Comparative effects of angiotensin II on the contractility of muscularis mucosae and detrusor in the pig urinary bladder

To explore contractile actions of angiotensin II (ATII) on the muscularis mucosae (MM) of the bladder, ATII‐induced contractions were compared between MM and the detrusor smooth muscle (DSM) of the pig bladder by isometric tension recordings. Effects of ATII on spontaneous Ca²⁺ transients in MM were visualized using Cal‐520 fluorescence. ATII receptor type 1 (ATR1) expression in MM and DSM was also examined by immunohistochemistry. ATII (1 nM–1 μM) caused phasic contractions of MM in a concentration‐dependent manner, while ATII (10 nM–10 μM) had no or marginal effects on DSM contractility. ATII (100 nM)‐induced MM contractions had an amplitude of approximately 70% of carbachol (1 μM)‐induced or 90% of U46619 (100 nM)‐induced contractions. Candesartan (10 nM), an ATR1 blocker, prevented the contractile effects of ATII (1 nM) in MM, while ATR1 immunofluorescence was greater in MM than DSM. ATII (10–100 pM) increased the frequency but not the amplitude of spontaneous Ca²⁺ transients in MM. Both urothelium‐intact and ‐denuded MM strips developed comparable spontaneous phasic contractions, but ATII, carbachol and U46619‐induced contractions were significantly larger in urothelium‐denuded than urothelium‐intact MM strips. In conclusion, the MM appears to have a much greater sensitivity to ATII compared with DSM that could well sense circulating ATII, suggesting that MM may be the predominant target of contractile actions induced by ATII in the bladder while the urothelium appears to inhibit MM contractility.     

Protective effects of melatonin against oxidative injury in rat testis induced by wireless (2.45 GHz) devices

Wireless devices have become part of everyday life and mostly located near reproductive organs while they are in use. The present study was designed to determine the possible protective effects of melatonin on oxidative stress–dependent testis injury induced by 2.45‐GHz electromagnetic radiation (EMR). Thirty‐two rats were equally divided into four different groups, namely cage control (A1), sham control (A2), 2.45‐GHz EMR (B) and 2.45‐GHz EMR+melatonin (C). Group B and C were exposed to 2.45‐GHz EMR during 60 min day^?1 for 30 days. Lipid peroxidation levels were higher in Group B than in Group A1 and A2. Melatonin treatment prevented the increase in the lipid peroxidation induced by EMR. Also reduced glutathione (GSH) and glutathione peroxidase (GSH‐Px) levels in Group D were higher than that of exposure group. Vitamin A and E concentrations decreased in exposure group, and melatonin prevented the decrease in vitamin E levels. In conclusion, wireless (2.45 GHz) EMR caused oxidative damage in testis by increasing the levels of lipid peroxidation and decreasing in vitamin A and E levels. Melatonin supplementation prevented oxidative damage induced by EMR and also supported the antioxidant redox system in the testis.     

The inhibitory role of melatonin on isolated guinea-pig urinary bladder: an endogenous hormone effect

OBJECTIVE: To investigate the effects of melatonin, an endogenous hormone, on acetylcholine and KCl-induced contractions of isolated guinea-pig detrusor muscle. MATERIALS AND METHODS: Detrusor smooth muscle strips isolated from guinea-pig bladders were placed in an organ bath containing physiological saline at 37 degrees C and pH 7.4, constantly bubbled with 95% oxygen and 5% CO2. The effects of cumulatively applied melatonin on the acetylcholine- and KCl-induced contractions of isolated bladder strips were examined using isometric contraction measurements. RESULTS: Melatonin (100 and 300 micromol/L) significantly inhibited the peak amplitude of both acetylcholine (10 micromol/L) and KCl (30 mmol/L)-induced contraction of the isolated bladder strips (P < 0.05). Similarly, melatonin caused a significant reduction in the contractile frequency induced by KCl (eight strips) in a concentration-dependent manner, while having no significant effect on the frequency of contractile response to acetylcholine, even at the highest concentration (300 micromol/L) used (P = 0.58, 14 strips). CONCLUSIONS: These results suggest that melatonin inhibits acetylcholine- and KCl-induced contractions in isolated bladder strips from guinea pigs. The endogenous nature of melatonin, with its low side-effect profile, makes it a potentially useful agent to be considered in the medical management of the overactive bladder.     

Effect of melatonin on age associated changes in Guinea pig bladder function

PURPOSE: The incidence of urinary incontinence increases with age but the cause and effect relationship between aging and altered bladder function is poorly understood. It was suggested that melatonin can ameliorate negative effects induced by aging by its free radical scavenging activity and its ability to decrease oxidative stress. We investigated the changes in bladder function evoked by aging and the possible benefits of melatonin treatment on age related bladder disturbances. MATERIALS AND METHODS: Bladder function was assessed using cystometry in conscious, freely moving female guinea pigs. Animals were grouped according to age as young adults (4 months old) and senescents (18 to 20 months old). A group of senescent animals were treated with 2.5 mg kg(-1) day(-1) melatonin for 21 days. RESULTS: Aging led to increased detrusor activity, as demonstrated by short micturition intervals, decreased bladder capacity and spontaneous contractions during the filling phase. During the voiding phase aged animals showed lower micturition pressures than young adults. Melatonin counteracted the cystometric changes in senescent animals and restored micturition parameters to those of young adults. CONCLUSIONS: These results show that in guinea pigs aging induces detrusor overactivity. Melatonin treatment improved age induced changes in bladder function. If similar effects can be demonstrated in humans, melatonin treatment may be a new approach to decrease the impact of age related bladder disorders.     

Melatonin and the skeleton

Melatonin may affect bone metabolism through bone anabolic as well as antiresorptive effects. An age-related decrease in peak melatonin levels at nighttime is well documented, which may increase bone resorption and bone loss in the elderly. In vitro, melatonin reduces oxidative stress on bone cells by acting as an antioxidant. Furthermore, melatonin improves bone formation by promoting differentiation of human mesenchymal stem cell (hMSC) into the osteoblastic cell linage. Bone resorption is reduced by increased synthesis of osteoprogeterin (OPG), a decoy receptor that prevents receptor activator of NK-κB ligand (RANKL) in binding to its receptor. Moreover, melatonin is believed to reduce the synthesis of RANKL preventing further bone resorption. In ovariectomized as well as nonovariectomized rodents, melatonin has shown beneficial effects on bone as assessed by biochemical bone turnover markers, DXA, and μCT scans. Furthermore, in pinealectomized animals, bone mineral density (BMD) is significantly decreased compared to controls, supporting the importance of sufficient melatonin levels. In humans, dysfunction of the melatonin signaling pathway may be involved in idiopathic scoliosis, and the increased fracture risk in nighttime workers may be related to changes in the circadian rhythm of melatonin. In the so-far only randomized study on melatonin treatment, no effects were, however, found on bone turnover markers. In conclusion, melatonin may have beneficial effects on the skeleton, but more studies on humans are warranted in order to find out whether supplementation with melatonin at bedtime may preserve bone mass and improve bone biomechanical competence.     

Comparison of the Efficacy of Melatonin and 1400W on Renal Ischemia/Reperfusion Injury: A Role for Inhibiting iNOS

Introduction. We investigated the roles of melatonin (a powerful antioxidant, iNOS inhibitor, and a scavenger of peroxynitrite) and 1400W (a strong and selective inhibitor of inducible nitric oxide) on renal dysfunction and injury induced by ischemia/reperfusion (I/R) of rat kidney, since oxidative and nitrosative injury are believed to be the major causes. Materials and methods. Thirty-two male Sprague-Dawley rats were divided into four groups of sham-operated, I/R, I/R + Melatonin and I/R + 1400W. Rats were given either melatonin (10 mg/kg) or 1400W (10 mg/kg) in the I/R + Melatonin and I/R + 1400W groups respectively at 6 h prior to ischemia and at the beginning of reperfusion via intraperitoneal route. I/R injury was induced by 60 min of bilateral renal ischemia followed by 6 h of reperfusion. After reperfusion, kidneys and blood were obtained for histopathologic and biochemical evaluation. Results. Melatonin and 1400W had an ameliorative effect on both oxidative and nitrosative stress in the kidneys against renal I/R injury in rats. In addition, melatonin significantly reduced elevated nitro-oxidative stress product, restored decreased antioxidant enzymes and attenuated histological alterations when compared with 1400W. Conclusions. Both Melatonin and 1400W were efficient in ameliorating experimental I/R injury of the kidneys. Moreover, melatonin was more effective than 1400W possibly through inhibiting iNOS as well as scavenging free oxygen radicals and peroxynitrite.     

Obstructive Bladder Dysfunction: Morphological,Biochemical and Molecular Changes

Obstruction can cause changes in bladder structure and function, which may at a certain point in time become irreversible. Both the rabbit and the rat have proven to be excellent models to study the morphological, biochemical and molecular changes that occur in the bladder following obstruction. Similarities between partial outflow obstruction in animals and obstructive dysfunction in man include increased bladder mass, increased fibrosis, reduced compliance, increased incidence of detrusor instability and decreased contractile ability. Obstructed bladder function can remain relatively normal for prolonged periods of time, even though bladder mass is increased (compensated stage). If the obstruction is not relieved, bladder function destabilizes and then decompensates, with subsequent risk of serious complications. It is hypothesized that the shift from the compensated to the decompensated stage is related to cyclical periods of ischaemia followed by reperfusion (I/R). This initiates degenerative membrane effects, which supports the process of bladder decompensation. It seems that relief of obstruction during the compensated stage, at least in animals, can induce a rapid and full restoration of the bladder function. However, if the obstruction is relieved during the decompensated phase, bladder function only partially recovers.Irreversible bladder decompensation may be prevented by reducing increased bladder mass and/or by reducing ischaemia/increasing blood supply to the bladder. The antioxidant Vitamin E seems to reduce the progression of decompensation in rabbits. Treatment of rats with the α₁-adrenoceptor antagonist doxazosin prior to partial outlet obstruction increases blood flow to the bladder, significantly decreases the effect of obstruction on bladder weight, and significantly protects the contractile function of the obstructed bladder. Pre-treatment of rabbits with the α₁-adrenoceptor antagonist tamsulosin partly prevents the development of bladder wall hypertrophy due to obstruction.In conclusion, there is evidence that I/R plays an important role in the pathogenesis of obstructive bladder dysfunction. Therefore, I/R should be prevented or relieved. As I/R is the consequence of increased bladder mass following obstruction, therapies that prevent or reduce increased bladder mass (such as the α₁-adrenoceptor antagonist tamsulosin) are likely to protect the bladder from (further) dysfunction. Therapies based on both the relief of I/R (increasing blood flow to the bladder, e.g. α₁-adrenoceptor antagonists) and preventing I/R induced cellular damage (e.g. antioxidant activity) have been shown experimentally to significantly reduce the severity of bladder dysfunction secondary to partial outflow obstruction. Of course, these potentially useful and novel mechanisms of action of therapy should also be investigated in humans.     

Perioperative melatonin use

Melatonin is a substance chiefly produced by the pineal gland and has a key role in the sleep-wake cycle. It also has an important antioxidant role. Exogenous melatonin has a short half-life and is available in a range of preparations. Newer analogues targeted for the recently discovered melatonin MT1 and MT2 receptors have also been developed. Exogenous melatonin is used as a resynchronisation agent in jet lag and for other sleep disturbances. Perioperatively, melatonin has been used as a premedicant, sedative and analgesic. It decreases paediatric emergence delirium. The antioxidant properties of melatonin are being investigated for use in sepsis and reperfusion injuries. It would appear that patients on melatonin supplements should continue taking them perioperatively because there may be benefits. Melatonin and its analogues will be increasingly encountered in the perioperative setting.     

Low concentrations of niflumic acid enhance basal spontaneous and carbachol-induced contractions of the detrusor

Purpose

The urinary bladder expresses Ca²⁺-activated Cl^? channels (CACC), but its physiological role in governing contractility remains to be defined. The CACC modulator niflumic acid (NFA) is widely used despite the variable results arisen from different drug concentrations used. This study was designed to examine the effects of NFA at low concentrations on detrusor strip contractility.

Methods

Rat detrusor strips with mucosa-intact (+MU) and mucosa-denuded (?MU) were prepared in transverse (Tr) and longitudinal (Lg) with respect to the bladder orientation. Isometric force measurements were made at baseline (for spontaneous phasic contractile activity) and during drug stimulation (by carbachol, CCh) with and without NFA.

Results

NFA (1 and 10 μmol/L) pretreatment enhanced CCh-induced contractions more in +MU than ?MU strips with no selectivity on contractile direction. For spontaneous phasic contractions, NFA-treated strips in the Tr direction showed increased phasic amplitude, while phasic frequency was unchanged.

Conclusions

The findings suggest low concentrations of NFA having a potentiating effect on detrusor contractions that was sensitive to the MU and contractile direction.     

Chronic ketamine treatment-induced changes in contractility characteristics of the mouse detrusor

Purpose

To understand bladder contractility changes induced by chronic ketamine treatment, noting the prevalence of its abuse worldwide.

Methods

A mouse model of chronic ketamine treatment was used and detrusor strip contractility was measured. Rising and falling phases of contractile responses as well as maximal, average sustained and phasic contractions were measured.

Results

While maximal contractility of ketamine-treated strips was identical to the saline controls, the former displayed slower contraction rates under K⁺-Krebs, carbachol and electrical stimulation. The decay phase of electrically stimulated responses was also slower at most stimulation frequencies in the ketamine-treated strips. Greater sensitivity to varying the strengths of stimuli was observed in the ketamine-treated strips.

Conclusions

Altered contractility characteristics of the bladder after chronic ketamine treatment were revealed, which could potentially be useful in the development of improved treatment regimens.     

Melatonin protects testes against lithium‐pilocarpine‐induced temporal lobe epilepsy in rats: a time course study

Male dysfunction is common in patients with temporal lobe epilepsy (TLE). We evaluated whether melatonin, as a supplement, can play a positive role in reducing the epileptogenesis imposing abnormalities of spermatozoa and testes in epileptic rats. Status epilepticus was induced based on the TLE lithium‐pilocarpine model. Two patterns of melatonin were administered to the epileptic animals along the mean durations of latent (14 days) and chronic (60 days) phases. Sperm parameters, different antioxidant enzyme levels, germ cell apoptosis, body and relative sex organ weights were evaluated in all groups 60 days following SE induction. Chronic TLE caused a significant reduction in sperm parameters. In the testis, the reduced level of antioxidant enzymes was accompanied by a significant increase in malondialdehyde concentration. The presence of oxidant condition in the testes of epileptic animals caused expanded apoptosis in the germ cell layer. Moreover, the amount of weight gain in epileptic animals was more prominent. Melatonin administration was able to improve sperm motility by increasing the total antioxidant level. There was also a significant reduction in the spermatogenic cell line apoptosis and the extra weight gain of melatonin‐treated animals. Melatonin supplementation might be considered as an acceptable cotreatment in epileptic patients.     

Impact of melatonin supplementation in the rat spermatogenesis subjected to forced swimming exercise

Oxygen consumption increases many times during exercise, which can increase reactive oxygen species. It negatively affects fertility in male athletes. Melatonin is exerting a regulatory role at different levels of the hypothalamic–pituitary–gonadal axis. However, there is no evidence that the protective effects of melatonin persist after long duration exercise on the spermatogenesis. Therefore, this study was conducted to examine the impacts of melatonin on the testis following the administration of swimming exercise. Rats were separated into five different groups, including Control, sham M: received the solvent of melatonin, M: received melatonin, S: the exercise protocol, MS: received melatonin and the exercise protocol. After 8 weeks, animals were scarified and antioxidant enzymes levels of testes, spermatogenic cells apoptosis and sperm quality were measured. Swimming decreased all parameters of spermatozoa. Nevertheless, melatonin could significantly improve the progressive motility of spermatozoa in MS rats. Swimming caused an increased apoptosis of S group and decreased all antioxidant enzymes. Melatonin could drastically reduce apoptosis and increased these enzymes. Therefore, melatonin seems to induce the production of antioxidant enzymes of testicular tissues and diminish the extent of apoptotic changes caused by forced exercise on the testis, which can, in turn, ameliorate the sperm parameters.     

The in vitro effects of melatonin on human sperm function and its scavenging activities on NO and ROS

Various systems of antioxidants exist endogenously in the body to help protect it against free radical damage by scavenging excessive ROS and RNS. Melatonin, a hormone secreted by the pineal gland, and responsible for controlling the circadian rhythm, is one such endogenous antioxidant. Melatonin has been reported to be present in human seminal fluid, but its antioxidant activities in semen are rather contradictory. This study aimed at establishing the effects of melatonin treatment on human spermatozoa. Spermatozoa were incubated with 2 mm melatonin (120 min, 37 °C, 5% CO₂) after which motility parameters were measured by computer aided motility analysis, while cell viability (PI), intracellular NO (DAF‐2/DA) and ROS (DCFH‐DA) were assessed using flow cytometry. In vitro melatonin treated samples (n = 12) showed a significantly higher percentage of motile, progressive motile and rapid cells, while simultaneously reducing the number of nonviable spermatozoa when compared with the control. Endogenous NO was significantly decreased, but no effect was observed on ROS levels. From these results, it can be concluded that melatonin was able to directly or indirectly scavenge NO, as indicated by the reduction in 4,5‐diaminofluorescein‐2/diacetate fluorescence. Future studies will indicate whether melatonin treatment during sperm preparation techniques could protect spermatozoa from excessive NO production.     

Effect of melatonin on burn-induced gastric mucosal injury in rats

We studied the effect of melatonin treatment on gastric mucosal damage induced by experimental burns and its possible relation to changes in gastric lipid peroxidation status. Melatonin was intraperitoneally applied immediately after third-degree burns over 30% of total body skin surface area of rats. Malondialdehyde (MDA), uric acid (UA) and sulphydril (SH) levels were determined in gastric mucosa and blood plasma and used as biomarkers of the oxidative stress. The results showed that the skin burn caused oxidative stress evidenced by accumulation of MDA and UA as well as the depletion of SHs in gastric mucosa. Plasma MDA concentrations were elevated, while plasma SH concentrations were decreased after burns. Melatonin (10 mg per kg body weight) protected gastric mucosa from oxidative damage by suppressing lipid peroxidation and activating the antioxidant defence. It may be hypothesised that melatonin restores the redox balance in the gastric mucosa and protects it from burn-induced oxidative injury. Melatonin has no significant influence on the concentrations of plasma MDA and antioxidants after burn; therefore, it should largely be considered as a limiting factor for tissue-damage.     

Effect of melatonin on cerebral edema in rats

OBJECTIVE: Melatonin (5-methoxy-N-acetyltrypamine), a chemical naturally produced in the pineal gland, has been suggested to be a free radical scavenger and an antioxidant. In the present study, the effect of melatonin on cold-induced brain edema was evaluated by determination of cerebral water content, blood-brain barrier permeability, and areas of infarct; the effects were also studied histopathologically. METHODS: Brain edema was produced in rats by creating a lesion via cortical freezing. Animals were separated into four groups: sham-operated (craniectomy only); control (cold injury); sham-vehicle (cold injury plus saline); and melatonin treatment (cold injury plus melatonin). Melatonin was administered (50 mg/kg intraperitoneally) 15 minutes after the cold injury was induced. Twenty-four hours later, tissue samples from the core, from the periphery of the cold-injured hemisphere, and from the contralateral hemisphere symmetrical to the cold injury were obtained. RESULTS: Melatonin treatment reduced edema (mean +/- standard deviation; 86.22 +/- 1.54% in the control group versus 80.78 +/- 2.76% in the melatonin treatment group, P < 0.001) and blood-brain barrier permeability (45.34 +/- 2.75% in the control group versus 38.26 +/- 3.40% in the melatonin treatment group, P < 0.001) at the periphery of cold injury. Area of infarct reduced from 5.84 +/- 0.58% in the control group to 3.30 +/- 0.89% in the melatonin treatment group (P < 0.001). The effect of melatonin was also confirmed histopathologically. CONCLUSION: Melatonin was found to be neuroprotective in instances of cold-induced brain edema. Thus, melatonin may be a valuable therapeutic agent in the treatment of cerebral edema.     

Sustained anti-beta-adrenergic effect of melatonin in guinea pig heart papillary muscle

OBJECTIVE: Anti-ss-adrenergic actions of several substances influence heart function significantly. The anti-ss-adrenergic effect of melatonin was investigated, with special attention to protein kinase C (PKC) and nitric oxide (NO). DESIGN: Guinea pig papillary muscles were exposed to melatonin (500 pM) for 15 min and 20 min washout. Contractile force was measured during a bolus of isoproterenol (300 nM) given before melatonin, at the end of melatonin-exposure and after washout. In separate experiments blockers of PKC, NO-synthase (NOS) and melatonin receptors were added, or forskolin (10 microM) substituted for isoproterenol. RESULTS: Melatonin significantly reduced the increase in contractile force in response to isoproterenol, both when present and after melatonin-washout. The reduction was unaffected by inhibition of PKC, while inhibition of melatonin receptors or NOS seemed to abolish the effect. Melatonin induced a sustained but not acute reduction of contractile force response with forskolin stimulation. This was abolished by NOS-inhibition. CONCLUSION: Receptor-mediated immediate and sustained anti-ss-adrenergic effects of melatonin were demonstrated in contractile function. A role for NO in the response was indicated, while a role for PKC was not verified.     

The influence of ovariectomy and estradiol replacement on urinary bladder function in rats.

Female Fischer 344 rats were ovariectomized or sham operated and treated with oil or estradiol cypionate (100 mg./100 gm./month) for two or four months. Rats were then placed in metabolism cages for measurement of micturition characteristics, and bladders were removed for bladder strip studies. Ovariectomy had no effects on micturition characteristics. However, estradiol treatment of ovariectomized rats caused significant increases in water consumption and urine excretion, and in mean and maximal micturition volumes compared to both ovariectomized and sham-operated rats. These effects were more pronounced at four months. Estradiol treatment also caused significant increases in bladder body mass, while ovariectomy was without effect. Two months after ovariectomy and/or estradiol treatment, there were no differences in contractile responses of bladder body or base strips to contractile agents when compared to shams. However, after four months, ovariectomy caused significant decreases in contractile responsiveness to nerve stimulation. ATP, carbachol, and KCl compared to sham-operated rats. Estradiol treatment caused increased responsiveness to nerve stimulation, ATP, carbachol, and KCl compared to ovariectomized rats, and to carbachol compared to sham operated rats. Possible causes for the effects of ovariectomy on bladder contractility include decreases in calcium influx. Although estradiol reversed the effects of ovariectomy on bladder function, in addition we observed some indirect effects which were probably the result of estradiol-induced polyuria and increases in bladder mass.     

Neuroprotective Effect of Melatonin on Cortical Impact Injury in the Rat

Summary  The pineal hormone melatonin is a highly efficient physiological scavenger of free radicals involved in secondary brain damage. A variety of experimental studies have demonstrated a neuroprotective effect for melatonin, based on its antioxidant activity. The purpose of the present study was to investigate the time-dependency and a possible protective effect of exogenous melatonin in the cortical impact model in rats. The protective effect was quantified determining contusion volume, brain edema and brain water content.  45 anesthetized male Sprague-Dawley rats (250–350 mg) were subjected to cortical impact injury of moderate severity (7 m/s, deformation 2 mm). Melatonin (100 mg/kg bw i.p.), or a vehicle was injected 20 min before trauma, immediately after, and 1 and 2 hours after trauma during daytime and nighttime. Posttraumatic lesion volume using hematoxylin-eosin staining, hemispheric swelling, brain water content, cerebral perfusion pressure and intracranial pressure 24 hours after injury were investigated.  Melatonin, given during nighttime, significantly reduced contusion volume corresponding to a mean reduction of contusion volume of 27% (placebo, n=7: 41.9±5.2 mm³, melatonin, n=8: 30.5±4.2 mm³, p<0.05). Given during daytime, the reduction in contusion volume was not significant (placebo, n=8: 42.1±5.1 mm³, melatonin, n=8: 35.9±2.2 mm³, reduction of 15%, p=0.08, n.s.). Hemispheric swelling was unchanged by melatonin treatment. Mean arterial blood pressure and rectal temperature remained stable before and after the cortical impact injury and injection of melatonin. This study shows that melatonin significantly reduces contusion volume with major effects during night.     

Norepinephrine content and adrenoceptor function in the bladder of cats with feline interstitial cystitis

PURPOSE: Interstitial cystitis is a chronic syndrome affecting humans and domestic animals, including cats (feline interstitial cystitis). The aggravation of interstitial cystitis symptoms by stress suggests involvement of the sympathetic nervous system. Studies have identified increased sympathetic nervous system activity in patients with interstitial cystitis but to our knowledge effects on bladder function have not been reported. To address this question we measured bladder norepinephrine (NE) content, the electrical field stimulation flux of NE and acetylcholine (ACh), and the effects of feline interstitial cystitis on adrenoceptor (AR) mediated bladder strip contractility. MATERIALS AND METHODS: Bladders were obtained from healthy cats and cats with feline interstitial cystitis. In experiment 1 bladder tissue NE content was determined and the simultaneous release of 3H-NE and 14C-ACh in perfusion bath effluent after electrical field stimulation was measured. NE and ACh release was calculated from the area under the efflux curve. In experiment 2 electrical field stimulation induced contractility of bladder body strips was measured in the presence of 100 nM. to 25 microM. NE only or combined with atipamezole (an alpha2-AR antagonist), propranolol (a beta-AR antagonist) or phentolamine (an alpha-AR antagonist). Antagonists were added to the bath at least 15 minutes before stimulation, after which NE was added in cumulative doses and dose response curves were constructed. RESULTS: Significant increases in NE content and efflux in the absence of alterations in ACh efflux were identified. In the bladder strip studies decreased alpha2 and beta1-AR function was found in strips from cats with feline interstitial cystitis, whereas beta3 or atypical beta-ARs were tentatively identified. CONCLUSIONS: These results support and extend previous studies by identifying an effect of increased sympathetic activity on bladder function in cats with feline interstitial cystitis.