Atropine resistance of transmurally stimulated isolated human bladder muscle

Species differences in characteristics and distribution of [3H] alpha,beta-methylene ATP binding sites in urinary bladder and urethra of rat, guinea-pig and rabbit

The characteristics and distribution of [3H] alpha,beta-methylene ATP ([3H] alpha,beta-MeATP, a radioligand for P2x-purinoceptors) binding sites in the urinary bladder of rat, guinea-pig and rabbit were examined. Autoradiographic localization of [3H] alpha,beta-MeATP binding sites was also carried out on the urethra of the three species. Receptor binding assay showed that the rat bladder possesses the highest density of specific binding sites, followed by rabbit and guinea-pig bladder. Semi-quantitative analysis of autoradiograms showed that the grain densities in the bladders of rat, guinea pig, and rabbit were parallel to those obtained from receptor binding assay. The grain densities were greatly reduced in the presence of beta,gamma-methylene ATP (beta,gamma-MeATP). No significant specific binding was detected in the smooth muscle of rat and guinea-pig urethra, while a very low level of specific binding was observed in the rabbit urethra. Differences of grain densities in different regions (dome, body, and trigone) of the same bladder were also observed, but they were not as remarkable as those between species. The results of this study demonstrate species differences of P2X-purinoceptor densities in the urinary bladder, which may reflect differing degrees of purinergic neurotransmitter control of the bladder detrusor muscle.

Muscarinic receptor stimulation of phosphoinositide hydrolysis in the human isolated urinary bladder

The stimulatory action of carbachol and acetylcholine (ACh) on phosphoinositide turnover, as well as their contractile effects, were investigated in human isolated detrusor muscle. Carbachol, and ACh in combination with 10(-7) M physostigmine, induced increases in phosphoinositide turnover. However, at all the concentrations tested, carbachol was more effective than ACh (plus physostigmine), and at the highest concentration used (10(-4) M), the difference was significant (p less than 0.05). Also in a Ca(2+)-free medium containing the chelator EGTA (10(-4) M), both agonists (10(-4) M) induced small but distinct increases in phosphoinositide breakdown. Carbachol and ACh contracted the detrusor preparations concentration-dependently, and the responses were almost identical when ACh was combined with 10(-7) M physostigmine. In Ca(2+)-free medium the agonists elicited a moderate but concentration-dependent contractile response at high concentrations. The results show that muscarinic receptor agonists stimulate phosphoinositide turnover in the human bladder. Possibly, this effect is coupled to multiple muscarinic receptor subtypes. More studies are required to elucidate to what extent phosphoinositide breakdown participates in the contractile activation of this tissue.

Human, pig and guinea-pig bladder smooth muscle cells generate similar inward currents in response to purinoceptor activation

The contribution of purinergic neurotransmission to bladder excitation in pigs and man is small. Exogenously-applied adenosine-trisphosphate (ATP) however, elicits large inward currents in dispersed bladder smooth muscle cells in both species. The essential properties of the ATP-induced current in human and pig detrusor are similar and the current intensity is comparable to those in the guinea-pig, which has a powerful purinergic excitatory innervation. This suggests that other features of the tissue such as the closeness of the innervation and the degree of cell-to-cell coupling may be important in determining the effectiveness of purinergic transmission.

Patients with lower motor spinal cord lesion: a decrease of vasoactive intestinal polypeptide, calcitonin gene-related peptide and substance P, but not neuropeptide Y and somatostatin-immunoreactive nerves in the detrusor muscle of the bladder

Specimens of the detrusor muscle of the bladder from four patients with lower motor neurone lesion and three patients with carcinoma of the bladder used as "controls", were studied immunohistochemically for vasoactive intestinal polypeptide, neuropeptide Y, calcitonin-gene related peptide, substance P and somatostatin. The greatest density of nerves in the bladder from "control" patients contained neuropeptide Y, followed in a decreasing order by vasoactive intestinal polypeptide, calcitonin gene-related peptide, substance P and somatostatin. Neuropeptide Y- and vasoactive intestinal polypeptide-immunoreactive nerves were found throughout the smooth muscle and the base of the mucosa, while calcitonin gene-related peptide-, substance P- and somatostatin-immunoreactive nerves were found predominantly in nerve bundles with a few single fibres at the base of the mucosa. Vasoactive intestinal polypeptide-, neuropeptide Y- and calcitonin gene-related peptide-immunoreactive nerves were also located around blood vessels. In patients with lower motor neurone lesion, there was a decrease in the density of vasoactive intestinal polypeptide-, calcitonin gene-related peptide- and substance P-immunoreactive nerves, but there was little change in neuropeptide Y- or somatostatin-immunoreactive nerves. Urinary retention, bladder areflexia and deficient sensation may be directly linked to neuropeptide neuropathy in patients with lower motor neurone lesion.

Effect of bladder outlet obstruction on the morphology, physiology, and pharmacology of the bladder

Bladder outlet obstruction secondary to benign prostatic hyperplasia induces numerous changes in bladder morphology, physiology, and pharmacology. These changes have been studied experimentally in various animal models, and while each species has advantages and disadvantages, it is unclear which is most like man. It has been shown that tissue hypertrophy leading to an increase in tissue mass develops rapidly after bladder outlet obstruction. Ischemia induced by the obstruction results in acute muscle dysfunction. The degree of functional impairment is directly related to the degree of tissue hypertrophy. However, the bladder contractile apparatus appears to have a surprising regenerative ability, such that recovery of bladder function becomes obvious 14 days after obstruction. Urodynamic changes include an increase in urinary frequency and voiding pressure and a decrease in voided volume. Clinically, involuntary bladder contractions are often present. Determination of which of these specific aspects of outlet obstruction the investigator is interested in studying will dictate the selection of the most appropriate animal model.

Nerve-mediated functions in the circular and longitudinal muscle layers of the proximal female rabbit urethra

In the present study, nerve mediated functions in the circular and longitudinal muscle layers of the female rabbit urethra were characterized. Based on light microscopic findings, the interest was focused on the proximal third of the organ. A microsurgical dissection technique was developed, allowing separation of the two muscle layers. The following studies were carried out: functional in vitro investigations including exogenous application of drugs and electrical field stimulation, investigations of the release of 3H-noradrenaline (NA), and autoradiography for visualization of muscarinic receptors. The results can be summarized as follows: the adrenergic nervous influence, which was mediated mainly via alpha 1-adrenoceptors, dominated the contractile response of the circular layer and contributed significantly to the contraction of the longitudinal layer. A previously described fast, non-adrenergic, non-cholinergic response was found in the circular muscle layer. This response should probably be ascribed to striated muscle with a different innervation and/or structure than skeletal muscle in general. Muscarinic cholinoceptors were abundant in the outer parts of the urethral wall and decreased in density in luminal direction. A significant cholinergic contractile component was demonstrated in the longitudinal muscle. A non-adrenergic, non-cholinergic nerve-mediated relaxant response was found in both layers, although more pronounced in the circular one. Vasoactive intestinal polypeptide completely relaxed both circular and longitudinal preparations contracted by noradrenaline. A possible basis for an interaction between adrenergic and cholinergic nerve endings was demonstrated in the circular muscle layer. Stimulation of muscarinic receptors on the adrenergic nerve endings markedly reduced the release of 3H-NA. The present results support the findings in previous studies on circularly and longitudinally oriented full-thickness preparations of the female urethra and further underline the differences in structure, innervation and receptor functions between the different muscle layers of the urethral wall.

Abnormalities of responses to autonomic stimulation in the mouse urinary bladder associated with Semliki Forest virus-induced demyelination

The responses to autonomic stimulation of the urinary bladder were studied in mice infected with Semliki Forest Virus, which has been proposed as an animal model for multiple sclerosis. Mice infected with Semliki Forest Virus showed a decreased body weight when compared with control animals, although their bladders were proportionately heavier. The pharmacological results indicated a selective change in purinergic transmission in the bladders of mice infected with Semliki Forest Virus, while cholinergic transmission remained unchanged. This was demonstrated by a significant increase in the contractile response to beta,gamma-methylene ATP accompanied by an increase in the proportion of the nerve-mediated response blocked by alpha,beta-methylene ATP. In contrast, the contractile response to acetylcholine and the atropine-sensitive component of the neurogenic response were not significantly different between the two groups of animals. Active length-tension curves were also unchanged in the mice infected with Semliki Forest Virus when compared with controls. The results are discussed in relation to those obtained from models of urinary bladder dysfunction associated with hypertrophy; whether the alteration of atropine-resistant (purinergic) function reported here is a general secondary feature of this type of bladder dysfunction or a change specific to the Semliki Forest Virus model of multiple sclerosis is not resolved. This study provides evidence that peripheral changes as well as central nervous system demyelination occur in the Semliki Forest Virus-infected mouse.

Distribution and density of neuropeptide Y-immunoreactive nerve fibres and cells in the horse urinary bladder

The distribution and density of neuropeptide Y (NPY)-immunoreactive nerve fibres and cells were determined in the urinary bladder of the horse by using the peroxidase-antiperoxidase (PAP) immunohistochemical method. Numerous undulating NPY-immunoreactive nerve fibres were found throughout the vesical wall, sometimes forming nerve bundles which ramified repeatedly as they coursed through the connective tissue septa to give rise to smaller bundles or single fibres which projected into the muscle fascicles forming muscular nerve plexuses, mainly in the bladder base. In the submucosa of this region, NPY-immunoreactive fibres formed a rather dense subepithelial plexus. Numerous NPY-immunoreactive nerve fibres supplied blood vessels and were widely distributed on the vascular adventitia constituting rich perivascular nerve plexuses. In addition, intramural ganglia containing NPY-immunoreactive nerve cell bodies and fibres were identified at the uretero-vesical junction. These results suggest that the equine urinary bladder possesses a rich NPY-peptidergic innervation which shows regional variations in the density of the muscular and subepithelial plexuses, the bladder base being the most richly innervated region. At least some of these NPY-immunoreactive nerve fibres have an intrinsic origin in ganglion cells within the vesical wall.

Potent contractile activity of endothelin on the human isolated urinary bladder

Endothelin (1 nM-0.3 microM) produced a concentration-related contraction of mucosa-free muscle strips excised from the dome of the human urinary bladder. The response to endothelin was unaffected by either atropine (1 microM) or nifedipine (1 microM) at concentrations that abolished the response to carbachol and KCl, respectively. These findings indicate that mechanisms other than activation of dihydropyridine- and voltage-sensitive calcium channels may be involved in the action of endothelin on smooth muscles.

Tolerability and steady-state pharmacokinetics of terodiline and its main metabolites in elderly patients with urinary incontinence

The elderly form an important target group for the treatment of urinary urge incontinence with drugs such as terodiline (Mictrol, Terolin). In order to evaluate its steady-state pharmacokinetics and tolerability in geriatric patients terodiline 12.5 mg b.d. was given to 28 hospitalized patients with urinary incontinence (mean age 85 years) for six weeks. The patients were monitored during the study and for 6 weeks afterwards, blood samples being taken at regular intervals. In addition to these multi-diseased and polymedicated patients, a small, homogenous group of healthy volunteers (mean age 40 years) was studied as a reference group, being given terodiline 12.5 mg b.d. for 2 weeks. Terodiline was generally well tolerated by the patients and no significant change in blood pressure or heart rate were found. One patient was withdrawn due to adverse effects. The mean terminal half-life of terodiline was 131 h and the clearance after oral administration (clearance/systemic availability) was 39 ml.min-1. The corresponding figures for the healthy volunteers were 57 h and 75 ml.min-1. The average steady-state serum concentration was 518 micrograms.l-1 in the geriatric patients and 238 micrograms.l-1 in the healthy volunteers. Steady-state was reached within 3 weeks in 20 of the 28 patients and within 5 weeks in 7 patients. In the geriatric patients the steady-state serum concentration of the main metabolite p-hydroxyterodiline, during the last three weeks on terodiline was 45 micrograms.l-1, 57 micrograms.l-1, and 45 micrograms.l-1, respectively, and a similar value was found in the healthy volunteers, 47 micrograms.l-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Further studies on the motor response of the human isolated urinary bladder to tachykinins, capsaicin and electrical field stimulation

1. Muscle strips from the dome of the human urinary bladder responded to field stimulation with contractions which were atropine- (3 microM) and tetrodotoxin- (1 microM) sensitive. These contractions were sensitive to omega conotoxin (CTX, 0.1 microM). The atropine- and tetrodotoxin-resistant contractions produced by field stimulation were totally unaffected by CTX. 2. DMPP (30-100 microM), a nicotinic agonist, produced transient bladder contractions which were hexamethonium- and atropine-sensitive. 3. Tachykinins produced a contraction of the human bladder. Among several synthetic tachykinin analogs only those having activity at the NK-2 receptor produced a consistent contractile response. 4. Either capsaicin (1 microM) or calcitonin gene-related peptide (10 nM-0.1 microM) had no motor effect. At 10 microM, capsaicin exerted a depressant effect on nerve-mediated contractions but this effect did not exhibit desensitization. 5. These findings provide evidence that NK-2 receptors are the main if not the sole mediators of the contractile response of the muscle from the dome of the human isolated bladder to tachykinins. 6. No evidence was found for a tachykininergic component in the excitatory response to field stimulation nor for motor responses mediated by capsaicin-sensitive nerves. 7. CTX-sensitive calcium channels are probably present on cholinergic nerve terminals in the human bladder muscle.

Actions of terodiline, its isomers and main metabolite on isolated detrusor muscle from rabbit and man

The effects of racemic terodiline on isolated detrusor preparations from rabbit and man were compared with those of its (+)- and (-)-isomers, and with those of its main metabolite, parahydroxy-terodiline. Concentration-response (c-r) relations for carbachol and frequency-response relations for electrical stimulation were determined before and after addition of drugs. In preparations from both rabbit and man, all the drugs tested concentration-dependently shifted the c-r curve for carbachol to the right. (+)-Terodiline was more potent than (+/-)-terodiline, whereas (-)-terodiline and parahydroxy-terodiline were less potent. All drugs in concentrations greater than 10(-6) M had a non-competitive effect, depressing the maximum of the carbachol contraction. All drugs had a depressant effect on electrically evoked contractions. (+)-Terodiline was as effective (rabbit) or more effective (man) than (+/-)-terodiline, whereas (-)-terodiline and parahydroxy-terodiline were less effective. It is concluded that (+)-terodiline contributes to a main part of the detrusor effects of the racemate, and that part of this action is anticholinergic. Parahydroxy-terodiline had a profile of action similar to that of (+/-) terodiline, but its potency was low. Since it is present in plasma in low concentrations, its contribution to the clinical effects of terodiline is probably small. (+)-Terodiline may have a therapeutic potential.

Contents and effects of substance P and vasoactive intestinal polypeptide in the bladder of rats with and without infravesical outflow obstruction

The concentrations of substance P and vasoactive intestinal polypeptide (VIP) were determined in the upper, middle, and lower part of the bladder of rats with and without infravesical outflow obstruction. In the obstructed animals there was a significant increase in bladder weight and the total amounts of substance P and VIP were increased. However, the concentrations of substance P were significantly lower than in the control bladders. The concentrations of VIP, on the other hand, were significantly higher in the middle and lower parts of obstructed bladders than in the controls. In isolated strips of the normal and obstructed bladders VIP had neither contractile nor relaxant effects. The peptide had no effect on electrically induced contractions. Substance P produced concentration-dependent contractions in both normal and obstructed bladders. However, obstructed bladders were significantly less sensitive than controls. It is concluded that the bladder instability seen in rats with infravesical outflow obstruction cannot be explained only in terms of changes in the bladder content of substance P or VIP.

Tetrodotoxin-resistant contractions induced by electrical stimulation of bladder muscle from man, rabbit and rat

Isolated detrusor preparations from man, rabbit and rat were suspended in an organ bath and isometric tension was recorded. The preparations were stimulated electrically in the presence of Bay K8644 and nifedipine before and after neuronal blockade with tetrodotoxin. Transmural electrical stimulation produced frequency-dependent contractions in all preparations. Bay K8644 significantly increased and nifedipine decreased these contractions. TTX effectively suppressed the response to electrical field stimulation in all species. When Bay K8644 was added to TTX blocked preparations, the responses to electrical stimulation were partly restored in bladder strips from man and rat. No increase in response was seen in the rabbit preparations. However, if the extracellular K+-concentration was increased to 10 mM (which per se did not affect the response) Bay K8644 significantly increased the contractions. All responses elicited by electrical stimulation in the presence of TTX were abolished by nifedipine. It is concluded that if the bladder smooth muscle is exposed to factors that can increase its sensitivity to contractile agents, this may result in uncontrolled (unstable) bladder contractions. Such contractions may use the 'normal' transmitter substances, but may be triggered at a lower stimulus intensity than normal. As a non-specific increase in membrane excitability seems to be associated with an influx of calcium through voltage-sensitive calcium channels, calcium antagonists, together with agents specifically blocking relevant transmitter substances, would offer an effective therapy against the unstable bladder.

Contractile response of the human isolated urinary bladder to neurokinins: involvement of NK-2 receptors

The contractile response to substance P (SP), neurokinin A (NKA) and arginin-neurokinin B (Arg-NKB) (a water soluble analogue of NKB) was investigated in detrusor muscle strips from the dome of the urinary bladder obtained from patients undergoing total cystectomy for carcinoma of the bladder base. Spontaneous activity and response to nerve stimulation indicated that the material used in this study has characteristics similar to those described for 'normal' human detrusor muscle. All neurokinins induced a concentration-related contraction with sensitivity at nM concentrations and the following rank order of potency: NKA (90) greater than Arg-NKB (22) greater than SP (1). These findings indicate the involvement of NK-2 receptors in the contractile response of human detrusor muscle to neurokinins.

Role of adenine compounds in autonomic neurotransmission

Clearly adenine compounds exert numerous effects throughout the autonomic nervous system. The responses of various peripheral tissues to purines are summarized in Table 2. The evidence supporting a possible excitatory neurotransmitter function for ATP is very good in the vas deferens and good in both the bladder detrusor and certain blood vessels. ATP may also be an excitatory neurotransmitter in the colon, hepatocytes and frog atrium. These responses appear to be mediated by P2x-purinoceptors. There is good evidence supporting a role for ATP as an inhibitory neurotransmitter in the taenia coli and duodenum, and some support in the anal sphincter and possibly the rabbit portal vein; these responses appear to be mediated by P2y-purinoceptors. There is good evidence against ATP being an inhibitory neurotransmitter in the stomach fundic muscle and ileum. ATP (or more likely its metabolite adenosine) may act as an inhibitory neurotransmitter by interacting with postsynaptic P1-purinoceptors in cultured sympathetic neurones and also in the parasympathetic vesicle ganglion of the cat. It seems likely that ATP released from heart, platelets or vascular endothelium could be an endogenous relaxant of blood vessels through its actions on the endothelium. Although the addition of exogenous adenosine affects many tissues, evidence supporting modulatory functions for endogenous extracellular adenosine has only been clearly demonstrated in the ileum, gallbladder, vas deferens, fallopian tubes, kidney, blood vessels, carotid sinus, heart and adipose tissue. Both ATP and adenosine, released during periods of hypoxia or ischemia, could exert negative inotropic, chronotropic and dromotropic actions in the heart. In many cases, the potential sources of extracellular purines have not been established. This is particularly important when attempting to establish a neurotransmitter function for ATP in a tissue. For instance, the one outstanding piece of evidence required to confirm that ATP is an excitatory neurotransmitter released from sympathetic nerves in blood vessels is the unequivocal demonstration that it is, in fact, released from the sympathetic nerves when they are stimulated. To date, only the release of radiolabeled metabolites of ATP, possibly from post- rather than presynaptic sites, has been detected. Studies of the release of ATP are complicated by its rapid degradation extracellularly by ecto-ATPase. Unfortunately, there are no specific inhibitors of ecto-ATPase available at present, but one hopes that a suitable inhibitor will be developed shortly.(ABSTRACT TRUNCATED AT 400 WORDS)

Pathophysiology of idiopathic detrusor instability and detrusor hyper-reflexia. An in vitro study of human detrusor muscle

Muscle strips from urodynamically normal bladders and from bladders exhibiting idiopathic detrusor instability or detrusor hyper-reflexia were compared under isometric conditions in an organ bath. Spontaneous contractions developed more often in unstable and hyper-reflexic muscle and were of greater amplitude, frequency and basal tension. Electrical field stimulation caused a frequency-dependent contraction which was largely abolished by both tetrodotoxin (TTX) and atropine in all three muscle types. Comparison of their frequency response curves demonstrated a significantly greater sensitivity than that of unstable and hyper-reflexic muscle to low stimulation frequencies. Acetylcholine caused a dose-related contractile response in all muscle types. There were no significant differences between the dose response curves of unstable and hyper-reflexic muscle, and those of normal muscle. The results suggest that the pathophysiology of the involuntary detrusor contraction is common to both idiopathic detrusor instability and detrusor hyper-reflexia and that this is related to a disorder of an intrinsic neuromodulatory mechanism within the detrusor muscle.

Galanin: a potent modulator of excitatory neurotransmission in the human urinary bladder

Galanin (GAL) produced a concentration (0.3-100 nM)-related inhibition of the atropine-sensitive component of the contractions induced by field stimulation of detrusor strips from the dome of the human urinary bladder. GAL had an ED50 of 2 nM for the inhibition. The effect of GAL was prevented by atropine (1 microM) and was not seen when the strips were stimulated with a cholinomimetic or KCl. These data suggest a possible neuromodulator role of GAL in the human urinary bladder.

A study of bladder dysfunction during streptozotocin-induced diabetes in the rat using an in vitro whole bladder preparation

An in vitro whole bladder preparation has been used in this study to examine the effects of eight and 16 week streptozotocin-induced diabetes on detrusor function in the rat. In eight week animals cystometric recordings showed an increase in bladder capacity associated with a decrease in intraluminal pressure. Concentration-response curves revealed a significant increase in sensitivity of the detrusor to beta,gamma-methylene ATP, a potent purinergic agonist, and a trend towards subsensitivity to acetylcholine in bladders from eight week diabetic rats when compared to controls. The atropine-resistant (purinergic) response to neurogenic stimulation was increased over the frequency range two to 30 Hz and was significantly greater at two Hz. In 16 week animals the cystometrogram had partially recovered; capacity had decreased compared to eight week diabetics and intraluminal pressure was within the normal range. Concentration-response curves revealed no significant difference in the response to acetylcholine and a greatly reduced response to beta,gamma-methylene ATP in the 16 week diabetics compared to controls. The atropine-resistant neurogenic response was slightly, but not significantly reduced. The results are discussed in relation to clinical urodynamic measurements of human detrusor dysfunction in diabetes.

Non-cholinergic, non-adrenergic nerve-mediated relaxation of pig and human detrusor muscle in vitro

Previously unrecognised, nerve-mediated relaxation in pig and human detrusor muscle is described. The relaxation was mediated via non-cholinergic, non-adrenergic and non-prostaglandin transmitter or modulator systems and was present in 12 of 15 detrusor strips from six pigs and in four of 15 detrusor strips from seven patients. A contractile phase preceded relaxation in all strips; in contrast to the contractile phase, relaxation was augmented by an increase in basal tension in a complex way and possibly by the slowest stimulation frequencies.

Isolation and individual electrical stimulation of single smooth-muscle cells from the urinary bladder of the pig

In contrast to striated muscle, measurements on strips of smooth muscle cannot be uniquely interpreted in terms of an array of contractile units. Therefore scaling down to the single-cell level is necessary to gain detailed understanding of the contractile process in this type of muscle. The present study describes the development of a method for isolating contractile single smooth muscle cells from pig urinary bladders. Contractile responses evoked by individual electrical stimulation were used as a measure of cell quality during development of the method. Responses were evaluated by measuring latency, contraction and relaxation times, as indicated by visible length changes, and stored on-line in a computer. Initial length, relative shortening and shortening speed were determined by measuring cell lengths in previously timed still video frames using a computer-controlled crosshair device. Increase of stimulus pulse duration resulted in improved responses, indicating that the observed shortening represented a physiological contractile response. Ultimately this method of evaluation was applied to two sets of cell preparations obtained by two different methods, one using only collagenase digestion, the other using mechanical manipulation as well. Both sets showed two main patterns of response to electrical stimulation: a pattern of contraction upon stimulation followed by enhanced contraction when stimulation was switched off (CK), and a pattern of contraction upon stimulation followed by relaxation when the stimulus was switched off (CR). The set of preparations containing the highest percentage of CR cells was found to be superior (i.e. greater initial length, shorter latency and contraction times, increased shortening and higher shortening speed). The method of isolation used for this set gives a high yield of contractile cells available for experimental use over a long span of time.

Effects of calcium, calcium channel blockers and Bay K 8644 on contractions induced by muscarinic receptor stimulation of isolated bladder muscle from rabbit and man

In isolated bladder smooth muscle from both rabbit and man, carbachol-induced contractions were reduced by the calcium channel blocker nifedipine, whereas the calcium channel promotor Bay K 8644 had no effect. In nominally calcium-free medium containing 10(-4) M EGTA, carbachol-induced contractions were reduced by 69% (rabbit) and 87% (man). These contractions were abolished by nifedipine, whereas Bay K 8644 significantly increased their amplitude, in rabbit preparations almost to control level. Electrical field stimulation produced contractions which could be suppressed by scopolamine by about 50% (rabbit) and more than 90% (man). These contractions were abolished by calcium-free medium (10(-4) M EGTA), suppressed by nifedipine, but significantly enhanced by Bay K 8644. The depressant effects of nifedipine, verapamil and diltiazem were reversed by Bay K 8644. The calcium channel blockers relaxed K+-induced contractions to base line, and this action was counteracted by Bay K 8644, less effectively when relaxations were induced by diltiazem. It is concluded that contractions produced by muscarinic receptor stimulation are primarily dependent on calcium bound to the outside of the membrane of the smooth muscle, and/or coming from the extracellular medium. Electrically evoked, scopolamine sensitive contractions seem to be mediated by a mechanism different from that of contractions produced by exogenously added muscarinic receptor agonist. The present data support the view that combined blockade of muscarinic receptors and calcium channels is an effective way of inhibiting bladder contractions in both rabbit and man.

Depressant action of oxybutynin on the contractility of intestinal and urinary tract smooth muscle

Experiments were carried out in-vitro using segments of guinea-pig ileum, taenia caeci, ureter and detrusor. In the ileum, oxybutynin (30, 100 nM) competitively antagonized acetylcholine-induced contractions but did not alter those induced by histamine. Higher concentrations of oxybutynin (up to 10 microM) induced a non-competitive depression of responses to both agonists and caused a parallel shift to the right of the Ca2+-induced contractions in taenia caeci strips bathed in a Ca2+-free, high-K+ medium. In the ureter, oxybutynin (1-10 microM) impaired rhythmic muscular contractions in normal medium and after CaCl2 addition in Ca2+-free medium. Similarly to verapamil (10, 30 microM), oxybutynin (10, 30 microM) depressed both the cholinergic and non-adrenergic, non-cholinergic components of the electrically-induced contractions of detrusor strips. It is concluded that oxybutynin has anticholinergic properties and, at higher concentrations, exerts a direct spasmolytic activity possibly mediated by blockade of the transmembrane Ca2+ fluxes responsible for smooth muscle contraction.

Action of pirenzepine on the human urinary bladder in vitro

The novel compound pirenzepine was tested for its antimuscarinic effect on the human urinary bladder "in vitro." Its behavior towards the contractions induced by acetylcholine or bethanechol and towards electrically induced contractions was identical to that of atropine. However, its potency was 100 to 300 times lower than that of atropine. Results obtained with ganglion blocking agents, tetrodotoxin and cooled preparations of urinary bladder seem to indicate the virtually total absence of ganglionic cells. On the other hand they point out the fundamental role of post-synaptic muscarinic M2 receptors as the most important component of the cholinergic system in the bladder. Of course the existence of other transmitters released at the cholinergic nerve endings after electrical field stimulation cannot be excluded on the basis of our experiments.

Non-cholinergic neurotransmission and the effects of peptides on the urinary bladder of guinea-pigs and rabbits

Supramaximal repetitive field stimulation with pulses of 50 microseconds produced contraction of strips of bladder from rabbits and guinea-pigs. Atropine reduced responses at all frequencies to about 60% and the contraction was poorly maintained. With the double sucrose-gap technique large excitatory junction potentials (e.j.p.s) were recorded with superimposed action potentials. These were not reduced by atropine or phentolamine. Substance P (SP) produced contraction and increased the frequency of spontaneous action potentials recorded with micro-electrodes from bladder strips. Vasoactive intestinal peptide (VIP) produced relaxation and slowed action potentials in rabbit but had no effect in guinea-pig; neurotensin, somatostatin and leu-enkephalin were without action in either species. When the tissue was kept in contact with SP, a second application after 10 min produced only a small contraction suggesting that SP receptors were desensitized. However, the electrical response to field stimulation was unchanged and the mechanical response was increased. Chymotrypsin reduced mechanical responses to SP but had no effect on responses to field stimulation. The SP analogue, D-Pro2, D-Phe7, D-Trp9-SP, had no effect on responses to SP or to field stimulation. It is concluded that the bladder receives excitatory non-cholinergic innervation which is responsible for a large excitatory junction potential and contraction. Although SP can contract the detrusor muscle, it is unlikely that it is an excitatory transmitter or that any of the five peptides act as modulators of transmitter release.

Pharmacological evidence for the existence of two components in the twitch response to field stimulation of detrusor strips from the rat urinary bladder

Isolated strips from the anterior dome of the rat urinary bladder respond to single pulse field stimulation with a contraction. Two distinct components of this contraction ("early' and "late') could be observed, both of which were unaffected by hexamethonium (10 microM) and almost abolished by tetrodotoxin (1 microM) indicating their dependence on neurotransmitter release from postganglionic nerve endings. Atropine (3 microM) inhibited the "late' component (over 60%) to a significantly greater extent than the "early' component (less than 10%) Amplitude of the "early' component was usually greater than that of the "late' component. There was almost no difference between the "early' and "late' component in respect of their relationship to stimulus strength and pulse duration. Physostigmine (0.03 microM) enhanced both components of the nerve-mediated contraction, although enhancement of the "late' component was much greater than that of the "early' one. Tetraethylammonium (TEA, 0.5-5 mM) enhanced, in a concentration-related manner, both "early' and "late' components of the nerve-mediated contraction. Following exposure to physostigmine or TEA (5 mM) both "early' and "late' components of contraction were almost completely inhibited by tetrodotoxin. Atropine inhibition was more evident on the "late' as compared to "early' component of contraction. These findings demonstrate the presence, in the twitch response of rat isolated urinary bladder to field stimulation, of two nerve-mediated components which exhibit a different susceptibility to atropine and physostigmine.

Characterization of the muscarinic cholinoceptors in the human detrusor

Contractions of the human detrusor are thought to be mediated mainly via cholinergic muscarinic receptors. In the present study, we used a receptor-binding technique with 1-quinuclidinyl[phenyl 4-3H]benzilate ((-)3H-QNB) as radioligand to directly demonstrate the presence of muscarinic receptors in homogenates of the human detrusor. The binding of (-)3H-QNB was of high affinity (KD = (1.2 +/- 0.1) X 10(-10) M), saturable (Ro = 160 +/- 15 fmol./mg. protein) and possessed the pharmacological specificity expected of an interaction with muscarinic receptors. Muscarinic receptor antagonists were bound to a virtually uniform population of sites, whereas muscarinic receptor agonists recognized more than one population of muscarinic binding sites. The affinities of a series of antimuscarinic drugs, determined in competition experiments with (-)3H-QNB, were found to correlate with the capacity to inhibit carbachol-induced contractions in isolated human bladder muscle. Binding data together with the functional data indicated that the human detrusor does not contain any significant number of muscarinic spare receptors. The results suggest that a selective effect on the muscarinic receptors of human bladder is not possible to obtain with presently available antimuscarinic agents.

Atropine blockade of nerve-mediated stimulation of the human detrusor

The effect of atropine on the isometric contractile response of isolated human detrusor muscle strips to electrical field stimulation has been studied. A 94.1% reduction in the response in the presence of tetrodotoxin demonstrated the neuronal nature of the stimulus. Atropine caused a 92.7% inhibition of the response. It was concluded that the nerve-mediated stimulus in human detrusor is cholinergic in nature and that "atropine resistance" does not occur in man.

Vasoactive intestinal polypeptide in the hyper-reflexic neuropathic bladder

The distribution of nerves containing vasoactive intestinal polypeptide (VIP) in the hyper-reflexic neuropathic bladder was investigated using immunocytochemistry and radioimmunoassay. Biopsy specimens were taken from the bladders of 21 patients with urodynamically proven detrusor hyper-reflexia and from 20 control patients with no urodynamic abnormality. The results showed a reduction in the number of VIP immunoreactive nerves and a reduction in VIP concentration in the hyper-reflexic bladder when compared with control samples.

A new in vitro microsuperfusion technique for investigation of human detrusor muscle

There is a paucity of information regarding the behaviour of human detrusor muscle in vitro. This is mainly due to the dependence of muscle bath techniques on large strips of material, which can be obtained only at open operations and which may not be viable because of limited diffusion of oxygen and metabolites through the tissue. We report a new technique for the in vitro study of muscle obtained during endoscopic procedures by cup biopsy. The results obtained from normal muscle show that this technique gives consistent and reproducible results.

A comparison of spontaneous and nerve-mediated activity in bladder muscle from man, pig and rabbit

Spontaneous activity in bladder muscle strips from man, pig and rabbit has been compared using an in vitro superfusion technique. Field stimulation was used to study nerve-mediated activity. Bladder muscle strips from all areas of the rabbit bladder displayed rhythmic spontaneous activity. Spontaneous activity was regularly present in strips from the trigone region in man and pig, but was present in only 18 and 19% respectively of strips from the dome of the bladder. Strength-duration curves in the presence of tetrodotoxin (10(-7) g/ml) were constructed. The 'chronaxie' of the muscle was found to be considerably shorter than that of other smooth muscles, ranging from 6.1 ms in the rabbit to 12.9 ms in man. Frequency-response curves were constructed using trains of stimuli. The responses were not antagonized by hexamethonium (10(-4) M), but were markedly inhibited by tetrodotoxin (10(-7) g/ml), indicating that the responses were mediated by excitation of post-ganglionic nerves. Physostigmine (10(-7)-5 X 10(-6) M) produced a dose-related increase in the contractile response to field stimulation in all three species. Atropine (10(-8)-10(-6) M) produced an inhibition of the contractile response, but the maximum degree of inhibition differed considerably between the species. In the rabbit, 58% of the control response was attained, whilst in the pig this was only 22%. Atropine completely abolished nerve-mediated contractions in human bladder muscle. Phentolmaine (10(-7)-2.5 X 10(-7) M) had no significant effect on the frequency-response curve in any of the three species, and did not depress the atropine-resistant component in rabbit and pig. It is concluded that nerve-mediated activity in human bladder muscle is exclusively cholinergic, in contrast to most other mammals studied in which there is a significant non-cholinergic component. The finding of a shorter chronaxie in bladder muscle than in other smooth muscles suggests important differences in its physiological properties that merit further investigation.

Direct effects of adenosine and adenine nucleotides on isolated human urinary bladder and their influence on electrically induced contractions

Adenosine triphosphate concentration-dependent contracted strips of isolated human urinary bladder. Three types of responses were recognized. One consisted of an initial, transient, phasic contraction followed by a sustained tonic response, another lacked the tonic part and the 3rd had intermediate-type characteristics. Adenosine diphosphate produced an intermediate type of contraction, while adenosine monophosphate, adenosine and 2-chloroadenosine had no effect. Preparations obtained from hypertrophic bladders were more sensitive to adenosine triphosphate than macroscopically normal preparations. Indomethacin abolished tonic responses and reduced phasic adenosine triphosphate and adenosine diphosphate induced responses by about 30 per cent; addition of PGE2 and PGF2 alpha reestablished the phasic responses. Atropine, physostigmine, hexamethonium and phentolamine had no effect on the adenosine triphosphate induced contractions. These contractions were reduced by 33 to 48 per cent after nifedipine pretreatment and abolished within 10 minutes in a calcium-free medium. The response to transmural nerve stimulation was initially stimulated and then reduced by 30 to 80 per cent by purines in the order of potency ATP greater than APPCP = ADP greater than AMP greater than adenosine = 2-chloroadenosine. Acetylcholine induced contractions were reduced by 10 to 30 per cent. Indomethacin inhibited the response to transmural nerve stimulation by about 30 per cent but did not influence inhibition produced by adenosine triphosphate. Atropine-resistant responses to transmural nerve stimulation were significantly reduced by both adenosine triphosphate and indomethacin; nifedipine abolished the responses. The results suggest that adenosine triphosphate has a calcium-dependent direct contractive effect on isolated human urinary bladder and also that it may release prostaglandins. Muscular hypertrophy seems to increase the sensitivity to adenosine triphosphate. The response to transmural nerve stimulation was influenced by adenosine triphosphate probably both by prejunctional and postjunctional effects.