Contraction of urinary bladder by central norepinephrine originating in the locus coeruleus

Efficacy and safety of desmopressin in nocturia and nocturnal polyuria control of neurological patients: A systematic review and meta-analysis

PURPOSE

Evidence on the efficacy of desmopressin in nocturia in patients with neurological diseases is still very limited except for multiple sclerosis (MS). Our aim was to evaluate the efficacy and safety of desmopressin treatment on nocturia in patients with underlying neurological diseases.

METHODS

Studies were identified by electronic search of PubMed, Embase, Cochrane, CINAHL, and Google Scholar databases. Studies were considered if they provided information on the effectiveness and safety of desmopressin (1-desamino-8-d-arginine vasopressin, or DDAVP) in the treatment of nocturia and their participants had acquired neurological pathology. Two researchers independently extracted the articles using specified datasets, such as quality-of-study indicators. Statistical meta-analysis was carried out using Review Manager (RevMan) 5.4 statistical software (Cochrane Collaboration).

RESULTS

Of a total of 1042 articles in the initial search, 14 studies were included. Most of the published papers were related to MS (n = 7), two were on spinal cord injury, and other conditions were neural tube defect, myelodysplasia, Parkinson's disease, stroke, and multiple system atrophy. Overall, a total of 200 patients (mostly females) were enrolled. Thirteen studies evaluated the intranasal formulation of desmopressin and one study evaluated oral desmopressin. A significant decrease in nocturia episodes was reported in seven studies evaluating this topic. An increase in the maximum hours of uninterrupted sleep was reported in the three studies in which this outcome was assessed. A significant reduction in the volume of nocturnal incontinence was found in one study. Three studies were eligible to include in the meta-analysis. The results showed that desmopressin compared to placebo, significantly reduced nighttime urination (mean difference: -0.75, 95% CI: -1.10 to -0.41; p < 0.00001). The rate of adverse events ranged from 0% to 68.42%. The critical appraisal results for all trials showed that most of the studies had low or moderate quality.

CONCLUSIONS

Our results emphasized desmopressin's safety and efficacy in reducing nocturia episodes, with transient adverse effects on neurological patients. However, the data were achieved from low or medium-quality trials, and further well-designed randomized controlled trials are needed.

Serotonin Discharge Regulation by Additional Neurotransmitters of Rat Hippocampus Associated With the Continence Central Circuit

Purpose

The lower urinary tract is believed to be centrally regulated with the involvement of a range of neurotransmitters. The parasympathetic excitatory input to the urinary bladder is suppressed when the serotonergic system is activated, and thereby voiding is blocked. In healthy people, continence is usually underpinned by hippocampal formation (circuit 3). In order to advance knowledge of how serotoninergic neurons and additional nerve fibers were correlated, the purpose of the present work was to research how the discharge of serotonin from hippocampal slices was affected by different neurotransmitters in rat models.

Methods

The adopted procedure involved administration of the central neurotransmitters acetylcholine, norepinephrine, dopamine, N-methyl-D-aspartate (NMDA), gamma-aminobutyric acid (GABA), glycine, and neuropeptide Y as well as monitoring of the alterations in the discharge of [³H]5-hydroxytryptamine (5-HT). Furthermore, to determine whether the effect of the neurotransmitters was influenced by interneuron, tetrodotoxin was also employed.

Results

Acetylcholine (10^-5M) did not alter [³H]5-HT discharge, whereas more 5-HT was discharged from the hippocampal slices of rats under stimulation by norepinephrine (10^-5M) as well as dopamine (10^-5M) and tetrodotoxin (10^-6M) did not inhibit the discharge. By contrast, tetrodotoxin inhibited the discharge of [³H]5-HT that was exacerbated by NMDA (10^-4M). Meanwhile, compared to control, GABA (10^-5M), glycine (10^-5M), or neuropeptide Y (10^-6M) did not alter the [³H]5-HT discharge.

Conclusions

From the research findings, it can be concluded that 5-HT discharge from rat hippocampus is enhanced by norepinephrine and dopamine through direct effect on the 5-HT neuronal terminal. By contrast, 5-HT discharge is intensified by NMDA by activating interneurons.

Autonomic consequences of spinal cord injury

Spinal cord injury (SCI) results not only in motor and sensory deficits but also in autonomic dysfunctions. The disruption of connections between higher brain centers and the spinal cord, or the impaired autonomic nervous system itself, manifests a broad range of autonomic abnormalities. This includes compromised cardiovascular, respiratory, urinary, gastrointestinal, thermoregulatory, and sexual activities. These disabilities evoke potentially life-threatening symptoms that severely interfere with the daily living of those with SCI. In particular, high thoracic or cervical SCI often causes disordered hemodynamics due to deregulated sympathetic outflow. Episodic hypertension associated with autonomic dysreflexia develops as a result of massive sympathetic discharge often triggered by unpleasant visceral or sensory stimuli below the injury level. In the pelvic floor, bladder and urethral dysfunctions are classified according to upper motor neuron versus lower motor neuron injuries; this is dependent on the level of lesion. Most impairments of the lower urinary tract manifest in two interrelated complications: bladder storage and emptying. Inadequate or excessive detrusor and sphincter functions as well as detrusor-sphincter dyssynergia are examples of micturition abnormalities stemming from SCI. Gastrointestinal motility disorders in spinal cord injured-individuals are comprised of gastric dilation, delayed gastric emptying, and diminished propulsive transit along the entire gastrointestinal tract. As a critical consequence of SCI, neurogenic bowel dysfunction exhibits constipation and/or incontinence. Thus, it is essential to recognize neural mechanisms and pathophysiology underlying various complications of autonomic dysfunctions after SCI. This overview provides both vital information for better understanding these disorders and guides to pursue novel therapeutic approaches to alleviate secondary complications.

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.

α(1)-Adrenoceptors in the urinary tract

α(1)-Adrenoceptors have been identified and characterized extensively by functional, radioligand-binding, and molecular biological techniques. Molecular clones have been isolated for three α(1)-subtypes (α(1a), α(1b), and α(1d)), and these subtypes are also functionally characterized. α(1)-Adrenoceptors are present in the prostate, urethra, bladder (urothelium, smooth muscle, and afferent nerves), ureter, vas deferens, peripheral ganglia, nerve terminals, vascular tissues, and central nervous system (CNS), and they could all potentially influence overall urinary function and contribute to both the therapeutic and adverse effects of α(1)-adrenoceptor antagonists in patients with benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS). This review aimed to discuss the relevant physiological and pharmacological roles and molecular biology of α(1)-adrenoceptor subtypes in the prostate, urethra, bladder, ureter, and CNS.

Neurophysiology of the lower urinary tract

The lower urinary tract (LUT) has two functions: (1) the storage of waste products in the form of urine and (2) the elimination of those wastes through micturition. The LUT operates in a simple "on-off" fashion, either storing urine or releasing it during voiding. While this activity may seem simple, micturition is controlled by a complex set of peripheral neurons that are, in turn, coordinated by cell groups in the spinal cord, brainstem, and brain. When this careful coordination is interrupted, the control of the bladder is lost, resulting in incontinence or retention of urine. The purpose of this chapter is to review how the neural systems coordinating the activity of the lower urinary tract form neural circuits that are responsible for either maintaining continence (the storage reflex) or inducing micturition (the voiding reflex). We will also discuss the brain centers that enable higher organisms to voluntarily choose the time and place for voiding. Finally, we will discuss how defects in the pathways controlling micturition can lead to urinary incontinence and which treatments may normalize LUT function.

Role of supraspinal and spinal α1-adrenergic receptor subtypes in micturition reflex in conscious rats

α1-Adrenergic receptor subtypes are widely distributed in the central nervous system and are involved in autonomic functions such as micturition. We investigated the presence and the role of supraspinal and/or spinal α1-adrenergic receptors in modulating the micturition reflex in conscious female Wistar rats. The expression of α1-adrenergic receptor subtypes in rat brain and lumbosacral spinal cord was studied using RT-PCR. Continuous-infusion cystometrograms were obtained in conscious rats, and α1-adrenergic receptor antagonists were administered via intracerebroventricular or intrathecal routes. The mRNA expression of α1A-, α1B-, and α1D-adrenergic receptors was detected in rat brain (midbrain and pons) and lumbosacral spinal cord (dorsal and ventral parts of spinal cord). In addition, intracerebroventricular injection of the α1-adrenergic receptor antagonist tamsulosin (1–10 μg), the selective α1A-adrenergic receptor antagonist silodosin (1–10 μg), and the selective α1D-adrenergic receptor antagonist BMY 7378 (1–10 μg) significantly prolonged the intercontraction interval (ICI) but did not alter maximum voiding pressure (MVP). Although intrathecal injection of BMY 7378 (0.0001–10 μg) did not affect ICI, tamsulosin and silodosin prolonged ICI in a dose-dependent manner. MVP was significantly reduced by intrathecal injection of tamsulosin (10 μg) but not by silodosin or BMY 7378 (0.0001–10 μg). Supraspinal α1A- and α1D-adrenergic receptors are apparently important for the regulation of reflex-bladder activity in conscious rats. Noradrenergic projection from the brain stem to the lumbosacral spinal cord may promote the afferent limb rather than the efferent limb of the micturition reflex pathway via α1A-adrenergic receptors.

Pupillometric assessment of autonomic nervous system in children with functional enuresis

Functional enuresis is defined as repeated voiding of urine into bed or clothes in children after 5 years of age following the exclusion of major somatic diseases. Autonomic nervous system dysregulation has been proposed as a pathophysiologic mechanism in the etiopathogenesis. The objective of this study was to evaluate autonomic nervous system functions with pupil diameter measurement in enuretic children. The study group consisted of 17 children with functional enuresis (ten boys, seven girls), and the control group consisted of 34 healthy children (20 boys, 14 girls). Pupil diameter measurements were performed under photopic and mesopic lighting conditions by using a pupillometer. Mean photopic pupil diameter was found to be larger in the enuretic children than in the healthy controls (4.47 +/- 0.52 mm vs. 4.03 +/- 0.75 mm; P = 0.03). Autonomic nervous system imbalance of the ocular system is considered to be part of the autonomic nervous system dysregulation in functional enuretic children.

Alpha1 Adrenoceptors in Human Urinary Tract: Expression, Distribution and Clinical Implications

Adrenergic receptors (ARs) are a class of proteins belonging to the G protein-coupled receptor family. Pharmacological and molecular studies allowed dividing ARs into three different categories: α1, α2 and β. In this review, we focused on α1 ARs and α1 AR antagonists, since α 1 ARs play an important role in the pathophysiology of a number of urinary tract (UT) dysfunctions. α1 ARs are widely expressed in human UT; in particular, the three ureter areas (distal, medial and proximal) show different patterns of receptor expression (i.e. distal > medial = proximal), giving the molecular basis for the use of α1 ARs antagonist in the expulsive therapy of distal ureter calculi. Bladder areas are characterized by important differences among trigone, detrusor and neck, the first showing a different pattern of expression compared to the other parts. Further, there are evidences of both density and subtype gender-dependent expressions. α1 ARs expression in prostate and detrusor is a widely investigated area of research, mainly due to the clinical impact of benign prostatic hyperplasia (BPH). Urethra has not been well studied in human, although it plays a role in the control of continence.

Studies carried out on α1 AR subtype expression in the UT indicate that, although the presence of each subtype is observed, α1A firstly and then α1D ARs seem to be more expressed than α1B ARs. Thus, drugs that demonstrate high α1A/D AR selectivity have drawn the researchers’ attention. As it relates specifically to the α1 AR antagonists used in the treatment of lower UT symptoms, the concept of uroselectivity has been operationally defined; indeed, in a number of recent publications uroselectivity has been defined as the degree to which a given compound inhibits norepinephrine-induced increase in urinary muscle contractions and/or its propensity to generate unwanted cardiovascular effects, such as decreases in blood pressure.

Alpha1-, alpha2- and beta-adrenoceptors in the urinary bladder, urethra and prostate

1 We have systematically reviewed the presence, functional responses and regulation of alpha(1)-, alpha(2)- and beta-adrenoceptors in the bladder, urethra and prostate, with special emphasis on human tissues and receptor subtypes. 2 Alpha(1)-adrenoceptors are only poorly expressed and play a limited functional role in the detrusor. Alpha(1)-adrenoceptors, particularly their alpha(1A)-subtype, show a more pronounced expression and promote contraction of the bladder neck, urethra and prostate to enhance bladder outlet resistance, particularly in elderly men with enlarged prostates. Alpha(1)-adrenoceptor agonists are important in the treatment of symptoms of benign prostatic hyperplasia, but their beneficial effects may involve receptors within and outside the prostate. 3 Alpha(2)-adrenoceptors, mainly their alpha(2A)-subtype, are expressed in bladder, urethra and prostate. They mediate pre-junctional inhibition of neurotransmitter release and also a weak contractile effect in the urethra of some species, but not humans. Their overall post-junctional function in the lower urinary tract remains largely unclear. 4 Beta-adrenoceptors mediate relaxation of smooth muscle in the bladder, urethra and prostate. The available tools have limited the unequivocal identification of receptor subtypes at the protein and functional levels, but it appears that the beta(3)- and beta(2)-subtypes are important in the human bladder and urethra, respectively. Beta(3)-adrenoceptor agonists are promising drug candidates for the treatment of the overactive bladder. 5 We propose that the overall function of adrenoceptors in the lower urinary tract is to promote urinary continence. Further elucidation of the functional roles of their subtypes will help a better understanding of voiding dysfunction and its treatment.

Clinical implications from studies of alpha1 adrenergic receptor knockout mice

alpha1-Adrenergic receptors (alpha1-ARs) modulate a large number of physiological functions in cardiovascular and noncardiovascular tissues. Because individual members of the alpha1-AR family (alpha1A-, alpha1B-, and alpha1D-ARs) have overlapping expression profiles in most tissues, elucidation of the precise physiological roles of individual alpha1-AR subtypes remains a challenging task. To alleviate this constraint, a gene targeting approach has been employed to generate mutant mice lacking one or two alpha1-AR genes. Recent studies on these mutant mouse strains are discussed in this article, with an emphasis on the role of alpha1-AR in the central nervous system and lower urinary tracts. These are two major tissues of particular interest for the development of new therapeutic strategies targeted to the alpha1-ARs. By combining gene targeting techniques with pharmacological tools, the specific roles of alpha1-AR subtypes could be delineated.

Use of sympathetic alpha antagonists in the management of pediatric urologic disorders

PURPOSE OF REVIEW

To update the physician regarding the use of alpha-adrenergic antagonists in the management of various pediatric urologic problems.

RECENT FINDINGS

The use of alpha-adrenergic antagonist for the treatment of pediatric urologic disorders has expanded greatly over the past decade. This review summarizes the current use of these medications in the treatment of pediatric voiding dysfunction, neurogenic bladder, chronic lower urinary tract symptomatology, idiopathic urethritis, and the passage of ureteral calculi.

SUMMARY

Currently alpha antagonist therapy although not useful in the primary treatment of voiding dysfunction is equivalent in potency to biofeedback therapy for the treatment of recalcitrant voiding dysfunction. In the management of neurogenic bladder and chronic lower urinary tract symptomatology, alpha antagonists working alone or in conjunction with anticholinergic medications will improve clinical symptoms, increase bladder compliance, and decrease detrusor instability. In addition, alpha antagonists may decrease the intensity and duration of symptoms in patients with idiopathic urethritis. Compared with placebo, alpha-adrenergic antagonists will also aid significantly in the spontaneous passage of distal ureteral calculi, thereby reducing the need for surgical intervention and analgesia. The findings noted above significantly expand the clinical usefulness of alpha antagonist therapy within the field of pediatric urology.

Role of Barrington's nucleus in micturition

Barrington's nucleus is a central component of the micturition circuit. This nucleus projects axons to the sacral parasympathetic nucleus, where preganglionic neurons innervating the urinary bladder are located. To clarify the functional role of this nucleus, the firing properties of Barrington's neurons that project axons to the spinal cord were examined. Based on these studies, a model begins to emerge that places Barrington's nucleus in the micturition pathway that is involved in increasing bladder pressure rapidly and strongly, while also maintaining high bladder pressure. In addition, Barrington's neurons are suggested to have another role, that is, increasing the probability of micturition contraction by activating a spinal excitatory pathway or disinhibiting a spinal inhibitory mechanism. In contrast to the excitatory role of Barrington's nucleus, this nucleus does not seem to trigger bladder relaxation.

Activation of α 1D Adrenergic Receptors in the Rat Urothelium Facilitates the Micturition Reflex

PURPOSE

Previous studies have revealed that the activation of alpha(1) adrenergic receptors in urothelial cells releases neurotransmitters. We determined if alpha(1D) adrenergic receptors are expressed in the urothelium of the rat bladder and if inhibition of these receptors affects reflex voiding.

MATERIALS AND METHODS

Female Wistar rats were used in the experiments. Receptor expression was evaluated by Western blot. The effects of receptor activation were studied using cystometrograms, measurement of adenosine triphosphate concentrations in the bladder lumen and afferent nerve recording. The alpha(1D) antagonist naftopidil (0.75 to 1.66 mg/kg) was administered intravenously into the external jugular vein.

RESULTS

The expression of alpha(1D) adrenergic receptors was detected in urothelial tissue with Western blot and immunohistochemistry. The alpha(1D) receptor antagonist naftopidil prolonged the intercontraction interval during continuous infusion cystometrograms in conscious rats (143% of the control value) and suppressed the excitatory effect of intravesical infusion of acetic acid (0.1%) on the intercontraction interval (220%). Naftopidil inhibited the bladder afferent nerve activity induced by bladder distention (32.0%) and acetic acid infusion (30.4%), and decreased adenosine triphosphate levels in the bladder perfusate during bladder distention (36.6%).

CONCLUSIONS

Endogenous catecholamines appear to act on alpha(1D) receptors in the urothelium to facilitate mechanosensitive bladder afferent nerve activity and reflex voiding.

Combined use of alpha-adrenergic and muscarinic antagonists for the treatment of voiding dysfunction

PURPOSE

We provide an overview of the medical literature supporting the combined use of muscarinic and alpha-adrenergic antagonist therapy for the treatment of voiding dysfunction.

MATERIALS AND METHODS

The MEDLINE database (1966 to 2004) of the United States National Library of Medicine was searched for pertinent studies.

RESULTS

Although the mechanism of action of alpha-adrenergic antagonist therapy for voiding dysfunction has traditionally been assumed to be relaxation of the periurethral, prostatic and bladder neck smooth muscle, substantial evidence supports action at extraprostatic sites involved in micturition, including the bladder dome smooth muscle, peripheral ganglia, spinal cord and brain. Likewise the mechanism of action of anticholinergic therapy has been traditionally assumed to be inhibition of the M3 muscarinic receptor subtypes that mediate normal bladder contractions. However, M2 receptor mediates hypertrophied bladder contractions and there is evidence for an M2 component to the suprasacral control of voiding.

CONCLUSIONS

Based on the physiology of alpha-adrenergic and muscarinic receptors the inhibition of each one would be expected to be more beneficial than that of either alone because they would work on 2 components of detrusor function. Patients who would likely benefit from this combination therapy are men with lower urinary tract symptoms, women with urgency/frequency syndrome (overactive bladder), patients with uninhibited bladder contractions due to neurogenic bladder, and patients with pelvic pain and voiding symptoms, ie interstitial cystitis and chronic prostatitis/chronic pelvic pain syndrome.

Central nervous control of micturition and urine storage

The micturition reflex is one of the autonomic reflexes, but the release of urine is regulated by voluntary neural mechanisms that involve centers in the brain and spinal cord. The micturition reflex is a bladder-to-bladder contraction reflex for which the reflex center is located in the rostral pontine tegmentum (pontine micturition center: PMC). There are two afferent pathways from the bladder to the brain. One is the dorsal system and the other is the spinothalamic tract. Afferents to the PMC ascend in the spinotegmental tract, which run through the lateral funiculus of the spinal cord. The efferent pathway from the PMC also runs through the lateral funiculus of the spinal cord to inhibit the thoracolumbar sympathetic nucleus and the sacral pudendal nerve nucleus, while promoting the activity of the sacral parasymapathetic nucleus. Inhibition of the sympathetic nucleus and pudendal nerve nucleus induces relaxation of the bladder neck and the external urethral sphincter, respectively. There are two centers that inhibit micturition in the pons, which are the pontine urine storage center and the rostral pontine reticular formation. In the lumbosacral cord, excitatory glutamatergic and inhibitory glycinergic/GABAergic neurons influence both the afferent and efferent limbs of the micturition reflex. The activity of these neurons is affected by the pontine activity. There are various excitatory and inhibitory areas co-existing in the brain, but the brain has an overall inhibitory effect on micturition, and thus maintains continence. For micturition to occur, the cerebrum must abate its inhibitory influence on the PMC.

1-(2-pyrimidinyl)-piperazine, a buspirone metabolite, modulates bladder function in the anesthetized rat

AIMS

To examine the effects of 1-(2-pyrimidinyl)-piperazine (1-PP), a buspirone metabolite, on bladder function in vivo.

METHODS

Micturition reflexes in the rat were evaluated in two models of bladder function; a constant infusion model employing 0.5% acetic acid and an isovolumic model.

RESULTS

In the constant infusion model, 1-PP (0.14-1.32 mg/kg) dose-dependently and significantly decreased the number of bladder contractions measured during a 30 min recording period, with little effect on the pressure developed during each contraction. 1-PP is an alpha2-adrenergic receptor antagonist. The alpha2 antagonists BRL44408 (alpha2A vs. alpha2B selective; 0.3 and 1 mg/kg), imiloxan (alpha(2B) vs. alpha2A selective; 1 mg/kg), and yohimbine (non-subtype selective; 1 mg/kg; but not 0.3 mg/kg) also significantly reduced the number of contractions. Vehicle was without effect. In the isovolumic model, 1-PP (0.03-1.0 mg/kg) produced a dose-dependent and significant reduction in the number of bladder contractions recorded during a 15 min assessment period, with the maximum effect observed at 0.3 mg/kg. 1-PP had little effect on blood pressure; the only effect was observed at the highest dose (1 mg/kg) where it produced a transient 17% decrease in pressure. Cromakalim and tolterodine served as comparitors in all studies.

CONCLUSIONS

1-PP decreased the number of bladder contractions evoked by the micturition reflex at doses that had little effect on either the pressure developed during each bladd er contraction or on blood pressure. The effects of 1-PP are likely mediated primarily by alpha2 receptor antagonism.

Short-term effect of a single levodopa dose on micturition disturbance in Parkinson's disease patients with the wearing-off phenomenon

We investigated the short-term effects of a single dose of levodopa (L-dopa) on micturition function in PD patients with wearing-off phenomenon. Eighteen PD patients who had median Hoehn and Yahr scores of 5 during the off phase and 3 during the on phase were recruited. We carried out urodynamic studies before and about 1 hour after the patients had taken 100 mg of L-dopa with dopa-decarboxylase inhibitor (DCI). After taking the L-dopa/DCI, urinary urgency and urge incontinence aggravated, whereas voiding difficulty was alleviated in all 12 patients. When compared to the baseline assessment, urodynamic study results after taking 100 mg of L-dopa/DCI showed aggravated detrusor hyperreflexia; decreased maximum bladder capacity (P = 0.006); an increased maximum Watts Factor value (P = 0.001), reflecting the detrusor power on voiding; an increased Abrams-Griffiths number (P = 0.042), reflecting urethral obstruction on voiding; decreased residual urine volume (P = 0.025); and increased static urethral closure pressure (P = 0.012). One hundred milligrams of L-dopa/DCI worsened detrusor hyperreflexia, producing worsened urinary urgency and urge incontinence during the storage (bladder-filling) phase. It also increased detrusor contractility much more than it did urethral obstruction in the voiding phase, producing overall lessening of voiding difficulty and improving voiding efficiency in our PD patients with the wearing-off phenomenon.

Current and future pharmacological treatment for overactive bladder

PURPOSE

Urinary incontinence and overactive bladder are important and common conditions that have received little general medical attention. We reviewed the magnitude and impact of these conditions, and discuss pharmacotherapy as well as new drugs under investigation.

MATERIALS AND METHODS

The main emphasis of this review is pharmacological therapy for the bladder. We discuss currently available agents, drugs under development and pharmacological targets that would be suitable targets for treating overactive bladder. Drugs such as duloxetine that target not bladder smooth muscle, but rather central nervous system control of the micturition reflex are undergoing clinical trials. We also discuss intravesical therapy and alternative drug delivery methods, such as intravesical capsaicin and botulinum toxin, with special emphasis on approaches to modulate bladder afferent nerve function for preventing overactive bladder.

RESULTS

There are many advantages to advanced drug delivery systems, including long-term therapeutic efficacy, decreased side effects and improved patient compliance. Future speculation such as gene therapy holds great promise for overactive bladder because it is possible to access all genitourinary organs via endoscopy and other minimally invasive techniques that are ideally suited for gene therapy.

CONCLUSIONS

Traditional anticholinergic therapies are limited in their effectiveness. There is great hope for future research regarding voiding dysfunction and urinary incontinence through a focus on afferent nerve intervention for preventing overactive bladder.

Bladder contractility-related neurons in Barrington's nucleus: axonal projections to the spinal cord in the cat

Barrington's nucleus projects directly to the sacral parasympathetic nucleus. The purpose of this study was to clarify whether neurons in Barrington's nucleus that increase their firing during bladder contractions project to the spinal cord and, if so, to which level(s) the axon reaches. Single units were recorded in Barrington's nucleus of cat with glass microelectrodes, and the termination level of descending axons was determined by antidromic stimulation of the spinal cord. Thirty-nine neurons projecting to the spinal cord were located in rostral parts of the dorsolateral pontine tegmentum, medial and ventral to the mesencephalic trigeminal tract. This finding is consistent with previous neuronal tracing studies. All neurons increased their firing rates during contraction associated with micturition. In 19 examined neurons, the most caudal level of the descending axon distributed between the L7 and the S3 level. Stimulation of the axon at this most caudal level resulted in antidromic spike latencies ranging between 19.5 msec and 45.0 msec. These antidromic latencies were much smaller than previously reported orthodromic conduction times between neurons in Barrington's nucleus and sacral preganglionic neurons innervating the bladder. The mean conduction velocity of the descending axon from the cell body to the border between Th13 and the L1 ranged between 7.2 m/sec and 27.7 m/sec. The decrease of the mean conduction velocity was observed at the lumbar as well as at the sacral segments, suggesting that axons issue collaterals to the lumbar level as well as to the sacral level.

Effects of intrathecal injection of tamsulosin and naftopidil, alpha-1A and -1D adrenergic receptor antagonists, on bladder activity in rats

The effects of intrathecal injection of tamsulosin (an alpha-1A adrenergic receptor antagonist) and naftopidil (an alpha-1D adrenergic receptor antagonist) on isovolumetric bladder contraction were investigated in rats under urethane anesthesia. Intrathecal injection of tamsulosin (10-30 microg) or naftopidil (0.1-30 microg) transiently abolished isovolumetric rhythmic bladder contraction. Following the recovery of bladder contraction, the interval between contractions was the same as the control value before the injection. The amplitude of bladder contraction was decreased by intrathecal injection of naftopidil (3-30 microg), but not by tamsulosin. Therefore, in addition to the antagonistic action of these agents on the alpha-1 adrenergic receptors of prostatic smooth muscle, both agents (especially naftopidil) may also act on the lumbosacral cord, and thus may improve collecting disorders in patients with benign prostatic hyperplasia.

The effects of a selective noradrenaline reuptake inhibitor on the urethra: an in vitro and in vivo study

OBJECTIVE

To identify the effects of a selective noradrenaline reuptake inhibitor (venlafaxine) on urethral perfusion pressure (UPP) in rabbits and rats, and thus assess its therapeutic potential for treating stress urinary incontinence.

MATERIALS AND METHODS

Strips of bladder and proximal urethra were prepared from female New Zealand White rabbits. Each strip was electrically stimulated and the contractile responses of controls strips compared with those after pretreatment with venlafaxine (100 micromol/L). In separate experiments using 80 adult female Sprague-Dawley rats (250-300 g), changes in intravesical pressure and UPP after the intra-arterial and intra-urethral administration of phenylephrine, phentolamine, fluoxetine and venlafaxine were monitored using double-lumen catheters.

RESULTS

Pretreatment with venlafaxine significantly decreased the contraction of bladder strips (P=0.01) and significantly increased the contraction of urethral strips (P=0.008). In vivo, phenylephrine administered by both routes significantly increased UPP (P=0.02); phentolamine (arterial) significantly decreased UPP (P=0.001); fluoxetine (arterial) had no effect on UPP, and venlafaxine (both routes) significantly increased UPP (both P<0.001). The intravesical pressure was not changed significantly in any animal.

CONCLUSIONS

Venlafaxine effectively increased UPP both in vitro and in vivo; these results imply that venlafaxine may be useful for treating stress urinary incontinence, by increasing the UPP.

Tachykinins as modulators of the micturition reflex in the central and peripheral nervous system

In the normal urinary bladder, tachykinins (TKs) are expressed in a population of bladder nociceptors that is sensitive to the excitatory and desensitizing effects of capsaicin (i.e., capsaicin-sensitive primary afferent neurons (CSPANs)). Several endobiotics or xenobiotics excite CSPANs and release TKs and other mediators at both the peripheral and spinal cord level. The peripheral release of TKs determines a set of responses (known as neurogenic inflammation) that includes vasodilatation, plasma protein extravasation, smooth muscle contraction and stimulation of afferent nerves. Following chronic inflammation, both immune cells and capsaicin-resistant sensory neurons can de novo express TKs: whether these pools of TKs are releasable and contribute to inflammatory processes is presently unsettled. At the spinal cord level, the release of TKs contributes in determining an altered pattern of vesicourethral reflexes in response to nociceptive stimulation of the bladder by conveying: (a) the afferent transmission to supraspinal sites, and (b) descending or sensory inputs to the sacral parasympathetic nucleus (SPN). Recent evidence also attribute a synergetic role of TKs in the supraspinal modulation of the sensory arm of the micturition reflex. The overall available information suggests that TK receptor antagonists may affect bladder motility/reflexes which occur during different pathological states, while having little influence on the normal motor bladder function.

Pharmacology of the lower urinary tract

The functions of the lower urinary tract, to store and periodically release urine, are dependent on the activity of smooth and striated muscles in the urinary bladder, urethra, and external urethral sphincter. This activity is in turn controlled by neural circuits in the brain, spinal cord, and peripheral ganglia. Various neurotransmitters, including acetylcholine, norepinephrine, dopamine, serotonin, excitatory and inhibitory amino acids, adenosine triphosphate, nitric oxide, and neuropeptides, have been implicated in the neural regulation of the lower urinary tract. Injuries or diseases of the nervous system, as well as drugs and disorders of the peripheral organs, can produce voiding dysfunctions such as urinary frequency, urgency, and incontinence or inefficient voiding and urinary retention. This chapter will review recent advances in our understanding of the pathophysiology of voiding disorders and the targets for drug therapy.

Effect of TAK-637, a tachykinin NK1-receptor antagonist, on lower urinary tract function in cats

The effect of TAK-637 ((aR,9R)-7-[3,5-bis(trifluoromethyl)benzyl]-8,9,10,11-tetrahydro-9-methyl-5-(4-methylphenyl)-7H[1,4]diazocino[2,1g][1,7]naphthyridine-6,13-dione), a tachykinin NK1-receptor antagonist, on lower urinary tract function was investigated in cats. TAK-637 (0.1, 0.3, 1 and 3 mg/kg, i.v.) produced a dose-dependent increase in bladder capacity without any significant reduction in voiding efficiency in decerebrate cats. The maximal increase in bladder capacity was 94%. By contrast, oxybutynin at 1 and 3 mg/kg (i.v.) produced a 18% and 35% increase in bladder capacity, respectively, with a 47% and 45% reduction in voiding efficiency. TAK-637 (3 mg/kg, i.v.) did not inhibit the micturition reflex induced by electrical stimulation of the rostral brainstem near the locus coeruleus, indicating that it does not impair the well-organized micturition reflex (bladder contraction and urethral relaxation). These results suggest that TAK-637 increases bladder storage capability without inhibiting the voiding function of the lower urinary tract, presumably by inhibiting the afferent pathway of the micturition reflex, rather than the efferent pathway.

Role of spinal alpha1-adrenoceptor subtypes in the bladder reflex in anesthetized rats

The contribution of different subtypes of alpha1-adrenoceptors in the lumbosacral spinal cord to the control of the urinary bladder was examined in urethane-anesthetized rats. Bladder pressure was recorded via a transurethral catheter under isovolumetric conditions. Drugs were administered intrathecally at the L6-S1 segmental level of spinal cord. RS-100329 (an alpha1A-antagonist) in doses of 25, 50, and 100 nmol significantly decreased bladder-contraction amplitude by 38%, 52%, and 95%, respectively, whereas (+)-cyclazosin (an alpha1B-antagonist) significantly decreased bladder-contraction amplitude (48% reduction) only in a 50-nmol but not a 100-nmol dose. Fifty nanomoles of RS-100329 and (+)-cyclazosin increased bladder-contraction frequency by 54% and 44%, respectively. BMY7378 (an alpha1D-antagonist), in doses of 25, 50, and 100 nmol, did not change bladder activity. These studies suggest that reflex-bladder activity is modulated by two types of spinal alpha1-adrenergic mechanisms: 1) alpha1A- or alpha1B-inhibitory control of the frequency of voiding reflexes presumably mediated by an alteration in the processing of bladder afferent input and 2) alpha(1A)-facilitatory modulation of the descending efferent limb of the micturition-reflex pathway. Spinal alpha1D-adrenoceptors do not appear to have a significant role at either site.

Effects of adrenergic alpha2-receptor agonists on urinary bladder contraction in conscious rats

We investigated the effects of the adrenergic alpha2-receptor agonists clonidine, oxymetazoline and tizanidine on bladder contractions induced by infusing fluid into the bladders of conscious male rats. I.v. clonidine and oxymetazoline (both 0.01 to 0.1 mg/kg) caused bladder hyperactivity, expressed by shortening of the intercontraction interval. Tizanidine (0.1 mg/kg, i.v.) caused slight shortening of the intercontraction interval. The rank order of potency was clonidine = oxymetazoline >> tizanidine. Intrathecal (i.t.) injection of 10 microg clonidine and oxymetazoline, and intracerebroventricular (i.c.v) injection at 15 microg, produced almost the same pattern of bladder hyperactivity as that observed after i.v. injection of these drugs (0.03 mg/kg, i.v.). For all three administration routes of clonidine and oxymetazoline, i.v. idazoxan (0.3 mg/kg) exerted an inhibitory effect on the bladder hyperactivity induced by these drugs, except i.c.v injection of oxymetazoline. I.t. phenylephrine (30 microg) did not change the intercontraction interval. Although i.c.v. phenylephrine (15 microg) shortened the intercontraction interval, the potency was weaker than those of i.c.v. clonidine and oxymetazoline (15 microg). These results suggest that clonidine and oxymetazoline cause bladder hyperactivity by acting at adrenergic alpha2 receptors in the micturition centers of the lumbosacral and supraspinal regions.

Role of spinal alpha(1)-adrenergic mechanisms in the control of lower urinary tract in the rat

The role of spinal alpha(1)-adrenergic mechanisms in the control of urinary bladder function was examined in urethane (1.2 g/kg s.c.) anesthetized and decerebrate unanesthetized female Sprague-Dawley rats (250-320 g). Bladder activity was recorded via a transurethral catheter during continuous infusion (0.21 ml/min) cystometrograms or under isovolumetric conditions. All drugs were administered intrathecally at the L(6)-S(1) segmental level of spinal cord. During cystometrograms, 3 or 30 nmol of phenylephrine (alpha(1)-adrenergic agonist) did not alter bladder activity; whereas 300 nmol increased the intercontraction interval by 98% and pressure threshold for inducing micturition by 115%, but did not change bladder contraction amplitude. A large dose of phenylephrine (3000 nmol) completely blocked reflex voiding and induced overflow incontinence at a high baseline pressure (mean: 33 cmH(2)O; range: 28-42 cmH(2)O). Under isovolumetric conditions, 3-30 nmol of phenylephrine abolished bladder activity for 22-45 min; whereas smaller doses (0.003-0.3 nmol) were inactive. Doxazosin (50 nmol), an alpha(1)-adrenergic antagonist, decreased intercontraction intervals but did not change bladder contraction amplitude during cystometrograms. Under isovolumetric conditions this dose of doxazosin increased bladder contraction frequency and decreased bladder contraction amplitude. Smaller doses (5 or 25 nmol) of doxazosin did not alter bladder activity. These studies suggest that two types of spinal alpha(1)-adrenergic mechanisms are involved in reflex bladder activity: (1) inhibitory control of the frequency of voiding reflexes presumably by regulating afferent processing in the spinal cord and (2) facilitatory modulation of the descending limb of the micturition reflex pathway.

Effects of spinal alpha 1-adrenoceptor antagonism on bladder activity induced by apomorphine in conscious rats with and without bladder outlet obstruction

To test the hypothesis that the spinal control of micturition involves alpha 1-adrenoceptors, the urodynamic effects of intrathecal and intraarterial alpha 1-adrenoceptor blockade on apomorphine-induced bladder activity in rats were studied. Continuous cystometry was performed in conscious female Sprague-Dawley rats with and without bladder outflow obstruction. In normal rats, subcutaneous apomorphine, 30 micrograms/kg, induced bladder activity that was abolished or attenuated by the alpha 1-adrenoceptor antagonists indoramin and doxazosin given intrathecally or intra-arterially. In rats with outlet obstruction, apomorphine 30 micrograms/kg caused no change in cystometric parameters. However, at a dose of 100 micrograms/kg the drug induced bladder activity, which was attenuated by intrathecal indoramin or doxazosin. These results suggest that the bladder activity evoked by apomorphine-stimulation of bulbospinal pathways can be influenced by alpha 1-adrenoceptors at the spinal and peripheral levels, both in normal rats and in rats with bladder hypertrophy secondary to outlet obstruction.

The role of spinal and peripheral alpha1- and alpha2-adrenoceptors on bladder activity induced by bladder distension in anaesthetized rat

OBJECTIVE

To elucidate the effects of alpha1- and alpha2-adrenoceptor antagonists on the micturition reflex induced by bladder distension in the anaesthetized rat at the peripheral and spinal level. Materials and methods Using continuous cystometry in 80 anaesthetized female Sprague-Dawley rats, changes in basal pressure (BaP), micturition pressure (MP), bladder capacity (BC), micturition volume (MV), interval of bladder contraction (frequency) and residual volume (RV) to the selective intra-arterial and intrathecal administration of drugs were monitored and analysed.

RESULTS

The intra-arterial administration of phentolamine, prazosin, doxazosin and tamsulosin significantly decreased the MP; doxazosin increased MV, BC, RV and frequency. MP was inhibited more by intra-arterial doxazosin than by prazosin or tamsulosin. Intrathecal phentolamine increased BaP, BC, RV and decreased MP and MV; tamsulosin decreased frequency and increased BC. Clonidine markedly increased BaP and frequency, whereas MV and BC were significantly lower; yohimbine increased MV, BC and decreased RV. Intra-arterial yohimbine significantly increased MV.

CONCLUSIONS

At the spinal level, the micturition reflex evoked by bladder distension was preferentially suppressed by phentolamine or yohimbine, suggesting the involvement of alpha2-adrenoceptors. In the periphery, alpha1-adrenoceptor blockers preferentially suppressed the reflex. We suggest that both alpha1- and alpha2-adrenoceptors play a role in the distension-evoked micturition reflex in the rat.

Role of supraspinal tachykinins for volume- and L-dopa-induced bladder activity in normal conscious rats

To clarify the roles of tachykinins in volume-induced micturition and in bladder hyperactivity, presumed to originate from supraspinal structures, normal, female Sprague-Dawley rats were investigated cystometrically before and after intracerebroventricular (i.c.v) administration of RP 67,580, a selective antagonist of NK-1 receptors, and/or SR 48,968, a selective antagonist of NK-2 receptors. The effects of RP 67,580 and SR 48,968 on intra-peritoneal (i.p.) L-dopa-induced bladder hyperactivity were also investigated. I.c.v. administration of RP 67,580 (20 nmol) SR 48,968 (20 nmol) suppressed micturition. Combination of i.c.v. RP 67, 580 (2 nmol) and SR 48,968 (2 nmol) significantly decreased micturition pressure (18%), and increased bladder capacity (26%), micturition volume (18%), and residual volume (223%). In rats pretreated with i.p. carbidopa 50 mg/kg, i.p. L-dopa 50 mg/kg caused bladder hyperactivity that was attenuated by the combination of i.c. v. RP 67,580 (2 nmol) and SR 48,968 (2 nmol). The results suggest that tachykinins, via stimulation of NK receptors in supraspinal structures, are involved in both volume and L-dopa-induced stimulation of bladder activity. This may imply that tachykinins can influence both the supraspinal and spinal control of the urinary bladder. It also implies that supraspinal NK receptors are a possible target for drugs aimed for elimination of bladder hyperactivity mediated via these pathways. Neurourol. Urodynam. 19:101-109, 2000.

Oxytocin-induced stimulation and inhibition of bladder activity in normal, conscious rats--influence of nitric oxide synthase inhibition

The role of the oxytocin-containing projections to the autonomic nuclei of the spinal cord for lower urinary tract function has not been clarified. The hypothesis was tested that oxytocin acts as a mediator of bladder contraction at the spinal cord level. In conscious female rats undergoing continuous cystometry, intrathecal oxytocin (30 ng approximately 30 pmoles) significantly increased micturition pressure (P<0.001), and decreased bladder capacity (P<0.01) and micturition volume (P<0.01). Residual volume increased (P<0.05), and so did the amplitude and frequency of non-voiding contractions (P<0.01). Immediately after administration of oxytocin, the animals showed frequent stretching movements and yawning, and they licked their tails. The effects of oxytocin were dose-dependent; high concentrations (100 ng) were ineffective. Intra-arterial injection of oxytocin (30 ng) near the bladder had no effect. In isolated detrusor strips, oxytocin caused a concentration-dependent contraction; the concentration response curve was concentration-dependently shifted to the right by the oxytocin antagonist, 1-deamino, 2-D-Tyr(OEt), 4-Thr, 8-Orn-OT. Intrathecal injection of the antagonist (500 ng), had per se no effect on micturition. However, when the antagonist was given intrathecally 4-5 min prior to intrathecal oxytocin (30 ng), the effects of oxytocin were reduced or completely prevented. When given after intrathecal administration of the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester, intrathecal oxytocin (30 ng) abolished micturition within 5-7 min; all animals developed overflow incontinence, and paralysis of the hindlimbs. These results suggests that in the rat, oxytocin, released from descending pathways, may act as a modulator of the micturition reflex at the spinal level, and that it may interact with nitric oxide. The physiological implications of the findings remain to be established.

Micturition in conscious rats with and without bladder outlet obstruction: role of spinal alpha 1-adrenoceptors

1. In normal rats and rats with bladder hypertrophy secondary to outflow obstruction, undergoing continuous cytometry, we examined the responses to the selective alpha 1-adrenoceptor antagonist doxazosin given intrathecally (i.t.) and intra-arterially (i.a.). In addition, we investigated the effects of the drug on L-dopa-induced bladder hyperactivity in normal, unobstructed rats. 2. Doxazosin 50 nmol (approximately 60 micrograms kg-1), given i.t., decreased micturition pressure in normal rats and in animals with post-obstruction bladder hypertrophy. The effect was much more pronounced in the animals with hypertrophied/overactive bladders. Doxazosin did not markedly affect the frequency or amplitude of the unstable contractions observed in obstructed rats. In contrast, however, doxazosin reduced L-dopa-induced bladder overactivity. When tested, the enantiomers of doxazosin produced qualitatively similar effects to doxazosin, but there was no evidence of stereoselectivity. 3. The results suggest that in addition to the well documented action on prostatic and lower urinary tract smooth muscle, and an effect on the sympathetic outflow to the bladder, bladder neck, prostate, and external urethral sphincter, doxazosin may have an action at the level of the spinal cord and ganglia, thereby reducing activity in the parasympathetic nerves to the bladder. This effect is more pronounced in rats with bladder hypertrophy than in normal rats.

Beneficial effect of intranasal desmopressin for nocturnal polyuria in Parkinson's disease

Patients with Parkinson's disease (PD) are known to experience autonomic nervous system dysfunction: this disruptive symptomatology includes urinary urgency, frequency, and nocturnal polyuria. Anticholinergic and tricyclic medications can be beneficial in controlling these urinary symptoms, but have unpleasant side effects in some patients. Desmopressin has been used to treat nocturnal polyuria successfully in a number of conditions, such as central diabetes insipidus, enuresis, and autonomic failure. The purpose of the present study was to assess the efficacy of desmopressin in patients with PD with significant nocturia. Eight patients were recruited into the study. They were first asked to establish a baseline of number of nocturnal voids; the patients were then prescribed the intranasal form of desmopressin and asked to continue to record the number of nocturnal voids. The five patients who completed the trial demonstrated clinically and statistically significant reductions in the frequency of nocturnal voids. One patient became hyponatremic and confused during desmopressin administration; his symptoms resolved soon after the desmopressin was discontinued. Two patients failed to complete the trial due to compliance problems. Thus, desmopressin appears to be a safe and effective medication for nocturnal polyuria in PD.

Locus coeruleus noradrenergic neurons as a micturition center

The micturition reflex arch is composed of an afferent pathway from the urinary bladder to the pontine micturition center via the pelvic nerve and spinal cord. The efferent pathway projects from the center to the bladder through the sacral parasympathetic center of intermediolateral column cells. The pontine micturition center is thought to be noradrenergic (NA) neurons in the locus coeruleus (LC) due to the following observations: (1) LC stimulation induces bladder contraction in cats, and this response is blocked by intrathecal application of alpha 1-adrenergic antagonist (prazosin), but not the alpha 2- nor beta-adrenergic antagonist. Although this contraction is not observed after NA depletion with reserpine, with subsequent i.v. injection of L-dopa a NA precursor induces recurrence of the response. (2) The micturition reflex induced by bladder distention is similarly reversed with alpha 1-adrenergic antagonist and chemical destruction of NA cells by injecting 6-hydroxydopamine in the LC. However, subsequently applied alpha 1-adrenergic agonist induces the contraction due to bladder distention. (3) LC stimulation elicits spike generation of sacral intermediolateral cells. Microiontophoretically applied alpha 1-adrenergic antagonist inhibits the LC stimulation-induced spikes of the neuron, which is not antidromically activated by pelvic nerve stimulation. However, spikes in neurons activated antidromically were not affected by the drug. This indicates that the former and latter neurons are interneuron and parasympathetic projecting neurons, respectively. The existence of NA terminals from the LC and alpha 1-adrenergic receptors in the intermediolateral column cells supports the concept that NA cells in the LC are units constituting the micturition center.

Interactions between glutamatergic and monoaminergic systems controlling the micturition reflex in the urethane-anesthetized rat

The effects of MK-801 (0.001-3 mg/kg i.v.), a non-competitive NMDA glutamate receptor antagonist, on the micturition reflex were examined during continuous saline infusion (0.21 ml/min) cystometrograms (CMGs) in urethane-anesthetized (1.2 g/kg s.c.) rats pretreated with either reserpine (5 mg/kg i.p.), p-chlorophenylalanine (p-CPA; 150 mg/kg i.p., twice a day, 3 consecutive days), L-DOPA (200 mg/kg i.p. + carbidopa 100 mg/kg i.p.) or apomorphine (10 mg/kg i.v.). Pretreatment with reserpine 8-12 h prior to the CMG recording, antagonized the inhibitory effect of MK-801 on the amplitude of micturition contractions while pretreatment with vehicle had no effect. However, pretreatment with the same dose of reserpine 18-22 h prior to the experiment failed to antagonize the inhibitory effect of MK-801. Both reserpine pretreatments enhanced the amplitude of reflex bladder contractions. Pretreatment with p-CPA did not alter bladder activity or the inhibitory effect of MK-801 on amplitude of micturition contractions. When administered 15 min prior to the MK-801, L-DOPA or apomorphine reduced by 70% or 63%, respectively, the maximal inhibitory effect of MK-801 on the amplitude of reflex bladder contractions. These data suggest that there is an interaction between glutamatergic and monoaminergic mechanisms in the regulation of micturition reflex. Since reserpine which reduces both catecholamine and serotonin levels in the nervous system altered the depressant effect of MK-801 on bladder activity, but p-CPA, an agent which depletes serotonin stores, did not, it is concluded that catecholaminergic pathways are involved in this interaction.(ABSTRACT TRUNCATED AT 250 WORDS)