Sensory substance P-innervation of the urinary bladder: possible site of action of capsaicin in causing urine retention in rats

Autonomic Nervous System Dysfunction Is Related to Chronic Prostatitis/Chronic Pelvic Pain Syndrome

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a common and non-lethal urological condition with painful symptoms. The complexity of CP/CPPS's pathogenesis and lack of efficient etiological diagnosis results in incomplete treatment and recurrent episodes, causing long-term mental and psychological suffering in patients. Recent findings indicate that the autonomic nervous system involves in CP/CPPS, including sensory, sympathetic, parasympathetic, and central nervous systems. Neuro-inflammation and sensitization of sensory nerves lead to persistent inflammation and pain. Sympathetic and parasympathetic alterations affect the cardiovascular and reproductive systems and the development of prostatitis. Central sensitization lowers pain thresholds and increases pelvic pain perception in chronic prostatitis. Therefore, this review summarized the detailed processes and mechanisms of the critical role of the autonomic nervous system in developing CP/CPPS. Furthermore, it describes the neurologically relevant substances and channels or receptors involved in this process, which provides new perspectives for new therapeutic approaches to CP/CPPS.

Pathways and parameters of sacral neuromodulation in rats

The stimulation paradigm for sacral neuromodulation has remained largely unchanged since its inception. We sought to determine, in rats, whether stimulation-induced increases in bladder capacity correlated with the proportion of sensory pudendal (PudS) neurons at each stimulated location (L6, S1). If supported, this finding could guide the choice of stimulation side (left/right) and level (S2, S3, S4) in humans. Unexpectedly, we observed that acute stimulation at clinically relevant (low) amplitudes [1-1.5 × motor threshold (Tm)], did not increase bladder capacity, regardless of stimulus location (L6 or S1). More importantly for the ability to test our hypothesis, there was little anatomic variation, and S1 infrequently contributed nerve fibers to the PudS nerve. During mapping studies we noticed that large increases in PudS nerve activation occurred at amplitudes exceeding 2Tm. Thus, additional cystometric studies were conducted, this time with stimulation of the L6-S1 trunk, to examine further the relationship between stimulation amplitude and cystometric parameters. Stimulation at 1Tm to 6Tm evoked increases in bladder capacity and decreases in voiding efficiency that mirrored those produced by PudS nerve stimulation. Many animal studies involving electrical stimulation of nerves of the lower urinary tract use stimulation amplitudes that exceed those used clinically (∼1Tm). Our results confirm that high amplitudes generate immediate changes in cystometric parameters; however, the relationship to low-amplitude chronic stimulation in humans remains unclear. Additional studies are needed to understand changes that occur with chronic stimulation, how these changes relate to therapeutic outcomes, and the contribution of specific nerve fibers to these changes.NEW & NOTEWORTHY Acute low-amplitude electrical stimulation of sacral nerve (sacral neuromodulation) did not increase bladder capacity in anesthetized CD, obese-prone, or obese-resistant rats. Increasing stimulation amplitude correlated with increases in bladder capacity and pudendal sensory nerve recruitment. It is unclear how the high-amplitude acute stimulation that is commonly used in animal experiments to generate immediate effects compares mechanistically to the chronic low-amplitude stimulation used clinically.

The role of capsaicin-sensitive C-fiber afferent pathways in the control of micturition in spinal-intact and spinal cord-injured mice

We examined bladder and urethral sphincter activity in mice with or without spinal cord injury (SCI) after C-fiber afferent desensitization induced by capsaicin pretreatment and changes in electrophysiological properties of mouse bladder afferent neurons 4 wk after SCI. Female C57BL/6N mice were divided into four groups: 1) spinal intact (SI)-control, 2) SI-capsaicin pretreatment (Cap), 3) SCI-control, and 4) SCI-Cap groups. Continuous cystometry and external urethral sphincter (EUS)-electromyogram (EMG) were conducted under an awake condition. In the Cap groups, capsaicin (25, 50, or 100 mg/kg) was injected subcutaneously 4 days before the experiments. In the SI-Cap group, 100 mg/kg capsaicin pretreatment significantly increased bladder capacity and decreased the silent period duration of EUS/EMG compared with the SI-control group. In the SCI-Cap group, 50 and 100 mg/kg capsaicin pretreatment decreased the number of nonvoiding contractions (NVCs) and the duration of reduced EUS activity during voiding, respectively, compared with the SCI-control group. In SCI mice, hexamethonium, a ganglionic blocker, almost completely blocked NVCs, suggesting that they are of neurogenic origin. Patch-clamp recordings in capsaicin-sensitive bladder afferent neurons from SCI mice showed hyperexcitability, which was evidenced by decreased spike thresholds and increased firing rate compared with SI mice. These results indicate that capsaicin-sensitive C-fiber afferent pathways, which become hyperexcitable after SCI, can modulate bladder and urethral sphincter activity in awake SI and SCI mice. Detrusor overactivity as shown by NVCs in SCI mice is significantly but partially dependent on capsaicin-sensitive C-fiber afferents, whereas the EUS relaxation during voiding is enhanced by capsaicin-sensitive C-fiber bladder afferents in SI and SCI mice.

Netupitant, a Potent and Highly Selective NK1 Receptor Antagonist, Alleviates Acetic Acid-Induced Bladder Overactivity in Anesthetized Guinea-Pigs

Introduction. Tachykinins potently contract the isolated urinary bladder from a number of animal species and play an important role in the regulation of the micturition reflex. On the guinea-pig isolated urinary bladder we examined the effects of a new potent and selective NK1 receptor antagonist (netupitant) on the contractions induced by a selective NK1 receptor agonist, SP-methylester (SP-OMe). Moreover, the effects of netupitant and another selective NK1 antagonist (L-733,060) were studied in anesthetized guinea-pigs using two experimental models, the isovolumetric bladder contractions and a model of bladder overactivity induced by intravesical administration of acetic acid (AA). Methods and Results. Detrusor muscle strips were mounted in 5 mL organ baths and isometric contractions to cumulative concentrations of SP-OME were recorded before and after incubation with increasing concentrations of netupitant. In anesthetized female guinea-pigs, reflex bladder activity was examined under isovolumetric conditions with the bladder distended with saline or during cystometry using intravesical infusion of AA. After a 30 min stabilization period, netupitant (0.1-3 mg/kg, i.v.) or L-733,060 (3-10 mg/kg, i.v.) were administered. In the detrusor muscle, netupitant produced a concentration-dependent inhibition (mean pKB = 9.24) of the responses to SP-OMe. Under isovolumetric conditions, netupitant or L-733,060 reduced bladder contraction frequency in a dose-dependent manner, but neither drug changed bladder contraction amplitude. In the AA model, netupitant dose-dependently increased intercontraction interval (ICI) but had no effect on the amplitude of micturition (AM). L-733,060 dose-dependently increased ICI also but this effect was paralleled by a significant reduction of AM. Conclusion. Netupitant decreases the frequency of reflex bladder contractions without altering their amplitude, suggesting that this drug targets the afferent limb of the micturition reflex circuit and therefore may be useful clinically in treating bladder overactivity symptoms.

Immunohistochemical characteristics of suburothelial microvasculature in the mouse bladder

The morphological characteristics of smooth muscle cells (SMCs) and their innervation of the suburothelial microvasculature of the mouse bladder were investigated by immunohistochemistry. Whole mount bladder mucosal preparations were immune-stained for α-smooth muscle actin (α-SMA) and/or neuronal markers and examined using confocal laser scanning microscopy. Suburothelial arterioles consisted of α-SMA-immunopositive circular smooth muscle cells, while the venular wall composed of α-SMA-positive SMCs that displayed several processes which extended from their cell bodies to form an extensive meshwork. In larger venules, a complex meshwork of stellate-shaped SMCs were observed. NG2 chondroitin sulphate proteoglycan-immunoreactive cell bodies of capillary pericytes were not immunoreactive for α-SMA. In the rat bladder suburothelial venules, circular SMCs were the dominant cell type expressing α-SMA-immunoreactivity. Since α-SMA-positive SMCs in suburothelial arterioles and venules in the mouse bladder had quite distinct morphologies, the innervation of both vessels could be examined by double labelling for α-SMA and various neuronal markers. Varicose nerve bundles immunoreactive for tyrosine hydroxylase (sympathetic nerves), choline acetyltransferase (cholinergic nerves) or substance P (primary afferent nerves) were all detected along side suburothelial arterioles. Single varicose nerve fibres positive for these three neuronal markers were also detected around the venules. Thus, whole mount preparations are useful when examining the morphology of α-SMA-positive SMCs of the microvasculature in the suburothelium of mouse bladder as well as their relationship with their innervations. In conclusion, arterioles and venules of the bladder suburothelium are the target of sympathetic, cholinergic and primary afferent nerve fibres.

Autonomic control of the urogenital tract

The urogenital tract houses many of the organs that play a major role in homeostasis, in particular those that control water and salt balance, and reproductive function. This review focuses on the anatomical and functional innervation of the kidneys, urinary ducts and bladders of the urinary system, and the gonads, gonadal ducts, and intromittent organs of the reproductive tract. The literature, especially in recent years, is overwhelmingly skewed toward the situation in mammals. Nevertheless, where specific neurochemical markers have been investigated, common patterns of innervation can be found in representatives from most vertebrate classes. Not surprisingly the vasculature, epithelia and smooth muscle of all urogenital organs receives adrenergic innervation. These nerves may contain non-adrenergic non-cholinergic (NANC) neurotransmitters such as ATP and NPY. Cholinergic nerves increase motility in most urogenital organs with the exception of the kidney. The major NANC nerves found to influence urogenital organs include those containing VIP/PACAP, galanin and neuronal nitric oxide synthase. These can be found associated with both smooth muscle and epithelia. The role these nerves play, and the circumstances where they are activated are for the most part unknown.

Ion channel and receptor mechanisms of bladder afferent nerve sensitivity

Sensory nerves of the urinary bladder consist of small diameter A(delta) and C fibers running in the hypogastic and pelvic nerves. Neuroanatomical studies have revealed a complex neuronal network within the bladder wall. Electrophysiological recordings in vitro and in vivo have revealed several distinct classes of afferent fibers that may signal a wide range of bladder stimulations including physiological bladder filling, noxious distension, cold, chemical irritation and inflammation. The exact mechanisms that underline mechanosensory transduction in bladder afferent terminals remain ambiguous; however, a wide range of ion channels (e.g., TTX-resistant Na(+) channels, Kv channels and hyperpolarization-activated cyclic nucleotide-gated cation channels) and receptors (e.g., TRPV1, TRPM8, TRPA1, P2X(2/3), etc) have been identified at bladder afferent terminals and implicated in the generation and modulation of afferent signals. Experimental investigations have revealed that expression and/or function of these ion channels and receptors may be altered in animal models and patients with overactive and painful bladder disorders. Some of these ion channels and receptors may be potential therapeutic targets for bladder diseases.

The dual function of capsaicin-sensitive sensory nerves in the bladder and urethra

The sensory innervation of the urinary bladder and urethra plays a key role in a variety of reflexes involved in urine storage and voiding. Dysfunction of these systems is a possible cause of many disturbances related to urine continence but basic knowledge in this field has been hampered by the lack of tools for studying sensory nerves. The use of capsaicin, the pungent ingredient of red peppers, allowed us to investigate the anatomical and functional properties of a specific subset of sensory neurons in the lower urinary tract. These 'capsaicin-sensitive' neurons play a dual sensory and 'efferent' function, determined by transmitter release from their central and peripheral nerve endings. Tachykinins, including substance P, and other neuropeptides such as calcitonin gene-related peptide, mediate the functions of these sensory neurons. The 'sensory' function includes regulation of micturition threshold, activation of cardiovascular reflexes and perception of pain from the urinary bladder. The 'efferent' function includes local regulation of muscle cell activity, nerve excitability, blood flow and plasma protein extravasation. Recent data suggest that capsaicin-sensitive sensory nerves could be present in the human bladder.

Combination of Wu Lin San and Shan Zha ameliorates substance P-induced hyperactive bladder via the inhibition of neutrophil NADPH oxidase activity

Substance P (SP) via neurokinin type 1 receptor activates leukocytes to produce burst release of reactive oxygen species (ROS) and increases leukocytes adhesion to the vessels in the inflamed bladder. Activation of neutrophil nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity may contribute to the neutrophil ROS production. We explored the therapeutic effect of traditional Chinese formula for urinary dysfunction, Wu Lin San (WLS), and a modified formula WLS plus Shan Zha (WLSSZ) on SP-induced bladder hyperactivity. We evaluated WLS, Shan Zha, and WLSSZ effect on neutrophils NADPH oxidase activity in SP-stimulated neutrophils in vitro, and isovolumetric cystometrogram and ROS activity in vivo in anesthetized rat bladder with SP stimulation. Our results showed that WLS, Shan Zha, and WLSSZ inhibited SP-induced NADPH oxidase activity in an order WLSSZ>Shan Zha>WLS. Exogenous SP enhanced systemic vasodilation, bladder hyperactivity and bladder ROS. One week of oral administration of WLS or WLSSZ significantly reduced SP-induced bladder ROS amount and leukocyte accumulation and ameliorated the hyperactive bladder response. The therapeutic action was better in WLSSZ than in WLS. Our results indicate that a modified formula Wu Lin San plus Shan Zha can potentially ameliorate SP-induced neurogenic inflammation possibly via the inhibition of leukocyte NADPH oxidase activity.

Interaction between neurotransmitter antagonists and effects of sacral neuromodulation in rats with chronically hyperactive bladder

OBJECTIVE

To investigate to what extent antagonists of spinal neurotransmitters interact with the effects of sacral neuromodulation in a rat model of a chronically hyperactive urinary bladder.

MATERIALS AND METHODS

In female rats the urinary bladder was instilled with turpentine oil 2.5% to induce cystitis. After surviving for 10 days the rats were anaesthetized with urethane, the bladder catheterized and connected to a pressure transducer. Stimulating electrodes were placed in the sacral foramina bilaterally. The spinal cord was exposed by a laminectomy, and a small pool was placed on the cord for intrathecal administration of neurotransmitter antagonists. Sacral neuromodulation was applied before and after administering the antagonists. The antagonists used were: memantine, an antagonist for N-methyl-D-aspartate (NMDA) receptors; CNQX, an antagonist for non-NMDA receptors, and L-NAPNA, a blocker of nitric oxide synthase.

RESULTS

With no electrical neuromodulation, memantine and L-NAPNA abolished the cystitis-induced bladder contractions for approximately 4 and approximately 37 min, respectively. The effect of CNQX was similar to that of artificial cerebrospinal fluid. Electrical sacral modulation with no antagonists also transiently abolished the bladder contractions; at the highest intensity used, the pause was 2-3 min. Superfusion of the spinal cord with CNQX reduced this effect of neuromodulation significantly, whereas memantine had no influence, and L-NAPNA increased the neuromodulation-induced pause.

CONCLUSIONS

The results suggest that non-NMDA receptors are involved in the effects of sacral neuromodulation, whereas NMDA receptors appear to have no role. Nitric oxide is essential for maintaining the chronic hyperactive state of the urinary bladder.

INTRALUMINAL ANTIBODIES TO MACROPHAGE MIGRATION INHIBITORY FACTOR DECREASE SUBSTANCE P INDUCED INFLAMMATORY CHANGES IN THE RAT BLADDER AND PROSTATE

PURPOSE

Noxious stimuli induce substance P (SP) secretion from nerve terminals, resulting in plasma extravasation, edema and hyperalgesia, commonly referred to as neurogenic inflammation. Since SP is a short-lived molecule, additional proinflammatory mediators maintain continued inflammation. The bladder contains stores of preformed macrophage migration inhibitory factor (MIF), a proinflammatory cytokine, which is released into the lumen in response to SP. MIF may act in an amplifying manner to maintain or increase inflammation. Inducing inflammatory changes with SP, while sequestering released luminal MIF with an antibody, tested this hypothesis.

MATERIALS AND METHODS

In anesthetized rats the ureters were cut to isolate the bladder and the bladder contents were replaced with saline or antiMIF antibody (5 or 15 microg/ml), immediately followed by systemic SP or saline. Changes in the expression of inflammatory cytokines, and histological changes in the bladder and prostate were evaluated 1 hour later.

RESULTS

: Targeted array analysis identified increases in proinflammatory gene expression in the bladder and prostate as a result of SP. SP induced changes in MIF, cyclooxygenase-2, nerve growth factor, c-fos and edema were decreased by intraluminal anti-MIF.

CONCLUSIONS

SP increased MIF amounts in the bladder lumen. Sequestering luminal MIF with an antiMIF antibody decreased SP induced inflammatory changes in the bladder and prostate, suggesting that MIF is involved in acute pelvic visceral neurogenic inflammation. These data indicate that MIF released from the bladder sustains or amplifies SP induced inflammation, a possibility that agrees with known MIF proinflammatory functions. These data continue to support our hypothesis that MIF is a new target for intervention in pelvic viscera inflammation.

Catechins prevents substance P-induced hyperactive bladder in rats via the downregulation of ICAM and ROS

We previously reported substance P (SP) via neurokinin type 1 receptor facilitates bladder afferent signaling and reactive oxygen species (ROS) formation in bladder connected with neurogenic inflammation [Am. J. Physiol. Renal Physiol. 284 (2003) F840]. Increased intercellular adhesion molecule expression and subsequent leukocyte adhesion in the inflamed bladder contribute to SP-induced oxidative injury. Here we investigate the effect of green tea extract (catechins) on SP-induced bladder hyperactivity. We evaluated isovolumetric cystometrogram, adhesion molecular expression, and ROS activity in anesthetized rat bladder with SP stimulation. Our results showed that SP increased the amount of leukocyte ROS production in vitro in a dose-dependent manner and the enhanced ROS can be inhibited by catechins treatment. Exogenous SP increased ROS in vivo in the bladder via increased intercellular adhesion molecule expression and subsequent leukocyte adhesion, a primary source of ROS in the inflamed bladder. Two weeks of catechins pretreatment reduced SP-induced bladder intercellular adhesion molecule expression and ROS amount and ameliorated the hyperactive bladder response. These results indicate that catechins pretreatment can ameliorate SP-induced neurogenic inflammation via the action of antioxidant, anti-adhesion, and anti-inflammatory activity.

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

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

The Effect of Short-Term Epidural Local Anesthetic Blockade on Urinary Levels of Substance P in Interstitial Cystitis

We investigated the effect of epidural local anesthetic blockade on urinary substance P levels in five patients suffering from painful flare-ups of interstitial cystitis. Urine was collected in 24-h intervals commencing at the onset of an epidural bolus of 0.25% bupivacaine followed by maintenance epidural infusions of 0.05% bupivacaine. Substance P was measured by radioimmunoassay. After initiation of the epidural infusion, urinary substance P levels increased and then declined in all patients. All patients reported a decrease in pain intensity. We hypothesize that acute release, followed by depletion, of substance P from bladder sensory nerve endings accounts for the transient increase of peptide levels in urine and may contribute to the decrease in pain intensity during a 3-day epidural infusion.

IMPLICATIONS

Substance P levels in urine initially increased and then declined in a series of 5 patients who achieved pain control by epidural local anesthetic infusion during a flare-up of interstitial cystitis.

Bladder and cutaneous sensory neurons of the rat express different functional P2X receptors

The expression and functional responses of P2X receptors in bladder and cutaneous sensory neurons of adult rats and mice have been studied using immunohistochemistry and patch clamp techniques. Cell bodies of bladder pelvic afferents were identified in L6 and S1 dorsal root ganglia (DRG), following Fast Blue injection into the muscle wall of the urinary bladder. Similarly, cutaneous sensory neurons were identified in L3 and L4 DRG, following Fast Blue injection into the saphenous nerve innervating the skin. Bladder sensory neurons contained only weak to moderate P2X(3)-immunoreactivity (IR), in contrast to strong P2X(3)-IR observed in a sub-population of cutaneous afferents. Whole-cell patch-clamp recordings revealed that approximately 90% of bladder afferent neurons responded to alpha beta-methylene ATP (alpha beta meATP) and ATP (30 microM) with persistent currents, which were inhibited by 2',3'-O-trinitrophenyl-ATP (TNP-ATP) (0.3 microM) to 6.4+/-1.9% and 8.0+/-2.6% of control, respectively (n=8). The remaining bladder sensory neurons demonstrated biphasic, transient or no response to P2X agonists. In contrast, only 24% of cutaneous afferent neurons gave persistent currents to alpha beta meATP (30 microM), with 66% of cells giving transient or biphasic currents and the remaining 10% being non-responsive. Our results suggest that, in contrast to DRG neurons in general, bladder sensory neurons projecting via pelvic nerves express predominantly P2X(2/3) heteromeric receptors, which are likely to mediate the important roles of ATP as a signaling molecule of urinary bladder filling and nociception.

Peripheral tachykinin receptors as potential therapeutic targets in visceral diseases

More than 10 years of intensive preclinical investigation of selective tachykinin (TK) receptor antagonists has provided a rationale to the speculation that peripheral neurokinin (NK)-1, -2 and -3 receptors may be involved in the pathophysiology of various human diseases at the visceral level. In the airways, despite promising effects in animal models of asthma, pilot clinical trials with selective NK-1 or -2 receptor antagonists in asthmatics have been ambiguous, whereas the potential antitussive effects of NK-1, -2 or -3 antagonists have not yet been verified in humans. In the gastrointestinal (GI) tract, irritable bowel syndrome (IBS) and pancreatitis are appealing targets for peripherally-acting NK-1 and -2 antagonists, respectively. In the genito-urinary tract, NK-1 receptor antagonists could offer some protection against nephrotoxicity and cytotoxicity induced by chemotherapeutic agents, whereas NK-2 receptor antagonists appear to be promising new agents for the treatment of neurogenic bladder hyperreflexia. Finally, there is preclinical evidence for hypothesising an effect of NK-3 receptor antagonists on the cardiovascular disturbance that characterises pre-eclampsia. Other more speculative applications are also mentioned.

Estrogen receptor expression in lumbosacral dorsal root ganglion cells innervating the female rat urinary bladder

We have investigated whether bladder afferent neurons are likely to be targets for circulating estrogens by mapping estrogen receptor (ER) distribution in lumbosacral dorsal root ganglia (DRG) of adult female rats. Sensory neurons innervating either the detrusor or trigone regions were identified by application of fluorescent retrograde tracer dyes to the bladder wall. Labelled neurons were classified by their immunoreactivity for either type of ER (ERalpha or ERbeta) and further compared with subpopulations of neurons containing substance P, calcitonin gene-related peptide and vanilloid receptor (a marker of polymodal nociceptors). Both ER types were expressed in numerous sensory neurons of either upper lumbar (L1/L2) or lower lumbar/sacral (L6/S1) ganglia and there was almost complete coexpression of ERalpha and ERbeta. ER-positive neurons were mainly small-medium size (18-25-microm diameter), indicating that they may be nociceptors and/or supply visceral targets. Most bladder-projecting neurons expressed ERs and the majority of these also expressed neuropeptides or vanilloid receptor. Afferent neurons supplying detrusor and trigone regions had similar immunohistochemical features. About a third of the bladder-projecting neurons expressed both ER and vanilloid receptor, suggesting a mechanism by which estrogens could influence bladder pain. The prevalence of different chemical classes of ER-positive bladder-projecting neurons was reflected throughout the entire population of neurons in dorsal root ganglia of these spinal levels, suggesting that neurons supplying other pelvic visceral targets may have similar chemical profiles. These results suggest that many functional classes of sensory neurons innervating the lower urinary tract are likely to be targets for circulating estrogens, including many nociceptor neurons. The coexistence of ERalpha and ERbeta suggests a broad range of potential mechanisms by which estrogens may exert their genomic effects in this system.

Substance P via NK1 receptor facilitates hyperactive bladder afferent signaling via action of ROS

We explored whether substance P (SP) via neurokinin (NK) receptor facilitates bladder afferent signaling and reactive oxygen species (ROS) formation in bladder in association with neurogenic inflammation. We evaluated ROS activity and cystometrograms as well as pelvic nervous activity in anesthetized rat bladder with SP stimulation. Our results showed that endogenous SP via NK(1), not NK(2), receptor mediated a micturition reflex. An increase in SP by electrical stimulation of the pelvic nerve or an increase in exogenous SP by intra-arterial or intrathecal administration can facilitate myogenic and neurogenic bladder contractions. Furthermore, exaggerated SP release increased ROS in the bladder and whole blood via increased mast cell degranulation, intercellular adhesion molecule expression, and leukocyte adhesion, a primary source of ROS in the inflamed bladder. Treatment with NK(1)-receptor antagonists or ROS scavengers reduced bladder intercellular adhesion molecule expression and ROS and ameliorated the hyperactive bladder response. Our study indicates that the mechanism by which SP participates in the neurogenic bladder may be complicated by its proinflammatory activity and its ability to stimulate ROS generation.

Experimental neurogenic cystitis

Recent advances in basic and clinical research indicate that interstitial cystitis (IC) is a form of neurogenic inflammation, thereby opening new avenues for research into this painful disease. With this in mind, we have recently developed a rat model of neurogenic inflammation of the bladder produced by a central nervous system viral disease. As in IC, the inflammation in this model develops without direct injury or trauma to the bladder, is non-infectious, and is limited to the bladder. Our most recent studies aimed at further testing the similarity of this animal model to IC by assessing the urine content in histamine with the occurrence of mast cell degranulation in the bladder wall. We further verified for a sex difference in the occurrence of the disease. Our results showed increased levels of urine histamine and mast cell activation during the early stages of the disease. We additionally observed that females had a greater degree of plasma extravasation, while males had a greater cellular infiltration together with worse behavioral signs. Gonadectomy prevented the bladder inflammation altogether in both males and females. These findings further validate our model of neurogenic cystitis to study the neurogenic component of IC.

Vanilloid receptor 1 expression in the rat urinary tract

Previous findings have shown that the capsaicin sensitivity of sensory fibres is due to the expression of a specific membrane protein, the vanilloid receptor type 1 (VR1). In the present work we studied the distribution, morphology and the neurochemical content of nerve fibres expressing this receptor in the rat urinary tract. Immunolabelling was performed against the VR1 and the positive fibres were examined by light and electron microscopy. Colocalisation of VR1 and substance P or calcitonin gene-related peptide immunoreactivities, and isolectin B4 binding, was evaluated under the confocal microscope. In addition, the effect of intravesical administration of resiniferatoxin, an ultra-potent vanilloid receptor agonist, in the receptor expression in the bladder was also studied. Numerous VR1-immunoreactive fibres were found in the mucosa and muscular layer of the entire urinary tract except the kidney. In the bladder, most fibres were also substance P- or calcitonin gene-related peptide-immunoreactive but did not bind isolectin B4. Under the electron microscope VR1 immunoreactivity was confined to unmyelinated axons and varicosities containing small clear and large dense-core synaptic vesicles. They occurred beneath or among epithelial cells or closely apposed to smooth muscle cells. Intravesical resiniferatoxin decreased VR1 immunoreactivity transiently. These data indicate that primary sensory fibres expressing VR1 are extremely abundant in the rat urinary tract and that, in contrast to the skin, they belong almost exclusively to the peptide-containing sub-population of primary afferents. As capsaicin-sensitive bladder afferents are involved in nociception and reflex micturition control, the numerous free terminal nerve endings expressing VR1 in the mucosa seem more adequate to accomplish the former function. However, the close apposition between VR1-expressing fibres and smooth muscle cells suggests that they may also encode the tonus of the muscular layer.

Enhancement of neurokinin A-induced smooth muscle contraction in human urinary bladder by mucosal removal and phosphoramidon: relationship to peptidase inhibition

Neurokinin A (NKA) is potent in contracting the human detrusor muscle. Here, we have investigated whether these contractile responses are influenced by the presence of the mucosa, by the peptidase inhibitor phosphoramidon or by possible modulators, prostaglandins and nitric oxide. Contractile responses to neurokinin A were unaffected by indomethacin or N-omega-nitro-L-arginine, but were significantly reduced in strips containing mucosa. Phosphoramidon, an inhibitor of neutral endopeptidase 24.11 (neprilysin, CD10), was ineffective at 10 microM, but at 100 microM, significant increase in the maximum response was achieved by neurokinin A in detrusor strips with and without mucosa. In immunohistochemical studies, neutral endopeptidase immunoreactivity occurred in peripheral nerve trunks in the detrusor and in a fibrous meshwork in the subepithelial lamina propria. Our data indicate that neutral endopeptidase is present in bladder mucosa and detrusor, and support the concept that this metalloprotease and/or related enzymes are important in regulating the actions of tachykinins.

Afferent fibers of the hypogastric nerves are involved in the facilitating effects of chemical bladder irritation in rats

To evaluate the role of bladder afferent fibers in the hypogastric nerves (HGN) in modulation of the micturition reflex induced by chemical bladder irritation, voiding behavior, continuous cystometry, and spinal c-fos expression following intravesical acetic acid instillation were investigated in rats with or without HGN transection. Voiding behavior and continuous cystometry were examined in unanesthetized conscious rats. Following chemical bladder irritation, a significant increase in urinary frequency associated with a marked decrease in the voided volume per micturition, was noted in control rats with the intact HGN, but not in HGN-transected rats. Continuous infusion of acetic acid in control rats elicited irritative bladder responses characterized by a marked decrease in the intercontraction interval and a marked increase in maximal vesical pressure, both of which were absent in capsaicin-desensitized rats. HGN transection prevented the decrease in the intercontraction interval but not an increase in maximal vesical pressure following chemical bladder irritation. Compared with saline infusion, acetic acid infusion caused a significant increase in c-fos expression at L(1) and L(6) of the spinal cord, and HGN transection significantly reduced c-fos expression in the dorsal horn of the spinal cord at L(1) but not at L(6). These results suggest that capsaicin-sensitive bladder afferent fibers in the HGN, which travel through the rostral lumbar spinal cord, have a role in urinary frequency caused by chemical bladder irritation.

Capsaicin receptor VR1 and ATP-gated ion channel P2X3 in human urinary bladder

OBJECTIVES

To determine the presence, distribution and molecular forms of the vanilloid receptor VR1, and confirm the presence and distribution of the ATP-gated ion channel P2X3 in the human urinary bladder. Materials and methods Normal urinary bladder tissues were obtained at postmortem from four subjects. Eight urinary bladder biopsies were also taken from patients with detrusor hyper-reflexia treated with intravesical resiniferatoxin. The specimens were studied using affinity-purified specific antibodies to VR1 and P2X3 by Western blotting and immunocytochemistry, and compared with immunostaining using antibodies to the pan-neuronal marker PGP 9.5 and Schwann cell marker S-100.

RESULTS

VR1- and P2X3-immunoreactive fine nerve fibres were scattered throughout the suburothelium of the normal bladder and cystoscopic biopsies, and traversed the muscle layer. They had a similar distribution to PGP 9.5-immunoreactive fibres, but there were fewer, suggesting localization in subsets of axons. Western blot studies showed an expected 100-kDa VR1 protein and a P2X3-immunoreactive 66-kDa protein. Conclusion VR1 and P2X3 are present in the human urinary bladder and may contribute to distinct pathophysiological states of bladder overactivity, in accord with their differential expression in sensory neurones. Intravesical vanilloids act via VR1 and are effective in the treatment of detrusor hyper-reflexia. P2X3 may represent a selective therapeutic target for other causes of overactive bladder.

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.

Peptide immunoreactivity and ultrastructure of rat urinary bladder nerve fibers after topical desensitization by capsaicin or resiniferatoxin

In the present study the decrease of neuropeptide containing nerve fibers and the increase in the volume threshold to reflex micturition occurring in the rat bladder after intravesical application of capsaicin or resiniferatoxin were compared. The ultrastructure of bladder terminal axons was evaluated at the moment of maximal peptide depletion and compared to that of nerve fibers after systemic capsaicin application. Adult Wistar rats were treated intravesically for 30 min with 0.5 ml of 100 nM RTX, 1 mM capsaicin or 30% ethanol in saline, the vehicle solution. Twenty-four hours and 1, 2, 3, 4 and 8 weeks later the bladders were immunostained for CGRP, SP, VIP and NPY. Cystomanometric studies were performed 24 h and 1, 8, and 12 weeks after vanilloid instillation. Twenty-four hours after systemic capsaicin or intravesical capsaicin or RTX, bladders were prepared for electron microscopic (EM) observation. Intravesical capsaicin or RTX decreased, in a similar way, the number of CGRP and SP-IR (immunoreactive) fibers coursing in the muscular layer and the mucosa. IR fibers amounted to less than 20% of controls at 24 h and returned to normal levels in the eighth week. At the EM level, bladders treated with topical vanilloids did not show morphological changes in terminal axons coursing in the mucosa. In contrast, bladders from animals treated systemically with capsaicin contained numerous grossly degenerated nerve fibers. VIP and NPY-IR fibers were not affected by the treatment. Cystometrograms showed an increase of the volume threshold to reflex micturition that started at 24 h and disappeared at 12 weeks. We conclude that intravesical capsaicin or RTX were equally effective in terms of reducing the number of SP and CGRP-IR fibers and increasing the volume threshold for reflex micturition. Both changes were transient and were not associated with ultrastructural changes of the bladder nerve fibers, excluding terminal axon degeneration as the main mechanism of action of intravesical vanilloids.

Effects of vagal perineural capsaicin treatment on vagal efferent and airway neurogenic responses in anesthetized rats

The acute effect of vagal perineural capsaicin treatment (VPCT) on parasympathetic bradycardia and tracheal neurogenic protein extravasation was examined. In nine anesthetized male Wistar rats the effect of VPCT on the bradycardia induced by electrical stimulation of the vagus was examined. In 24 anesthetized male Wistar rats the effect of VPCT on the tracheal protein extravasation induced by the inhalation of capsaicin aerosols was also studied. VPCT did not alter the bradycardia induced by vagal stimulation or the tracheal protein extravasation induced by the inhalation of capsaicin aerosol. The results of these studies further demonstrate the selectivity of perineural capsaicin treatment on vagal sensory nonmyelinated fibers in the rat and indicate that it is a useful tool for examining the role of sensory vagal C-fibers in pulmonary and cardiovascular reflexes and in isolating C-fiber-mediated reflex responses from those mediated by the release of neuropeptides.

Possible site of action of TAK-637, a tachykinin NK(1) receptor antagonist, on the micturition reflex in guinea pigs

TAK-637((aR,9R)-7-[3,5-bis(trifluoromethyl)benzyl]-8,9,10, 11-tetrahydro-9-methyl-5-(4-methylphenyl)-7H-[1,4]diazocino[2,1-g] [1,7]naphthyridine-6,13-dione) is a novel tachykinin NK(1) receptor antagonist that has been shown to inhibit the micturition reflex in guinea pigs. The aim of this study was to clarify its mechanism of action in guinea pigs. TAK-637 inhibited the spinal vesico-vesical reflex induced by electrical stimulation of the proximal cut end of the pelvic nerve in spinal animals, but not bladder contractions induced by electrical stimulation of the distal cut end of the nerve. Furthermore, TAK-637 had no effect on carbachol- or electrical field stimulation-induced contractions of isolated bladder muscle strips in an organ bath, whereas drugs used for abnormally frequent micturition inhibited both contractions. These results suggest that TAK-637 inhibits the micturition reflex by acting, at least in part, on the spinal cord, and its mechanism of action clearly differs from those of antimuscarinics or spasmolytics.

Neuroanatomical effects of capsaicin on the primary afferent neurons

Studies by N. JANCSO and his associates in the 1970's established that capsaicin in paprika exerts selective damage on nociceptive primary sensory neurons. The physiological and pharmacological aspects of capsaicin's effect have been repeatedly reviewed, but no report seems available concerning the neuroanatomical changes caused by capsaicin. This paper first reviews the neuroanatomical aspect of the lesion caused by capsaicin. Special attention is paid to quantitative estimations made by our group and others on the loss of dorsal root ganglion (DRG) cells, dorsal root nerve fibers, the saphenous nerve, chorda tympani nerve, and pulp nerves after neonatal treatment with capsaicin. The degenerating process of DRG cells induced by capsaicin is discussed with respect to necrosis and apoptosis. The capsaicin receptors found recently are concisely introduced with reference to their action. A discrepancy between a marked loss of dorsal root C-fibers and an unexpectedly intact response to noxious heat in mice treated with capsaicin at neonate is discussed, and attension is given to nerves sprouting from capsaicin-resistant DRG cells in the superficial dorsal horn. In addition, the architecture of the synapses between the central endings of the capsaicin-sensitive primary afferent neurons and the intrinsic inhibitory interneurons is described and its possible significance considered in terms of the transmission of nociceptive information.

Effects of TAK-637, a tachykinin receptor antagonist, on the micturition reflex in guinea pigs

The effects of a new tachykinin NK(1) receptor antagonist, (aR, 9R)-7-[3,5-bis(trifluoromethyl)benzyl]-8,9,10, 11-tetrahydro-9-methyl-5-(4-methylphenyl)-7H-[1,4]diazocino[2,1-g] [1, 7]naphthyridine-6,13-dione (TAK-637), on the micturition reflex were compared with those of drugs used for abnormally frequent micturition or incontinence. TAK-637 showed a characteristic effect on the distension-induced rhythmic bladder contractions in guinea pigs. The systemic administration of TAK-637 decreased the number but not the amplitude of the distension-induced rhythmic bladder contractions. A similar effect was observed in animals in which the spinal cord had been severed. TAK-637 also inhibited the micturition reflex induced by topical application of capsaicin onto the surface of bladder dome. From these results, it is concluded that TAK-637 inhibits sensory transmissions from the bladder evoked by both physiological and nociceptive stimuli by blocking tachykinin NK(1) receptors, possibly at the level of the spinal cord. On the other hand, the other drugs such as oxybutynin, tolterodine, propiverine, and inaperisone showed no effects on the frequency of the distension-induced rhythmic bladder contractions but decreased the contraction amplitude. Therefore, TAK-637 may represent a new class of drugs, which would be effective for abnormally frequent micturition without causing voiding difficulties due to decreased voiding pressure.

The effect of intravesical capsaicin on the suburothelial innervation in patients with detrusor hyper-reflexia

OBJECTIVE

To determine the effect of intravesical capsaicin on the suburothelial innervation in patients with detrusor hyper-reflexia, in whom a single dose of intravesical capsaicin (1-2 mmol/L) increases the bladder capacity for 3-6 months.

PATIENTS AND METHODS

Thirteen patients with detrusor hyper-reflexia underwent cystometry and had flexible cystoscopic biopsies taken before and 6 weeks after receiving instillations of intravesical capsaicin (1 mmol/L). Similar biopsies were also obtained from a control group of 12 neurologically normal patients with microscopic haematuria and normal bladders. Frozen sections were stained using antibodies to S100 and PGP 9.5. Using computerized analysis, the mean nerve density scores were expressed as nerves/mm2 for S100-positive structures and 'red%' and 'red in frame' for PGP 9.5.

RESULTS

The mean (SEM) functional bladder capacity increased from 193.2 (28.17) mL before to 396.3 (41.96) mL at 6 weeks after treatment with capsaicin, in nine of the 13 patients. The mean nerve density of S100-positive structures in the control group was 83 (3.18) nerves/mm2. In hyper-reflexic patients who responded to capsaicin by improved bladder capacity, the mean nerve density of S100-positive structures was reduced from 100 (12.2) before to 66 (9.4) nerves/mm2 6 weeks after treatment. In those who did not respond to capsaicin there was no significant difference in these scores. Similarly the 'red%' and 'red in frame' reduced from 3.41 (1.06) to 1.15 (0.32) and 824.7 (246.3) to 297.9 (83.5) units, respectively, before and 6 weeks after capsaicin treatment. The difference in those not responding was not significant.

CONCLUSIONS

Intravesical capsaicin causes a reduction in suburothelial nerve densities in the bladder of patients with detrusor hyper-reflexia. This may explain its prolonged beneficial effect in these patients.

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.

Intravesical capsaicin and resiniferatoxin therapy: spicing up the ways to treat the overactive bladder

PURPOSE

Pharmacological treatment of the overactive bladder relies on partially blocking the efferent parasympathetic innervation to the detrusor with anticholinergic drugs. However, often these drugs have troublesome side effects and doses are insufficient to restore continence in patients with detrusor instability. We present the background, basic and clinical research with intravesical instillation of capsaicin and resiniferatoxin as treatments for the overactive bladder.

MATERIALS AND METHODS

Capsaicin, the main pungent ingredient in hot peppers of the genus Capsicum, is a specific neurotoxin that desensitizes C fiber afferent neurons which may be responsible for signals that trigger detrusor overactivity.

RESULTS

In the last 6 years studies have demonstrated encouraging improvement in lower urinary tract symptoms with minimal long-term complications. Most of these studies have also demonstrated that the acute pain and irritation associated with capsaicin are major deterrents to widespread use. Therefore, resiniferatoxin, an ultra-potent analogue of capsaicin which appears to have similar efficacy but less acute side effects, may be more useful.

CONCLUSIONS

Intravesical capsaicin and resiniferatoxin are novel and promising treatments for the overactive bladder, with profound basic and clinical implications.

Retrograde and transganglionic transport of horseradish peroxidase-conjugated cholera toxin B subunit, wheatgerm agglutinin and isolectin B4 from Griffonia simplicifolia I in primary afferent neurons innervating the rat urinary bladder

In the present study, we investigated and compared the ability of the cholera toxin B subunit, wheat germ agglutinin and isolectin B4 from Griffonia simplicifolia I conjugated to horseradish peroxidase, to retrogradely and transganglionically label visceral primary afferents after unilateral injections into the rat urinary bladder wall. Horseradish peroxidase histochemical or lectin-immunofluorescence histochemical labelling of bladder afferents was seen in the L6-S1 spinal cord segments and in the T13-L2 and L6-S1 dorsal root ganglia. In the lumbosacral spinal cord, the most intense and extensive labelling of bladder afferents was seen when cholera toxin B subunit-horseradish peroxidase was injected. Cholera toxin B subunit-horseradish peroxidase-labelled fibres were found in Lissauer's tract, its lateral and medial collateral projections, and laminae I and IV-VI of the spinal gray matter. Labelled fibres were numerous in the lateral collateral projection and extended into the spinal parasympathetic nucleus. Labelling from both the lateral and medial projections extended into the dorsal grey commissural region. Wheat germ agglutinin-horseradish peroxidase labelling produced a similar pattern but was not as dense and extensive as that of cholera toxin B subunit-horseradish peroxidase. The isolectin B4 from Griffonia simplicifolia I-horseradish peroxidase-labelled fibres, on the other hand, were fewer and only observed in the lateral collateral projection and occasionally in lamina I. Cell profile counts showed that a larger number of dorsal root ganglion cells were labelled with cholera toxin B subunit-horseradish peroxidase than with wheat germ agglutinin- or isolectin B4-horseradish peroxidase. In the L6-S1 dorsal root ganglia, the majority (81%) of the cholera toxin B subunit-, and almost all of the wheat germ agglutinin- and isolectin B4-immunoreactive cells were RT97-negative (an anti-neurofilament antibody that labels dorsal root ganglion neurons with myelinated fibres). Double labelling with other neuronal markers showed that 71%, 43% and 36% of the cholera toxin B subunit-immunoreactive cells were calcitonin gene-related peptide-, isolectin B4-binding- and substance P-positive, respectively. A few cholera toxin B subunit cells showed galanin-immunoreactivity, but none were somatostatin-, vasoactive intestinal polypeptide-, or neuropeptide Y-immunoreactive or contained fluoride-resistant acid phosphatase. The results show that cholera toxin B subunit-horseradish peroxidase is a more effective retrograde and transganglionic tracer for pelvic primary afferents from the urinary bladder than wheat germ agglutinin-horseradish peroxidase and isolectin B4-horseradish peroxidase, but in contrast to somatic nerves, it is transported mainly by unmyelinated fibres in the visceral afferents.

Effects of ZD6169, a KATP channel opener, on bladder hyperactivity and spinal c-fos expression evoked by bladder irritation in rats

Cystometrographic recording and immunocytochemical techniques were used to examine the effects of ZD6169, an ATP-sensitive K+-channel opener, and capsaicin, an afferent neurotoxin, on urinary bladder hyperactivity and immediate early gene expression in the spinal cord induced by acetic acid (0.25%) irritation of the bladder. Chemical irritation of the bladder of the rat increased the frequency of voiding reflexes by 8 fold and increased c-fos expression in neurons in the dorsal commissure (DCM), sacral parasympathetic nucleus (SPN) as well as the medial and lateral dorsal horn (MDH, LDH) of L6 and S1 segments of the spinal cord. Pretreatment with ZD6169 (30 nM) for 1 h reduced the effect of acetic acid on voiding frequency as reflected by an increase in the intercontraction interval (ICI, 137+/-48% increase, P<0.05). ZD6169 also decreased the number of Fos positive neurons in the L6 spinal cord, in the DCM (62.1+/-7.1% decrease), SPN (48.8+/-7%), MDH (50+/-7.3%) and LDH regions (38. 8+/-10.5%). Similar reductions were noted in the S1 spinal cord: 65. 1+/-10.8% in DCM, 53.8+/-11% in SPN, 56+/-10.4% in MDH and 25.3+/-18. 1% in LDH. Capsaicin pretreatment (125 mg/kg, s.c., 4 days prior to the experiments) also reduced bladder hyperactivity (550% increase in ICI) and decreased the numbers of acetic acid-induced Fos positive neurons 78.8+/-6.3% in DCM, 73+/-7.8% in MDH, 59.2+/-16% in LDH and 45.2+/-17% in SPN of L6 segment of the spinal cord. These results suggest that ZD6169 can influence bladder hyperactivity by suppressing the firing of capsaicin-sensitive C-fiber bladder afferents which are known to modulate the micturition reflex.

Pituitary adenylate cyclase activating polypeptide immunoreactivity in capsaicin-sensitive nerve fibres supplying the rat urinary tract

Pituitary adenylate cyclase activating peptide is a new member of the vasoactive intestinal polypeptide family of peptides which is present in the brain as well as neuronal elements of a number of peripheral organs. Pituitary adenylate cyclase activating peptide occurs in two forms, pituitary adenylate cyclase activating peptide-38 and the C-terminally truncated 27 amino acid form, pituitary adenylate cyclase activating peptide-27, both derived from the same precursor which in addition gives rise to a structurally-related peptide, pituitary adenylate cyclase activating peptide-related peptide. Using specific radioimmunoassays for pituitary adenylate cyclase activating peptide-38, pituitary adenylate cyclase activating peptide-27 and pituitary adenylate cyclase activating peptide-related peptide we found that all three pituitary adenylate cyclase activating peptide-precursor-derived peptides were present in tissue extracts from the ureter, the urinary bladder and the urethra. Pituitary adenylate cyclase activating peptide-38 was the dominating peptide with the highest concentration in the ureter. When extracts from the urinary bladder were fractionated by reverse phase high pressure liquid chromatography immunoreactive components corresponding to synthetic pituitary adenylate cyclase activating peptide-38, pituitary adenylate cyclase activating peptide-27 and pituitary adenylate cyclase activating peptide-related peptide were identified with the respective antisera. By immunohistochemistry, using a specific monoclonal mouse anti-pituitary adenylate cyclase activating peptide antibody, pituitary adenylate cyclase activating peptide-immunoreactivity was shown to have a widespread distribution in the rat urinary tract, localized exclusively to nerve fibres. No immunoreactive neuronal cell bodies were observed in any of the tissues. Pituitary adenylate cyclase activating peptide was shown to be located in varicose nerve fibres associated with blood vessels and smooth muscle. The majority of pituitary adenylate cyclase activating peptide-positive nerve fibres and bundles were, however, present in subepithelial plexuses from which delicate varicose nerve fibres entered the urothelium. Double immunostaining for pituitary adenylate cyclase activating peptide and a marker for sensory neurons, calcitonin-gene related peptide, disclosed that the two peptides were almost completely co-localized while the co-existence between pituitary adenylate cyclase activating peptide and the structurally related peptide vasoactive intestinal polypeptide, was scarce. Neonatal capsaicin-treatment caused a marked reduction in the concentration of immunoreactive pituitary adenylate cyclase activating peptide in all regions of the rat urinary tract, being most prominent in the ureter. By immunohistochemistry it was shown that the sensory neurotoxin caused a reduction in the number and intensity of pituitary adenylate cyclase activating peptide-immunoreactive nerve fibres in all organs of the urinary tract which was most prominent in the epithelial and subepithelial layers. Identical changes were observed for the calcitonin-gene related peptide-containing nerve fibres, while vasoactive intestinal polypeptide-positive nerve fibres were unaffected by capsaicin-treatment. In conclusion pituitary adenylate cyclase activating peptide is present in the rat urinary tract mainly in the form of pituitary adenylate cyclase activating peptide-38. Immunoreactive nerve fibres were associated with the epithelium, blood vessels and smooth musculature. Pituitary adenylate cyclase activating peptide was almost completely co-localized with calcitonin-gene related peptide and by neonatal capsaicin treatment the two peptides were identically affected. The findings suggest that pituitary adenylate cyclase activating peptide is a sensory neurotransmitter in the rat urinary tract.

The tachykinin NK1 receptor. Part II: Distribution and pathophysiological roles

The tachykinin NK1 receptor is widely distributed in both the central and peripheral nervous system. In the CNS, NK1 receptors have been implicated in various behavioural responses and in regulating neuronal survival and degeneration. Moreover, central NK1 receptors regulate cardiovascular and respiratory function and are involved in activating the emetic reflex. At the spinal cord level, NK1 receptors are activated during the synaptic transmission, especially in response to noxious stimuli applied at the receptive field of primary afferent neurons. Both neurophysiological and behavioural evidences support a role of spinal NK1 receptors in pain transmission. Spinal NK1 receptors also modulate autonomic reflexes, including the micturition reflex. In the peripheral nervous system, tachykinin NK1 receptors are widely expressed in the respiratory, genitourinary and gastrointestinal tracts and are also expressed by several types of inflammatory and immune cells. In the cardiovascular system, NK1 receptors mediate endothelium-dependent vasodilation and plasma protein extravasation. At respiratory level, NK1 receptors mediate neurogenic inflammation which is especially evident upon exposure of the airways to irritants. In the carotid body, NK1 receptors mediate the ventilatory response to hypoxia. In the gastrointestinal system, NK1 receptors mediate smooth muscle contraction, regulate water and ion secretion and mediate neuro-neuronal communication. In the genitourinary tract, NK1 receptors are widely distributed in the renal pelvis, ureter, urinary bladder and urethra and mediate smooth muscle contraction and inflammation in response to noxious stimuli. Based on the knowledge of distribution and pathophysiological roles of NK1 receptors, it has been anticipated that NK1 receptor antagonists may have several therapeutic applications at central and peripheral level. At central level, it is speculated that NK1 receptor antagonists could be used to produce analgesia, as antiemetics and for treatment of certain forms of urinary incontinence due to detrusor hyperreflexia. In the peripheral nervous system, tachykinin NK1 receptor antagonists could be used in several inflammatory diseases including arthritis, inflammatory bowel diseases and cystitis. Several potent tachykinin NK1 receptor antagonists are now under evaluation in the clinical setting, and more information on their usefulness in treatment of human diseases will be available in the next few years.

Increase of growth-associated protein-43 immunoreactivity following cyclophosphamide-induced cystitis in rats

We examined the effect of inflammation on immunoreactivity of growth-associated protein (GAP-43) in the rat urinary bladder in which acute cystitis was induced with cyclophosphamide (CPA). Following CPA injection, the number of GAP-43 labeled nerves was significantly increased in the muscle layer. Immunoreactivity of PGP9.5, which was used as an axonal marker, was not augmented following CPA injection. Double fluorescence immunohistochemistry revealed that substance P immunoreactivity was present in most GAP-43 immunoreactive fibers (90.2%) in the inflamed bladder. Electron microscopic examination showed that GAP-43 immunoreactivity was localized on axons. Some GAP-43 positive axons showed degeneration. Possible significance of the increase of GAP-43 immunoreactive afferent nerve fibers in the muscle layer of acutely inflamed bladder was discussed.

Postnatal development of the autonomic and sensory innervation of the musculature in the rat urinary bladder

The postnatal development of the innervation of the muscle layer in the rat urinary bladder was analysed in whole mount preparations using immunohistochemistry against protein gene-product 9.5 (PGP; general neuronal marker), growth-associated protein 43 (GAP), dopamine beta-hydroxylase (DBH), neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and substance P (SP). Immunoreactive nerve fibres for all markers were already present at birth. The density of PGP- and GAP-positive nerve fibres was similar and remained constant throughout the postnatal development. The rank order of densities for the other markers relative to PGP was NPY (129-189%) > CGRP (20-63%) > SP (7-23%) > DBH (7-12%) > VIP (2-11%). While the density of presumably efferent VIP- and DBH-positive fibres did not change postnatally, NPY-positive fibres reached adult density at the fifth postnatal day. Sensory CGRP- and SP-positive nerve fibres approached adult levels at the end of the second week, shortly before the micturition reflex was completely developed. The data suggest that a sufficient relative density of sensory and certain efferent elements might be a prerequisite for the development of the mature micturition reflex.

Expression of neuropeptides and nitric oxide synthase in neurones innervating the inflamed rat urinary bladder

Micturition reflexes become hyperexcitable with the development of a cystitis. In the present study the question is addressed, whether alterations in the expression of neuropeptides and nitric oxide synthase (NOS) in the neuronal pathways to the bladder may be involved in the hyperexcitability. Primary sensory neurones in the dorsal root ganglia (DRG) L1, L2, L6 and S1 as well as postganglionic efferent neurones in the major pelvic ganglia (MPG) that innervate the rat urinary bladder were labeled with retrogradely transported Fast Blue (FB). Immunocytochemical techniques were used to determine alterations in the expression of calcitonin gene-related peptide (CGRP), substance P (SP), galanin (GAL) and NOS in these neurones following mustard oil-induced inflammation of the urinary bladder. Instillation of 2.5% mustard oil into the bladder led to a massive leukocyte infiltration of the vesical tissues, partial damage of the mucosal layer and a marked hyperreflexia of the detrusor muscle. 48 h after induction of the cystitis the proportion of FB-labeled bladder afferent neurones that expressed CGRP and SP were significantly increased in both the rostral lumbar DRGs (L1, L2) and the lumbosacral DRGs (L6, S1) (CGRP, +15-38%; SP, +47-158%) as compared to control animals. However, there was a differential effect of the inflammation on the expression of GAL and NOS in bladder afferents at the two segmental levels examined. Significant alterations in the number of FB-labeled afferents exhibiting GAL immunoreactivity were mainly restricted to the lumbosacral DRGs L6 (+169%) and S1 (+60%). On the contrary, the proportion of NOS-immunoreactive bladder afferents significantly increased only in the rostral lumbar DRGs L1 (+144%) and L2 (+193%), while the level of NOS-expression was unaffected at the lumbosacral levels. Inflammation furthermore induced a significant increase (+275%) in the number of FB-labeled neurones in the MPGs that exhibited NOS immunoreactivity. These results indicate that an upregulation of CGRP-, SP-, GAL- and NOS-synthesis in sensory and efferent neurones is involved in the response to an acute cystitis. Because of the differences in the segmental pattern and degree of upregulation of these substances in bladder afferents that project to the rostral lumbar and lumbosacral spinal cord a different regulation of the sympathetic and parasympathetic efferent outflow to the urinary bladder is suggested. The involvement of CGRP, SP, GAL and NOS in the modulation of both excitatory and inhibitory mechanisms that control the cystitis-induced detrusor hyperreflexia is discussed.

Morphological and functional evidence against a sensory and sympathetic origin of nitric oxide synthase-containing nerves in the rat lower urinary tract

To establish which type of nerves (parasympathetic, sympathetic or sensory) produce nitric oxide in the rat lower urinary tract, chemical denervation of primary afferents and sympathetic nerves was carried out by systemic treatment with capsaicin and 6-hydroxydopamine, respectively, followed by identification of neuronal nitric oxide synthase immunoreactivity. Functional in vitro studies were also performed to examine whether the synthesis and release of nitric oxide was affected following treatment with the respective neurotoxins. Nerve fibres immunoreactive for substance P and calcitonin gene-related peptide were found in control tissue, but could not be detected following capsaicin treatment. In comparison, nitric oxide synthase-immunoreactive fibres appeared to be unaffected by capsaicin treatment. Administration of 6-hydroxydopamine resulted in a complete disappearance of tyrosine hydroxylase-immunoreactive nerves, whereas nitric oxide synthase-containing nerve fibres did not appear to be affected by the treatment. In ultrastructural studies, nitric oxide synthase immunoreactivity, as studied by colloidal gold particles, was found in the axoplasm and not in association with intraneuronal structures or synaptic vesicles. Gold particles representing substance P immunoreactivity were seen as clusters associated with large granular vesicles. In consecutive sections of nerve fibres, substance P and nitric oxide synthase were not found in the same axon profile. In functional studies on urethral tissue, application of capsaicin (1 microM) produced a long-lasting relaxation. The nitric oxide synthase inhibitor NG-nitro-L-arginine (0.1 mM) had no effect on this response. Systemic treatment with capsaicin or 6-hydroxydopamine had no effect on nerve-evoked, nitric oxide-mediated relaxations. The data suggest that nitric oxide synthase-containing nerves in the rat lower urinary tract do not belong to nerve populations sensitive to either the sympathetic neurotoxin, 6-hydroxydopamine, or the sensory neurotoxin, capsaicin.