Effects of denervation on muscarinic receptors in the at bladder (original) (raw)
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Acta pharmacologica et …, 1986
Ah.~/rirc./: Parasympathetic deiiervation ol' the urinary bladder results in supersensitivity to muscarinic agonists and in bladder hypertrophy. I n the present study, thc effects of dcncrvation on the muscarinic receptors in the rat bladder were investigated, using a receptor binding technique with (-)3H-QNB as radioligand. The dcnsity of inuscarinic receptors was incrcascd in dcnervated, hypertrophied bladders hut it was decreased, below that in control bladders, whcn the development of hypertrophy was prevented by urinary diversion. A decreased receptor deiisity was also found in innervated bladders after urinary diversion, whereas the receptor density was unaffected by hypertrophy alone. Competition experiments with methacholine revealed no changes in the agonist binding properties of the receptors. When the present data are combined with those in previous functional studics, it seems unlikely that the muscarinic receptors in the bladder are involved in thc dcvclopmcnt of supersensitivity. It is suggested that the density of muscarinic receptors in the bladder may be related to the bladder function. K c y~w d r : Muscarinic receptors (-)'H-QNBurinary bladderdeiicrvationrats.
Brain Research, 2010
Effects of a muscarinic receptor agonist oxotremorine-M (oxo-M) on bladder afferent nerve (BAN) activity were studied in an in vitro bladder-pelvic nerve preparation. Distension of the bladder induced rhythmic bladder contractions that were accompanied by multiunit afferent firing. Intravesical administration of 25 and 50 μM oxo-M significantly increased afferent firing from 41 ± 2 spikes/s to 51 ± 4 spikes/s and 60.5 ± 5 spikes/s, respectively, but did not change the maximum amplitude of spontaneous bladder contractions. The afferent nerve firing induced by isotonic distension of the bladder (10-40 cmH 2 O) was increased 22-100% by intravesical administration of 50 μM oxo-M. Electrical stimulation on the surface of the bladder elicited action potentials (AP) in BAN. Oxo-M significantly decreased the voltage threshold by 40% (p < 0.05) and increased by 157% (p < 0.05) the area of the AP evoked at a submaximal stimulus intensity. These effects were blocked by intravesical injection of 5 μM atropine methyl nitrate (AMN). Intravesical administration of 5 μM AMN alone did not alter BAN firing or the amplitude of bladder contractions. The facilitatory effects induced by oxo-M on BAN activity were also suppressed (p < 0.05) by intravesical administration of 2′,3′-0trinitrophenyl-ATP (TNP-ATP) (30 μM). In preparations pretreated with capsaicin (125 mg/kg, s.c.) the facilitatory effects of 50 μM oxo-M on BAN activity were absent. These results suggest that activation of muscarinic receptors facilitates mechano-sensitive, capsaicinsensitive BAN activity in part by mechanisms involving purinergic receptors located near the luminal surface of the bladder and ATP release which presumably occurs in the urothelium.
American journal of physiology. Regulatory, integrative and comparative physiology, 2002
M(3) muscarinic receptors mediate cholinergic-induced contraction in most smooth muscles. However, in the denervated rat bladder, M(2) receptors participate in contraction because M(3)-selective antagonists [para-fluoro-hexahydro-sila-diphenidol (p-F-HHSiD) and 4-DAMP] have low affinities. However, the affinity of the M(2)-selective antagonist methoctramine in the denervated bladder is consistent with M(3) receptor mediating contraction. It is possible that two pathways interact to mediate contraction: one mediated by the M(2) receptor and one by the M(3) receptor. To determine whether an interaction exists, the inhibitory potencies of combinations of methoctramine and p-F-HHSiD for reversing cholinergic contractions were measured. In normal bladders, all combinations gave additive effects. In denervated bladders, synergistic effects were seen with the 10:1 and 1:1 (methoctramine:p-F-HHSiD wt/wt) combinations. After application of the sarcoplasmic reticulum ATPase inhibitor thapsiga...
M3 Muscarinic Receptor-Like Immunoreactivity in Sham Operated and Obstructed Guinea Pig Bladders
The Journal of Urology, 2011
Type 3 muscarinic receptors, which are present in the bladder wall, are important for bladder function. However, their role in the context of the urothelium is not well defined. Understanding the role of type 3 muscarinic receptors has been limited by the lack of specific type 3 muscarinic receptor antibodies. Thus, we identified a specific type 3 muscarinic receptor antibody and investigated the site of type 3 muscarinic receptors in sham operated and obstructed guinea pig bladders. Materials and Methods: The specificity of 4 commercially available type 3 muscarinic receptor antibodies was determined. Immunohistochemistry was then done in bladder tissue from sham operated and obstructed guinea pig bladders. Results: One of the 4 antibodies examined had the needed specificity in terms of blocking peptide and Western blot characterization. Using this antibody type 3 muscarinic receptor immunoreactivity was associated with muscle cells, nerves and interstitial cells. Four types of interstitial cells were identified, including suburothelial, lamina propria, surface muscle and intramuscular interstitial cells. In the obstructed model the bladder wall was hypertrophied and there was nerve fiber loss. The number of lamina propria, surface muscle and intramuscular interstitial cells was increased but not the number of suburothelial interstitial cells. Also, surface muscle interstitial cells appeared to form clusters or nodes with type 3 muscarinic receptor immunoreactivity. Conclusions: Nerve loss and the up-regulation of interstitial cells with type 3 muscarinic receptor immunoreactivity may underlie major functional changes in the pathological bladder. This indicates that type 3 muscarinic receptor specific anticholinergic drugs may affect not only the detrusor muscle, as previously thought, but also interstitial cells and nerve fibers.
Activation of Muscarinic Receptors in Rat Bladder Sensory Pathways Alters Reflex Bladder Activity
Journal of Neuroscience, 2008
Antimuscarinic drugs affect bladder sensory symptoms such as urgency and frequency, presumably by acting on muscarinic acetylcholine receptors (mAChRs) located in bladder sensory pathways including primary afferent nerves and urothelium. However, the expression and the function of these receptors are not well understood. This study investigated the role of mAChRs in bladder sensory pathways in vivo in urethane anesthetized rats. Intravesical administration of the mAChR agonist oxotremorine methiodide (OxoM) elicited concentration-dependent excitatory and inhibitory effects on the frequency of voiding. These effects were blocked by intravesical administration of the mAChR antagonist atropine methyl nitrate (5 M) and were absent in rats pretreated with capsaicin to desensitize C-fiber afferent nerves. Low concentrations of OxoM (5 M) decreased voiding frequency by ϳ30%, an effect blunted by inhibiting nitric oxide (NO) synthesis with L-NAME (N -nitro-L-arginine methyl ester hydrochloride; 5 mg/kg; i.v.). High concentrations of OxoM (40 M) increased voiding frequency by ϳ45%, an effect blunted by blocking purinergic receptors with PPADS (0.1-1 mM; intravesically). mAChR agonists stimulated release of ATP from cultured urothelial cells. Intravenous administration of OxoM (0.01-5 g/kg) did not mimic the intravesical effects on voiding frequency. These results suggest that activation of mAChRs located near the luminal surface of the bladder affects voiding functions via mechanisms involving ATP and NO release presumably from the urothelium, that in turn could act on bladder C-fiber afferent nerves to alter their firing properties. These findings suggest that the urothelial-afferent nerve interactions can influence reflex voiding function.
British Journal of Pharmacology, 1997
1 Urinary bladder smooth muscle is enriched with muscarinic receptors, the majority of which are of the M 2 subtype whereas the remaining minority belong to the M 3 subtype. The objective of the present study was to assess the functional role of M 2 and M 3 receptors in the urinary bladder of rat in vitro and in vivo by use of key discriminatory antagonists. 2 In the isolated bladder of rat, (+)-cis-dioxolane produced concentration-dependent contractions (pEC 50 =6.3) which were unaected by tetrodotoxin (0.1 mM). These contractions were antagonized by muscarinic antagonists with the following rank order of anity (pA 2 ) estimates: atropine (9.1) 4 4diphenyl acetoxy-methyl piperidine methiodide (4-DAMP) (8.9) 4 darifenacin (8.5) 4 para¯uoro hexahydrosiladifenidol (p-F-HHSiD) (7.4) 4 pirenzepine (6.8) 4 methoctramine (5.9). These pA 2 estimates correlated most favourably (r=0.99, P50.001) with the binding anity (pK i ) estimates of these compounds at human recombinant muscarinic m 3 receptors expressed in Chinese hamster ovary cells, suggesting that the receptor mediating the direct contractile responses to (+)-cis-dioxolane equates with the pharmacologically de®ned M 3 receptor.
Life sciences, 2013
To determine if the muscarinic agonist, bethanechol, inhibits the non-cholinergic, atropine-resistant (i.e. putatively purinergic) component of naturally occurring (i.e. reflexogenic) bladder contractions in vivo in the rat, as previously described in vitro. Our second aim was to determine if elevation of endogenous acetylcholine (ACh) with distigmine, an acetylcholine esterase (AChE) inhibitor, could also inhibit non-cholinergic component of reflexogenic bladder contractions. Cystometry was performed in urethane anesthetized adult female Sprague Dawley rats. The nonselective muscarinic receptor (mAChR) antagonist, atropine, was administered intravenously (i.v.) before and after i.v. administration of the non-selective mAChR agonist, bethanechol, the AChE inhibitor, distigmine or the neurokinin receptor 2 agonist, [βAla(8)]-Neurokinin A(4-10). Intermicturition interval (IMI), bladder contraction amplitude (BCA), postvoid bladder pressure (PVBP), and voiding efficiency (VE) were meas...
Journal of Receptors and Signal Transduction, 1999
Our previous data indicate that M, muscarinic receptors mediate carbachol induced bladder contrac,tions. The data presented here were obtained by selective alkylation of M, receptors with 4-DAMP mustard and suggest that the M, receptor subtype may be involved in inhibition of P-adrenergic receptor induced relaxation, therefore, allowing recontraction. Alkylation resulted in 85% of M, receptors and zy 65% of M, receptors unable to bind radioligand as demonstrated by subtype selective immunoprecipitation. Rat bladder strips subjected to our alkylation procedure contracted submaximally, and direct carbachol contractions were inhibited by antagonists with affinities consistent with M, receptor mediated contraction. In contrast, the affinities of antagonists for inhibition of carbachol induced recontractions following isoproiterenol stimulated relaxation in the presence of 90 mM KCI, indicated a contractile hnction for the M, receptor that was not observed in control strips. In conclusion, these studies demonstrate a possible role for the Mz subtype in bladder smooth muscle contraction.
Naunyn-Schmiedeberg's Archives of Pharmacology, 1989
The inhibitory effects of some muscarinic agonists on tritiated acetylcholine release evoked by field stimulation were investigated in the rat urinary bladder strip. The acetylcholine stores of the preparation were labelled with 3H-choline. Electrical field stimulation caused an outflow of tritium, reflecting the release of 3H-acetylcholine. The release of 3H-acetylcholine was decreased in a concentrationdependent manner by all the agonists tested: oxotremorine, muscarone, muscarine, carbachol and methylfurtrethonium. On the contrary, only muscarine and muscarone enhanced the basal efflux of tritium in a concentration-dependent fashion. Concentration-response curves were determined both at 2 Hz and at 1 Hz by using intermittent administration of the drugs. Maximal depression in release (by 7 8 -82%) was observed in experiments at 1 Hz. A similar inhibition was obtained at 2 Hz frequency only when a low concentration of calcium (0.6 mM) in the medium was used. Oxotremorine was the most potent among the tested compounds with the same intrinsic activity as the other drugs. In contrast to the other agonists investigated, oxotremorine showed in about 10-fold greater potency at pre-than at postjunctional muscarine receptors in the rat urinary bladder. This difference might depend either on heterogeneity of muscarine receptors or on different mechanism(s) relating to the transducing properties of receptors at the pre-and postjunctional level. A comparison between the relative prejunctional potencies in the rat urinary bladder and in the guinea pig myenteric plexus (data from the literature) suggests that prejunctional muscarine receptors are similar in these tissues. Furthermore, the findings obtained with a low concentration of calcium in the medium may support the view that intraneuronal availability of calcium plays a significant role in modulating the prejunctional negative feed-back mechanism in the rat urinary bladder.
Muscarinic Receptor Subtypes in the Lower Urinary Tract
Pharmacology, 2009
Acetylcholine acting on muscarinic M3 receptors on the detrusor muscle is the principal stimulus for inducing the contractile response for urinary bladder voiding. The urinary bladder expresses, however, all cloned muscarinic receptor subtypes (M1–M5). In terms of quantity, the M2 subtype dominates over the M3 subtype in the detrusor, and its role in contraction seems to be primarily indirect, by blocking stimuli from cAMP-coupled receptors that induce relaxation. The excitatory M1 and inhibitory M2 and/or M4 subtypes are also expressed prejunctionally. Muscarinic M1 and M2/M4 autoreceptors facilitate and inhibit, respectively, the release of acetylcholine. The urothelium had been considered to be a passive barrier; however, during the last decade, it has been shown that the urothelium is of importance for bladder function. In a state of bladder pathology, muscarinic receptor changes occur in the detrusor, prejunctionally, and in the urothelium, but the character of the change diffe...