Macroscopic electrical propagation in the guinea pig urinary bladder.

There is little knowledge about macroscopic electrical propagation in the wall of the urinary bladder. Recording simultaneously from a large number of extracellular electrodes is one technology that could be used to study the patterns of macroscopic electrical propagations. The urinary bladders from 14 guinea pigs were isolated and placed in an organ bath. A 16 × 4-electrode array was positioned at various sites on the serosal bladder surface, and recordings were performed at different intravesical volumes. In four experiments, carbachol (CCH; 10(-6) M), nifedipine (10 mM), or tetrodotoxin (TTX; 10(-6) M) was added to the superfusing fluid. After the experiments, the extracellular signals were analyzed and propagation maps were constructed. Electrical waves were detected at all sites on the bladder surface and propagated for a limited distance before terminating spontaneously. The majority of waves (>90%) propagated in the axial direction (i.e., from dome to base or vice versa). An increase in vesicle volume significantly decreased the conduction velocity (from 4.9 ± 1.5 to 2.7 ± 0.7 cm/s; P < 0.05). CCH increased, nifedipine decreased, while TTX had little effect on electrical activities. In addition, a new electrical phenomenon, termed a "patch," was discovered whereby a simultaneous electrical deflection was detected across an area of the bladder surface. Two types of electrical activities were detected on the bladder surface: 1) electrical waves propagating preferentially in the axial direction and 2) electrical patches. The propagating electrical waves could form the basis for local spontaneous contractions in the bladder during the filling phase.

Neuropeptides in the rat corpus cavernosum and seminal vesicle: effects of age and two types of diabetes.

AIMS: To observe the development of neuropathic changes in two types of experimental diabetes using changes in concentrations of NPY, CGRP and amines in the corpora cavernosa and seminal vesicles. Type I diabetes was studied in Wistar rats after 12 and 16 weeks of STZ-induced hyperglycaemia, and Type II diabetes was studied in prediabetic GK rats aged 52 weeks. Both were compared with age-matched normal Wistar rats. METHODS: NPY and CGRP were estimated using radioimmunoassay, and amines using HPLC. RESULTS: There were significant changes in [CGRP] in the normal corpus cavernosum and in [NPY] in the normal seminal vesicle with age. STZ-diabetes, induced at 10 weeks of age, resulted in significant elevation of [NPY] and [CGRP] in the corpora cavernosa and seminal vesicles after 12 and 16 weeks of hyperglycaemia, relative to age-matched control rats. The GK rats were intolerant of glucose at 52 weeks of age, but did not have raised fasting blood glucose levels. [NPY], [CGRP] and [noradrenaline] in corpora cavernosa were significantly increased in the prediabetic GK animals relative to age-matched Wistar control rats. The seminal vesicles of GK rats showed a significant increase in [NPY], a non-significant increase in [CGRP], and a fall in [noradrenaline] relative to the age-matched Wistar controls. CONCLUSIONS: The results indicate increased levels of NPY and noradrenaline in autonomic nerves, and of CGRP in sensory nerves, innervating the corpus cavernosum in Type I and in prediabetic Type II GK rats.

Neuropeptide Y and CGRP concentrations in the rat tail artery: Effects of age and two types of diabetes.

The changes in concentrations of two neuropeptides, neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) in different segments of the rat tail artery have been investigated (a) after 12 and 16 weeks of streptozotocin (STZ)-induced hyperglycemia that has been induced at the age of 10 weeks, and (b) in 52-week-old Goto-Kakizaki (GK) rats that were intolerant of glucose, and age-matched Wistar controls. In the control animals at 22, 26 and 52 weeks of age, the concentration of CGRP was significantly greater in distal, relative to proximal, segments of normal arteries, and this contrasted with the pattern of distribution of NPY, which was consistently greater in the proximal than the distal segments. STZ-induced diabetes caused significant reductions in the concentrations of NPY and CGRP in the middle and distal segments of the vessel after 12 and 16 weeks of hyperglycemia. In the glucose-intolerant Goto-Kakizaki (GK) rats, the noradrenalin and adrenalin levels increased significantly in the distal segment of the artery relative to controls; in contrast there was a significant fall in dopamine concentration. The only significant change in the level of NPY in 52-week-old GK rats was an increase in the proximal segment, suggesting that in Type II pre-diabetes, noradrenalin and its co-transmitter NPY are affected independently. The concentration of CGRP increased significantly in all segments of the artery of the 12-month-old GK rats relative to controls. The similarities and differences between these measurements in Type I and Type II diabetic models are discussed.

Long-term changes in sympathetic innervation in the corpus cavernosum of the STZ-diabetic rat.

The noradrenaline (NA) concentration in the rat corpus cavernosum (CC) increased to approximately 350% of control values after about 8 weeks of hyperglycaemia induced by the intraperitoneal injection of streptozotocin (STZ) at 10 weeks of age. These changes were maintained for at least a further 32 weeks of hyperglycaemia and occurred without any significant change in the weight in the tissue. Smaller but significant increases in NA concentration occurred in the glans penis (GP) reaching 150-175% of the control levels during the period of prolonged hyperglycaemia. In contrast, there was no significant change in the NA concentration in the penile urethra. Measurements have also been made that relate to changes in the synthesis and reuptake of NA in the CC during the period during which high NA concentration is maintained. Immunohistochemical studies for the synthetic enzyme tyrosine hydroxylase in the CC indicate that the intensity of staining in the tissue had increased after 10, 20 and 32 weeks of hyperglycaemia, relative to the tissues from control animals. Dilated nerve fibres and engorged endings were present in the CC of the diabetic animals at these times. Reuptake of tritiated NA by the terminal axonal membranes in the CC was raised to 181% of control values after 12 weeks of hyperglycaemia (P<0.05), but later declined to values that are not significantly different from the control levels (after 26 and 64 weeks of hyperglycaemia). There are few studies of the effects of prolonged diabetes on functional aspects of sympathetic postganglionic neurones in the CC, and this paper suggests that the changes described represent remodelling of noradrenergic axonal terminals starting about after 8-10 weeks of hyperglycaemia; this delay in onset of the neuropathic changes is also a feature of type I diabetes in humans.

Asymptotic scaling in turbulent pipe flow.

The streamwise velocity component in turbulent pipe flow is assessed to determine whether it exhibits asymptotic behaviour that is indicative of high Reynolds numbers. The asymptotic behaviour of both the mean velocity (in the form of the log law) and that of the second moment of the streamwise component of velocity in the outer and overlap regions is consistent with the development of spectral regions which indicate inertial scaling. It is shown that an 'inertial sublayer' in physical space may be considered as a spatial analogue of the inertial subrange in the velocity spectrum and such behaviour only appears for Reynolds numbers R+>5 x 10(3), approximately, much higher than was generally thought.

The effects of age and streptozotocin diabetes on the sympathetic innervation in the rat penis.

The objective was to describe the changes in catecholamine levels, noradrenaline (NA) release and the ultrastructural and immunohistochemical changes in the sympathetic nerves in the penis of STZ-diabetic rats. Amines were measured using HPLC. Nerves were studied using immunocytochemistry for tyrosine hydroxylase, and electron microscopy. Diabetic animals were compared with age-matched controls. The concentration of penile NA increases at least 2.5-fold after about 10 weeks of hyperglycaemia, is maintained for over 40 weeks. The rate of release of NA in the diabetics also increases approximately by fourfold. Immunohistochemical staining for tyrosine hydroxylase showed either no change or an increase in the levels of the enzyme around the central arteries and the outer coverings of the corpus cavernosum. Cavernosal nerves show increased intensity of staining for tyrosine hydroxylase, and the presence of dilated nerve fibres and engorged endings. The axons of the dorsal nerve of the diabetic penis have a smaller cross-sectional area that is most marked in unmyelinated axons. In the diabetic penis, the nerve endings appear to contain significantly more NA than the controls, and the turnover of noradrenaline is increased substantially. There is immunocytochemical evidence of an increase in staining for tyrosine hydroxylase, suggesting an increase in synthetic activity. These results are discussed in relation to the existing literature on the role of amines in normal and disordered erectile function. In particular, the increased concentration and turnover of NA in the diabetic rat contrasts with the fall in NA in cavernosal blood described during normal erection in humans.

The effect of streptozotocin-induced diabetes on the rat seminal vesicle: A possible pathophysiological basis for disorders of ejaculation.

In the streptozotocin (STZ)-diabetic rat major increases in noradrenaline concentration and content of the seminal vesicles were evident as early as 7 weeks following induction of hyperglycemia and returned toward normal after 34 weeks of hyperglycemia. There were significant reductions in the concentration and content of dopamine at 19-42 weeks of diabetes, and small occasionally significant reductions in the content of serotonin and adrenaline, particularly around 19-26 weeks after STZ treatment. The uptake of tritiated noradrenaline in the diabetics was increased at 12 weeks compared to the controls, and decreased to control levels with increasing age. Release of tritiated noradrenline was increased in response to electrical field stimulation and high potassium solutions, and raising calcium concentration caused increased release at rest and during electrical stimulation. Immunohistochemical demonstration of tyrosine hydroxylase was increased during the period when the noradrenaline concentration and content were elevated. It is concluded that there are significant changes in the sympathetic innervation of the seminal vesicle during the course of STZ diabetes, and that alterations in the reuptake, release, and synthesis of the neurotransmitter noradrenaline may contribute to changes in the concentration of the amine in the tissue. It is possible that the changes observed are related to the remodeling and regrowth of sympathetic nerve endings damaged in the early stages of hyperglycemia. These changes may also contribute to disorders of ejaculation in diabetes.

Linkage/association study of a locus modulating total serum IgE on chromosome 14q13-24 in families with asthma.

BACKGROUND: A study was undertaken to validate a locus modulating total serum IgE levels on 14q13-24. METHODS: A linkage and association study was performed between total serum IgE and a panel of seven microsatellites which map to the 14q13-24 region in 69 families with asthma recruited from Leeds, UK. RESULTS: Non-parametric, multipoint, sib pair analysis showed no evidence of genetic linkage between the quantitative trait "log IgE" and any of the tested markers. However, a significant association was observed between locus D14S63 (14q23) and total serum IgE (p = 0.017). Allelic analysis showed an association between low total IgE and allele 157 of D14S63 (p = 0.01, OR = 0.63, 95% CI 0.44 to 0.90). Modelling of allele 157 genotypes as a continuous covariate indicated evidence of a significant inverse linear trend across the three genotypes where 157 homozygotes had the lowest mean log IgE (p = 0.045). Association of D14S63 with log IgE was confirmed in the analysis of a combined dataset of 53 families from Southampton, UK and the 69 families from Leeds (total 122 families). An association was observed at the locus level (p = 0.022) and the allelic level where allele 165 showed an association with high total IgE (p = 0.001, OR = 3.79, 95% CI 1.54 to 9.7) and allele 157 showed an association with low total IgE (p = 0.041, OR = 0.77, 95% CI 0.6 to 0.99). The transmission disequilibrium test was positive for allele 165 (p<0.05) and negative for allele 157 (p>0.05). CONCLUSIONS: Despite the lack of linkage, the findings of this study support the previous observation of a gene(s) at 14q23 that modulates total serum IgE.

Effects of age and streptozotocin-induced diabetes on biogenic amines in rat tail artery.

The changes in amine concentrations in different segments of the rat tail artery have been investigated at different ages and after different durations of streptozotocin-induced diabetes. There was a significant positive slope to the relationship between amine concentrations and age in proximal portion of the normal tail artery, and a significant additional increase in amine concentrations following induction of diabetes. The peak of the latter response occurred between 10 and 20 weeks following the induction of diabetes. There was also a significant dependence on the length of the post-ganglionic neurones, which may be related to the failure of axonal transport of some of the essential enzymes or transporters for these biogenic amines. This model of altered catecholamine metabolism and handling requires further investigation so that alterations in the mechanisms involved in processing of these amines in diabetic autonomic neuropathy may be elucidated.

Reynolds number dependence of streamwise velocity spectra in turbulent pipe flow.

Spectra of the streamwise velocity component in fully developed turbulent pipe flow are presented for Reynolds numbers up to 5.7x10(6). Even at the highest Reynolds number, streamwise velocity spectra exhibit incomplete similarity only: while spectra collapse with both classical inner and outer scaling for limited ranges of wave number, these ranges do not overlap. Thus similarity may not be described as complete, and a region varying with the inverse of the streamwise wave number, k(1), is not expected, and any apparent k(-1)(1) range does not attract any special significance and does not involve a universal constant. Reasons for this are suggested.

The interaction of nitric oxide and prostaglandins in the control of corporal smooth muscle tone: evidence for production of a cyclooxygenase-derived endothelium-contracting factor.

OBJECTIVE: To investigate the interaction of endothelium-derived nitric oxide (NO) and prostaglandins (PGs) in regulating corporal smooth muscle tone in vitro. Materials and methods Strips of rabbit corpus cavernosum were mounted in organ chambers for the measurement of isometric tension. Strips were submaximally contracted with noradrenaline and concentration-response curves (CRCs) to acetylcholine (ACh) were constructed before and after treatment with 5 micromol/L atropine, 20 micromol of the cyclooxygenase inhibitor indomethacin and 10 micromol of the PGH2/thromboxane A2 receptor antagonist SQ29548. The NO synthase (NOS) inhibitors L-NG-monomethyl arginine (L-NMMA) and L-NG-nitroarginine (L-NOARG) were added to strips at tonic tension in the presence and absence of indomethacin, and after this CRCs to ACh were constructed. RESULTS: The addition of ACh to strips produced a concentration-dependent relaxation which was inhibited by atropine. Indomethacin, but not SQ29548, significantly increased relaxation to ACh. Relaxation to ACh was impaired by L-NMMA, but adding ACh to strips treated with L-NOARG resulted in contractile responses, whilst both effects were reversed by indomethacin. L-NMMA and L-NOARG led to increases in tonic tone which were unaffected by indomethacin. CONCLUSIONS: In rabbit corpus cavernosum there is a tonic release of NO which does not appear to be inhibited by a vasoconstrictor prostanoid. Endothelium-dependent relaxation to ACh results in the dual production of NO and a cyclooxygenase-derived endothelium contracting factor which acts in opposition to NO; this factor is unlikely to act on PGH2/TXA2 receptors.

Advanced glycation end-products are responsible for the impairment of corpus cavernosal smooth muscle relaxation seen in diabetes.

OBJECTIVE: To determine if advanced glycation end-products (AGEs) are responsible for the lower neuronal and endothelial-derived nitric oxide (NO)-mediated relaxation of corpus cavernosum in tissue in diabetic rats than in control rats. MATERIALS AND METHODS: Diabetes was induced in male Wistar rats by an intraperitoneal injection with streptozotocin (60 mg/kg). One group of diabetic rats was given free access to water and standard diet. A second group was given standard diet and aminoguanidine with their water (50 mg/100 mL) from the initiation of diabetes. Two groups of rats that were not diabetic acted as age-matched controls. After 8 weeks animals were killed by cervical dislocation, corpus cavernosal tissue strips harvested and mounted in an organ bath to measure isometric tension. After 90 min of equilibration at optimal resting tension and contraction with 1 micromol/L noradrenaline, the response to either acetylcholine or electrical field stimulation (EFS) after adding guanethidine (5 micromol/L) and atropine (1 micromol/L) was determined for each group. RESULTS: There was no difference between the baseline characteristics of all the experimental groups. After 8 weeks the mean body mass and glycosylated haemoglobin (HbA1c) were significantly greater in the diabetic than in control animals. Aminoguanidine had no effect on the recorded body mass or HbA1c. The in vitro relaxation response to the application of acetylcholine or EFS of tissue strips from age-matched control animals fed a standard diet and those supplemented with aminoguanidine were the same. The administration of aminoguanidine to diabetic animals for 8 weeks reversed the expected impaired relaxation response to acetylcholine; the response to EFS was similar. CONCLUSION: AGEs are more prevalent in erectile tissue from diabetic than in control animals. Aminoguanidine reversed the impairment in neuronal and endothelial NO-mediated penile smooth muscle relaxation seen in diabetes. As aminoguanidine prevents AGE formation, erectile dysfunction in diabetes is probably caused partly by the generation of AGEs.

Nitric oxide-mediated corpus cavernosal smooth muscle relaxation is impaired in ageing and diabetes.

OBJECTIVE: To examine nitric-oxide (NO)-mediated relaxation in cavernosal smooth muscle in a rat model of diabetes, as previous experiments showed that HbA1c (an isoform of glycosylated haemoglobin and a marker of long-term diabetic control) impaired NO-mediated relaxation of normal corpus cavernosal tissue through the generation of superoxide anions. MATERIALS AND METHODS: Eight weeks after the induction of diabetes, male Wistar rats were killed and cavernosal tissue obtained. Strips were contracted with 1 micromol/L noradrenaline before applying acetylcholine or electrical field stimulation (EFS) or sodium nitroprusside (SNP). Relaxation responses were repeated in the presence of L-arginine (100 micromol/L), indomethacin (10 micromol/L) or superoxide dismutase (SOD, 120 IU/mL). Young and age-matched control animals were examined in the same way. RESULTS: Eight weeks of uncontrolled diabetes caused a significant impairment in mean relaxation responses to acetylcholine (P < 0.05) and to EFS (P < 0.05), but not to SNP, compared with young and age-matched controls, respectively. L-arginine, indomethacin and SOD had no significant effect on this impairment. Ageing caused a lesser but significant impairment in EFS-mediated cavernosal smooth muscle relaxation (P < 0.05). CONCLUSION: Diabetes impairs endothelial and neuronal NO-mediated cavernosal smooth muscle relaxation in rats in vitro. This effect is not mediated by an alteration in the intracellular action of NO, the availability of NO, superoxide anion inactivation of NO or the generation of constrictor prostanoids. It is possible that cholesterol or advanced glycation end products are responsible for the effect of diabetes on penile smooth function.

Catecholamines in the heart and adrenal gland of the STZ-diabetic rat.

The concentrations of noradrenaline (NA), adrenaline (ADR), 5-hydroxyindoleacetic acid (5-HIAA), serotonin (5-HT) and dopamine (DOP) have been studied in the left ventricle and the left adrenal gland of control and streptozotocin (STZ) - treated rats at various intervals (12, 24, 30, 34, 38 and 42 weeks) after the induction of diabetes. The only amines detected in the heart were NA, 5-HIAA and DOP, whereas those detected in the adrenal gland were NA and ADR. Differential changes in the catecholamine concentrations occurred in the heart and the adrenal gland at different stages of the metabolic disorder. In the heart the initial changes in short-term diabetes included an increase in NA concentration but this did not persist in the longer term diabetic animals (30-38 weeks following STZ injection). In the adrenal gland there was an initial reduction followed by a steady increase in the concentration of NA and ADR throughout the period of the study.

Endothelial and neuronal-derived nitric oxide mediated relaxation of corpus cavernosal smooth muscle in a rat, in vitro, model of erectile function.

We set out to establish a simple, reproducible, rat in vitro model of erectile function and to use this to demonstrate the functional importance of both neuronal- and endothelial-derived nitric oxide within this animal. Two corpora cavernosal smooth muscle strips were harvested from sexually mature male Wistar rats and mounted in an organ bath for measurement of isometric tension. Following contraction with noradrenaline the strips were relaxed by the addition of either acetylcholine or sodium nitroprusside. Electrical field stimulation was performed in the presence of atropine and guanethidine. Relaxation responses were repeated in the presence of methylene blue, L-arginine, L-NNA and haemoglobin +/- L-arginine. Methylene blue abolishes the relaxation to acetylcholine and EFS; L-NNA and haemoglobin cause a significant impairment in the relaxation response. L-arginine reverses the effect of haemoglobin. In conclusion, the inhibitory, relaxant stimulus of rat corpora cavernosa is due to both neuronal nitric oxide and endothelial-derived nitric oxide released in response to cholinergic stimulation.

Evidence for a role of HLA DRB1 alleles in the control of IgE levels, strengthened by interacting TCR A/D marker alleles.

BACKGROUND: MHC class II alleles at human chromosome 6p21.1 and alleles in the TCR A/D locus at human chromosome 14q11.2 have been implicated in susceptibility to specific allergies and the modulation of total serum IgE. It has also been hypothesized that HLA and TCR allelic interactions may have a strong influence on predisposition to allergic disease. OBJECTIVE: This study was performed to investigate the influence of HLA-DRB and DQB1 alleles and D14S50 alleles (adjacent to TCR A/D locus on 14q11.2), individually and in-combination, on total serum IgE levels, and on the development of specific allergies. METHODS: We performed an association study between HLA-DRB, HLA-DQB1 polymorphisms, D14S50 alleles, total serum IgE expression and specific allergies to house dust mite, grass pollens and cat fur. A sample of 181 individuals was drawn from a larger set of 2415 adults, sampled at random from a district in Nottingham. RESULTS: Strong association was observed between HLA-DRB1*0701 allele and high total serum IgE expression (P < 0.001). D14S50 alleles alone showed no evidence for independent association. However, there was a significant interaction between DRB1*0701 and D14S50 allele 170 such that, when both were present, there was a further increase in total serum IgE levels. CONCLUSION: This study suggests that DRB1*0701 allele is involved in the modulation of total serum IgE, and that there is an interaction between DRB1*0701 and a marker adjacent to TCR A/D in the control of IgE expression.

Lack of linkage between chromosome 5q23-33 markers and IgE/bronchial hyperreactivity in 67 Scottish families.

BACKGROUND: Raised serum immunoglobulin E (IgE) and bronchial hyperreactivity (BHR) are risk factors for the expression of the asthma phenotype. Previous studies have reported evidence for linkage between these traits and markers on the 5q23-33 cytokine gene cluster. OBJECTIVE: To test for linkage between total serum IgE/BHR and microsatellite markers which map to the 5q23-33 region in an ethnically distinct cohort of families from Aberdeen, Scotland. METHODS: We performed a linkage study between five polymorphic markers (spanning the chromosome 5q23-33 region) and total serum IgE and BHR traits. A cohort of 67 families, who were recruited originally to study the natural history of wheeze, were clinically characterized and genotyped for D5S404, IL4, IRF-1, IL9, D5S436 markers. Linkage analyses were performed using the nonparametric Haseman-Elston algorithm for the quantitative trait log IgE, and the nonparametric LOD score (NPL-score) of the GENEHUNTER package for the qualitative traits serum IgE and BHR. RESULTS: The results of the nonparametric linkage analysis using either the Haseman-Elston algorithm or NPL-score were consistent and showed no evidence for linkage with IgE. There was also no evidence for linkage between the BHR traits (at cut-off values of PD20FEV1 < 8 mmol and 16 mmol) and any of the tested five microsatellite markers. CONCLUSIONS: This study presents evidence against the presence of a gene with a major effect on total serum IgE or BHR in the 5q23-33 region, in this ethnic group.

Impairment of corpus cavernosal smooth muscle relaxation by glycosylated human haemoglobin.

OBJECTIVE: To examine the effect of HbA1c, an isoform of glycosylated haemoglobin (GHb, a product of non-enzymatic reactions between elevated blood glucose and haemoglobin), on nitric oxide-mediated corpus cavernosal smooth muscle relaxation, and to categorize the mechanisms involved. MATERIALS AND METHODS: Corpus cavernosal tissue from Wistar rats (300-350 g body weight) was prepared for the measurement of isometric tension. After equilibration in Krebs solution gassed with 95% O2/5% CO2 at 37 degrees C for 90 min, optimal resting tension was applied. Tissue was precontracted with 1 micromol/L noradrenaline (NAd) and either relaxed with incremental doses of acetylcholine (ACh) or sodium nitroprusside (SNP). After washout, strips were again precontracted with NAd and then incubated with pyrogallol (100 micromol/L), 100 microL of haemoglobin or 100 microL of GHb in the presence of either L-arginine (100 micromol/L), indomethacin (10 micromol/L), allopurinol (100 micromol/L), deferoxamine (100 micromol/L), catalase (600 IU/mL), or superoxide dismutase (SOD) (120 IU/mL) before ACh- or SNP-induced relaxation responses were repeated. RESULTS: Haemoglobin and GHb significantly impaired the relaxation of rat corpus cavernosum to ACh in a dose-dependent manner. L-arginine reversed the impairment caused by Hb, but not GHb. A donor of superoxide anions, pyrogallol, mimicked this impairment to ACh when added to control strips. Catalase, deferoxamine, indomethacin and allopurinol had no significant effect on the impaired relaxation response to ACh, whilst L-arginine partially reversed it. SOD completely reversed the GHb-induced impaired relaxation; GHb did not alter the relaxation response to SNP. CONCLUSION: GHb significantly impairs endothelial NO-mediated corpus cavernosal relaxation in the rat, in vitro. This effect is caused partly by the generation of superoxide anions and the extracellular inactivation of NO.

Purinergic sensory neurotransmission in the urinary bladder: an in vitro study in the rat.

OBJECTIVES: To determine the response of mechanosensitive pelvic nerve afferents, arising from the rat urinary bladder, to the purinergic agonist alpha,beta-methylene ATP and to the purinergic antagonist suramin. MATERIALS AND METHODS: Using a newly developed in vitro bladder-pelvic nerve afferent model, multiunit recordings were taken from mechanosensitive pelvic nerve afferents arising from the rat urinary bladder, in response to bladder distension. Control experiments were performed by distending the bladder with saline at 0.04 mL/min, and recording the total afferent nerve activity and the bladder pressure response to the distension. Bladder distensions were then repeated using a solution of the stable purinergic agonist alpha,beta-methylene ATP (10 micromol/L), which is known to desensitize P2X-purinoceptors after prolonged exposure, and the total afferent activity and bladder pressure response were again measured. In a separate series of experiments the afferent nerve activity and bladder pressure response to bladder distension with saline was determined in the presence of the purinergic antagonist suramin (10 micromol/L) and repeated after washout of the drug. In both series of experiments, afferent nerve responses were compared with control using the paired t-test, whilst the bladder pressure responses were compared using one-way analysis of variance. RESULTS: Bladder distension with alpha,beta-methylene-ATP produced a statistically significant reduction in afferent nerve activity, by up to 75% compared with the control, whilst having no significant effect on the bladder pressure response. Bladder distension with saline in the presence of suramin (10 micromol/L) produced a significant reduction in the resultant afferent nerve activity, by 50%, which returned to normal after washout of the drug. CONCLUSION: These findings are consistent with the notion that ATP is released endogenously during bladder distension in the rat and is involved significantly in the activation of pelvic nerve afferents arising from the rat urinary bladder.