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Aronsson P, Stenqvist J, Ferizovic E, Danielsson E, Jensen A, Simonsen U, Winder M. Soluble guanylate cyclase mediates the relaxation of healthy and inflamed bladder smooth muscle by aqueous nitric oxide. Front Physiol 2023; 14:1249560. [PMID: 37731544 PMCID: PMC10507315 DOI: 10.3389/fphys.2023.1249560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 08/22/2023] [Indexed: 09/22/2023] Open
Abstract
Introduction: Due to its chemical properties, functional responses to nitric oxide (NO) are often difficult to examine. In the present study, we established a method to produce NO in an aqueous solution and validated its capacity to evoke functional responses in isolated rat bladders. Furthermore, we compared the NO responses to the commonly used NO donor sodium nitroprusside (SNP). We also investigated the impact of ongoing inflammation on the involvement of soluble guanylate cyclase (sGC) dependent signaling in NO relaxation. Methods: A setup to produce an aqueous NO solution was established, allowing the production of an aqueous solution containing a calculated NO concentration of 2 mM. Sixty male Sprague-Dawley rats received either no treatment (controls) or cyclophosphamide (CYP; 100 mg*kg-1 i.p., 60 h prior to the experiment) to induce experimental cystitis. Bladder strip preparations were mounted in organ baths and studied at basal tension or pre-contracted with methacholine (3 μM). Aqueous NO solution (40-400 μL; 2 mM corresponding to 4-40 μM) or SNP (1-1,000 μM) was added cumulatively in increasing concentrations. Relaxation to aqueous NO was also studied in the presence of the sGC inhibitor ODQ (0.25-25 μM). The expression of sGC was investigated by immunohistochemical analysis. Results: The NO solution caused functional relaxations in both controls and inflamed bladder preparations. NO-induced relaxations were significantly greater in inflamed bladder strips at basal tension, whereas no differences were seen in methacholine pre-contracted strips. In the presence of the sGC inhibitor ODQ in a high concentration, the NO-evoked relaxations were abolished in both control and inflamed preparations. At a lower concentration of ODQ, only NO relaxations in inflamed preparations were attenuated. Immunohistochemical analysis showed that sGC was expressed in the detrusor and mucosa, with a significantly lower expression in the inflamed detrusor. Conclusion: In the present study, we found that aqueous NO solution induces relaxation of the rat detrusor by activating soluble guanylate cyclase in both control and inflamed bladder strips. Induction of inflammation conceivably leads to decreased sGC expression in the detrusor, which may explain the different susceptibility towards inhibition of sGC in inflamed versus control tissue. The use of an aqueous NO solution should be further considered as a valuable complement to the pharmacological tools currently used.
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Affiliation(s)
- Patrik Aronsson
- Department of Pharmacology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Johanna Stenqvist
- Department of Pharmacology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Ena Ferizovic
- Department of Pharmacology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Emelie Danielsson
- Department of Pharmacology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Anna Jensen
- Department of Pharmacology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Ulf Simonsen
- Department of Biomedicine, Faculty of Health, University of Aarhus, Aarhus, Denmark
| | - Michael Winder
- Department of Pharmacology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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Modulation of lower urinary tract smooth muscle contraction and relaxation by the urothelium. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2018; 391:675-694. [DOI: 10.1007/s00210-018-1510-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 05/08/2018] [Indexed: 10/14/2022]
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Rahnama’i M, Biallosterski B, Van Kerrebroeck P, van Koeveringe G, Gillespie J, de Wachter S. Distribution and sub-types of afferent fibre in the mouse urinary bladder. J Chem Neuroanat 2017; 79:1-11. [DOI: 10.1016/j.jchemneu.2016.10.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 10/19/2016] [Accepted: 10/19/2016] [Indexed: 12/29/2022]
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Moro C, Edwards L, Chess-Williams R. 5-HT 2A receptor enhancement of contractile activity of the porcine urothelium and lamina propria. Int J Urol 2016; 23:946-951. [PMID: 27531585 DOI: 10.1111/iju.13172] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 06/26/2016] [Indexed: 12/15/2022]
Abstract
OBJECTIVES To examine the effect of 5-hydroxytryptamine (5-HT; serotonin) on the contractile properties of the urothelium and lamina propria, as a better understanding of bladder physiology might aid the development of new treatments. METHODS Strips of porcine urothelium and lamina propria were suspended in gassed Krebs-bicarbonate solution, and cumulative concentration-response curves for 5-HT were generated in the absence and presence of 5-HT antagonists, Nω-nitro-l-arginine and indomethacin. Responses to α-methyl-5-HT were also examined. RESULTS Strips of urothelium/lamina propria developed spontaneous contractions, whereas the addition of 5-HT induced concentration-dependent increases in contractile tone with maximal contractions of 50.43 ± 2.78 mN/g tissue weight (n = 100). Tonic contractions to 5-HT were unchanged in the presence of Nω-nitro-l-arginine (100 μmol/L) or indomethacin (5 μmol/L). Selective concentrations of the antagonists methiothepin (5-HT1&2 , 100 nmol/L), RS102221 (5-HT2C , 30 nmol/L), ondansetron (5-HT3 , 30 nmol/L), GR113808, (5-HT4 , 100 nmol/L), SB699551 (5-HT5 , 10 nmol/L), SB399885 (5-HT6 , 100 nmol/L) and SB269970 (5-HT7 , 10 nmol/L) did not influence responses to 5-HT. However, the 5-HT2A antagonist, ketanserin (30-300 μmol/L), caused a shift of the 5-HT curve yielding an affinity estimate of 7.9. CONCLUSIONS The results show that contractile responses of the urothelium/lamina propria to 5-HT are predominantly mediated through the 5-HT2A receptor.
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Affiliation(s)
- Christian Moro
- Centre for Urology Research, Faculty of Health Sciences and Medicine, Bond University, Gold Coast, Queensland, Australia.
| | - Lily Edwards
- Centre for Urology Research, Faculty of Health Sciences and Medicine, Bond University, Gold Coast, Queensland, Australia
| | - Russ Chess-Williams
- Centre for Urology Research, Faculty of Health Sciences and Medicine, Bond University, Gold Coast, Queensland, Australia
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Michel MC, Igawa Y. Therapeutic targets for overactive bladder other than smooth muscle. Expert Opin Ther Targets 2015; 19:687-705. [DOI: 10.1517/14728222.2015.1009447] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Recovery of urothelial mediator release but prolonged elevations in interleukin-8 and nitric oxide secretion following mitomycin C treatment. Naunyn Schmiedebergs Arch Pharmacol 2015; 388:781-91. [DOI: 10.1007/s00210-015-1092-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 01/15/2015] [Indexed: 01/14/2023]
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7
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Rahnama’i MS, Hohnen R, Van Kerrebroeck PEV, van Koeveringe GA. Phosphodiesterase type 2 distribution in the guinea pig urinary bladder. World J Urol 2014; 33:1623-33. [DOI: 10.1007/s00345-014-1455-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 11/24/2014] [Indexed: 12/20/2022] Open
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Eastham JE, Gillespie JI. The concept of peripheral modulation of bladder sensation. Organogenesis 2013; 9:224-33. [PMID: 23917648 PMCID: PMC3896594 DOI: 10.4161/org.25895] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 07/17/2013] [Accepted: 07/23/2013] [Indexed: 01/23/2023] Open
Abstract
It is recognized that, as the bladder fills, there is a corresponding increase in sensation. This awareness of the volume in the bladder is then used in a complex decision making process to determine if there is a need to void. It is also part of everyday experience that, when the bladder is full and sensations strong, these sensations can be suppressed and the desire to void postponed. The obvious explanation for such altered perceptions is that they occur centrally. However, this may not be the only mechanism. There are data to suggest that descending neural influences and local factors might regulate the sensitivity of the systems within the bladder wall generating afferent activity. Specifically, evidence is accumulating to suggest that the motor-sensory system within the bladder wall is influenced in this way. The motor-sensory system, first described over 100 years ago, appears to be a key component in the afferent outflow, the afferent "noise," generated within the bladder wall. However, the presence and possible importance of this complex system in the generation of bladder sensation has been overlooked in recent years. As the bladder fills the motor activity increases, driven by cholinergic inputs and modulated, possibly, by sympathetic inputs. In this way information on bladder volume can be transmitted to the CNS. It can be argued that the ability to alter the sensitivity of the mechanisms generating the motor component of this motor-sensory system represents a possible indirect way to influence afferent activity and so the perception of bladder volume centrally. Furthermore, it is emerging that the apparent modulation of sensation by drugs to alleviate the symptoms of overactive bladder (OAB), the anti-cholinergics and the new generation of drugs the β 3 sympathomimetics, may be the result of their ability to modulate the motor component of the motor sensory system. The possibility of controlling sensation, physiologically and pharmacologically, by influencing afferent firing at its point of origin is a "new" concept in bladder physiology. It is one that deserves careful consideration as it might have wider implications for our understanding of bladder pathology and in the development of new therapeutic drugs. In this overview, evidence for the concept peripheral modulation of bladder afferent outflow is explored.
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Affiliation(s)
- Jane E Eastham
- Uro-physiology Research Group; The Dental and Medical School; Newcastle University; Newcastle upon Tyne, England
| | - James I Gillespie
- Uro-physiology Research Group; The Dental and Medical School; Newcastle University; Newcastle upon Tyne, England
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Rahnama'i MS, van Koeveringe GA, Hohnen R, Ona S, van Kerrebroeck PE, de Wachter SG. Distribution of phosphodiesterase type 5 (PDE5) in the lateral wall of the guinea pig urinary bladder. BJU Int 2013; 112:246-57. [DOI: 10.1111/bju.12031] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
| | | | - Ramona Hohnen
- European Graduate School of Neuroscience; Department of Psychiatry and Neuropsychology; Maastricht University; Maastricht; The Netherlands
| | - Samsya Ona
- Lehman College of The City University of New York; New York; NY; USA
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Lin CS, Albersen M, Xin Z, Namiki M, Muller D, Lue TF. Phosphodiesterase-5 expression and function in the lower urinary tract: a critical review. Urology 2013; 81:480-7. [PMID: 23333001 DOI: 10.1016/j.urology.2012.11.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 11/15/2012] [Accepted: 11/19/2012] [Indexed: 01/20/2023]
Abstract
Both clinical and preclinical studies have mostly shown beneficial effects for Phosphodiesterase-5 (PDE-5) inhibitors in the treatment of lower urinary tract symptoms. Molecular studies have consistently shown abundant PDE-5 expression in bladder smooth muscle. Data concerning urethral PDE-5 expression have been surprising because striated muscle was not only positively identified, but also found to express more PDE-5 than the smooth muscle. In the prostate, highly variable results have been obtained. For PDE-5 expression, the data have ranged from extremely low to highly abundant. PDE-5 has been found in the glandular epithelium, vascular smooth muscle, endothelium, and fibromuscular stroma.
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Affiliation(s)
- Ching-Shwun Lin
- Knuppe Molecular Urology Laboratory, Department of Urology, School of Medicine, University of California, San Francisco, CA 94143-0738, USA.
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Contractile activity of the bladder urothelium/lamina propria and its regulation by nitric oxide. Eur J Pharmacol 2012; 674:445-9. [DOI: 10.1016/j.ejphar.2011.11.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 11/02/2011] [Accepted: 11/04/2011] [Indexed: 11/22/2022]
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Urothelial/Lamina Propria Spontaneous Activity and the Role of M3 Muscarinic Receptors in Mediating Rate Responses to Stretch and Carbachol. Urology 2011; 78:1442.e9-15. [DOI: 10.1016/j.urology.2011.08.039] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 07/10/2011] [Accepted: 08/18/2011] [Indexed: 11/22/2022]
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Artim DE, Kullmann FA, Daugherty SL, Wu HY, de Groat WC. Activation of the nitric oxide-cGMP pathway reduces phasic contractions in neonatal rat bladder strips via protein kinase G. Am J Physiol Renal Physiol 2009; 297:F333-40. [PMID: 19493964 DOI: 10.1152/ajprenal.00207.2009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nitric oxide (NO), a neurotransmitter in the lower urinary tract, stimulates soluble guanylyl cyclase (sGC) and in turn cGMP-dependent protein kinase G (PKG) to modulate a number of downstream targets. NO donors reduce bladder hyperactivity in some pathological models but do not affect normal bladder activity in the adult rat. In this study, the NO donor S-nitroso-N-acetyl-DL-penicillamine (SNAP; 100 microM) decreased the amplitude and frequency of spontaneous and carbachol-enhanced contractions in neonatal rat bladder strips, which are intrinsically hyperactive. This effect was blocked by inhibition of sGC and mimicked by application of a membrane-permeable cGMP analog (8-bromo-cGMP, 100 microM). Inhibition of PKG prevented or reversed the inhibitory effects of 8-bromo-cGMP. A portion of the SNAP-mediated inhibition was also dependent upon PKG; however, a short-lasting, sGC-dependent inhibitory effect of SNAP was still present after PKG inhibition. Inhibition of NO synthase with L-NAME (100 microM) did not change the amplitude or frequency of contractions. However, inhibition of endogenous phosphodiesterase (PDE)-5 with zaprinast (25 microM) reduced the amplitude and frequency of phasic contractions and increased the magnitude of inhibition produced by maximal concentrations of SNAP, suggesting that endogenous PDEs are constitutively active and regulate cGMP production. These results suggest that the NO-cGMP-PKG pathway may be involved in inhibitory control of the neonatal rat bladder.
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Affiliation(s)
- Debra E Artim
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
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Abstract
During the last decades it turned out that the NO/cGMP signaling cascade is one of the most prominent regulators of a variety of physiological and pathophysiological processes in a broad range of mammalian tissues. Thus cGMP is a key second messenger and targeting this pathway by increasing intracellular cGMP levels is a very successful approach in pharmacology as shown for nitrates, PDE5 inhibitors and more recently for stimulators of the guanylate cyclase. Besides the beneficial effects of cGMP elevation in cardiac, vascular, pulmonary, renal or liver disorders the launch of PDE5 inhibitors for the treatment of erectile dysfunction 10 years ago, has directed a lot of attention to the NO/cGMP signaling in the lower urinary tract. Triggered by the use of PDE5 inhibitors in ED it turned out that cGMP is a common regulatory mechanism for lower urinary tract function also beyond ED. In recent years intense research and development efforts were undertaken to elucidate the role of the NO/cGMP and to fully exploit the therapeutic implications of cGMP elevation in urological disorders in ED and beyond. Therefore we have summarized the effects of cGMP elevation for treatment of erectile dysfunction in males and in females. We have also reviewed the recent pre-clinical and clinical lines of evidence for treatment options of benign prostatic hyperplasia and lower urinary tract symptoms in male patients and overactive bladder and urinary incontinence in female patients. In addition we also touch more speculative concepts using cGMP elevating drugs for the treatment of premature ejaculation, peyornies disease and stone disease.
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Finney SM, Stewart LH, Gillespie JI. Volume-induced responses in the isolated bladder: evidence for excitatory and inhibitory elements. BJU Int 2008; 102:1154-61. [DOI: 10.1111/j.1464-410x.2008.07893.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Yanai Y, Hashitani H, Hayase M, Sasaki S, Suzuki H, Kohri K. Role of nitric oxide/cyclic GMP pathway in regulating spontaneous excitations in detrusor smooth muscle of the guinea-pig bladder. Neurourol Urodyn 2008; 27:446-53. [PMID: 17929303 DOI: 10.1002/nau.20517] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AIMS The role of nitric oxide (NO)/cyclic GMP (cGMP) pathway in regulating detrusor smooth muscle (DSM) function is still to be elucidated. We have investigated the effects of NO donors and phosphodiesterase-5 (PDE5) inhibition on spontaneous excitations in DSM. METHODS Multibundle DSM of the guinea-pig bladder generated spontaneous phasic contractions. The effects of sodium nitroprusside (SNP) and 3-morpholinosydnonimine (SIN-1), NO donors, 8-bromo-cyclicGMP (8-Br-cGMP), a cell-permeable cGMP analog and sildenafil, a PDE5 inhibitor on these contractions were examined. The effects of these agents on spontaneous action potentials were also studied using intracellular recording technique in single-bundle DSM. RESULTS SNP and SIN-1 enhanced spontaneous contractions in multibundle DSM and increased the frequency of spontaneous action potentials in single-bundle DSM. These excitatory effects were not antagonized by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), an inhibitor for guanylate cyclase, but were attenuated by cyclopiazonic acid (CPA), an inhibitor of sarco- and endoplasmic Ca ATPase (SERCA). 8-Br-cGMP invariably suppressed spontaneous contractility. Sildenafil inhibited spontaneous contractions in about 65% of multibundle DSM but had no effects on the remainder. In single-bundle DSM, sildenafil had no effect on spontaneous action potentials. CONCLUSIONS These results suggested that NO caused an enhancement of spontaneous contractions in DSM by accelerating spontaneous action potentials through cGMP-independent mechanisms, which may involve the Ca release from intracellular stores, whilst cGMP itself has inhibitory effects on DSM contractility. Sildenafil may indirectly suppress DSM contractility by diminishing synchronicity between functional units of DSM bundles without inhibiting excitability of DSM themselves.
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Affiliation(s)
- Yoshimasa Yanai
- Department of Nephro-Urology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
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Sandner P, Hütter J, Tinel H, Ziegelbauer K, Bischoff E. PDE5 inhibitors beyond erectile dysfunction. Int J Impot Res 2007; 19:533-43. [PMID: 17625575 DOI: 10.1038/sj.ijir.3901577] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The phosphodiesterase type-5 (PDE5) inhibitors sildenafil, vardenafil and tadalafil are widely used first-line therapy for erectile dysfunction (ED). Since the advent of sildenafil in 1998, more than 40 million men worldwide have been successfully treated with these compounds. The safety and high tolerability of PDE5 inhibitors make them an attractive tool to investigate further physiological functions of PDE5, for example the modulation of intracellular cyclic GMP (cGMP) pools. As cGMP is a key component of intracellular signaling this may provide novel therapeutic opportunities beyond ED even for indications in which chronic administration is necessary. The approval of sildenafil for the treatment of pulmonary hypertension in 2005 was a notable success in this area of research. A number of other potential new indications are currently in various phases of preclinical research and development. In recent years, extensive but very heterogeneous information has been published in this field. The aim of this review is to summarize existing preclinical and clinical knowledge and critically discuss the evidence to support potential future indications for PDE5 inhibitors.
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Affiliation(s)
- P Sandner
- Product-Related Research, Bayer HealthCare, Wuppertal, Germany
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de Vente J, Markerink-van Ittersum M, Gillespie JI. Natriuretic peptide responsive, cyclic guanosine monophosphate producing structures in the guinea pig bladder. J Urol 2007; 177:1191-4. [PMID: 17296443 DOI: 10.1016/j.juro.2006.10.039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Indexed: 10/23/2022]
Abstract
PURPOSE We examined the localization of natriuretic peptide responsive, cyclic guanosine monophosphate producing cells in the guinea pig bladder. MATERIALS AND METHODS The bladder was removed from male guinea pigs sacrificed by cervical dislocation. The lateral wall of the bladder was cut into strips 2 mm thick. The tissue pieces were incubated in the presence of human atrial natriuretic peptide, rat brain natriuretic peptide and C-type natriuretic peptide or the nitric oxide donor DEANO (diethylamine NONOate or 1,1-diethyl-2-hydroxy-2-nitrosohydrazine) (Sigma). Cyclic guanosine monophosphate immunoreactivity was localized using an antibody against formaldehyde fixed cyclic guanosine monophosphate. RESULTS Atrial natriuretic peptide and brain natriuretic peptide stimulated cyclic guanosine monophosphate synthesis in suburothelial interstitial cells, whereas C-type natriuretic peptide was not effective. In contrast, DEANO stimulated cyclic guanosine monophosphate synthesis in urothelial umbrella cells, suburothelial interstitial cells, muscle interstitial cells and neurons. The effect of atrial natriuretic peptide and brain natriuretic peptide was not inhibited by ODQ (1H-[1, 2, 4]oxadiazolo[4-3a]quinoxalin-1-one), an inhibitor of nitric oxide responsive soluble guanylyl cyclase. CONCLUSIONS To our knowledge our findings show for the first time a localized effect of atrial natriuretic peptide and brain natriuretic peptide to the suburothelial cells of the guinea pig bladder. These cells express the soluble guanylyl cyclase and particulate guanylyl cyclase-A isoforms. The specific physiological role of these cells is not known but it was suggested that they may be involved in the generation or modulation of sensation. The results imply a role for natriuretic peptide-cyclic guanosine monophosphate signaling in the processing of sensory information in the bladder.
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Affiliation(s)
- J de Vente
- European Graduate School of Neuroscience, Department of Psychiatry and Neuropsychology, Maastricht University, The Netherlands.
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Chapple CR, Gormley EA. Developments in pharmacological therapy for the overactive bladder. BJU Int 2006; 98 Suppl 1:78-87; discussion 88-9. [PMID: 16911610 DOI: 10.1111/j.1464-410x.2006.06381.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christopher R Chapple
- Department of Urology, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield Hallam University, Sheffield, UK.
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Lagou M, Drake MJ, Markerink-VAN Ittersum M, DE Vente J, Gillespie JI. Interstitial cells and phasic activity in the isolated mouse bladder. BJU Int 2006; 98:643-50. [PMID: 16925766 DOI: 10.1111/j.1464-410x.2006.06255.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To describe the distribution of interstitial cells (ICs, defined as cells which show an increase in cGMP in response to nitric oxide, NO) in the isolated mouse bladder, and changes in phasic contractile activity after exposure to a NO donor. MATERIALS AND METHODS The whole bladder was removed from 17 female mice, killed by cervical dislocation. For immunohistochemistry (six mice) the bladder was incubated in carboxygenated Krebs' solution at 36 degrees C, containing 1 mm of the phosphodiesterase inhibitor isobutyl-methyl-xanthine. Individual pieces of tissue were exposed to 100 microm of the NO donor diethylamine NONOate for 10 min; control tissues remained in Krebs' solution. Tissues were then fixed in 4% paraformaldehyde and processed for cGMP immunohistochemistry. Bladder pressure was measured in bladders from 11 mice; the bladders were cannulated via the urethra and suspended in a heated chamber containing carboxygenated Tyrode solution at 33-35 degrees C and intravesical pressure recorded. All drugs were added to the solution bathing the abluminal surface. RESULTS NO induced an increase in cGMP in cells in the outer layers of the bladder wall, forming two distinct types based on their location; cells lying on the surface of the muscle bundles (surface muscle ICs) and cells within the muscle bundles (intramuscular ICs). Cholinergic nerve fibres were identified by the expression of vesicular acetylcholine transporter and neuronal NO synthase (nNOS). Choline acetyltransferase- and nNOS-positive nerves also had high cGMP levels in response to 100 microm diethylamine NONOate. In vitro exposure of an isolated whole unstimulated bladder to 100 microm diethylamine NONOate had no effect on resting bladder pressure. When whole bladders were exposed to muscarinic stimulation (30-100 nm arecaidine) there was an initial large transient rise in pressure followed by complex phasic changes in pressure. Adding 100 microm diethylamine NONOate abolished this phasic activity. Interestingly, the phasic activity was inhibited midway between the peak and trough of a phasic cycle. Such a pattern of inhibition might reflect the complexity of the phasic activity involving both excitatory and inhibitory components. CONCLUSIONS These data show the presence of NO/cGMP-sensitive ICs in the outer muscle layers of the mouse bladder. Activating these cells alters the pattern of muscarinic-induced phasic activity. We suggest that the role of the ICs in the outer muscle layers is to generate and modulate phasic activity. If so, then this is the first report of a functional role for ICs in the bladder.
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Affiliation(s)
- Magdalini Lagou
- The Urophysiology Research Group, School of Surgical and Reproductive Sciences, The Medical School, The University, Newcastle upon Tyne, UK
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Hashitani H. Interaction between interstitial cells and smooth muscles in the lower urinary tract and penis. J Physiol 2006; 576:707-14. [PMID: 16945972 PMCID: PMC1890411 DOI: 10.1113/jphysiol.2006.116632] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Smooth muscles in the lower urinary tract and corporal tissue exhibit spontaneous contractile activity which depends on L-type Ca(2+) channels. The mechanism underlying this activity is spontaneous electrical activity which shows varied form and property between these tissues. Recent studies revealed that interstitial cells (ICs) are widely distributed in the genitourinary system, and suggested their involvement in spontaneous muscle activity. ICs in the system are not a simple analogy of interstitial cells of Cajal (ICC) in the gut, which act as electrical pacemaker, but represent variability amongst tissues which may account for individual characteristics of each organ. In the bladder and corporal tissue, where smooth muscle cells are capable of generating spontaneous electrical activity, ICs may modulate smooth muscle activity. ICs in corporal tissue release prostaglandins via cyclooxygenase-2 (COX-2) activity and reinforce not only spontaneous but also nerve-mediated alpha-adrenergic contractions. In the bladder, their fundamental role in the integration of signals between populations of cells has been proposed, and thus changes in ICs may contribute to an overactive bladder, a pathological condition which results from increased excitability in detrusor smooth muscles. In the urethra, ICs may act as electrical pacemakers as do ICC. However, overall contractility of urethral smooth muscles does not necessarily rely on pacemaking of ICs, and thus some population of smooth muscles may also have their own excitability.
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Affiliation(s)
- Hikaru Hashitani
- Department of Regulatory Cell Physiology & Nephrourology, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
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Streng T, Hedlund P, Talo A, Andersson KE, Gillespie JI. Phasic non-micturition contractions in the bladder of the anaesthetized and awake rat. BJU Int 2006; 97:1094-101. [PMID: 16643498 DOI: 10.1111/j.1464-410x.2006.06137.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To characterize the contractile activity that occurs in the bladder during the filling phase of the micturition cycle (non-micturition contractions, NMCs), which generate transient rises in intravesical pressure not associated with urine flow. MATERIALS AND METHODS The experiments were conducted using anaesthetized (chloral hydrate) and un-anaesthetized rats. In un-anaesthetized rats bladder contractile activity was measured using an intravesical cannula implanted under full surgical anaesthesia 3 days previously. In the anaesthetized rats the bladder was exteriorized and a cannula inserted through the dome. In these experiments electrical activity within the detrusor was also measured with a suction electrode on the bladder surface. For each rat, the experimental protocol involved filling the bladder at a constant rate (10 mL/h) to evoke micturition cycles, or infusion of a fixed volume and recording made under effective isovolumetric conditions. RESULTS In both anaesthetized and un-anaesthetized rats there were transient rises in bladder pressure (0.5-3 cmH2O). In the anaesthetized rats the amplitude of the transients increased throughout the filling phase, with little change in frequency. The phasic NMCs generating these pressure transients were accompanied by electrical changes in the detrusor. In the middle phase of bladder filling the slow pressure changes were accompanied by slow waves of electrical activity which changed in the pressure cycles immediately before micturition to high-frequency low-amplitude signals. In the un-anaesthetized rats there was a period immediately after voiding where there was no activity. As filling proceeded, low-amplitude low-frequency NMCs appeared that gradually increased in frequency and amplitude during the filling phase. However, the frequency of the transients decreased immediately before micturition despite an increase in amplitude. Similar responses were seen during isovolumetric recording. CONCLUSION The present results show the presence of NMCs in the rat bladder, identify volume-dependent changes in the pattern of this activity during the micturition cycle, and show that NMCs are accompanied by electrical changes in the detrusor. The physiological significance of NMCs is not known but it might be linked to the generation of afferent discharge from mechanoreceptors in the wall, so contributing to sensations related to bladder volume.
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Affiliation(s)
- Tomi Streng
- Department of Clinical and Experimental Pharmacology, Lund University Hospital, Sweden
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Gevaert T, Ost D, De Ridder D. Comparison study of autonomous activity in bladders from normal and paraplegic rats. Neurourol Urodyn 2006; 25:368-78; discussion 379-80. [PMID: 16832821 DOI: 10.1002/nau.20206] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
AIM To identify differences in the pattern of pressure generated by isolated bladders from normal and paraplegic rats. MATERIALS AND METHODS Nine female Wister rats were made paraplegic by spinal cord transsection at the vertebral level T8-T9 and sacrificed between D21 and D28. A further group (n = 9) was used as a control group. Each bladder was excised and placed in an organ bath where intravesical pressures were measured. Pressure changes were divided in two well-defined groups: macro-transients and spikes. The effects of intravesical volume load and muscarinic (M) agonists were studied. RESULTS We demonstrated a higher frequency, a longer duration, and a higher variance of duration in macro-transients in the neurogenic group. Intravesical volume load influenced the amplitude and frequency of macro-transients in both groups similarly. The effects of the muscarinic (M(2))-selective agonist arecaïdine were different in neurogenic bladder; the effects of the non-selective muscarinic (M)-agonist carbachol were similar in both groups. CONCLUSION We showed that the pattern of autonomous activity was significantly different between normal and neurogenic rat bladders. We also found evidence for alterations in the muscarinic response of isolated neurogenic rat bladders. This model offers an exciting new research tool to evaluate the detrusor activity in neurogenic and normal conditions.
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Wheeler MA, Ayyagari RR, Wheeler GL, Weiss RM. Regulation of cyclic nucleotides in the urinary tract. J Smooth Muscle Res 2005; 41:1-21. [PMID: 15855736 DOI: 10.1540/jsmr.41.1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Cyclic nucleotide levels are controlled through their synthesis from nucleotide triphosphates by cyclases and their degradation to 5'-monophosphates by phosphodiesterases (PDEs). Components controlling cyclic AMP-induced relaxation in the urinary tract include receptors, inhibitory and stimulatory G-proteins, isoforms of adenylyl cyclase and PDEs. The responsiveness of PDEs to a variety of physiological challenges is related to the presence of multiple families of isoenzymes with specific localization within tissues and within cells. At least 11 families of PDEs encode more than 50 PDE proteins produced in mammalian cells. In the urinary tract, characterization of PDE isoforms has lagged behind other systems and much of the literature was published prior to identification of PDE7, 8, 9, 10, 11. Specific PDE inhibitors regulate smooth muscle function in the bladder, urethra, prostate and ureter. The pharmacological potential of these inhibitors may include treatment of urge incontinence and the low compliance bladder, and treatment of prostate cancer. G-proteins also regulate cyclic AMP production. Changes in specific G- protein isoforms with aging, most prominently Gialpha2, cause decreased relaxation response in the aging bladder. As we have seen here with aging and certainly in other disease processes, levels of the components of adenylyl cyclase/phosphodiesterase/protein kinase can change and thus affect the relaxation response. By exploitation of differences in PDE expression in disease, such as the overexpression of PDEs in cancer, treatment options may present themselves.
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Affiliation(s)
- Marcia A Wheeler
- The Department of Surgery, Section of Urology, Yale University School of Medicine, New Haven, CT 06520-8041, USA.
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Abstract
Although caution should be used when applying animal data to human physiology, if care is taken to differentiate between general principles and complications of detail, particular to the species being examined, then experimentation on animal models can reveal basic phenomena in the bladder that offer clues to the origin of urgency. Recent data from the whole isolated bladder of guinea pigs showed unexpected complexities in autonomous activity during the filling phase of the micturition cycle: small, transient increases in intravesical pressure were associated with propagating waves of contractile activity and localized stretches of bladder wall. This complex, coordinated activity suggests that there are mechanisms within the bladder wall devoted specifically to generating phasic activity. Thus, there appear to be two systems controlling detrusor contractions: one associated with overall contractions similar to the micturition contraction and the other generating phasic activity. The mechanisms generating the phasic activity appear to be the point of complex integration of both excitatory and inhibitory inputs. There is evidence that local activity in the bladder wall generates afferent discharge, which probably contributes to bladder sensations. Animal data suggest a novel motor/sensory system incorporating contractile (motor) events, which cause stretches resulting in activation of afferent nerves (sensory). The motor element of this system appears to be controlled in a highly complex fashion such that the amplitude and frequency of the motor activity can be modulated by a variety of inputs. This raises the possibility that the sensitivity of the system informing the central nervous system, and thus awareness of the bladder's state during the micturition cycle, can be manipulated, possibly via novel drugs targeted at areas involved in overactive bladder, including urgency incontinence.
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Affiliation(s)
- James I Gillespie
- Urophysiology Research Group, School of Surgical and Reproductive Sciences, University of Newcastle, Newcastle upon Tyne, UK.
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Abstract
PURPOSE OF REVIEW Detrusor overactivity is a relatively common yet embarrassing symptom complex with significant impact on quality of life. The mainstay of current pharmacological treatment involves the use of muscarinic receptor antagonists, but their therapeutic effectiveness is limited by a combination of limited efficacy and troublesome side effects and has recently been challenged by Herbison et al. Recognition of the limitations of existing therapy has started the search for pharmacotherapeutic agents acting on alternative pathways underlying detrusor overactivity with the intention of improving storage symptoms of urgency, frequency and urge incontinence. RECENT FINDINGS Recent research has suggested that several transmitters may modulate bladder storage. However, no agents currently available, acting via mechanisms other than muscarinic receptors have entered clinical practice so far. It is clear that far from being a passive container for urine, the urothelium is a crucial area within the bladder wall and its functions are complex and only now beginning to be appreciated. The release of several neurotransmitters from urothelium in response to distension and its action on receptors on sensory neurons is being increasingly recognized. The role for this afferent stimulation on the micturition reflex is gradually gaining importance in the pathophysiology of detrusor overactivity. SUMMARY In this article, the recent developments in basic science related to the pathogenesis and pharmacological basis for future drug targets for effective management of overactive bladder are discussed.
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Affiliation(s)
- Vivek Kumar
- Department of Urology, Royal Hallamshire Hospital, Sheffield S10 2JF, UK.
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Gillespie JI, Markerink-van Ittersum M, de Vente J. Expression of neuronal nitric oxide synthase (nNOS) and nitric-oxide-induced changes in cGMP in the urothelial layer of the guinea pig bladder. Cell Tissue Res 2005; 321:341-51. [PMID: 15965654 DOI: 10.1007/s00441-005-1151-3] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Accepted: 04/20/2005] [Indexed: 10/25/2022]
Abstract
The urothelium plays a sensory role responding to deformation of the bladder wall; this involves the release of adenosine trisphosphate (ATP) and nitric oxide (NO), which affect afferent nerve discharge and bladder sensation. The urothelial cells responsible for producing ATP and NO and the cellular targets, other than afferent nerves, for ATP and NO remain largely unexplored. Sub-urothelial interstitial cells (SU-ICs) lie immediately below the urothelium and respond to NO with a rise in cGMP. To determine which cells might target SU-ICs by producing NO, areas of dome, lateral wall and base wall were treated with isobutyl-methyl-xanthine, exposed to the NO donor diethylamino NONOate and then fixed for immunohistochemistry. Surface urothelial cells (SUCs) in the base and dome expressed neuronal nitric oxide synthase (nNOS), whereas those in the lateral wall did not. Distinct populations of SUCs were present in the bladder base. SUCs with significant amounts of nNOS lay adjacent to cells with low levels of nNOS. In specific base regions, the few SUCs present contained nNOS within discrete intracellular particles. In the basal urothelial cell (BUC) layer of the lateral wall, nNOS-positive (NOS(+)) BUCs neither showed an elevation in cGMP in response to NO, nor expressed the beta1 sub-unit of soluble guanylate cyclase, protein kinase I or protein kinase II. Thus, they produced but did not respond to NO. The BUC layer also stained for the stem cell factor c-Kit suggesting its involvement in urothelial cell development. No NOS(+) BUCs were present in the SUC-sparse region in the bladder base. Exogenous NO produced an elevation in cGMP in SUCs and SU-ICs. The distribution and proportion of these target cells varied between the dome, lateral wall and base. cGMP(+) SU-ICs were present as a dense layer in the bladder base but were rarely seen in the lateral wall, which contained nNOS(+) BUCs. No nNOS(+) BUCs and cGMP(+) SU-ICs were apparent in the dome. The degree of complexity in nNOS distribution and NO target cells is therefore greater than has previously been described and may reflect distinct physiological functions that have yet to be identified.
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Affiliation(s)
- J I Gillespie
- The Urophysiology Research Group, School of Surgical and Reproductive Sciences, The Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, UK.
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Ho MH, Bhatia NN, Khorram O. Physiologic role of nitric oxide and nitric oxide synthase in female lower urinary tract. Curr Opin Obstet Gynecol 2005; 16:423-9. [PMID: 15353953 DOI: 10.1097/00001703-200410000-00012] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW In recent years nitric oxide (NO) has gained increasing recognition as an important neurotransmitter and cell signaling molecule with a broad range of functions in the lower urinary tract. This review discusses recently published data related to the physiologic and pathophysiologic roles of NO and nitric oxide synthase (NOS) in the female lower urinary tract. RECENT FINDINGS Expression of three isoforms of NOS, namely endothelial NOS, neuronal NOS and inducible NOS, has been identified in various tissues of the lower urinary tract in animals and humans. In addition to its relaxation effects on bladder and urethra, NO also serves as a neurotransmitter in the lower urinary tract. The physiologic roles of NO in overactive bladder, bladder outlet obstruction, diabetic cystopathy, interstitial cystitis, and bladder inflammation have been demonstrated. SUMMARY NO plays an important role in the micturition process and in disorders of the lower urinary tract. Improved understanding of the pathophysiologic role of NO/NOS system and of the L-arginine-NO-cGMP pathway may allow us to identify suitable therapeutic targets for lower urinary tract disorders. However, there is a need for further investigation to determine the precise function of NO in human lower urinary tract because most work thus far has been done in animal models.
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Affiliation(s)
- Mat H Ho
- Department of Obstetrics and Gynecology, Harbor-UCLA Medical Center, David Geffen School of Medicine, University of California, Los Angeles, California, USA.
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Gillespie JI. Inhibitory actions of calcitonin gene-related peptide and capsaicin: evidence for local axonal reflexes in the bladder wall. BJU Int 2005; 95:149-56. [PMID: 15638914 DOI: 10.1111/j.1464-410x.2005.05268.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVES To explore the actions of capsaicin and the neurotransmitters released by capsaicin (substance P and calcitonin gene-related peptide, CGRP) on the phasic contractile activity generated in the whole isolated guinea pig bladder by muscarinic stimulation, and to examine the hypothesis that collateral fibres of sensory axons contribute to a local reflex in the bladder wall. MATERIALS AND METHODS All experiments used whole isolated bladders from female guinea pigs (270-300 g). Bladders were cannulated via the urethra to measure intravesical pressure and suspended in a heated chamber containing oxygenated Tyrode's solution at 33-35 degrees C. All drugs were added to the solution bathing the abluminal surface. RESULTS Application of capsaicin (10 micromol/L) to the whole isolated bladder resulted in complex changes in the frequency and amplitude of phasic activity generated by muscarinic stimulation; an initial burst of activity involving a rise in frequency, a second phase of reduced amplitude and frequency and a third phase where the amplitude of the transients recovered and the frequency increased. Capsaicin had no effect on the phasic activity generated by the nicotinic ligand lobeline (30 micromol/L). As capsaicin releases the neurotransmitter content of the sensory nerves, experiments explored the actions of CGRP and substance P on the muscarinic-induced activity. CGRP (3-30 nmol/L) reduced the amplitude and slowed the frequency of the phasic activity. On washing off CGRP the amplitude and frequency of the transient activity recovered and there was a transient increase in frequency above the levels before stimulation. There was also evidence of a desensitization to CGRP on repeated application. In contrast, substance P (100-300 nmol/L) increased the frequency of the transients, while on removing it there was an inhibition of both amplitude and frequency. CONCLUSIONS These results suggest that neurotransmitters released from sensory nerve endings in the guinea pig bladder wall affect phasic activity. The direct application of CGRP inhibited phasic activity while substance P was excitatory, indicating the specific contributions of these neurotransmitters. The excitation after stimulation with CGRP and inhibition with substance P may indicate that these neurotransmitters feed back on the sensory nerves to induce transmitter release. Taken together, these observations suggest the presence of a local reflex in the bladder wall, where axon collaterals of afferent sensory fibres innervate the pacemaker mechanism in the bladder wall responsible for generating phasic activity. The possible importance of this reflex in the physiology and pathophysiology of the bladder is discussed.
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Affiliation(s)
- James I Gillespie
- The Urophysiology Research Group, School of Surgical and Reproductive Sciences, The Medical School, The University, Newcastle upon Tyne NE2 4HH, UK.
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Abstract
OBJECTIVES To: (i) determine the effects of changing intravesical volume on autonomous activity in the isolated whole bladder of the guinea pig; (ii) identify the mechanisms which might contribute to induced changes; and (iii) explore the idea that changes in bladder volume which affect phasic activity are part of a local reflex operating within the bladder wall. MATERIALS AND METHODS Bladders were isolated from female guinea pigs, cannulated via the urethra and maintained in vitro in Tyrode's solution. The intravesical pressure (IVP) was monitored and drugs added to the bathing solution. RESULTS The isolated unstimulated bladder containing 500-600 microL of fluid generates small (1-2 cm H2O) phasic rises in IVP, i.e. autonomous activity. When the bladder volume was increased, autonomous activity increased. In the presence of muscarinic agonists (100 nmol/L arecaidine and carbachol 100 nmol/L) autonomous activity is augmented, giving rise to large (>10 cm H2O) phasic rises in IVP. When the volume was increased, both the amplitude and frequency of the transients increased. When the bladder volume was reduced there was a period of marked inhibition of phasic activity. To explore the mechanisms underlying these changes the possible involvement of local neural reflexes was explored. The neurotoxin tetrodotoxin had no effect on the volume-induced changes. Sensory nerves are insensitive to tetrodotoxin and thus to assess their possible contribution bladders were exposed to capsaicin (10 micromol/L) to stimulate and eliminate sensory fibres; capsaicin caused complex changes in phasic activity, i.e. an initial increase, a secondary slowing and decrease, followed by a period of recovering amplitude and increased frequency. These changes suggest actions of the sensory nerves on the phasic mechanism indicative of a local axonal reflex. Once the phasic activity had returned to levels before capsaicin, changes in bladder volume still produced increases in activity and inhibition after the volume decrease. Interstitial cells (cells capable of increasing cGMP) are found in the bladder wall; to assess their possible role in the volume-induced changes, bladders were treated with 30 micromol/L ODQ, an inhibitor of guanyl cyclase, for 30-60 min. The volume-induced rise in frequency was little affected but the inhibition seen on volume reduction was reduced. CONCLUSIONS These results show that there are components in the bladder wall which respond to distension by affecting phasic activity. This stimulus/response may reflect a volume 'reflex' within the bladder wall, consisting of excitatory and inhibitory components. This local reflex does not appear to involve directly motor or sensory nerves, although the latter can affect phasic activity, and their actions may represent a further reflex mechanism in the bladder wall. The possible involvement of guanyl cyclase in the volume-induced inhibition may indicate a role for interstitial cells. The physiological role of these mechanisms as a component of a motor/sensor system in the bladder wall is discussed.
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Affiliation(s)
- Magdalini Lagou
- The Urophysiology Research Group, School of Surgical and Reproductive Sciences, The Medical School, The University, Newcastle upon Tyne, UK
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