Nitric oxide synthase-immunoreactive, adrenergic, cholinergic, and peptidergic nerves of the female rat urinary tract: a comparative study

Somatostatin immunoreactivity within the urinary bladder nerve fibers and paracervical ganglion urinary bladder projecting neurons in the female pig

The study was designed to examine the distribution and chemical coding of somatostatin-immunoreactive (SOM-IR) nerve fibers supplying the urinary bladder wall and to establish the distribution and immunohistochemical characteristics of the subpopulation of paracervical ganglion (PCG) SOM-IR neurons projecting to this organ in female pigs. The PCG-urinary bladder projecting neurons (PCG-UBPN) were visualized with retrograde neuronal tracer Fast Blue (FB). Double-labeling immunohistochemistry performed on cryostat sections from the urinary bladder wall revealed that the greatest density of SOM-IR nerve fibers was found in the muscle layer and around blood vessels, a moderate number of these nerve terminals supplied the submucosa and only single SOM-IR axons were encountered beneath the urothelium. In all the investigated sections the vast majority of SOM-IR nerve fibers were immunopositive to vesicular acetylcholine transporter (VAChT) and many SOM-IR axons contained immunoreactivity to neuropeptide Y (NPY). Approximately 65 % of FB-positive (FB+) PCG-UBPN were immunoreactive to SOM. Moreover, PCG FB+/SOM + nerve cells were simultaneously immunoreactive to choline acetyltransferase (ChAT; 64.6 ± 0.6 %), NPY (59.7 ± 1.2 %), neuronal nitric oxide synthase (nNOS; 46.1 ± 0.7 %), vasoactive intestinal polypeptide (VIP; 29.9 ± 2.2 %), Leu⁵-enkephalin (L-ENK; 19.5 ± 6.3 %), dopamine β-hydroxylase (DβH; 14.9 ± 1.9 %) or pituitary adenylate cyclase-activating polypeptide (PACAP; 14.8 ± 2.4 %). The present study reveals the extensive expression of SOM in both the nerve fibres supplying the porcine urinary bladder wall and the PCG neurons projecting to this organ, indicating an important regulatory role of SOM in the control of the urinary bladder function.

The Influence of an Adrenergic Antagonist Guanethidine on the Distribution Pattern and Chemical Coding of Caudal Mesenteric Ganglion Perikarya and Their Axons Supplying the Porcine Bladder

This study was aimed at disclosing the influence of intravesically instilled guanethidine (GUA) on the distribution, relative frequency and chemical coding of both the urinary bladder intramural sympathetic nerve fibers and their parent cell bodies in the caudal mesenteric ganglion (CaMG) in juvenile female pigs. GUA instillation led to a profound decrease in the number of perivascular nerve terminals. Furthermore, the chemical profile of the perivascular innervation within the treated bladder also distinctly changed, as most of axons became somatostatin-immunoreactive (SOM-IR), while in the control animals they were found to be neuropeptide Y (NPY)-positive. Intravesical treatment with GUA led not only to a significant decrease in the number of bladder-projecting tyrosine hydroxylase (TH) CaMG somata (94.3 ± 1.8% vs. 73.3 ± 1.4%; control vs. GUA-treated pigs), but simultaneously resulted in the rearrangement of their co-transmitters repertoire, causing a distinct decrease in the number of TH⁺/NPY⁺ (89.6 ± 0.7% vs. 27.8 ± 0.9%) cell bodies and an increase in the number of SOM-(3.6 ± 0.4% vs. 68.7 ± 1.9%), calbindin-(CB; 2.06 ± 0.2% vs. 9.1 ± 1.2%) or galanin-containing (GAL; 1.6 ± 0.3% vs. 28.2 ± 1.3%) somata. The present study provides evidence that GUA significantly modifies the sympathetic innervation of the porcine urinary bladder wall, and thus may be considered a potential tool for studying the plasticity of this subdivision of the bladder innervation.

Immunohistochemical characteristics and distribution of neurons in the paravertebral, prevertebral and pelvic ganglia supplying the urinary bladder in the male pig

The distribution and chemical coding of neurons supplying urinary bladder in the male pig were studied in the sympathetic chain ganglia, inferior mesenteric ganglia and anterior pelvic ganglia. The combined retrograde tracing and immunohistochemistry for tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), neuropeptide Y (NPY), somatostatin(SOM), galanin (GAL), vasoactive intestinal polypeptide(VIP), nitric oxide synthase (NOS), calcitonin gene related peptide (CGRP), substance P (SP), choline acetyltransferase (ChAT) and vesicular acetylcholine transporter(VAChT) were applied in the experiment. Bladder projecting neurons were found in all the ganglia studied. The majority of sympathetic ganglia neurons (inferior mesenteric ganglia and sympathetic chain ganglia) expressed immunoreactivity(IR) to DBH. In sympathetic chain ganglia these neurons simultaneously expressed NPY, GAL or VAChT,while in inferior mesenteric ganglia they contained NPY, SOM and/or GAL. A small number of these bladder projecting neurons was VAChT-IR and some contained NPY. In the pelvic ganglia bladder-projecting neurons formed two populations: DBH- and VAChT-IR. Some of DBH-IR neurons contained IR to NPY, SOM or GAL, while VAChTIR neurons were NPY-, SOM- or NOS-IR. The results indicate that sympathetic ganglia contain mainly adrenergic neurons,while pelvic ganglia contain both adrenergic and cholinergic neurons. All these neurons contain typical combinations of neuropeptides.

Signalling molecules in the urothelium

The urothelium was long considered to be a silent barrier protecting the body from the toxic effects of urine. However, today a number of dynamic abilities of the urothelium are well recognized, including its ability to act as a sensor of the intravesical environment. During recent years several pathways of these urothelial abilities have been proposed and a major part of these pathways includes release of signalling molecules. It is now evident that the urothelium represents only one part of the sensory web. Urinary bladder signalling is finely tuned machinery of signalling molecules, acting in autocrine and paracrine manner, and their receptors are specifically distributed among different types of cells in the urinary bladder. In the present review the current knowledge of the formation, release, and signalling effects of urothelial acetylcholine, ATP, adenosine, and nitric oxide in health and disease is discussed.

Characterization of axons expressing the artemin receptor in the female rat urinary bladder: a comparison with other major neuronal populations

Artemin is a member of the glial cell line-derived neurotrophic factor (GDNF) family that has been strongly implicated in development and regeneration of autonomic nerves and modulation of nociception. Whereas other members of this family (GDNF and neurturin) primarily target parasympathetic and nonpeptidergic sensory neurons, the artemin receptor (GFRα3) is expressed by sympathetic and peptidergic sensory neurons that are also the primary sites of action of nerve growth factor, a powerful modulator of bladder nerves. Many bladder sensory neurons express GFRα3 but it is not known if they represent a specific functional subclass. Therefore, our initial aim was to map the distribution of GFRα3-immunoreactive (-IR) axons in the female rat bladder, using cryostat sections and whole wall thickness preparations. We found that GFRα3-IR axons innervated the detrusor, vasculature, and urothelium, but only part of this innervation was sensory. Many noradrenergic sympathetic axons innervating the vasculature were GFRα3-IR, but the noradrenergic innervation of the detrusor was GFRα3-negative. We also identified a prominent source of nonneuronal GFRα3-IR that is likely to be glial. Further characterization of bladder nerves revealed specific structural features of chemically distinct classes of axon terminals, and a major autonomic source of axons labeled with neurofilament-200, which is commonly used to identify myelinated sensory axons within organs. Intramural neurons were also characterized and quantified. Together, these studies reveal a diverse range of potential targets by which artemin could influence bladder function, nerve regeneration, and pain, and provide a strong microanatomical framework for understanding bladder physiology and pathophysiology.

Nitric oxide/cyclic guanosine monophosphate signalling mediates an inhibitory action on sensory pathways of the micturition reflex in the rat

BACKGROUND

Overactive bladder can be associated with a hyperexcitability of bladder afferent C-fibres. Several studies have suggested that nitric oxide (NO) or its downstream signalling could modulate the micturition reflex (MR) by reducing the excitability of bladder afferents.

OBJECTIVES

To evaluate the role of the NO/cyclic guanosine monophosphate (cGMP) signalling pathway on the MR in a model of bladder hyperactivity (BHA) associated with C-fibre activation in the rat.

DESIGN, SETTING, AND PARTICIPANTS

Adult female Sprague Dawley rats were used.

MEASUREMENTS

Cystometry was performed in anaesthetised rats. The effects of 0.1 mg/kg of sodium nitroprusside (SNP), an NO donor; 10 mg/kg of 8Br-cGMP, a cGMP analogue; 3 mg/kg of sildenafil and 1 mg/kg of vardenafil, two phosphodiesterase type 5 inhibitors (PDE5-I); 10 mg/ml of L-N(G)-nitroarginine methyl ester (L-NAME), an NO synthase inhibitor; and 1 mg/kg of LY-83583, a guanylate cyclase inhibitor, were investigated on BHA during intravesical capsaicin (30 micromol/l) instillation. All drugs were delivered intravenously except for L-NAME, which was intravesically administered.

RESULTS AND LIMITATIONS

SNP, 8Br-cGMP, and PDE5-I increased the intercontraction interval (ICI), while SNP and PDE5-I increased the micturition pressure threshold (MPT). L-NAME and LY-83583 decreased MPT, and L-NAME decreased ICI. 8Br-cGMP decreased the maximum intravesical pressure (MP), contrary to L-NAME and LY-83583. SNP and PDE5-I had no effect on MP. SNP increased the voided volume (VV). PDE5-I and 8Br-cGMP also increased VV, although not significantly. In contrast, L-NAME tended to decrease VV. Although 8Br-cGMP decreased the baseline intravesical pressure, LY-83583 increased it. Neither SNP nor PDE5-I nor L-NAME had any effect on baseline pressure.

CONCLUSIONS

Compounds activating the NO/cGMP pathway inhibited BHA, whereas compounds inhibiting the NO/cGMP pathway increased it. These results indicate that the NO/cGMP signalling pathway is involved in the regulation of the MR, with an action that seems more predominant on the sensory rather on the motor component of the MR in a rat model of BHA associated with C-fibre afferent activation.

Functional evidence of nitrergic neurotransmission in the human urinary bladder neck

Nitric oxide (NO) is involved in the non-adrenergic non-cholinergic (NANC) inhibitory neurotransmission of the lower urinary tract. However, functional evidence of this involvement in the human urinary bladder neck has not been consistently demonstrated. Therefore, the current study investigates the relaxations to endogenously released and/or exogenously added NO, in the human bladder neck. Urothelium-denuded bladder neck strips were dissected and mounted in isolated organ baths, containing a physiological saline solution (PSS) at 37 degrees C and continuously gassed with 5% CO(2) and 95% O(2), for isometric force recording. The relaxations to transmural nerve stimulation (EFS) or to exogenously applied NO, as an acidified solution of NaNO(2) were carried out on strips precontracted with phenylephrine, and treated with guanethidine and atropine, to block noradrenergic neurotransmission and muscarinic receptors, respectively. EFS (0.5-16Hz) and exogenous NaNO(2) (1muM to 1mM) evoked frequency- and concentration-dependent relaxations, respectively. The nerve responses were abolished by the blockade of neuronal voltage-activated Na(+) channels with tetrodotoxin, indicating their neurogenic character. N(G)-nitro-l-arginine (l-NOARG), a NO synthase inhibitor, abolished the relaxations to nerve stimulation, which were partially reversed by the substrate of NO synthesis l-arginine. l-NOARG failed to modify the relaxations to exogenous NaNO(2). These results suggest that NO is the major NANC inhibitory neurotransmitter in the human urinary bladder neck. Blockers of NO synthase could be useful in therapy for the urinary incontinence produced by intrinsic sphincteric deficiency.

Differential vulnerabilities of urethral afferents in diabetes and discovery of a novel urethra-to-urethra reflex

Urethral reflexes are important regulators of micturition, and impairment of urethral afferent neuronal function may disrupt coordinated bladder and urethral activity, thereby contributing to voiding dysfunction in lower urinary tract disorders. Chemical stimulation by intraurethral irritant solution perfusion was used to determine whether urethral afferent neuronal function is altered in diabetes mellitus (DM). Sprague-Dawley rats were studied 10 wk after streptozotocin injection to induce DM or vehicle alone. Escalating doses of capsaicin (0.1-30 microM) or acetic acid (0.01-1%; AA) were perfused intraurethrally while recording isovolumetric bladder activity, urethral perfusion pressure, and electromyography of the external urethral sphincter (EUS-EMG). Some rats were additionally treated with alpha-bungarotoxin, hexamethonium, or bilateral transection of the sensory branches of the pudendal nerves (PudSNx). Intraurethral capsaicin inhibited bladder contractions in six out of seven control rats but not in any of six DM rats. Low-frequency oscillations (LFOs) of intraurethral pressure were observed in five out of six control rats with capsaicin-induced bladder inhibition. In contrast, intraurethral AA inhibited bladder contractions and enhanced tonic EUS-EMG activity in six out of six control and five out of six DM rats. LFOs occurred in four out of six control and three of five DM rats with AA-induced bladder inhibition. Chemically induced bladder inhibition and LFOs were not prevented by alpha-bungarotoxin but were eliminated by PudSNx and hexamethonium. Finally, LFOs were followed by phasic EUS activity. These findings show that DM affects urethral afferent neurons differentially, compromising those expressing TRPV1 receptors. Urethral smooth muscle LFOs are neurogenically mediated and induce EUS activity, revealing the existence of a hitherto undescribed reflex pathway: a smooth-to-striated muscle urethra-to-urethra reflex.

Role of neuronal voltage-gated K(+) channels in the modulation of the nitrergic neurotransmission of the pig urinary bladder neck

BACKGROUND AND PURPOSE

As nitric oxide (NO) plays an essential role in the inhibitory neurotransmission of the bladder neck of several species, the current study investigates the mechanisms underlying the NO-induced relaxations in the pig urinary bladder neck.

EXPERIMENTAL APPROACH

Urothelium-denuded bladder neck strips were dissected and mounted in isolated organ baths containing a physiological saline solution at 37 degrees C and continuously gassed with 5% CO(2) and 95% O(2), for isometric force recording. The relaxations to transmural nerve stimulation (EFS), or to exogenously applied acidified NaNO(2) solution were carried out on strips pre-contracted with phenylephrine, and treated with guanethidine and atropine, to block noradrenergic neurotransmission and muscarinic receptors, respectively.

KEY RESULTS

EFS (0.2-1 Hz) and addition of acidified NaNO(2) solution (1 microM-1 mM) evoked frequency- and concentration-dependent relaxations, respectively. These responses were potently reduced by the blockade of guanylate cyclase and were not modified by the K(+) channel blockers iberiotoxin, charybdotoxin, apamin or glibenclamide. The voltage-gated K(+) (Kv) channels inhibitor 4-aminopyridine, greatly enhanced the nitrergic relaxations evoked by EFS, but did not affect the NaNO(2) solution-induced relaxations.

CONCLUSIONS AND IMPLICATIONS

NO, whose release is modulated by pre-junctional Kv channels, relaxes the pig urinary bladder neck through a mechanism dependent on the activation of guanylate cyclase, in which post-junctional K(+) channels do not seem to be involved. Modulation of Kv channels could be useful in the therapy of the urinary incontinence produced by intrinsic sphincteric deficiency.

Effects of l-arginine and N(G)-nitro-l-arginine methyl ester treatments on expression of neuronal nitric oxide synthase in the guinea-pig bladder after partial bladder outlet obstruction

This study was aimed to examine the effects of pharmacological intervention on partial bladder outlet obstruction (PBOO) on expression of neuronal nitric oxide synthase (nNOS) and nitric oxide (NO) production and NO-related free radical damage using nitrotyrosine as a marker in the guinea-pig bladder. Partial urethral ligation was performed in young male guinea pigs which were then intraperitoneally administered l-arginine, N(G)-nitro-l-arginine methyl ester (l-NAME) or vehicle (saline) for 2 or 4 weeks. At the respective time points, the bladder was removed for nNOS immunohistochemistry, Western blot analysis, nitrotyrosine enzyme-linked immunosorbent assay test and NO colorimetric assay. In l-arginine-treated animals killed at 2 and 4 weeks, the total number of nNOS positive intramural neurons was significantly increased when compared with the corresponding control. Some neurons projected long extending fibers that were closely associated with the blood vessels. Furthermore, at 4 weeks, the nNOS protein content and NO production as reflected by the concentration of nitrite and nitrate were drastically elevated as measured by Western blot analysis and NO colorimetric assay, respectively. In l-NAME-treated group killed at 2 weeks, the number of nNOS positive neurons was markedly reduced when compared with the controls, but the change was not significant at 4 weeks. In the latter, however, the NO production as reflected by the concentration of nitrite and nitrate was markedly reduced; in addition, the nitrotyrosine concentration was significantly lower than the control. The present results support the role of NO in the pathophysiological changes following PBOO. We suggest the potential therapeutic application of l-arginine and l-NAME in PBOO; however, ultimately balancing the bidirectional effects of NO would be essential.

Pre-junctional alpha2-adrenoceptors modulation of the nitrergic transmission in the pig urinary bladder neck

AIMS

To investigate the nitric oxide (NO)-mediated nerve relaxation and its possible modulation by pre-junctional alpha2-adrenoceptors in the pig urinary bladder neck.

METHODS

Urothelium-denuded bladder neck strips were dissected, and mounted in isolated organ baths containing a physiological saline solution (PSS) at 37 degrees C and continuously gassed with 5% CO2 and 95% O2, for isometric force recording. The relaxations to transmural nerve stimulation (electrical field stimulation [EFS]) or exogenously applied NO were carried out on strips pre-contracted with 1 microM phenylephrine (PhE) and treated with guanethidine (10 microM) and atropine (0.1 microM), to block noradrenergic neurotransmission and muscarinic receptors, respectively.

RESULTS

EFS (0.2-1 Hz, 1 msec duration, 20 sec trains, current output adjusted to 75 mA) evoked frequency-dependent relaxations which were abolished by the neuronal voltage-activated Na+ channel blocker tetrodotoxin (TTX, 1 microM). These responses were potently reduced by the nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine (L-NOARG, 30 microM) and further reversed by the NO synthesis substrate L-arginine (L-ARG, 3 mM). The alpha2-adrenoceptor agonist BHT-920 (2 microM) reduced the electrically evoked relaxations, its effectiveness being higher on the responses induced by low frequency stimulation. BHT-920-elicited reductions were fully reversed by the alpha2-adrenoceptor antagonist rauwolscine (RAW, 1 microM). Exogenous NO (1 microM-1 mM) induced concentration-dependent relaxations which were not modified by BHT-920, thus eliminating a possible post-junctional modulation.

CONCLUSIONS

These results indicate that NO is involved in the non-adrenergic non-cholinergic (NANC) inhibitory neurotransmission in the pig urinary bladder neck, the release of NO from intramural nerves being modulated by pre-junctional alpha2-adrenoceptor stimulation.

Nitric oxide/cGMP-mediated effects in the outflow region of the lower urinary tract--is there a basis for pharmacological targeting of cGMP?

Treatment with alpha-adrenoceptor antagonists that reduce the tone of prostatic stromal and urethral smooth muscle has beneficial effects in patients with benign prostatic hyperplasia (BPH) and lower urinary tracts symptoms (LUTS) and has brought attention to regulatory mechanisms of smooth muscle contractility of the outflow region. The prostate, urethra and bladder neck are densely supplied by nitric oxide (NO)-synthase-containing nerves that cause relaxation upon activation. In various experimental models, altered function or activity of the NO/cGMP pathway of the bladder neck and urethra may be related to inappropriate or un-coordinated functions of the bladder outlet and detrusor, but causal connections between alterations in this signaling system, a dysfunctional bladder outlet, and the development of LUTS are not established for humans. The present review focuses on regulatory functions of smooth muscle contractility by the NO/cGMP-pathway in the bladder neck, urethra, and prostate. Disease-related alterations in the NO/cGMP-pathway, and putative options for pharmacological modification of this signaling pathway in the out-flow region are briefly discussed.

Pharmacology of the lower urinary tract: basis for current and future treatments of urinary incontinence

The lower urinary tract constitutes a functional unit controlled by a complex interplay between the central and peripheral nervous systems and local regulatory factors. In the adult, micturition is controlled by a spinobulbospinal reflex, which is under suprapontine control. Several central nervous system transmitters can modulate voiding, as well as, potentially, drugs affecting voiding; for example, noradrenaline, GABA, or dopamine receptors and mechanisms may be therapeutically useful. Peripherally, lower urinary tract function is dependent on the concerted action of the smooth and striated muscles of the urinary bladder, urethra, and periurethral region. Various neurotransmitters, including acetylcholine, noradrenaline, adenosine triphosphate, nitric oxide, and neuropeptides, have been implicated in this neural regulation. Muscarinic receptors mediate normal bladder contraction as well as at least the main part of contraction in the overactive bladder. Disorders of micturition can roughly be classified as disturbances of storage or disturbances of emptying. Failure to store urine may lead to various forms of incontinence, the main forms of which are urge and stress incontinence. The etiology and pathophysiology of these disorders remain incompletely known, which is reflected in the fact that current drug treatment includes a relatively small number of more or less well-documented alternatives. Antimuscarinics are the main-stay of pharmacological treatment of the overactive bladder syndrome, which is characterized by urgency, frequency, and urge incontinence. Accepted drug treatments of stress incontinence are currently scarce, but new alternatives are emerging. New targets for control of micturition are being defined, but further research is needed to advance the pharmacological treatment of micturition disorders.

Nerve induced responses and force-velocity relations of regenerated detrusor muscle after subtotal cystectomy in the rat

AIMS

To study the pharmacological and mechanical properties of newly developed detrusor muscle after subtotal cystectomy, to explore if the regenerated detrusor has characteristics similar to the normal bladder base, from which it regenerated, or to the normal bladder body which it replaces.

METHODS

Partial cystectomy was performed in female rats. Fifteen weeks later, detrusor strips were cut from supratrigonal and equatorial segments. Unoperated rats served as controls. Responses to field stimulation were obtained in the absence and presence of scopolamine, prazosin, and P2X1 blockade. Dose-response curves were obtained for carbachol, alpha,beta-methylene-ATP, and phenylephrine. Force-velocity data were obtained on maximally activated chemically skinned preparations.

RESULTS

Maximal contractile response to field stimulation was 60% of that to high-K+ with no difference between strips from control and cystectomy bladders. Prazosin had no effect. Scopolamine decreased maximal response of supratrigonal strips to 62 +/- 6 (controls) and 61 +/- 4% (operated) of that without blocker. For equatorial strips the decrease was to 81 +/- 5 (controls) and 58 +/- 8% (operated). Frequency-response relations were obtained during blockade with scopolamine, alpha,beta-methylene-ATP, and prazosin. Supratrigonal strips showed a pronounced additional inhibition up to 40 Hz. Equatorial strips from controls were completely inhibited at all frequencies. Equatorial strips from operated bladders were inhibited up to 20 Hz but not at 40 and 60 Hz. Carbachol EC(50) values were similar in all groups. Maximum response to phenylephrine was 10-20% of high-K+ response. Maximal shortening velocity (Vmax) was similar in control supratrigonal and equatorial strips, but was significantly lower in the operated bladders.

CONCLUSIONS

(1): A regional difference exists in pharmacological properties of control detrusor, with a considerable contractile response to stimulation remaining in the supratrigonal muscle after simultaneous cholinergic, adrenergic, and purinergic blockade. (2): The new detrusor was functionally well innervated with no supersensitivity to muscarinic stimulation. (3): The newly formed bladder body had pharmacological properties specific for the supratrigonal segment from which it had developed. (4): There was no regional difference in force-velocity characteristics of the control detrusor. (5): The lowered Vmax in the newly formed bladder might thus be related to growth and regeneration of muscle cells.

The effect of labor and/or ovariectomy on rodent continence mechanism--the neuronal changes

Many women develop stress urinary incontinence (SUI) after childbirth, but the exact neuronal changes are largely unknown. This study is designed to identify the neuronal changes associated with pregnancy, delivery and ovariectomy. A total of 10 virgin and 48 pregnant rats were used. Cystometry and stress/sneeze tests were performed in the virgin once and the pregnant rats at certain time points. Postpartum the rats were equally grouped as follows: group I: delivery, group II: delivery + ballooning, group III: delivery + ovariectomy, group IV: delivery + ballooning + ovariectomy. Tissues from bladder, bladder neck, and urethra were analyzed by immunostaining for PGP 9.5, CGRP, SP, NPY, VIP, TH, n-NOS. We found complex innervation changes in the different tissue samples. Since the bladder neck and the mid-urethra play an important role in the continence mechanism the neuronal changes in these areas contribute to the observed functional changes.

Increased expression of neuronal nitric oxide synthase in bladder afferent cells in the lumbosacral dorsal root ganglia after chronic bladder outflow obstruction

Nitric oxide (NO), a neurotransmitter in autonomic reflex pathways, plays a role in functional neuroregulation of the lower urinary tract. Upregulation of the levels of neuronal nitric oxide synthase (nNOS), the enzyme system responsible for NO synthesis, has been documented in the peripheral, spinal and supraspinal segments of the micturition reflex in diseases such as cystitis, bladder/sphincter dyssynergia following spinal cord injury and bladder overactivity after cerebral infarction. These observations suggest that NO might play a role in the development of bladder overactivity. In this study, nNOS-immunoreactivity (IR) was evaluated in bladder afferent and spinal neurons following bladder outflow obstruction (BOO) in male and female rats. Chronic BOO was induced by placing lumen reducing ligatures around the proximal urethra. Six weeks following the obstructive or sham surgery, bladder function was evaluated by awake cystometry. Bladder afferent neurons in L1, L2, L6 and S1 dorsal root ganglia (DRG) were identified by retrograde neuronal labeling with injection of Fast Blue into the bladder smooth muscle. A differential distribution of nNOS-IR was subsequently evaluated in bladder afferent neurons in the DRG and in the associated spinal cord segments. The percentage of bladder afferent neurons expressing nNOS-IR was increased in L6 (1.8-fold in males and 1.9-fold in females) and S1 (2.8-fold in males and 5.3-fold in females) DRG. In contrast, no changes in nNOS-IR in neurons or fiber distribution were observed in any spinal cord segments examined.

Activity and expression of nitric oxide synthase in the hypertrophied rat bladder and the effect of nitric oxide on bladder smooth muscle growth

PURPOSE

We investigated the expression and activity of nitric oxide synthase (NOS) and the localization of cyclic guanosine monophosphate (cGMP) in hypertrophied rat bladder. We also examined whether nitric oxide (NO) has a growth inhibitory effect in bladder smooth muscle cells.

MATERIALS AND METHODS

The urethra was partly ligated and the bladder was removed 3 days, 3 or 6 weeks after obstruction. NOS activity was determined as the conversion of L-[14C]citrulline from L-[14C]arginine (Amersham Life Science, Solna, Sweden). Neuronal NOS (nNOS) expression was studied with Western blot analysis and immunohistochemistry. The expression of inducible NOS (iNOS) and cGMP was evaluated by immunohistochemistry. The effect of NO on isolated bladder smooth muscle cell growth was assessed as protein and DNA synthesis by [3H]-leucine and [3H]-thymidine (NEN Life Science Products, Zaventem, Belgium) incorporation, respectively.

RESULTS

Ca independent iNOS activity increased after short-term obstruction. Immunohistochemical studies in obstructed bladders demonstrated iNOS expression primarily in urothelial and inflammatory cells. Ca dependent nNOS activity decreased after obstruction, as confirmed by Western blot analysis. The cGMP immunoreactive cells were mainly found within the serosal layer of obstructed bladders. The NO donor DETA-NONOate (Alexis Biochemicals, Lausen, Switzerland) (300 microM.) reduced [3H]-leucine and [ H]-thymidine incorporation by a mean of 29% +/- 2% and 95% +/- 2%, respectively, in cultured bladder smooth muscle cells.

CONCLUSIONS

Bladder obstruction caused a small increase in iNOS activity and a decrease in nNOS activity. NO was found to have a growth inhibitory effect in bladder smooth muscle cells, suggesting that changes in NOS activity may influence the progress of bladder hypertrophy.

Physiology of female micturition

Micturition is a dynamic physiologic process consisting of alternating storage and expulsion phases and is accomplished by complex interactions among innervation, smooth muscle, connective tissue, urothelium and supportive structures. Although our current understanding of the anatomy and physiology of the lower urinary tract is far from complete, intensive research over the last decade has dramatically improved our appreciation of the neural, biomechanical, biochemical, and morphologic properties of the bladder and urethra, as well as the hormonal influences and unique pelvic and perineal anatomy of women. Continued research related to the physiology of female micturition promises to offer new insights into the complex bladder-urethral interactions and to provide a basis for developing better management strategies for a variety of voiding dysfunctions in women.

Morphological and functional characterization of a rat vaginal smooth muscle sphincter

The aim of the present study was to gain information about adrenergic-, cholinergic- and non-adrenergic, non-cholinergic (NANC)- transmitter systems/mediators in the rat vagina, and to characterize its smooth muscles functionally. Tissue sections from vagina of Sprague Dawley rats were immunolabelled with antibodies against protein gene product 9.5 (PGP), synaptophysin (Syn), tyrosine hydroxylase (TH), vesicular acetylcholine transporter (VAChT), neuropeptide Y (NPY), nitric oxide synthase (NOS), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP). Circularly cut vaginal smooth muscle preparations from the distal vagina were studied in organ baths. In the paravaginal tissue, a large number of PGP-, NOS-, TH-, VIP-immunoreactive (IR) and few CGRP-IR nerve trunks were observed, giving off branches to the smooth muscle wall. The smooth muscle wall was supplied by a large number of PGP-, Syn-, VAChT-, NPY-, NOS- and TH- IR nerve terminals, whilst only a moderate to few numbers of CGRP-, VIP- and PACAP-IR terminals were identified. Especially the distal part of the vaginal wall, where the circularly running smooth muscle was thickened into a distinct sphincter structure, was very richly innervated, predominantly by PGP- and NOS-IR terminals. Below and within the basal parts of the epithelium in the distal half of the vagina, a large number of PGP- and few NOS- and PACAP-IR varicose terminals were observed. The vaginal arteries were encircled by plexuses of nerve terminals. A large number of these were PGP-, Syn-, VAChT-, NOS-, TH-, NPY- and VIP-IR, and few were CGRP- and PACAP-IR. In isolated preparations of the distal vagina, electrical field stimulation (EFS) caused frequency-dependent contractions, which were reduced by sildenafil, tetrodotoxin (TTX) and phentolamine. In preparations contracted by norepinephrine (NA), EFS produced frequency-dependent relaxations. Pretreatment with the NOS-inhibitor N(G)-nitro-L-arginine, TTX, or the inhibitor of soluble guanylate cyclase, ODQ, abolished the EFS relaxations. In NE precontracted preparations, cumulative addition of sildenafil caused concentration-dependent relaxation. Carbachol contracted the strips concentration-dependently from baseline. It can be concluded that the distal part of the rat vagina forms a distinct smooth muscle sphincter, which is richly innervated by adrenergic, cholinergic and NANC nerves. The present studies suggest that in the rat the L-arginine/NO-system not only plays an important role in the regulation of vaginal smooth muscle tone, but also affects blood flow, and may have sensory functions.

Nitric oxide-induced cGMP accumulation in the mouse bladder is not related to smooth muscle relaxation

The functional role of nitric oxide (NO) and the guanylate cyclase/cGMP second messenger system was investigated in the mouse bladder. Electrical field stimulation and the NO-donor 3-morpholino-sydnonimin hydrochloride (SIN-1) did not induce relaxation of the carbachol-precontracted bladder. However, sodium nitroprusside (10(-3) M) was found to enhance the contractile response to electrical field stimulation by 24+/-6% (n=8; P<0.05) without affecting the contractile response to carbachol. The enhancement of bladder contractility evoked by sodium nitroprusside was inhibited by the guanylate cyclase inhibitor 1H-[1,2, 4]oxadiazolo[4,3-a]quinoxalime-1-one (ODQ; 10(-6) M). Incubation of bladder strips with SIN-1 and sodium nitroprusside caused an increase in cGMP accumulation as measured by radioimmunoassay. Immunohistochemical studies showed cGMP-immunoreactivity in nerve fibres and in stromal cells, but not in smooth muscle bundles after exposure to NO-donors. The results show that NO-donors have no inhibitory effect on smooth muscle tone in the mouse bladder, but that NO may have a functional role as an excitatory neuromodulator. The targets of endogenous NO in the bladder may be the demonstrated cGMP-positive structures, i.e., nerves and stromal cells.

Effect of K+ channel openers, KRN2391 and Ki1769, and nitroglycerin on the urinary tract of rats in vivo

The effects of KRN2391 (N-cyano-N'-(nitroxyethyl)-3-pyridine carboximidamide methane-sulfonate), which possesses ATP-sensitive potassium (K+) channel opening (KCO) activity and nitrate activity; Ki1769 (N-cyano-N'-(phenylethyl)-3-pyridinecarboximidamide methanesulfonate), which possesses only KCO activity; and nitroglycerin (NG) were determined on the motility of the ureter, urinary bladder and urethra of rats. Bladder contraction was induced by infusion of fluid into the bladder of conscious rats and recorded on a cystometrogram. KRN2391 and Ki1769 (both 0.3 mg/kg, i.v.) prolonged the micturition interval immediately after the injection, but NG (5 mg/kg, i.v.) did not. Peristaltic movement of the ureter, recorded in anesthetized rats, was inhibited by i.v. injection of KRN2391 and Ki1769 (both 0.03 mg/kg). However, when NG, NaNO2, N-nitro L-arginine methylester and methylene blue were applied directly to the ureter, no change in movement of the ureter was detected. KRN2391 (0.03 mg/kg, i.v.) and Ki1769 (0.3 mg/kg, i.v.) reduced the resistance to fluid infusion through the urethral lumen in anesthetized rats, whereas NG (0.5 mg/kg, i.v.) only reduced this resistance transiently. These results indicate that KCO activity had an inhibitory effect on the motility of the ureter, bladder and urethra. On the other hand, nitrate activity had an inhibitory effect on urethral tonus, corresponding to that induced by KCO activity.

Morphological and biochemical investigation of nitric oxide synthase and related enzymes in the rat and pig urothelium

We investigated the enzymes involved in the NADPH-diaphorase (d) reaction in the rat and pig bladder urothelium. The urothelial cell layer displayed intense and uniform NADPH-d activity. Preincubation with the flavoprotein inhibitor diphenyleneiodionium chloride (DPI) and the alkaline phosphatase inhibitor levamisole concentration-dependently decreased the urothelial NADPH-d activity. Immunoreactivities to neuronal (n), endothelial (e), or inducible (i) nitric oxide synthase (NOS) were not detected in rat or pig urothelial cells. In rats, the urothelium was uniformly immunoreactive for NADPH cytochrome P450 reductase, whereas the pig urothelium displayed inconsistent labeling. In lipopolysaccharide (LPS)-treated rats, the bladder urothelium showed positive iNOS immunoreactivity. The iNOS labeling was found predominantly in cells located in the basal layer of the urothelium. In the pig bladder mucosa, a Ca2+-dependent NOS activity was evident in cytosolic and particulate fractions that was quantitatively comparable to the NOS activity found in the smooth muscle. In ultrastructural studies of urothelial cells, NADPH-d reaction products were found predominantly on membranes of the nuclear envelope, endoplasmatic reticulum and mitochondria. In conclusion, NADPH-d staining of the urothelium cannot be taken as an indicator for the presence of constitutively expressed NOS. Activity of alkaline phosphatase and cytochrome P450 reductase may account for part of the NADPH-d reaction in urothelial cells. However, LPS treatment of rats caused expression of iNOS in urothelial cells.

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.

Involvement of NGF in the induction of increased noradrenergic innervation of the ureter in neonatally capsaicin-treated rats

Neonatal denervation of primary afferents with capsaicin leads to increased sympathetic innervation of the rat ureter. In the present study the development and the immunohistochemical characterization of this sympathetic hyperinnervation as well as the specific involvement of nerve growth factor (NGF) was investigated. Noradrenaline levels were found elevated in neonatally capsaicin-treated rats by 2 weeks of age and remained at that high level into adulthood. Injections of an anti-NGF antiserum during postnatal days (PN) PN 8-14, PN 13-19 or during PN 17-23 counteracted the capsaicin effect and reduced noradrenaline towards control levels. Immunohistochemical localization of tyrosine hydroxylase (TH), a marker for sympathetic nerve fibres, revealed that the capsaicin-induced hyperinnervation was mainly represented by fibres in deeper muscle layers and to a smaller extent by fibres in the submucosa. In control animals and in rats treated with capsaicin and anti-NGF antiserum fibres were mainly distributed in the adventitia and in the outer part of the smooth muscle layer. These results show that NGF is responsible for the development of an increased noradrenergic innervation in the rat ureter after neonatal capsaicin treatment.

Nitrergic and cholinergic innervation of the rat lower urinary tract after pelvic ganglionectomy

The possible coexistence of nitric oxide (NO) and acetylcholine in the rat major pelvic ganglion (MPG) was examined by double immunohistochemistry using antisera raised against NO synthase (NOS) and choline acetyltransferase (ChAT). The smooth muscle responses of the isolated bladder and urethra were recorded after bilateral cryoganglionectomy of the MPG, focusing on the possible development of denervation supersensitivity. In the MPG, NOS immunoreactivity (ir) was seen in a large number of cell bodies, but it was not as abundant as ChAT-ir cell bodies. Double immunolabeling showed that all NOS-ir cell bodies also displayed ChAT-ir. In ganglionectomized bladders, the electrical field stimulation (EFS)-evoked contractile response was markedly reduced. When compared with control bladders, detrusor strips from ganglionectomized rats were more sensitive to carbachol as revealed by a lower negative logarithm of the drug concentration eliciting 50% relaxation (6.5 +/- 0.04 vs. 5.9 +/- 0.07). In the urethra, the NO-mediated relaxant response to EFS was practically abolished by ganglionectomy, whereas no difference was found in sensitivity to 3-morpholinosydnonimine hydrochloride (SIN-1). SIN-1 produced an equal increase in tissue levels of guanosine 3',5'-cyclic monophosphate in urethral preparations from control and ganglionectomized rats. The results suggest that the NOS-ir nerves that mediate inhibition of rat urethral smooth muscle tone originate from the MPG and contain ChAT. No denervation supersensitivity to nitrergic stimulation was observed in the urethra after ganglionectomy.

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.

Nitric oxide synthase-containing nerves and ganglia in the dog prostate: a comparison with other transmitters

The distribution of nitric oxide synthase immunoreactive nerves in the dog prostate was compared to the total innervation (as estimated by protein gene product 9.5 immunoreactivity), and to that of adrenergic (tyrosine hydroxylase-immunoreactive), cholinergic (acetylcholinesterase-positive), and some peptidergic nerves immunoreactive towards vasoactive intestinal peptide, pituitary adenylate cyclase-activating peptide, and helospectin. Clusters of ganglia with cell bodies containing acetylcholinesterase, or one of these six immunoreactive components, were found in the dorsal capsule. Coarse nerve trunks expressing these immunoreactive components extended from the ganglia, and divided into varicose terminals in the capsule and intraglandular smooth muscle strands, and gave off further branches, which surrounded acini and accompanied ducts. The labelling for nitric oxide synthase generally coincided with that for vasoactive intestinal peptide within cell bodies and nerves of various types. Cell bodies, nerve trunks and varicose terminals showing labelling for pituitary adenylate cyclase-activating peptide and helospectin were generally also labelled for vasoactive intestinal peptide. The innervation pattern suggests that nitric oxide may act in concert with vasoactive intestinal peptide and related peptides in the control of prostatic smooth muscle activity and secretion.