably involved in the voluntary control of micturition. Spinal cord injury at cervical or thoracic levels disrupts voluntary control of voiding as well as the normal reflex pathways that coordinate bladder and sphincter functions. Following spinal cord injury, the bladder is initially areflexic but then becomes hyperreflexic due to the emergence of a spinal micturition reflex pathway. Studies in animals indicate that the recovery of bladder function after spinal cord injury is dependent in part on plasticity of bladder afferent pathways and the unmasking of reflexes triggered by capsaicin-sensitive C-fiber bladder afferent neurons. The plasticity is associated with changes in the properties of ion channels and electrical excitability of afferent neurons, and appears to be mediated in part by neurotrophic factors released in the spinal cord and the peripheral target organs.

Suppression of bladder reflex activity in chronic spinal cord injured cats by activation of serotonin 5-HT1A receptors

The effects of 8-OH-DPAT (5-HT1A receptor agonist) and WAY100635 (5-HT1A receptor antagonist) on reflex bladder activity were investigated in alpha-chloralose anesthetized or conscious chronic spinal cord injured cats. The results were similar in both anesthetized and conscious animals. Cystometrograms revealed that 8-OH-DPAT (0.5 mg/kg, s.c.) significantly increased the bladder volume threshold for eliciting a large amplitude micturition contraction, but only slightly reduced the amplitude of the contractions and did not alter the small amplitude pre-micturition contractions. 8-OH-DPAT also reduced the amplitude of isovolumetric bladder contractions. The inhibitory effect of 8-OH-DPAT was reversed by WAY100635 (0.5 mg/kg) or blocked by pre-treatment with WAY100635. Reflex bladder contractions evoked by tactile stimulation of the perigenital region were not altered by 8-OH-DPAT. These results suggest that the inhibitory effect of 8-OH-DPAT is mediated by an action on interneuronal pathways in the spinal cord or on the C-fiber afferent limb of the spinal micturition reflex and not on bladder smooth muscle or the efferent limb of the reflex pathway. Drugs that activate 5-HT1A receptors might be useful in treating detrusor overactivity after spinal cord injury.

P2X2 and P2X3 receptor expression in postnatal and adult rat urinary bladder and lumbosacral spinal cord

P2X receptors mediate the effects of ATP in micturition and nociception. During postnatal maturation, a spinobulbospinal reflex and voluntary voiding replace primitive voiding reflexes. This may involve changes in neuroactive compounds and receptors in bladder reflex pathways. We examined P2X2 and P2X3 receptors in bladder and spinal cord from postnatal (P0-P36, indicating number of days) and adult Wistar rats. Western blot of whole bladders for P2X2 and P2X3 expression was performed. Immunostaining for P2X2 and P2X3 receptors in urothelium and detrusor smooth muscle whole mounts and spinal cord sections was examined. Western blot demonstrated an age-dependent decrease (R(2) = 0.96, P Collapse

Key Words

• postnatal development
• micturition reflexes
• sacral parasympathetic nucleus
• dorsal commissure
• dorsal horn

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MESH Headings

• Aging/metabolism
• Animals
• Female
• Lumbosacral Region
• Male
• Rats
• Rats, Wistar
• Receptors, Purinergic P2/metabolism
• Receptors, Purinergic P2X2
• Receptors, Purinergic P2X3
• Spinal Cord/metabolism
• Tissue Distribution
• Urinary Bladder/metabolism

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Grants

• DK-060481 NIDDK NIH HHS
• NS-040796 NINDS NIH HHS
• R01 DK065989 NIDDK NIH HHS
• R56 DK060481 NIDDK NIH HHS
• R29 DK051369 NIDDK NIH HHS
• DK-065989 NIDDK NIH HHS
• R01 DK060481 NIDDK NIH HHS
• R01 NS040796 NINDS NIH HHS
• DK-051369 NIDDK NIH HHS
• R01 DK051369 NIDDK NIH HHS

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Affiliation(s)

Simon Studeny Department of Neurology, Anatomy and
Ali Torabi Department of Neurology, Anatomy and
Margaret A. Vizzard Department of Neurology, Anatomy and Neurobiology, University of Vermont, College of Medicine, Burlington, Vermont, VT 05405

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Distribution and fate of cocaine- and amphetamine-regulated transcript peptide (CARTp)-expressing cells in rat urinary bladder: a developmental study

We examined the distribution and fate of cocaine- and amphetamine-regulated transcript peptide (CARTp)(55-102)-immunoreactive (IR) structures in the neonatal and adult rat urinary bladder. Double-labeling studies examining CARTp with tyrosine hydroxylase (TH), neuronal nitric oxide synthase (nNOS), or choline acetyltransferase (ChAT) were performed in wholemounts of urothelium or detrusor or cryostat sections of the bladder. In younger animals (postnatal day [P]1, P3), CARTp-IR cell bodies in detrusor smooth muscle were observed in large clusters ( approximately 100 cells/cluster) at the ureteral insertion and along thick bundles of nerve fibers at the bladder base. The total number of CARTp-IR cells was significantly reduced (by five-fold) at P14, and this reduced number persisted into adulthood. The decrease in the number of CARTp-expressing cells was complemented with positive staining for cleaved caspase-3, suggesting that apoptosis contributed to this decrease. At birth (P1), all CARTp-IR cells expressed the neuronal marker Hu. After birth, CARTp was expressed by some neurons (CARTp-IR, Hu-IR) that represent intramural ganglion cells and by cells that lacked a neuronal phenotype (CARTp-IR, Hu-) but did express TH. Neither of these cell populations expressed ChAT immunoreactivity in adult bladder. These cells (CARTp-IR, Hu-, TH-IR) may represent paraganglion or small intensely fluorescent (SIF) cells. The percentage of colocalization of CARTp-IR and nNOS or TH was dependent on postnatal age and showed an inverse relationship. At P1, 67.1 % of CARTp-IR cells expressed nNOS immunoreactivity. Decreased colocalization was observed with increasing postnatal age. In contrast, 19.5% of CARTp-IR cells expressed TH at P1, but colocalization increased with postnatal age. The suburothelial plexus lacked CARTp-IR nerve fibers until P14, when nerve fibers with varicosities were observed in the urethra and bladder neck region. In summary, we demonstrate 1) a decrease in the number of CARTp-IR cells in rat detrusor in early postnatal development; 2) apoptotic events in the bladder during early postnatal development; 3) rostral migration of CARTp-IR cells from the ureteral insertion toward the bladder body during postnatal development; 4) the presence of different populations of CARTp-IR cells, some with and others without a neuronal phenotype; and (5) age-dependent changes in chemical coding of CARTp-IR cells with postnatal development. This study demonstrates that CARTp-IR intramural ganglia and CARTp-IR paraganglion or SIF cells exist in the postnatal and adult rat bladder, although the role of these cell types remains to be determined.

Corticotropin-releasing factor (CRF) expression in postnatal and adult rat sacral parasympathetic nucleus (SPN)

The neural control of micturition undergoes marked changes during the early postnatal development. During the first few postnatal weeks, the spinal micturition reflex is gradually replaced by a spinobulbospinal reflex pathway that is responsible for micturition in adult animals. Upregulation of brainstem regulation of spinal micturition pathways may contribute to development of mature voiding patterns. We examined the expression of corticotropin-releasing factor (CRF), present in descending projections from Barrington's nucleus to the sacral parasympathetic nucleus (SPN), in postnatal (P0-P36) and adult Wistar rats (P60-90). CRF-immunoreactivity (IR) was present predominantly in the SPN region, although some staining was also observed in the dorsal horn and dorsal commissure in L5-S1 spinal segments. CRF-IR in spinal cord regions was age dependent (R2=0.87-0.98). The majority of the CRF-IR in the lumbosacral spinal cord was eliminated by complete spinalization (2-3 weeks). Double-label immunohistochemistry was combined with quantitative confocal laser scanning microscopy to quantify the number and percentage of colocalization between CRF-immunoreactive varicosities and preganglionic somas or proximal neurites in the SPN in postnatal and adult rats. Results demonstrate an age-dependent upregulation of CRF-IR in the SPN region and specifically in association with preganglionic parasympathetic neurons identified with neuronal nitric oxide synthase (nNOS)-IR. CRF-immunoreactive varicosities on or within a 1 microm perimeter of nNOS-immunoreactive somas or proximal neurites also increased with postnatal age. The upregulation of CRF-IR in bulbospinal projections to the SPN may contribute to mature voiding reflexes.

Targeting serotonin and norepinephrine receptors in stress urinary incontinence

Stress urinary incontinence (SUI) in women is prevalent, and there are no globally developed or widely approved drugs for the disease. One strategy for improving urinary continence is to augment the function of the urethral rhabdosphincter through neuropharmacology. The present review describes the innervation of the urethra, and the role of the central nervous system in controlling nerve activity. Targeting serotonin and norepinephrine (or noradrenaline) receptors in Onuf's nucleus is shown to augment the function of the urethral rhabdosphincter by increasing pudendal nerve efferent activity. It is proposed that the ability of serotonin and norepinephrine to enhance the effects of glutamate (the primary excitatory neurotransmitter for pudendal sphincter motor neurons) while having no direct effects of their own, allow facilitation of rhabdosphincter activity during urine storage while allowing complete relaxation during micturition. Duloxetine, a potent and balanced dual serotonin (5-HT)-norepinephrine reuptake inhibitor (SNRI), potentiates these physiological effects of endogenous serotonin and norepinephrine (by inhibiting the reuptake of these neurotransmitters in the pre-synaptic element) and thereby enhances the central nervous system's natural continence control mechanisms.

Pharmacotherapy for stress urinary incontinence : present and future options

Stress urinary incontinence (SUI) is the accidental leakage of urine associated with physical activities such as running, jumping or lifting, or with sneezing and coughing. Worldwide, SUI is a highly prevalent condition, both in young and elderly women, and is a condition fraught with social isolation, loss of self-esteem and significant financial burden. Most women with SUI assume that it is an inevitable part of aging and "suffer in silence", relying on absorbent pads or lifestyle changes to cope with their condition.Unfortunately, for those who do seek medical treatment, the absence of effective and well tolerated pharmacological treatments for SUI limits the clinician's choices to behavioural modification, biofeedback and surgery. Many of the nonsurgical approaches have low success rates, particularly in the elderly and more severely afflicted. Although most continence surgeries have been reported to produce very high cure rates, many women are willing to live with their condition rather than undergo such invasive options. In an attempt to help these patients, some physicians prescribe off-label agents, including tricyclic antidepressants such as imipramine, alpha- and beta-adrenoceptor agonists, and estrogen replacement therapy. The use of these therapies has been limited by unpredictable results and adverse reactions. In addition, acetylcholine receptor antagonists are often prescribed for SUI, despite the fact that these medications have never been shown to be effective in this condition. This lack of a reliable pharmaceutical agent led to the development of duloxetine, a balanced dual reuptake inhibitor of serotonin and norepinephrine that is also being studied for the treatment of major depressive disorder. Based on in vivo data in animals, duloxetine is believed to increase the strength of urethral sphincter contractions and, thereby, prevent accidental urine leakage by increasing urethral closure forces. In clinical trials in women with SUI, duloxetine has demonstrated efficacy in reducing incontinence episodes and increasing the quality of life with no serious adverse effects. Nausea was the most common adverse event; however, in most patients it was reported early in treatment, mild-to-moderate in severity and transient. A medication such as duloxetine, if approved, would go a long way towards expanding the available treatment options for patients with SUI.

Central nervous system control of the lower urinary tract: new pharmacological approaches to stress urinary incontinence in women

PURPOSE

Despite the prevalence of stress urinary incontinence in women there are no approved drugs for the disease.

MATERIALS AND METHODS

Designing medical therapies requires a comprehensive understanding of how the internal and external sphincters are neurologically controlled. In this review recent advances in mapping storage and micturition reflexes, and the association of serotonergic and noradrenergic systems with these reflexes are discussed.

RESULTS

Urine storage and micturition are controlled by a series of hard wired reflexes that are under the modulatory influence of serotonin and norepinephrine. Augmentation of the serotonergic and noradrenergic systems with duloxetine increases bladder capacity and urethral rhabdosphincter activity. The increase in sphincter activity is mediated by alpha1 adrenergic receptors and 5-hydroxytryptamine receptors.

CONCLUSIONS

Increasing rhabdosphincter activity with duloxetine may offer a therapeutic benefit in women with stress urinary incontinence.

Duloxetine vs placebo in the treatment of stress urinary incontinence: a four-continent randomized clinical trial

OBJECTIVES

To further assess, in a phase 3 study, treatment with duloxetine for women with stress urinary incontinence (SUI) in other geographical regions, including Argentina, Australia, Brazil, Finland, Poland, South Africa and Spain, as previous trials in North America and Europe provided evidence for the safety and efficacy of duloxetine as a pharmacological treatment for SUI in women.

PATIENTS AND METHODS

The study included 458 women aged 27-79 years enrolled in a double-blind, placebo-controlled trial. The patients with predominantly SUI were identified using a validated clinical algorithm. They were randomly assigned to receive placebo (231) or duloxetine 40 mg twice daily (227) for 12 weeks. The primary outcome variables included the incontinence episode frequency (IEF) and the Incontinence Quality of Life (I-QOL) questionnaire. Van Elteren's test was used to analyse the percentage changes in IEF where the stratification variable was weekly baseline IEF (IEF < 14 and > or = 14). Analysis of covariance was used to analyse I-QOL scores.

RESULTS

The mean baseline IEF was 18.4/week; 55% of patients had a baseline IEF of > or = 14. There was a significantly greater median decrease in IEF with duloxetine with placebo (54% vs 40%, P = 0.05), with comparable significant improvements in quality of life (I-QOL score increases of 10.3 vs 6.4, P = 0.007). The improvements with duloxetine were associated with significantly greater increases in voiding intervals than with placebo (20.4 vs 8.5 min, P < 0.001). The placebo response was 10.7% and 12.5% higher than those reported in two European and North American phase 3 trials. This may have been related to more patients being naïve for incontinence management in the current trial. Discontinuation rates for adverse events were 1.7% for placebo and 17.2% for duloxetine (P < 0.001), with nausea being the most common reason for discontinuation (3.1%); it was the most common adverse event with duloxetine, but was mild or moderate in most (81%), did not worsen in any patient and resolved within 7 days in 60% and within 1 month in 86% of continuing patients; 88% of women who experienced nausea while taking duloxetine completed the trial.

CONCLUSIONS

These results show improvements in incontinence and quality of life with duloxetine 40 mg twice daily for 12 weeks that are in keeping with those reported in two other recently completed phase 3 trials in Europe and North America.

Duloxetine versus placebo in the treatment of European and Canadian women with stress urinary incontinence

OBJECTIVE

To assess the efficacy and safety of duloxetine in women with stress urinary incontinence.

DESIGN

Randomised double-blind, placebo-controlled clinical trial.

SETTING

Fort-six centres in seven European countries and Canada.

POPULATION

Four hundred and ninety-four women aged 24-83 years identified as having predominant symptoms of stress urinary incontinence using a clinical algorithm that was 100% predictive of urodynamic stress urinary incontinence in a subgroup of 34 women.

METHODS

The case definition included a predominant symptom of stress urinary incontinence with a weekly incontinence episode frequency > or =7, the absence of predominant symptoms of urge incontinence, normal diurnal and nocturnal frequencies, a bladder capacity > or =400 mL and both a positive cough stress test and positive stress pad test. Subjects completed two urinary diaries prior to randomisation and three diaries during the active treatment phase of the study, each completed during the week prior to monthly visits. Subjects also completed quality of life questionnaires at each visit. Safety was assessed by the evaluation of treatment-emergent adverse events, discontinuation of treatment because of adverse events, serious adverse events, vital sign measurements, electrocardiograms (ECG) and clinical laboratory tests.

INTERVENTION

After a two-week placebo lead-in, women received placebo or duloxetine 40 mg BD for 12 weeks.

MAIN OUTCOME MEASURES

The percentage decrease in incontinence episode frequency and the change in the Incontinence Quality of Life (I-QOL) questionnaire total score were prespecified as co-primary outcome variables in the protocol.

RESULTS

Incontinence episode frequency decreased significantly with duloxetine compared with placebo (median decrease of 50%vs 29%; P= 0.002) with comparable improvements in the more severely incontinent subgroup (those experiencing at least 14 incontinence episodes per week at baseline; 56%vs 27% decreases; P < 0.001). The primary analysis of I-QOL scores did not reveal a significant difference between treatment groups, due primarily to the carrying forward of low scores from patients who discontinued treatment very early due to duloxetine-associated adverse events. The increase in I-QOL scores was significantly greater for duloxetine than for placebo at each of the three postrandomisation visits after 4, 8, and 12 weeks of treatment. Discontinuation rates for adverse events were higher for duloxetine (22%vs 5%; P < 0.001) with nausea being the most common reason for discontinuation (5.3%). Nausea tended to be mild to moderate, not progressive, and transient.

CONCLUSIONS

The findings support duloxetine as a potential treatment for women with stress urinary incontinence.

Duloxetine: a serotonin-noradrenaline re-uptake inhibitor for the treatment of stress urinary incontinence

Stress urinary incontinence (SUI) is the accidental leakage of urine associated with physical activities such as running, jumping or lifting or with sneezing and coughing. For many patients it can be a very bothersome symptom, causing social isolation, loss of self-esteem and increased financial outlays. Although there is currently no medication approved worldwide for the treatment of SUI, a variety of off-label agents are sometimes prescribed. Duloxetine (LY-248686; Eli Lilly), a new centrally acting compound with dual activity as a serotonin and noradrenaline re-uptake inhibitor, offers a promising new approach for treatment. Due to its inhibition of presynaptic neuron re-uptake of serotonin and noradrenaline in the sacral spinal cord, duloxetine is believed to increase the strength of urethral sphincter contractions and thereby prevent accidental urine leakage by increasing urethral closure pressure. In three published trials in women with the predominant symptom of SUI, duloxetine significantly reduced the number of incontinence episodes compared to placebo. Adverse events were usually observed early in treatment, were mild-to-moderate in severity and were transient. Nausea was the most common reason for discontinuation.

Suppression of the micturition reflex in urethane-anesthetized rats by intracerebroventricular injection of WAY100635, a 5-HT(1A) receptor antagonist

The influence of supraspinal 5-HT(1A) receptors on reflex bladder activity was evaluated in anesthetized rats by studying the effects of intracerebroventricular (i.c.v.) administration of WAY100635 (1-100 microg), a selective 5-HT(1A) receptor antagonist. The drug dose-dependently decreased the frequency and/or amplitude of isovolumetric reflex bladder contractions. Low doses (1-10 microg) increased the interval between contractions but only slightly reduced the amplitude of the contractions. However, 100 microg of WAY100635 elicited an initial complete block of bladder reflexes followed by a recovery period lasting 10-15 min during which the frequency of reflex contractions was normal but the amplitude was markedly suppressed by 70-80%. Mesulergine (0.1 mg/kg, i.v.), a 5-HT(2C) antagonist, which transiently eliminated bladder activity in some rats (five of 11), blocked the inhibitory effect of WAY100635 (10 or 100 microg, i.c.v.) in only two of six rats. Our data coupled with the results of previous studies suggest that spinal and supraspinal 5-HT(1A) receptors are involved in multiple inhibitory mechanisms controlling the spinobulbospinal micturition reflex pathway. The regulation of the frequency of bladder reflexes is presumably mediated by a suppression of afferent input to the micturition switching circuitry in the pons, whereas the regulation of bladder contraction amplitude may be related to an inhibition of the output from the pons to the parasympathetic nucleus in the spinal cord.

Neural control of the urethra and development of pharmacotherapy for stress urinary incontinence

This review discusses the control of the urethra by the central nervous system, emphasizing the importance of nervous system control and the role of serotonin and noradrenaline in storage, micturition and sphincter reflexes. The concept of pharmacological neuromodulation and the use of pharmacological therapy as first-line therapy for stress urinary incontinence (SUI) is presented. Coordination between the urinary bladder and urethra is mediated by many reflex pathways organized in the brain and spinal cord. During bladder filling, activation of mechanoreceptor afferent nerves in the bladder wall triggers firing in the cholinergic efferent pathways to the external urethral sphincter and in sympathetic adrenergic pathways to the urethral smooth muscle. These storage reflexes depend on interneuronal circuitry in the spinal cord and are modulated by descending pathways. It would therefore seem that neurotransmission in the central nervous system and periphery may be important in SUI, and moreover that pharmacological agents affecting these neurotransmitter pathways may be used to treat SUI. The central and peripheral mechanisms of action of duloxetine affect serotonin and noradrenaline neurotransmission in ways that may ameliorate the symptoms of SUI.

Duloxetina y otros antidepresivos tricíclicos: efectos farmacodinámicos en el tracto urinario inferior

INTRODUCTION

During years the pharmacology of the lower urinary tract function has been presided by the protagonism of the autonomic nervous system and its components, sympathetic and parasympathetic. Recent investigations proved a greater complexity of micturional dynamics, attributing a more important role to the central nervous system (SNC), to the striated sphincter and to the afferent arc, offering a new opportunity to the Tricyclic Antidepressants (T.A.), reason for this general review.

MATERIAL AND METHODS

Using as reference the work of the First Consultation on Incontinence (Montecarlo, 1999), the previous and later publications about T.A. have been reviewed, including experimental (isometric and "in vivo" studies) and clinical studies, investigating on pharmacological evidences, mechanism of action, tolerance and other effects of T.A.

RESULTS

Only a reduced group of T.A. have been submitted to experimental evaluations and employed in clinical trials. The recent works on Duloxetine have waked up a special interest by their pharmacological potential.

CONCLUSIONS

New knowledge on the peripheral and central control of the continence-miction dynamic offer new pathways for the treatment with T.A., whose effectiveness and tolerance are reviewed.

Spinal cord neural organization controlling the urinary bladder and striated sphincter

The storage and elimination of urine requires the coordination of activity between the autonomic nervous system (thoracolumbar sympathetic and sacral parasympathetic divisions) controlling the urinary bladder and urethra and the lumbosacral somatic motoneurons innervating the striated sphincter and pelvic floor muscles. These three efferent systems involved in the control of lower urinary tract function receive segmental sensory information from various visceral organs and the perineum, as well as inputs from supraspinal regions. Ascending and descending connections between the various spinal segments levels and supraspinal regions provide the reflex substrates participating in normal bladder continence and micturition reflexes. Many of the actions of descending and segmental reflexes are mediated by excitatory and inhibitory sacral spinal interneurons located within the region of the parasympathetic preganglionic autonomic neurons and the sphincter ventral horn motoneurons. This review will: (1) discuss the basic organization and spinal elements of the reflex pathways subserving continence and micturition; (2) describe features of the identified sacral interneuronal circuitry contributing to the control of the bladder and sphincter function; and (3) discuss how changes in the control of these reflex pathways and neurons may contribute to abnormal patterns of bladder and sphincter function commonly observed following spinal cord injury.

Effects of serotonin 1A agonist on acute spinal cord injury

STUDY DESIGN

We evaluated the effects of serotonin (5-HT) agonists on in vitro models of spinal cord compressive injury. Evoked potentials in injured rat spinal cords (n=24) were recorded during perfusion with 5-HT agonists.

OBJECTIVES

To evaluate the therapeutic effects of 5-HT agonists on the recovery of compound action potentials in injured spinal cords.

METHODS

Rat dorsal columns were isolated, placed in a chamber, and injured by extradural compression with a clip. Conducting action potentials were activated by supramaximal constant current electrical stimuli and recorded during perfusion with 5-HT agonists and antagonists.

RESULTS

After inducing compression injuries, mean action potential amplitudes were reduced to 33.9+/-5.4% of the pre-injury level. After 120 min of perfusion with Ringer's solution, the mean amplitudes recovered to 62.8+/-8.4% of the pre-injury level. At a concentration of 100 micro M, perfusion with tandospirone (a 5-HT1A agonist) resulted in a significantly greater recovery of mean action potential amplitudes at 2 h after the injury (86.2+/-6.9% of pre-injury value) as compared with the control Ringer's solution (62.8+/-8.4% of pre-injury value, P<0.05). In contrast, quipazine (a 5-HT2A agonist) accelerated the decrease of amplitude (54.5+/-11.7% of pre-injury value). 5-HT1A and 5-HT2A agonist did not consistently alter latencies of the action potentials.

CONCLUSION

The 5-HT1A receptor agonist was effective for the recovery of spinal action potential amplitudes in a rat spinal cord injury model.

The role of 5-HT(1A) receptors in control of lower urinary tract function in cats

In the present study, the role of 5-HT(1A) receptors in control of lower urinary tract function in cats was examined using 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) as agonists and WAY100635 and LY206130 as antagonists. Bladder function was assessed using cystometric infusion of saline or 0.5% acetic acid to produce bladder irritation. External urethral sphincter (EUS) function was assessed using electromyographic (EMG) recordings of activity recorded during cystometry or by recording electrically evoked pudendal reflexes. Both 5-HT(1A) receptor agonists caused dose-dependent decreases in bladder activity and increases in EUS EMG activity under conditions of acetic acid infusion. 5-HT(1A) receptor antagonists reversed both the bladder-inhibitory and sphincter-facilitatory effects. Thus, 5-HT(1A) receptor activation can have opposite effects on nociceptive afferent processing depending upon the efferent response being measured. During saline infusion of the bladder, 8-OH-DPAT produced moderate inhibition of bladder activity and had no significant effect on sphincter electromyographic (EMG) activity. 8-OH-DPAT either had no effect, or inhibited, low-threshold electrically evoked pudendal reflexes. These findings indicate that 5-HT(1A) receptor stimulation is inhibitory to bladder function in cats, especially under conditions where the bladder is hyperactive due to irritation. Furthermore, these bladder-inhibitory effects are the exact opposite of the bladder-excitatory effects of 8-OH-DPAT reported in rats. 5-HT(1A) receptor stimulation increases EUS motoneuron activity when driven by nociceptive bladder afferent inputs but not when driven by non-nociceptive afferent inputs. In summary, 5-HT(1A) receptor agonists facilitate a nociceptor-driven spinal reflex (sphincter activity) but inhibit a nociceptor-driven supraspinal reflex (micturition). This pattern of activity would facilitate urine storage and may be important under 'fight-or-flight' conditions when serotonergic activity is high.

Comparison of the effects of serotonin selective, norepinephrine selective, and dual serotonin and norepinephrine reuptake inhibitors on lower urinary tract function in cats

Previous studies showed that the dual serotonin (5-hydroxytryptamine, 5-HT) and norepinephrine (NE) reuptake inhibitor, duloxetine, increases bladder capacity and urethral sphincter electromyographic (EMG) activity in a cat model of acetic acid-induced bladder irritation. The present study aimed to determine the relative importance of 5-HT versus NE reuptake inhibition for mediating these effects by examining drugs that are selective for either the 5-HT or NE system or both. Similar to duloxetine, venlafaxine (0.1 to 10 mg/kg), also a dual serotonin and norepinephrine reuptake inhibitor, produced marked increases in bladder capacity and EMG activity that were reversed by methiothepin (0.3 mg/kg). S-norfluoxetine (0.01 to 10 mg/kg), a serotonin selective reuptake inhibitor, produced small but significant increases in bladder capacity and EMG activity at doses of 3 and 10 mg/kg. Thionisoxetine (0.01 to 3.0 mg/kg), a NE selective reuptake inhibitor, produced no effects on bladder capacity or sphincter EMG activity. Surprisingly, co-administration of thionisoxetine and s-norfluoxetine up to doses of 1 mg/kg of each compound produced no effect on lower urinary tract function. These doses were the maximum that could be administered in combination due to drug-induced emergence of skeletal muscle activity in chloralose-anesthetized animals. These results indicate that there are unexplained pharmacological differences between the effects of single compounds that exhibit dual NE and 5-HT reuptake inhibition and a combination of compounds that exhibit selective NE and 5-HT reuptake inhibition on lower urinary tract function.

Duloxetine versus placebo in the treatment of stress urinary incontinence

OBJECTIVE

The purpose of this study was to assess the efficacy and safety of duloxetine, a selective inhibitor of serotonin and norepinephrine reuptake, in the treatment of stress urinary incontinence.

STUDY DESIGN

A double-blind, randomized, placebo-controlled study was conducted in 553 women aged 18 to 65 years with a predominant symptom of stress urinary incontinence. Subjects were randomized to placebo (n = 138 women) or duloxetine at one of three doses (20 mg/d, n = 138 women; 40 mg/d, n = 137 women; or 80 mg/d, n = 140 women). Outcome variables that were assessed after 12 weeks of treatment included incontinence episode frequency recorded in a real-time diary and answers provided to the Patient Global Impression of Improvement scale and the Incontinence Quality of Life questionnaire.

RESULTS

Duloxetine was associated with significant and dose-dependent decreases in incontinence episode frequency that paralleled improvements that were observed in the Patient Global Impression of Improvement scale and the Incontinence Quality of Life questionnaire. The median incontinence episode frequency decrease with the use of the pooled diary analysis with placebo was 41% compared with 54% for duloxetine 20 mg per day (P =.06), 59% for duloxetine 40 mg per day (P =.002), and 64% for duloxetine 80 mg per day (P <.001). One half of the subjects at the 80 mg per day dose had a > or = 64% reduction in incontinence episode frequency (P <.001 vs placebo); 67% had > or = 50% reduction (P =.001 vs placebo). These improvements were observed despite significant concurrent dose-dependent increases in the average voiding interval in the duloxetine groups compared with the placebo group. Similar statistically significant improvements were demonstrated in a subgroup of 163 subjects who had more severe stress urinary incontinence (> or = 14 incontinence episode frequency per week; 49%-64% reduction in incontinence episode frequency in the duloxetine groups compared with 30% in the placebo group). Discontinuation rates for adverse events were 5% for placebo and 9%, 12%, and 15% for duloxetine 20, 40, and 80 mg per day, respectively (P =.04). Nausea was the most common symptom that led to discontinuation. None of the adverse events that were reported were considered to be clinically severe.

CONCLUSION

This trial provides evidence for the efficacy and safety of duloxetine as a pharmacologic agent for the treatment of stress urinary incontinence.

Influence of central serotonergic mechanisms on lower urinary tract function

The effects of serotonergic drugs on the central nervous system control of the lower urinary tract have revealed possible approaches for the treatment of detrusor overactivity and urinary incontinence. Studies in animals of the distribution of serotonergic nerves and receptors and the changes in voiding function induced by serotonin (5-hydroxytryptamine [5-HT]) receptor agonists and antagonists, as well as 5-HT reuptake inhibitors, form a basis for the development of such treatments. In rats and cats, spinal reflex circuits involved in voiding function exhibit a dense serotonergic innervation, multiple 5-HT receptors, and sensitivity to various drugs that affect serotonergic transmission. Although there is some evidence in the rat for serotonergic facilitation of voiding, most experiments in rats and cats indicate that activation of the central serotonergic system by 5-HT reuptake inhibitors, as well as by 5-HT1A and 5-HT2 receptor agonists, depresses reflex bladder contractions and increases the bladder volume threshold for inducing micturition. These data indicate that activation of the central serotonergic system can suppress voiding by enhancing efferent control of the urethral outlet and inhibiting the parasympathetic excitatory input to the urinary bladder. The 5-HT receptors and reuptake mechanisms, therefore, represent targets for the development of new treatments of detrusor overactivity and urinary incontinence.

Excitatory synaptic currents in lumbosacral parasympathetic preganglionic neurons elicited from the lateral funiculus

Excitatory postsynaptic currents (EPSCs) in parasympathetic preganglionic neurons (PGNs) were examined using the whole cell patch-clamp recording technique in L6 and S1 spinal cord slices from neonatal rats (6-16 days old). PGNs were identified by labeling with retrograde axonal transport of a fluorescent dye (Fast Blue) injected into the intraperitoneal space 3-7 days before the experiment. Synaptic responses were evoked in PGNs by field stimulation of the lateral funiculus (LF) in the presence of bicuculline methiodide (10 microM) and strychnine (1 microM). In approximately 40% of the cells (total, 100), single-shock electrical stimulation of the LF elicited short, relatively constant latency [3.0 +/- 0.1 (SE) ms] fast EPSCs consistent with a monosynaptic pathway. The remainder of the cells did not respond to stimulation. At low intensities of stimulation, the EPSCs often occurred in an all-or-none manner, indicating that they were mediated by a single axonal input. Most cells (n = 33) exhibited only fast EPSCs (type 1), but some cells (n = 8) had fast EPSCs with longer, more variable latency polysynaptic EPSCs superimposed on a slow inward current (type 2). Type 1 fast synaptic EPSCs were pharmacologically dissected into two components: a transient component that was blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 5 microM), a non-NMDA glutamatergic antagonist, and a slow decaying component that was blocked by 2-amino-5-phosphonovalerate (APV, 50 microM), a NMDA antagonist. Type 2 polysynaptic currents were reduced by 5 microM CNQX and completely blocked by combined application of 5 microM CNQX and 50 microM APV. The fast monosynaptic component of type 1 EPSCs had a linear current-voltage relationship and reversed at a membrane potential of 5.0 +/- 5.9 mV (n = 5), whereas the slow component exhibited a negative slope conductance at holding potentials greater than -20 mV. The type 1, fast synaptic EPSCs had a time to peak of 1.4 +/- 0.1 ms and exhibited a biexponential decay (time constants, 5.7 +/- 0.6 and 38.8 +/- 4.0 ms). In the majority of PGNs (n = 11 of 15 cells), EPSCs evoked by electrical stimulation of LF exhibited paired-pulse inhibition (range; 25-33% depression) at interstimulus intervals ranging from 50 to 120 ms. These results indicate that PGNs receive monosynaptic and polysynaptic glutamatergic excitatory inputs from axons in the lateral funiculus.

Effects of WAY100635, a selective 5-HT1A-receptor antagonist on the micturition-reflex pathway in the rat

5-Hydroxytryptamine (5-HT) receptors in the central nervous system have been implicated in the control of micturition. The present study was undertaken to evaluate the effects of a selective 5-HT1A-receptor antagonist [N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide trihydrochloride (WAY100635)] on the micturition-reflex pathway in urethane-anesthetized female Wistar rats. Rhythmic isovolumetric bladder contractions evoked by bladder distension were abolished by 0.3- to 3-mg/kg iv or 30- to 100-microg intrathecal (it) administration of WAY100635 in a dose-dependent manner for periods of 3-15 min. Intrathecal injection of WAY100635 was effective only if injected at the L6-S1 spinal cord level, but not at the thoracic or cervical cord levels. WAY100635 (30-100 microg it) significantly reduced the amplitude of bladder contractions evoked by electrical stimulation of the pontine micturition center. However, the field potentials in the rostral pons evoked by electrical stimulation of pelvic nerve were not affected by intrathecal or intravenous injection of WAY100635. These results suggest that 5-HT1A receptors at the L6-S1 level of the spinal cord have an important role in the tonic control of the descending limb of the micturition-reflex pathway in the rat.

5-Hydroxytryptophan-induced respiratory recovery after cervical spinal cord hemisection in rats

The present study investigates the role of serotonin in respiratory recovery after spinal cord injury. Experiments were conducted on C(2) spinal cord hemisected, anesthetized, vagotomized, paralyzed, and artificially ventilated rats in which end-tidal CO(2) was monitored and maintained. Before drug administration, the phrenic nerve ipsilateral to hemisection showed no respiratory-related activity due to the disruption of the descending bulbospinal respiratory pathways by spinal cord hemisection. 5-Hydroxytryptophan (5-HTP), a serotonin precursor, was administrated intravenously. 5-HTP induced time- and dose-dependent increases in respiratory recovery in the phrenic nerve ipsilateral to hemisection. Although the 5-HTP-induced recovery was initially accompanied by an increase in activity in the contralateral phrenic nerve, suggesting an increase in descending respiratory drive, the recovery persisted well after activity in the contralateral nerve returned to predrug levels. 5-HTP-induced effects were reversed by a serotonin receptor antagonist, methysergide. Because experiments were conducted on animals subjected to C(2) spinal cord hemisection, the recovery was most likely mediated by the activation of a latent respiratory pathway spared by the spinal cord injury. The results suggest that serotonin is an important neuromodulator in the unmasking of the latent respiratory pathway after spinal cord injury. In addition, the results also suggest that the maintenance of 5-HTP-induced respiratory recovery may not require a continuous enhancement of central respiratory drive.

Developmental expression of urinary bladder neurotrophic factor mRNA and protein in the neonatal rat

These studies were performed to determine the developmental expression pattern of neurotrophic factor (NTF: nerve growth factor (betaNGF), brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF), ciliary neurotrophic factor (CNTF), neurotrophin-3 (NT-3) and NT-4 mRNA and NGF, NT-3 and NT-4 protein in the urinary bladder of the postnatal Wistar rat. It was hypothesized that NTFs may contribute to the development of the spinobulbospinal micturition reflex that represents the adult micturition pattern. Changes in NTF mRNA or protein expression in the urinary bladder at the time of development of the mature micturition reflex (postnatal days (P) 16-18) may suggest an involvement of target-derived NTFs in this maturation process. Developmental ages, prior to (P5, P10, P15) or following (P20, P30, adult P90) the development of the spinobulbospinal micturition reflex were selected and the urinary bladder was analyzed for levels of neurotrophic factor mRNA or protein. Results from ribonuclease protection assays demonstrated a similar developmental pattern among each neurotrophic factor examined. Neurotrophic factor mRNA levels increased by P10 and reach a maximum by P15. Subsequently, NTF mRNA levels declined to adult levels that were less than the earliest postnatal time examined (P5). NTF mRNA expression was significantly (p</=0.05-0.001) greater at P10, P15, P20 and P40 (NT-4 mRNA) compared to adult levels for each NTF examined except GDNF mRNA. In general, NGF, NT-3 and NT-4 urinary bladder protein levels in early postnatal development, as determined by ELISA, were similar when compared to the corresponding mRNA expression. Differences in the correlation between NT-3 and NT-4 mRNA and protein expression were demonstrated in the adult urinary bladder where significantly (p</=0. 001) greater levels of protein were revealed despite relatively low abundance of NT-3 and NT-4 mRNA. The developmental expression pattern (maximum expression at the second to third postnatal week) of NTFs in the urinary bladder is consistent with a potential role in the development of the spinobulbospinal reflex. Relatively high expression of NT-3 and NT-4 protein in the adult urinary bladder suggests a potential importance of these factors in the adult lower urinary tract.

Maturation of bladder reflex pathways during postnatal development

Neuroanatomical and electrophysiological techniques have provided new insights into the organization of the spinal cord circuitry and the neurotransmitter mechanisms involved in primitive voiding reflexes in neonatal animals. In addition, studies of unitary synaptic transmission in spinal cord slice preparations indicate that developmental and spinal cord injury induced plasticity in sacral parasympathetic reflex pathways is due in part to alterations in glutamatergic excitatory transmission between interneurons and parasympathetic preganglionic neurons. It is proposed that these synaptic changes are due to competition between segmental and supraspinal inputs. Thus synaptic remodeling in the sacral parasympathetic nucleus is likely to be an important factor in the postnatal maturation of voiding reflexes.

Bladder afferent pathway and spinal cord injury: possible mechanisms inducing hyperreflexia of the urinary bladder

Lower urinary tract dysfunction is a common problem in patients with spinal cord injury (SCI). Since the coordination of the urinary bladder and urethra is controlled by the complex mechanisms in spinal and supraspinal neural pathways, SCI rostral to the lumbosacral level disrupts voluntary and supraspinal control of voiding and induces a considerable reorganization of the micturition reflex pathway. Following SCI, the urinary bladder is initially areflexic. but then becomes hyperreflexic because of the emergence of a spinal micturition reflex pathway. Recent electrophysiologic and histologic studies in rats have revealed that chronic SCI induces various phenotypic changes in bladder afferent neurons such as: (1) somal hypertrophy along with increased expression of neurofilament protein; and (2) increased excitability due to the plasticity of Na+ and K+ ion channels. These results have now provided detailed information to support the previous notion that capsaicin-sensitive, unmyelinated C-fiber afferents innervating the urinary bladder change their properties after SCI and are responsible for inducing bladder hyperreflexia in both humans and animals. It is also suggested that the changes in bladder reflex pathways following SCI are influenced by neural-target organ interactions probably mediated by neurotrophic signals originating in the hypertrophied bladder. Thus, increased knowledge of the plasticity in bladder afferent pathways may help to explain the pathogenesis of lower urinary tract dysfunctions after SCI and may provide valuable insights into new therapeutic strategies for urinary symptoms in spinal cord-injured patients.

Sacral spinal cord neurons responsive to bladder pelvic and perineal inputs in cats

In chloralose-anesthetized or decerebrate male cats, 70% of 73 sacral spinal cord neurons activated from the bladder branch of the pelvic nerve also received excitatory inputs from urethra and/or perineal cutaneous nerves (sensory pudendal in 55% and superficial perineal in 84% of neurons). Only 29% of these neurons were excited by the hindlimb skin and muscle nerves tested. The pelvic nerve-responsive neurons received monosynaptic urethral/perineal input in 25% of cases and required temporal summation of this input in 47% of cases. Of 211 neurons responding to superficial perineal nerve stimulation, 101 were not excited by the other nerves tested. Neurons activated by superficial perineal nerve stimulation were found predominantly in S2. It is likely that the superficial perineal nerve represents an important pathway whereby perineal stimulation influences bladder function.

Serotonergic modulation of spinal ascending activity and sacral reflex activity evoked by pelvic nerve stimulation in cats

Serotonin (5-HT) may be inhibitory to micturition at a spinal level. A potential mechanism of action for serotonergic inhibition of bladder function is a depression of the ascending limb of the supraspinal reflex mediating micturition. Ascending activity evoked by pelvic nerve stimulation was recorded in the thoracic spinal cord of anesthetized cats. For comparison, spinal reflex activity evoked by pelvic nerve stimulation was recorded on the pudendal nerve. The effects of intrathecal administration of serotonergic agents were examined to determine whether spinal and supraspinal responses to bladder afferent activation were modulated by 5-HT. Methysergide (60 nmol), a non-selective serotonergic antagonist, increased ascending activity by 61+/-7% and depressed spinal reflex activity by 38+/-6%. Zatosetron (10 nmol), a 5-HT3 antagonist had a similar effect on both activities (increased by 93+/-24% and decreased by 77+/-7%, respectively). The effect on ascending activity of blocking 5-HT3 receptors was also confirmed with ICS 205930 and MDL 72222. 2-Methyl-5-HT (800 nmol), a 5-HT3 agonist, depressed ascending activity to 46+/-9% of control, but enhanced spinal reflex activity by 73+/-92%. These results demonstrate that stimulation of 5-HT3 and methysergide-sensitive 5-HT receptors can inhibit ascending activity and facilitate spinal reflex activity elicited by activation of bladder afferents. It is suggested that descending serotonergic pathways may participate in the spinal coordination of urinary continence.

Spinal 5-HT2 receptor-mediated facilitation of pudendal nerve reflexes in the anaesthetized cat

1. 5-Hydroxytryptamine (5-HT) is intimately associated with central sympathetic and somatic control of the lower urinary tract. The sympathetic and somatic innervation of the lower urinary tract is conveyed through efferent axons of the hypogastric and pudendal nerves, respectively. 2. The present study examined the effects of 2,5-dimethoxy-4-iodophenylisopropylamine (DOI), a 5-HT2 receptor subtype-selective agonist, on evoked potentials recorded from the central ends of the hypogastric and pudendal nerves in response to electrical stimulation of afferent fibres in the pelvic and pudendal nerves, respectively. Various spinalization paradigms were employed to localize the site of action. All cats were pretreated with xylamidine (1 mg kg-1), a peripherally-restricted 5-HT2 receptor antagonist. 3. In acute spinal cats, DOI (0.01-3 mg kg-1, i.v.) reliably produced dose-dependent increases in the pudendal nerve reflex (to 228 +/- 31% of control). These increases were reversed by the 5-HT2 receptor-selective antagonist, LY53857 (0.3-3 mg kg-1, i.v.). On the other hand, in spinally-intact cats, DOI produced no significant changes in the pudendal reflex. However, within minutes of spinalization of DOI-pretreated cats, a marked increase (to 221 +/- 16% of control) in the pudendal reflex was observed which could be reversed by LY53857. No significant effects were observed on hypogastric reflexes in either acute spinal or spinally-intact cats following DOI administration. No effects were seen in either spinally-intact or acute spinal animals when LY53857 was administered as the initial drug. 4. These results indicate that activation of spinal 5-HT2 receptors facilitates pudendal reflexes. In spinally-intact cats, it is hypothesized that DOI activates supraspinal pathways that mediate inhibition of the pudendal reflexes and counteracts the facilitatory effects of spinal 5-HT2 receptor activation.

Serotonergic modulation of cat bladder function before and after spinal transection

Micturition was evoked in conscious cats by infusing saline into the bladder at a physiological rate. Drugs were administered intrathecally. Micturition volume threshold was increased by 5-hydroxytryptamine (5-HT, serotonin) and decreased by zatosetron, a 5-HT3 receptor antagonist, in spinally intact cats. Thus 5-HT3 receptors inhibit micturition. After complete spinal transection, serotonin reduced volume threshold in 3 of 4 cats, indicating an alteration in serotonergic control. However, 2-methyl-5-HT, a 5-HT3 receptor agonist, increased volume threshold. Thus 5-HT3 receptor-mediated inhibition of bladder function remains after spinal transection. We conclude that some, but not all, serotonergic modulation of bladder function is altered after spinal transection.

Detrusor-sphincteric dyssynergia in paraplegics compared with the synergia in a brain-dead human by using the single-fibre action potential recording method

(1) Humans with spinal cord lesions often show detrusor-sphincteric dyssynergia of the urinary bladder which is reflected urodynamically in the detrusor pressure and a simultaneous increase in electromyographic pelvic floor activity. (2) The time-course of the increase in the secondary muscle spindle afferent activity, induced by the parasympathetic nervous system in muscle spindles contributing to continence, is very similar to that of detrusor pressure. The detrusor-sphincteric dyssynergia is therefore analysed by comparing the natural impulse patterns of secondary muscle spindle afferents (SP2) and sphincteric motoneurons in a brain-dead human with those in patients with spinal cord lesion. The parasympathetic nervous system was activated by painful bladder catheter pulling. (3) In a brain-dead human the sphincteric motoneurons subserving continence were inhibited at a time, when preganglionic parasympathetic efferents increased their activity for 10 s and an SP2 fibre increased its activity for several minutes. In a paraplegic with a strong bladder dysfunction, the SP2 fibre activity increased, due to parasympathetic activation, lasted for approx. 1 min, showed undulations and its amplitude was smaller than that measured in a brain-dead human. The sphincteric motoneurons were not inhibited. (4) In the brain-dead human, an SP2 fibre showed doublet firing with interspike intervals (IIs) of a duration between 10 and 14 ms for low level parasympathetic activation. For high level parasympathetic activation this single parent spindle afferent fibre showed multi-ending regular firing of up to 6 endings with IIs of a duration of predominantly 15 to 25 ms. In one paraplegic with a strong bladder dysfunction the doublet firing was less regular, even though two II peaks at 10.2 and 11.2 ms occurred in a II distribution similar to the brain-dead human. The multi-ending regular firing was replaced by a repeated burst firing. In a second paraplegic with strong detrusor-sphincteric dyssynergia the burst firing consisted of up to 6 impulses with increasing IIs and a first II of approx. 0.2 ms (transmission frequency 5000 Hz). In a third paraplegic with a lesser dysfunction of the bladder a highly activated SP2 fibre showed an activity pattern intermediate to those of multi-ending regular firing and burst firing. (5) The time constant for the activity decrease of a spindle afferent fibre following parasympathetic activation was to 31 s in a paraplegic and approx. 40 s in a brain-dead human. It is concluded that the muscle spindles are unchanged following spinal cord lesion.(ABSTRACT TRUNCATED AT 400 WORDS)