Involvement of cyclic nucleotide-gated channels in spontaneous activity generated in isolated interstitial cells of Cajal from the rabbit urethra.

Cyclic nucleotide-gated (CNG) channels are non-selective cation channels that mediate influx of extracellular Na and Ca in various cell types. L-cis-Diltiazem, a CNG channel blocker, inhibits contraction of urethral smooth muscle (USM), however the mechanisms underlying this effect are still unclear. We investigated the possibility that CNG channels contribute to spontaneous pacemaker activity in freshly isolated interstitial cells of Cajal (ICC) isolated from the rabbit urethra (RUICC).

Proliferation of Interstitial Cells in the Cyclophosphamide-Induced Cystitis and the Preventive Effect of Imatinib.

Cyclophosphamide- (CYP-) induced cystitis in the rat is a well-known model of bladder inflammation that leads to an overactive bladder, a process that appears to involve enhanced nitric oxide (NO) production. We investigated the changes in the number and distribution of interstitial cells (ICs) and in the expression of endothelial NO synthase (eNOS) in the bladder and urethra of rats subjected to either intermediate or chronic CYP treatment. Pronounced hyperplasia and hypertrophy of ICs were evident within the lamina propria and in the muscle layer.

Changes in nerve- and endothelium-mediated contractile tone of the corpus cavernosum in a mouse model of pre-mature ageing.

Erectile dysfunction (ED) is very prevalent in the older population, although the ageing-related mechanisms involved in the development of ED are poorly understood. We propose that age-induced differences in nerve- and endothelium-mediated smooth muscle contractility in the corpus cavernosum (CC) could be found between a senescent-accelerated mouse prone (SAMP8) and senescent-accelerated mouse resistant (SAMR1) strains. We analysed the changes in muscle tension induced by electrical field stimulation (EFS) or agonist addition 'in vitro', assessing nerve density (adrenergic, cholinergic and nitrergic), the expression of endothelial nitric oxide synthase (eNOS), cGMP accumulation and the distribution of interstitial cells (ICs) by immunofluorescence.

Altered neuronal and endothelial nitric oxide synthase expression in the bladder and urethra of cyclophosphamide-treated rats.

Increased nitric oxide (NO) production seems to play a key role in cyclophosphamide (CYP)-induced cystitis, although the underlying mechanisms and the relative involvement of the different NO synthase (NOS) isoforms remain to be elucidated. Moreover, the role of the urethra in this process is also unclear. In this study, we have analyzed the changes in the expression and distribution of the inducible (iNOS), endothelial (eNOS) and neuronal (nNOS) isoforms of NOS, and the alterations in nerve-mediated contractility in the bladder and urethra of CYP-treated rats.

Changes in nerve-mediated contractility of the lower urinary tract in a mouse model of premature ageing.

Background And Purpose: A high incidence of lower urinary tract disorders is associated with ageing. In the senescent-accelerated prone (SAMP8) mouse strain and the senescent-accelerated resistant (SAMR1) strain, we compared smooth muscle contractility in responses to intrinsic neurotransmitters, both in the bladder and urethra.

Experimental Approach: We analysed micturition frequency, the changes in muscle tension induced by electrical field stimulation or agonist administration, the density of nerves (adrenergic, cholinergic and nitrergic) and interstitial cells (ICs), as well as cGMP accumulation in bladder and urethral preparations.

Presence of the Ca2+-activated chloride channel anoctamin 1 in the urethra and its role in excitatory neurotransmission.

We investigated the cellular distribution of the calcium-activated chloride channel (CaCC), anoctamin 1, in the urethra of mice, rats, and sheep by both immunofluorescence and PCR. We studied its role in urethral contractility by examining the effects of chloride-free medium and of several CaCC inhibitors on noradrenergic and cholinergic excitatory responses, and on nitrergic relaxations in urethral preparations. In all species analyzed, CaCC played a key role in urethral contractions, influencing smooth muscle cells activated by increases in intracellular calcium, probably due to calcium influx but with a minor contribution by IP(3)-mediated calcium release.

Direct coupling through gap junctions is not involved in urethral neurotransmission.

Interstitial cells of Cajal (ICC) are believed to participate in urethral neurotransmission and it was proposed that direct coupling of ICC and smooth muscle cells (SMC) through gap junctions (GJ) is involved, although this still remains unclear. Hence, we investigated the distribution of different connexins (Cx 43, Cx40, and Cx37) in the sheep and rat urethra, as well as their possible role in neurotransmission. Conventional PCR confirmed that three Cxs are expressed in the urethra.

Refractoriness of urethral striated muscle contractility to nitric oxide-dependent cyclic GMP production.

The purpose of this study was to investigate the role of cyclic GMP (cGMP) in the effects of nitric oxide (NO) on urethral striated muscle and its involvement in contractile function. The localization of cGMP, neuronal NO synthase (nNOS), vimentin, and neuronal markers was assessed by immunofluorescence in the sheep and rat urethra and the expression of nNOS was determined in Western blots. Nerve-mediated contractile responses to electrical field stimulation (EFS) were recorded in the sheep urethra.

Presence of cyclic nucleotide-gated channels in the rat urethra and their involvement in nerve-mediated nitrergic relaxation.

We have addressed the distribution of cGMP-gated channels (CNG) in the rat urethra for the first time, as well as their putative role in mediating of the relaxation elicited by electrical field stimulation of nitrergic nerves. Functional studies have shown that specifically blocking CNG with L-cis-diltiazem leads to the rapid inhibition of urethral relaxation induced either by nitric oxide (NO) released by the nerves or by soluble guanylate cyclase activated with YC-1. By contrast, nerve-mediated noradrenergic contractions were only slowly and mildly reduced by L-cis-diltiazem.

Interstitial cells of Cajal in the urethra are cGMP-mediated targets of nitrergic neurotransmission.

While interstitial cells of Cajal (ICC) in the urethra respond to nitric oxide (NO) donors by increasing cGMP, it remains unclear whether urethral ICC are functionally innervated by nitrergic nerves. We have addressed this issue in the rat and sheep urethra, where cGMP production and relaxation were compared in preparations subjected to electrical field stimulation (EFS; 2 Hz, 4 min) of nitrergic nerves or to exogenous S-nitroso-L-cysteine (SNC; 0.1 mM, 4 min).

Localization and thiol dependancy of endogenous nitro compounds-mediating urethral photo-relaxation.

Using a nitric oxide (NO)-specific fluorescent probe, we have examined the location of NO generation in the urethra from sheep and rat when induced by either electrical field- or light-stimulation (EFS and LS, respectively). In addition, we studied the effect of specific glutathione (GSH) modifiers, acting upon different cellular GSH pools, on NO release and on urethral relaxation. Both EFS and LS led to fluorescence emission from a fiber network associated with neuronal NO synthase (nNOS) immunoreactive nerves.

Partial nicotinic receptor blockade unmasks a modulatory role of nitric oxide on urethral striated neuromuscular transmission.

The objective of this study was to investigate the possible modulatory role of endogenous nitric oxide (NO) production on the urethral striated muscle (USM) function in the sheep urethra. Significant NO synthase (NOS) activity was measured in both the particulate and cytosolic fractions of USM homogenates. NOS activity was calcium-dependent and showed greater inhibition by NOS inhibitors selective of the neural NOS isoform (nNOS).

Atypical relaxation by scorpion venom in the lamb urethral smooth muscle involves both NO-dependent and -independent responses.

The sustained depolarisation induced by alpha-toxins from scorpion venom (20 microg/ml(-1)) was used to test the hypothesis that an endogenous, photo-sensitive, nitrocompound could act as a stable nitrergic transmitter in the sheep (lamb) urethra. Scorpion venom-treatment effectively abolished neurogenic responses to electrical field stimulation, but it did not modify the spontaneous urethral photorelaxation. On the other hand, scorpion venom induced an atypical relaxation in noradrenaline-contracted preparations, which could be reverted, but not prevented, by tetrodotoxin (TTX, 1 microM).

Nitric oxide synthase in the external urethral sphincter of the sheep: immunohistochemical and functional study.

Purpose: We studied the distribution of neuronal nitric oxide synthase (nNOS) and the effects of nitric oxide (NO) modulating drugs on contractile function of the external urethral sphincter of lambs. Gender differences were evaluated.

Materials And Methods: Longitudinal and transverse sections of the external urethral sphincter from 10 female and 10 male lambs were studied using reduced nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry and nNOS immunocytochemistry.

Nitrergic relaxation in urethral smooth muscle: involvement of potassium channels and alternative redox forms of NO.

We examined the contribution of K+ channels to the relaxation responses induced by different redox forms of nitric oxide (NO., NO- and NO+) in comparison with those evoked by electrical field stimulation (EFS) of nitrergic nerves in the sheep urethra. K+ channel blockers with different selectivity profile were used.

Spontaneous photo-relaxation of urethral smooth muscle from sheep, pig and rat and its relationship with nitrergic neurotransmission.

1. In the present work we have characterized the relaxant response induced by light stimulation (LS) in the lower urinary tract from sheep, pig and rat, establishing its relationship with nitrergic neurotransmission. 2.

Effects of superoxide anion generators and thiol modulators on nitrergic transmission and relaxation to exogenous nitric oxide in the sheep urethra.

The effects of superoxide anion generators, the nitric oxide (NO) scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoine-1-oxyl 3-oxide (carboxy-PTIO), the specific guanylate cyclase inhibitor 1H-[1,2,4]-oxadiazole-[4,3-a]-quinoxalin-1-one (ODQ), and thiol modulating agents were investigated on relaxations induced by nitrergic stimulation and exogenous NO addition in the sheep urethra. Methylene blue (MB, 10 microM), pyrogallol (0.1 mM) and xanthine (X, 0.

Differential mechanisms of urethral smooth muscle relaxation by several NO donors and nitric oxide.

We have examined the mechanisms of action of a broad spectrum of nitric oxide (NO) donors, including several S-nitrosothiols, sodium nitroprusside (SNP) and nitroglycerine (GTN), in relation to their relaxant activity of urethral smooth muscle. For all the compounds examined, NO release (in solution and in the presence of urethral tissue), relaxation responses, elevations in cGMP levels and the effect of thiol modulators were evaluated and compared with the effect of NO itself. Whilst all NO donors, except GTN, released NO in solution due to photolysis or chemical catalysis, this release was not correlated with their relaxant activity in sheep urethral preparations, which were furthermore not affected by the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (cPTIO; 0.

Cholinergic modulation of non-adrenergic, non-cholinergic relaxation in isolated, small coronary arteries from lambs.

The presence of cholinergic innervation of small coronary arteries in the lamb was investigated by measuring choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities and by performing in vitro experiments in a microvascular myograph to establish whether or not there is a cholinergic component in the response to electrical field stimulation (EFS). ChAT-specific activity was present in proximal coronary segments, but was significantly higher in small coronary arteries. AChE-positive ganglia and fibres were distributed within the adventitia and outer third of the media in proximal coronary segments, and dense perivascular nerve plexuses were observed in small coronary arteries.

Endothelin receptor-mediated Ca2+ mobilization and contraction in bovine oviductal arteries: comparison with noradrenaline and potassium.

1. The effects of endothelin-1 (ET-1) were studied in bovine oviductal arteries and compared to those of noradrenaline (NA) and high K+ (K+). The influence of endothelium, the receptor subtypes involved, and the mechanisms of Ca2+ mobilization were assessed.

Local regulation of oviductal blood flow.

1. Blood flow to the oviduct is implicated in the genesis and maintenance of oviductal fluid, in this way contributing to the creation of an adequate medium for ovum/embryo physiology. Therefore, factors controlling the tone of the vessels supplying the oviduct would be expected to affect its luminal environment.

Characterization of nitric oxide synthase activity in sheep urinary tract: functional implications.

1. To define further the role of nitric oxide (NO) in urinary tract function, we have measured the presence of nitric oxide synthase (NOS) activity, and its relationship with functional NO-mediated responses to electrical field stimulation (EFS) in the urethra, the detrusor and the ureter from sheep. NOS activity was assayed by the conversion of L-[14C]-arginine to L-[14C]-citrulline.

Relaxation mechanisms induced by stimulation of nerves and by nitric oxide in sheep urethral muscle.

Isolated transverse and longitudinally oriented preparations of sheep urethra precontracted with noradrenaline responded to electrical field stimulation (EFS) with stimulus-dependent non-adrenergic, non-cholinergic (NANC) relaxations. Exogenous nitric oxide (NO) (acidified NaNO2), S-nitroso-L-cysteine (NC), sodium nitroprusside (SNP), 8-Br-cGMP, dibutyryl-cAMP, forskolin and isoprenaline each relaxed precontracted transverse urethral preparations in a concentration-dependent manner in order of protency: NC > forskolin > isoprenaline = SNP > NO > 8-Br-cGMP = dibutyryl-cAMP. Longitudinally oriented preparations responded to NO and NC with concentration-dependent relaxation, no different from that observed in transverse strips.

NADPH-diaphorase and NANC relaxations are correlated in the sheep urinary tract.

The present investigation was performed with the purpose of revealing by histochemical examination of NADPH-diaphorase activity and electrical field stimulation (EFS) of isolated preparations in vitro, whether a nitrergic innervation is present in the lower urinary tract of the sheep. NADPH-diaphorase positive fibers were found in the trigone and urethra, but not in detrusor and ureter. EFS elicited L-nitroarginine-sensitive relaxations of precontracted preparations from the trigone and urethra while it did not relax detrusor and ureteral preparations.

Choline acetyltransferase activity associated with cerebral cortical microvessels does not originate in basal forebrain neurons.

Cerebral cortical microvessels are innervated by cholinergic fibers that are probably involved in the regulation of local cerebral blood flow and blood-brain barrier permeability. The possibility exists that the cholinergic terminals associated with the cortical microvasculature belong to neurons from the nucleus basalis magnocellularis (NBM), where 70% of the cortical cholinergic projections originate. To test this hypothesis, ibotenic acid (25 nmol) was injected unilaterally in the NBM in rats, and 14 days later, choline acetyltransferase (ChAT) activity was measured in the frontoparietal cortex and in a blood vessel fraction isolated from this region.