Multiple mechanisms in the motor responses of the guinea-pig isolated urinary bladder to bradykinin

Diabetes mellitus, systemic inflammation and overactive bladder

Background

Increasing evidence emphasizes the potential relationship between diabetes and OAB (overactive bladder). However, large population epidemiology is still lacking.

Methods

This cross-sectional study included six cycle NHANES surveys, with a total of 23863 participants. Logistic regression models were constructed to analyze the association between diabetes mellitus, diabetes-related markers, and inflammatory biomarkers with OAB. Restricted cubic splines were used to analyze the non-linear associations. Mediating analysis was performed to test the effect of inflammatory biomarkers on the relationship between diabetes-related markers and OAB. Finally, machine learning models were applied to predict the relative importance and construct the best-fit model.

Results

Diabetes mellitus participants' OAB prevalence increased by 77% compared with non-diabetes. As the quartiles of diabetes-related markers increased, the odds of OAB monotonically increased in three models (all p for trend < 0.001). Glycohemoglobin exhibited a linear association with OAB (p for nonlinearity > 0.05). White blood cells significantly mediated the associations between diabetes-related markers (glycohemoglobin, fasting glucose, and insulin) with OAB, and the proportions were 7.23%, 8.08%, and 17.74%, respectively (all p < 0.0001). Neutrophils partly mediated the correlation between (glycohemoglobin, fasting glucose, and insulin) and OAB at 6.58%, 9.64%, and 17.93%, respectively (all p < 0.0001). Machine learning of the XGBoost model constructs the best fit model, and XGBoost predicts glycohemoglobin is the most important indicator on OAB.

Conclusion

Our research revealed diabetes mellitus and diabetes-related markers were remarkably associated with OAB, and systemic inflammation was an important mediator of this association.

Urogynaecology and Ehlers-Danlos syndrome

Ehlers-Danlos syndrome (EDS) can lead to a presentation to urogynaecology services with multiple symptoms including vaginal prolapse, overactive bladder symptoms, voiding dysfunction, bladder pain syndrome, recurrent urinary tracts infections, stress urinary incontinence, recurring bladder diverticula, vesicoureteral reflux, pelvic floor pain or spasms, and complicated postnatal perineal wounds. This article explores the pathophysiology of these conditions in causing urinary urgency, incontinence, and infections; highlighting the key investigations and management considerations for women with EDS including conservative, pharmacological, and surgical.

TRP Channel Agonists Activate Different Afferent Neuromodulatory Mechanisms in Guinea Pig Urinary Bladder

Activation of TRP channels expressed in urinary bladder afferent nerves and urothelium releases neurotransmitters that influence bladder function. Experiments were undertaken to examine the mechanisms underlying effects of TRPA1 (allyl isothiocyanate, AITC), TRPV1 (capsaicin, CAPS), and TRPC (oleoyl-2-acetyl-sn-glycerol, OAG) agonists on guinea pig bladder activity. Effects of these agonists were compared with effects of nitro-oleic acid (OA-NO2), an electrophilic nitro-fatty acid, known to activate TRPV1, TRPA1 or TRPC channels in sensory neurons. AITC (100 μM) increased (231%) area of spontaneous bladder contractions (SBCs) an effect reduced by a TRPA1 antagonist (HC3-03001, HC3, 10 μM) and reversed to inhibition by indomethacin (INDO, 500 nM) a cyclooxygenase inhibitor. The post-INDO inhibitory effect of AITC was mimicked (39% depression) by calcitonin gene-related peptide (CGRP, 100 nM) and blocked by a CGRP antagonist (BIBN, 25 μM). CAPS (1 μM) suppressed SBCs by 30% in 81% of strips, an effect blocked by a TRPV1 antagonist (diarylpiperazine, 1 μM) or BIBN. SBCs were suppressed by OA-NO2 (30 μM, 21% in 77% of strips) or by OAG (50 μM, 30%) an effect blocked by BIBN. OA-NO2 effects were not altered by HC3 or diarylpiperazine. OA-NO2 also induced excitation in 23% of bladder strips. These observations raise the possibility that guinea pig bladder is innervated by at least two types of afferent nerves: [1] Type A express TRPA1 receptors that induce the release of prostaglandins and excite the detrusor, [2] Type B express TRPV1, TRPA1 and TRPC receptors and release CGRP that inhibits the detrusor.

Resveratrol prevents bradykinin-induced contraction of rat urinary bladders by decreasing prostaglandin production and calcium influx

Resveratrol, a polyphenol found in grapes and peanuts, exerts beneficial effects on a number of diseases of cardiovascular and central nervous system. However, effects of resveratrol on the urinary system have not been fully investigated. In the present study, we examined effects of resveratrol on bradykinin-induced contraction and release of prostaglandin E2 in isolated rat urinary bladders. The effects of resveratrol on contractions induced by several agonists (prostaglandin E2, prostaglandin F2α and carbachol) and high K+ were also examined. We found that resveratrol concentration-dependently reduced the bradykinin-induced contraction in the rat urinary bladder preparations. The higher concentration of resveratrol (100 μM) abolished the bradykinin-induced prostaglandin E2 release. Similar results were obtained when the cyclooxygenase inhibitor indomethacin (10 μM) was used instead of resveratrol. Resveratrol also attenuated the prostaglandin E2-, prostaglandin F2α-, and to a lesser extent carbachol-induced contractions. Contractile responses to bradykinin, prostaglandin E2 and carbachol were largely prevented by blockade of Ca2+ channels with diltiazem. Both resveratrol and diltiazem prevented contractions induced by an addition of Ca2+ (2.5- 10 mM) into Ca2+-free/50 mMK+ solution or by 50 mMK+ solution containing normal Ca2+ (2.5 mM). These results suggest that resveratrol prevents bradykinin-induced contractions by attenuating not only the production of prostaglandins but also actions of them. The effect of resveratrol on contractile actions seems to be in part due to inhibition of Ca2+ influx. Because bradykinin plays an important role in pathological conditions of urinary bladder function, resveratrol may exert beneficial effects on the urinary bladder diseases.

Characterization of kinin receptors in human cultured detrusor smooth muscle cells

BACKGROUND AND PURPOSE

Kinins have an important role in inflammatory cystitis and in animal pathophysiological models, by acting on epithelium, fibroblasts, sensory innervation and smooth muscle. The aim of this study was to characterize the receptors responsible for direct motor responses induced by kinins on human detrusor.

EXPERIMENTAL APPROACH

Human detrusor cells from biopsies were isolated and maintained in culture. B(1) and B(2) kinin receptors were characterized by means of radioligand and functional experiments (PI accumulation and PGE(2) release).

KEY RESULTS

[(3)H]-[desArg(9)]-Lys-BK and [(3)H]-BK saturation studies indicated receptor density (B(max)) and K (d) values of 19 or 113 fmol mg(-1), and 0.16 or 0.11 nM for the B(1) or B(2) receptors, respectively. Inhibition binding studies indicated the selectivity of the B(1) receptor antagonist [desArg(9)Leu(8)]-Lys-BK and of the B(2) receptor antagonists Icatibant and MEN16132. [DesArg(9)]-Lys-BK and BK induced PI accumulation with an EC(50) of 1.6 and 1.4 nM and different maximal responses (E(max) of [desArg(9)]-Lys-BK was 10% of BK). BK also induced prostaglandin E(2) release (EC(50) 2.3 nM), whereas no response was detected with the B(1) receptor agonist. The incubation of detrusor smooth muscle cells with interleukin 1beta (IL-1beta) or tumour necrosis factor-alpha (TNF-alpha) (10 ng ml(-1)) induced a time-dependent increase in radioligand-specific binding, which was greater for the B(1) than for the B(2) receptor.

CONCLUSIONS AND IMPLICATIONS

Human detrusor smooth muscle cells in culture retain kinin receptors, and represent a suitable model to investigate the mechanisms and changes that occur under chronic inflammatory conditions.

The use of the isolated mouse whole bladder for investigating bladder overactivity

The isolated mouse whole bladder was used to study in vitro bladder overactivity evoked by intramural nerve sensitization with bradykinin, mimicking neurogenic bladder overactivity secondary to bladder inflammation. Intravesical pressure responses to intramural electrical stimulation of intramural nerves were measured under isovolumetric condition. Validation showed that carbachol produced a dose-response curve closely mirroring that observed in the isolated muscle strips and demonstrated the dual nature of electrically evoked neurotransmission, consisting of a cholinergic component largely mediated by M(3) receptors and a purinergic component mediated by P2X receptors. ATP generated a biphasic dose-response curve, suggesting that the P2X receptors may be heterogeneous in distribution. Characterization of bradykinin receptors showed bradykinin to be extremely potent in exciting the bladder, producing a dose-response curve with an EC(50) of 90 nM, and bradykinin also enhanced electrically evoked bladder contractions. These effects were inhibited by the B(2) receptor antagonist HOE 140 (d-Arg(0)-Arg(1)-Pro(2)-Hyp(3)-Gly(4)-Thi(5)-Ser(6)-d-Tic(7)-Oic(8)-Arg(9)) but not the B(1) receptor antagonist desArg(10) HOE 140 (H-d-Arf-Arg-Pro-Hyp-Gly-Thi-Ser-d-Tic-Oic-OH) and were also modulated by alpha,beta,methyleneATP. The isolated mouse whole bladder has proved a viable, robust model in which to demonstrate the pharmacological characteristic of the bladder and adds to the repertoire of in vitro tools for investigating potential therapeutic agents.

Differential development of TRPV1-expressing sensory nerves in peripheral organs

In mouse ontogeny, neurons immunoreactive for transient receptor potential vanilloid receptor 1 (TRPV1) were observed primarily in the dorsal root ganglia (DRG) at embryonic day 13 (E13). In the embryonic period, the number of TRPV1(+) neurons decreased, but then gradually increased postnatally. Some of TRPV1(+) neurons were also immunoreactive for calcitonin gene-related peptide (CGRP). At postnatal day 7 (P7), 66% of CGRP(+) neurons were TRPV1(+), and 55% of TRPV1(+) neurons were also CGRP(+) in the L4 DRG. In the peripheral organs, TRPV1-immunorective nerve fibers were transiently observed in the skin at E14. They were also observed in the urinary tract at E14, and in the rectum at E15. Many TRPV1(+) nerve fibers in these organs were also CGRP(+). At P1, TRPV1(+) nerve fibers were observed in the respiratory organs, and to a lesser extent in the stomach, colon, skin, and skeletal muscles. The number of TRPV1(+) nerve fibers on each organ gradually increased postnatally. At P7, TRPV1(+) nerve fibers were also observed in the small intestine and kidneys. The percentage of total TRPV1(+) nerve fibers that co-localized with CGRP was greater in most organs at P7 than at P1. The present results indicate that TRPV1 expression on peripheral processes differs among organs. The differential time course of TRPV1 expression in the cell bodies might be related to the organs to which they project. Co-localization of TRPV1 with CGRP on nerve fibers also varies among organs. This suggests that the TRPV1-mediated neuropeptide release that occurs in certain pathophysiologic conditions also varies among organs.

Pharmacology of the lower urinary tract: basis for current and future treatments of urinary incontinence

The lower urinary tract constitutes a functional unit controlled by a complex interplay between the central and peripheral nervous systems and local regulatory factors. In the adult, micturition is controlled by a spinobulbospinal reflex, which is under suprapontine control. Several central nervous system transmitters can modulate voiding, as well as, potentially, drugs affecting voiding; for example, noradrenaline, GABA, or dopamine receptors and mechanisms may be therapeutically useful. Peripherally, lower urinary tract function is dependent on the concerted action of the smooth and striated muscles of the urinary bladder, urethra, and periurethral region. Various neurotransmitters, including acetylcholine, noradrenaline, adenosine triphosphate, nitric oxide, and neuropeptides, have been implicated in this neural regulation. Muscarinic receptors mediate normal bladder contraction as well as at least the main part of contraction in the overactive bladder. Disorders of micturition can roughly be classified as disturbances of storage or disturbances of emptying. Failure to store urine may lead to various forms of incontinence, the main forms of which are urge and stress incontinence. The etiology and pathophysiology of these disorders remain incompletely known, which is reflected in the fact that current drug treatment includes a relatively small number of more or less well-documented alternatives. Antimuscarinics are the main-stay of pharmacological treatment of the overactive bladder syndrome, which is characterized by urgency, frequency, and urge incontinence. Accepted drug treatments of stress incontinence are currently scarce, but new alternatives are emerging. New targets for control of micturition are being defined, but further research is needed to advance the pharmacological treatment of micturition disorders.

Possible involvement of Ca2+-independent phospholipase A2 in protease-activated receptor-2-mediated contraction of rat urinary bladder

Possible involvement of Ca(2+)-independent phospholipase A2 (iPLA2) was examined in protease-activated receptor-2 (PAR-2)-mediated contraction of the rat urinary bladder. Both PAR-2 activating peptide (PAR-2 AP; SLIGRL-NH2) and trypsin produced a concentration-dependent contractile response in the urinary bladder preparations. These contractions were significantly (p<0.01) attenuated by indomethacin (10 microM), an inhibitor of cyclooxygenase, or bromoenol lactone (BEL; 10 micro M), an inhibitor of iPLA2. On the other hand, the contractile responses to bradykinin were not significantly affected by BEL, although they were reduced by indomethacin. Arachidonyltrifluoromethyl ketone (AACOCF3; 30 microM), an inhibitor of cytosolic Ca(2+)-dependent phospholipase A2, did not affect the trypsin- and bradykinin-induced contractions. Both indomethacin and BEL had no inhibitory effect on the prostaglandin E2-induced contractions. These results suggest that PAR-2 activators and bradykinin stimulate the release of prostaglandins and thereby contract the rat urinary bladder smooth muscles. The release of prostaglandins by PAR-2 activators seems to be partly mediated by the iPLA2.

Peripheral tachykinin receptors as targets for new drugs

Tachykinins are widely distributed in the peripheral nervous system of the respiratory, urinary and gastrointestinal tract, stored in enteric neurons and in peripheral nerve endings of capsaicin-sensitive primary afferent neurons from which are released by stimuli having both pathological and physiological relevance. The most studied effects produced by tachykinins in these systems are smooth muscle contraction, plasma protein extravasation, mucus secretion and recruitment/activation of immune cells. The use of tachykinin receptor-selective antagonists and knockout animals has enabled to identify the involvement of tachykinin NK(1), NK(2) and NK(3) receptors as mediators of peripheral effects of tachykinins in different systems/species. The bulk of data obtained in experimental animal models suggests that tachykinins could contribute to the genesis of symptoms accompanying various human diseases including asthma/bronchial hyperreactivity, cystitis of various aetiology, inflammatory bowel diseases and irritable bowel syndrome. Tachykinin receptor antagonists are expected to afford therapeutically relevant effects.

Prostaglandin-release impairment in the bladder epithelium of streptozotocin-induced diabetic rats

Isolated epithelial layer preparations were obtained from urinary bladders of 4-week streptozotocin-diabetic rats and used for endogenous prostaglandins E(2) and F(2alpha) determination. Tissues were incubated in modified Krebs solution under basal conditions, or in the presence of either indomethacin (5x10(-7) M), ATP (10(-5) and 10(-3) M) or bradykinin (10(-7) and 10(-5) M), and samples of incubation medium were collected at 15 and 30 min. In the presence of indomethacin, the release of prostaglandins in the incubation medium was under the detection limit of the enzyme immunoassay (EIA). The epithelium from diabetic rat urinary bladders was thicker and heavier and the absolute amount of endogenous prostaglandins E(2) and F(2alpha) was higher than for control animals, but when prostaglandin production was expressed as a fraction of tissue weight, it was reduced in diabetic epithelium. ATP and bradykinin has significantly increased the endogenous release of both prostaglandins from the epithelium when compared with the release under basal conditions. This increase was time-dependent and was higher in diabetic than in control tissues. ATP evoked a phasic and tonic contraction in bladder strips that was abolished by epithelium removal. Concentration-response curves for ATP did not differ among groups. Bradykinin evoked a long-lasting tonic contraction that was reduced significantly by epithelium removal in diabetic rat bladders only. Concentration-response curves for prostaglandin E(2) and F(2alpha) in diabetic rat bladder differed significantly from that in controls and epithelium removal did not alter these responses. It is suggested that bradykinin receptors and P2X nucleotide receptors already found in the smooth muscle detrusor might be present in the epithelial layer of the bladder. The prostaglandin-release impairment observed in this study might be responsible, in part, for bladder abnormalities observed in pathological conditions, such as diabetes.

Characterization of bradykinin B(2) receptor antagonists in human and rat urinary bladder

The effect of three selective bradykinin B(2) receptor antagonists, MEN11270 (H-DArg-Arg-Pro-Hyp-Gly-Thi-c(Dab-DTic-Oic-Arg)c(7gamma-1 0alpha)), Icatibant (H-DArg-Arg-Pro-Hyp-Gly-Thi-Ser-DTic-Oic-Arg-OH), and FR173567 ((E)-3-(6-acetamido-3-pyridyl)-N-[N-[2, 4-dichloro-3-[(2-methyl-8-quinolinyl) oxymethyl] phenyl]-N-methylaminocarbonylmethyl]acrylamide) was evaluated in the human and rat urinary bladder in vitro and in vivo in anaesthetized rats. Bradykinin evoked a concentration-dependent contraction of human (pD(2)=7.2) and rat (pD(2)=7.7) detrusor muscle strips. In human preparations, all the antagonists tested produced a rightward-shift in the concentration-response curve for bradykinin. Schild plot analysis yielded pK(B) values of 8.4, 8.4 and 8.6 for MEN11270, Icatibant, and FR173567, respectively. In the rat preparations the three antagonists (at 100 nM concentration), produced a shift to the right which gave apparent pA(2) values of 8. 2, 8.0 and 8.1 for MEN11270, Icatibant, and FR173567, respectively. In anaesthetized rats, both MEN11270 and Icatibant (1-10 nmol/kg i.v. ) dose dependently reduced the bradykinin (100 nmol/kg i.v.)-induced urinary bladder contraction, their effect being prompt and long-lasting. In contrast, FR173567 (100 nmol/kg i.v.) produced a partial and short-lasting inhibition of bradykinin-induced bladder contractions. The present findings indicate that all the antagonists tested recognize with similar potencies the bradykinin B(2) receptors expressed in the detrusor muscle of both humans and rats. MEN11270 and Icatibant possess a higher potency and longer duration of action in vivo than FR173657, suggesting that the activity of this non-peptide antagonist in vivo is hampered by factors unrelated to its affinity for bradykinin B(2) receptors.

Ovalbumin-induced neurogenic inflammation in the bladder of sensitized rats

1. We have developed and characterized a model of immediate hypersensitivity/inflammation of the urinary bladder in vivo induced by local application of ovalbumin (OA) in OA- sensitive female rats. Two parameters of the inflammatory response were assessed following OA challenge: plasma protein extravasation (PPE) and changes in smooth muscle reactivity. The former was estimated by measurement of Evans blue extravasation at 0.5, 2, 4, 8 and 24 h time point following in vivo challenge. Changes in reactivity were determined by measurement of isotonic tension responses of urinary bladder strips following OA challenge in vitro. 2. Acute in vivo intravesical OA challenge (10 mg in 0.3 ml saline) in actively sensitized female Wistar rats caused a time-dependent PPE in the urinary bladder which was biphasic with peak responses at 2-4 and 24 h. 3. The PPE response to acute OA challenge, above base-line, at 2 h was abolished by systemic capsaicin pretreatment (50 mg kg(-1), s.c., 4 days before use) (P < 0.05) whilst the response at 24 h was unaffected. The 2 h time point was then used for further studies. 4. Degranulation of mast cells, achieved by pretreatment with compound 48/80 (5 mg kg(-1), s.c. for 3 consecutive days), completely abolished the PPE response to OA challenge at the 2 h time point. 5. The tachykinin NK1 receptor antagonist, SR 140333 (0.1 micromol kg(-1), i.v.), abolished the 2 h PPE response whilst the tachykinin NK2 receptor antagonist MEN 11420 (0.1 micromol kg(-1), i.v.) appeared to reduce the response by approximately 50% but this did not reach significance. The bradykinin B2 receptor antagonist, Hoe 140 (0.1 micromol kg(-1), i.v.), similarly to SR 140333, blocked the 2 h PPE response to OA, whereas the selective B1 receptor antagonist B 9858 (0.1 micromol kg(-1), i.v.) had no significant effect. Inhibition of cyclo-oxygenase (COX) achieved by pretreatment with the COX inhibitor dexketoprofen (5.3 micromol kg(-1), i.v.) also blocked the PPE response, whilst the leukotriene receptor antagonist ONO 1078 (1 micromol kg(-1), i.v.) significantly reduced PPE by about 80%. 6. In the rat isolated urinary bladder OA (1 mg ml(-1)) challenge produced a biphasic response with a rapidly achieved maximal contraction followed by a sustained contraction for approximately 25 min. In vitro capsaicin pretreatment (10 microM for 15 min) significantly attenuated the duration of the sustained contraction whilst having no effect on the maximum contractile response achieved. In vivo pretreatment of animals with compound 48/80 significantly attenuated (42%) the maximum contractile response. Combination of both treatments almost completely abolished the response. In vitro treatment with Hoe 140 (1 microM) had no significant effect on the response to OA and neither did ONO 1078 (1 microM). 7. These results show that both the early inflammatory response and alterations in smooth muscle reactivity to OA challenge in actively sensitized animals are dependent on mast cell degranulation and the activation of sensory C-fibres. Furthermore this model of allergic cystitis may be useful for investigating both the processes involved and potential novel therapies in the treatment of interstitial cystitis.

Potentiation by bradykinin and substance P of purinergic neurotransmission in urinary bladder

PURPOSE

The higher than normal levels of substance P (SP) and the kinins in patients suffering from interstitial cystitis suggest that they may contribute to the complex symptoms of the condition. The purpose of our experiments was to determine whether SP and bradykinin (BK) influence the excitatory motor innervation of the urinary bladder.

MATERIALS AND METHODS

Strips of guinea pig urinary bladder were placed in isolated tissue baths, and the influence of SP and BK on contractions induced by transmural electrical stimulation and cholinergic and purinergic agonists was evaluated.

RESULTS

Substance P and BK potentiated responses to the purinergic component of the neurogenic stimulation (that part of the contractile response that remains after treatment with atropine) and potentiated responses to exogenously applied adenosine triphosphate (ATP). The peptides did not potentiate the response to the cholinergic component of the nerve-induced contraction (that part of the neurogenic response that remains after desensitization of purinoceptors with alpha, beta-methylene ATP) nor responses to carbachol. The potentiating actions of SP and BK were reduced but not abolished by treatment with meclofenamic acid.

CONCLUSIONS

Substance P and BK potentiate the neurogenic response of the bladder by influencing the purinergic component of the excitatory motor innervation, apparently at a postjunctional site. Prostaglandins may be involved in mediating some of the actions of these peptides.

Protective activity of ketoprofen lysine salt against the pulmonary effects induced by bradykinin in guinea-pigs

We investigated the capacity of ketoprofen lysine salt (KLS) to counteract the pulmonary effects of some mediators of airway inflammation. The protective effect of KLS and its R-isomer against bradykinin (BK) induced plasma extravasation in the airways and bronchoconstriction was evaluated in anaesthetized guinea-pigs, in parallel with the capacity of KLS to inhibit the production of thromboxane A2 (TXA2). Moreover, we studied the ability of KLS to modulate leukotriene C4 (LTC4) and acetylcholine (ACH) induced bronchoconstriction and the associated production of TXA2. Nimesulide (NIM) was used as the reference compound. KLS dose-dependently inhibited the bronchoconstriction and the associated production of TXA2 induced by BK, with closely related ID50 values of 31.2 and 34.0 micrograms/kg i.v., respectively. The protection was evident 10 min after KLS administration and, at 100 micrograms/kg i.v., lasted up to 2h, Moreover, KLS dose-dependently inhibited the increase in capillary permeability induced by BK, with a potency (ID50 23.4 micrograms/kg i.v.) slightly higher than that shown against the bronchoconstriction. KLS also prevented the bronchoconstriction and TXA2 production triggered by LTC4, but not ACH induced bronchoconstriction. In all the models studied, KLS was about 10 times more potent than NIM. These data demonstrate the capacity of KLS to counteract the bronchoconstriction induced by BK and LTC4 and to a large extent the airway inflammation induced by BK. Blockade of prostanoid production is likely to account for this protective effect, since the R-isomer of KLS was devoid of significant activity.

Prostaglandin E2-induced bladder hyperactivity in normal, conscious rats: involvement of tachykinins?

In normal conscious rats investigated by continuous cystometry, intravesically instilled prostaglandin (PG) E2 facilitated micturition and increased basal intravesical pressure. The effect was attenuated by both the NK1 receptor selective antagonist RP 67,580 and the NK2 receptor selective antagonist SR 48,968, given intra-arterially, suggesting that it was mediated by stimulation of both NK1 and NK2 receptors. Intra-arterially given PGE2 produced a distinct increase in bladder pressure before initiating a micturition reflex, indicating that the PG had a direct contractant effect on the detrusor smooth muscle. The effect of intra-arterial PGE2 could not be blocked by intra-arterial RP 67,580 or SR 48,968, which opens the possibility that the micturition reflex elicited by intra-arterial PGE2 was mediated by pathways other than the reflex initiated when the PG was given intravesically. The present results thus suggest that intra-arterial PGE2, given near the bladder, may initiate micturition in the normal rat chiefly by directly contracting the smooth muscle of the detrusor. However, when given intravesically, PGE2 may stimulate micturition by releasing tachykinins from nerves in and/or immediately below the urothelium. These tachykinins, in turn, initiate a micturition reflex by stimulating NK1 and NK2 receptors. Prostanoids may, via release of tachykinins, contribute to both urge and bladder hyperactivity seen in inflammatory conditions of the lower urinary tract.

Pharmacological analysis of the local and reflex responses to bradykinin on rat urinary bladder motility in vivo

1. The topical application of bradykinin (BK) (0.05-5000 pmol/rat) onto the serosal surface of the urinary bladder in urethane-anaesthetized rats, evoked low amplitude tonic contractions (not exceeding 25 mmHg) or high amplitude (about 50 mmHg), phasic reflex contractions (chemoceptive micturition reflex) which were abolished by bilateral ablation of the pelvic ganglia. In ganglionectomized rats, BK induced only a local, tonic-type contraction. 2. Systemic capsaicin pretreatment (164 mumol kg-1, 4 days before) reduced the incidence of chemoceptive reflex induced by BK (500 pmol/rat) but had no effect on the magnitude of the tonic-type contraction elicited by BK in ganglionectomized rats. Indomethacin (11 mumol kg-1, 20 min before) reduced the incidence but not the amplitude of the reflex contractions induced by topical application of BK (500 pmol/rat). In ganglionectomized rats, indomethacin (11 mumol kg-1, 20 min before) decreased the amplitude of the tonic contraction evoked by BK. Indomethacin did not affect the chemoceptive reflex induced by topical application of capsaicin (15 nmol/rat) onto the bladder. 3. Intrathecal administration of the tachykinin NK1 receptor antagonists, RP 67,580 (10 nmol/rat) or SR 140,333 (10 nmol/rat), abolished the chemoceptive reflex induced by BK without modifying the magnitude of the tonic contraction. SR 140,333 (10 nmol/rat) also abolished the occurrence of the chemoceptive reflex induced by capsaicin. 4. Intravenous administration of the B2 receptor antagonist, Hoe 140 (35 nmol kg-1, 10 min before) abolished the reflex and local effects induced by BK on bladder motility but failed to modify the chemoceptive reflex induced by topical application of capsaicin (15 nmol/rat). 5. Intrathecal administration of Hoe 140 (10 nmol/rat) reduced the incidence of the chemoceptive reflex induced by BK but had no effect on the amplitude of the local motor response. Likewise, Hoe 140(10 nmol/rat, i.t.) reduced the incidence of reflex bladder contractions induced by topical application of capsaicin (15 nmol/rat) without affecting the magnitude of the tonic-type contraction.6. These findings indicate that BK stimulates motility through B2 receptors in the rat urinary bladder.BK activates the reflex response by stimulating capsaicin-sensitive afferent nerves with a contribution from prostanoids. At the spinal cord level, tachykinin NK1 and BK B2 receptors could also be involved in the chemoceptive reflex induced by BK or capsaicin.

Peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) activates capsaicin-sensitive primary afferent nerves in guinea-pig atria and urinary bladder

1. We have investigated the ability of the N-formyl-methionyl-leucyl-phenylalanine (FMLP) a synthetic analogue of a chemotactic peptide derived from a variety of bacteria, to activate capsaicin-sensitive primary afferents in the guinea-pig atria and urinary bladder. 2. In the isolated, electrically-driven left atria from reserpine-pretreated guinea-pigs (atropine in the bath), FMLP (3 nM-1 microM) produced a biphasic positive inotropic response. The late component of this response was selectively abolished by in vitro capsaicin pretreatment while both the early and late responses were abolished by indomethacin. 3. The inotropic response to FMLP in the guinea-pig atria was unaffected by ruthenium red. The late but not the early response was strongly inhibited or abolished by tetrodotoxin (TTX), omega-conotoxin (CTX) or by the C-terminal fragment (8-37) of human alpha-calcitonin gene-related peptide (hCGRP). hCGRP-(8-37) acts as competitive antagonist at CGRP receptors. 4. In the guinea-pig isolated bladder, FMLP (10 nM-10 microM) produced a concentration-dependent contraction which was unchanged by previous in vitro capsaicin, TTX or CTX pretreatment. The response to low concentrations of FMLP was suppressed by indomethacin, irrespective of the capsaicin pretreatment. 5. FMLP (10 microM) produced a significant increase in the outflow of CGRP-like immunoreactivity (CGRP-LI) from superfused guinea-pig atria or urinary bladder. CGRP-LI outflow induced by FMLP was blocked by indomethacin or in vitro capsaicin pretreatment. 6. These findings indicate that FMLP activates the 'efferent' function of capsaicin-sensitive primary afferents via prostanoid generation. This action could provide a neurogenic contribution to the overall inflammatory response produced by bacteria-derived peptides in inflamed tissues. In addition the present data indicate that endogenous prostanoids generated during exposure to FMLP produce peptide secretion from sensory nerves via a TTX- and CTX-sensitive but ruthenium red-resistant mechanism.

Prostaglandin-induced neuropeptide release from spinal cord

The studies reviewed in this chapter present a convincing argument that prostaglandins have direct actions at the level of the spinal cord to enhance nociception. Furthermore, an increasing body of evidence supports the hypothesis that one important site of action of these eicosanoids is the terminals of sensory neurons. Studies performed in our laboratory add to this evidence by demonstrating that relatively large concentrations of prostaglandins increase SP release, whereas lower amounts augment the capsaicin-stimulated release of both SP and CGRP from rat spinal cord slices. In neuronal cultures of rat dorsal root ganglia, prostaglandins also facilitate the evoked release of SP and CGRP, indicating a direct action of these autocoids on sensory neurons. Based on these studies, it is interesting to speculate that the actions of prostaglandins on peptide release are one mechanism to account for hyperalgesia produced by these eicosanoids. In addition, by a sustained action, prostaglandins may contribute to the enhanced excitability of sensory neurons during inflammation. Indeed, our observations that intrathecal Ketorolac abolished the elevation in SP release during inflammation support this possibility. Whether the effect of the NSAID are caused by the inhibition of prostaglandin synthesis in the spinal cord are yet to be determined. Further work is necessary to establish a role for prostaglandins in the adaptive changes of nociceptive neurons that occur in chronic pain states and in inflammation. In addition, the cellular mechanisms underlying the effects of prostaglandins on sensory neurons are yet to be elucidated.

Acute joint inflammation--mechanisms and mediators

1. This review discusses factors contributing to acute joint inflammation, particularly sensory neuropeptides. 2. Mediators known to contribute importantly to the inflammatory process include cytokines, eicosanoids, complement and the kinin systems, histamine and 5-hydroxytryptamine and sensory neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP). 3. The pro-inflammatory neurokinins, SP and CGRP, are present in nerves innervating joints and could significantly contribute to the increased vascular permeability and hyperaemia occurring in acute arthritis. 4. Although perhaps contributing to the pathogenesis of chronic inflammatory joint disease, there is little evidence for involvement of the sympathetic nervous system in acute models of inflammation.

Non-adrenergic, non-cholinergic control of the urinary bladder

In the urinary, bladder, ATP is an excitatory neuromuscular transmitter, possibly a cotransmitter with acetylcholine from postganglionic parasympathetic nerves, which activates P2X-purinoceptors. The synthesis of prostaglandins is closely linked to the activation of P2X-purinoceptors, and these compounds make a significant contribution to non-cholinergic neurogenic responses. Many neuropeptides, such as NPY, VIP, somatostatin, SP and CGRP, are found in nerves innervating the lower urinary tract, but it is unlikely that any is a neuromuscular transmitter in the detrusor; rather, they may act as potent modulators of sympathetic and parasympathetic transmission. Modulatory actions are shown by GABA par excellence; this compound is also well represented in vesicular neurons and, via activation of GABAA- or GABAB-receptors, can potentiate or inhibit parasympathetic transmission. Although not discussed in depth in this review, the urinary bladder shows extraordinary plasticity in expression of nerves and of their transmitters and receptors under pathophysiological conditions, including pregnancy and ageing as well as disease states. Finally, the accessibility of the urinary bladder and the enormous range of chemoreceptors that it possesses has led to its being used extensively for pharmacological investigations of transmitter and drug receptors and their subclasses.

Characterization of the capsaicin-sensitive component of cyclophosphamide-induced inflammation in the rat urinary bladder

1. Cyclophosphamide (CYP) (150 mg kg-1, i.p. 0.5-48 h before) caused a time-dependent plasma protein extravasation in the rat urinary bladder with the maximal extravasation occurring at between 2 and 4 h after administration of the drug. 2. Prior capsaicin desensitization of capsaicin-sensitive primary afferent neurones (CSPANs) (50 mg kg-1, s.c., 4 days before) resulted in approximately 50% inhibition of the magnitude of the extravasation response at the 2 h time-point. 3. Intraperitoneal (i.p.) pretreatment with the tachykinin NK1 receptor antagonist, RP 67,580 (0.44 mg kg-1) or the bradykinin B2 receptor antagonist, Hoe 140 (0.13 mg kg-1) had significant inhibitory effects, giving responses of 56 +/- 6% and 39 +/- 4% of the control extravasation response to CYP treatment after 2 h. Pretreatment with the tachykinin NK2 receptor antagonist, SR 48,968 (0.3 mg kg-1, i.p.), the histamine H1 receptor blocker, chlorpheniramine (10 mg kg-1, i.p.), the 5-HT receptor blocker, methysergide (6 mg kg-1, i.p.) or the cyclo-oxygenase inhibitor indomethacin (5 mg kg-1, i.p.) had no significant effect upon the development of the extravasation response at this same time-point. 4. In rat isolated urinary bladder strips, the active metabolite of CYP, acrolein (1-300 microM) produced a concentration-dependent contraction that was significantly reduced by in vitro capsaicin desensitization (10 microM for 15 min) indicating direct stimulation of CSPANs. CYP was without appreciable effect. 5. The effect of acrolein in vitro was significantly reduced by pretreatment of the bladder with a combination of tachykinin NK1 and NK2 receptor antagonists, RP 67,580 (3 microM) and SR 48,968 (1 microM). The dose-response curve to acrolein was also significantly inhibited by treatment with indomethacin (10 microM) and slightly affected by Hoe 140 (1 microM). 6. These findings demonstrate the contribution of CSPANs to the development of CYP-induced cystitis.Plasma protein extravasation involves activation of tachykinin NKI and bradykinin B2 receptors.Activation of CSPANs in the urinary bladder is likely to be due to the conversion of CYP into its active metabolite, acrolein, and not to a direct effect of CYP upon these nerve-endings.

Role of B1 and B2 receptors and of nitric oxide in bradykinin-induced relaxation and contraction of isolated rat duodenum

Bradykinin (BK) and its analogues induce a typical biphasic response (relaxation followed by contraction) in the isolated rat duodenum. We studied the role of B1 and B2 BK receptors and nitric oxide (NO) in relaxation and contraction of the isolated rat duodenum. Both effects are concentration-dependent: BK has shown an EC50 (contraction) of 3.8 +/- 1.9 x 10(-7) M and an IC50 (relaxation) of 3.0 +/- 0.7 x 10(-9). Similar results were obtained with the selective B2 receptor agonists [Hyp3,Tyr(Me)8]-BK and [Phe8 psi (CH2-NH)Arg9]-BK, showing an EC50 of 9.6 +/- 1.9 x 10(-7) M and 5.6 +/- 2.9 x 10(-7) M and an IC50 of 3.5 +/- 0.6 x 10(-10) M and 6.8 +/- 1.7 x 10(-10) M, respectively. Furthermore, the effects induced by these three agonists were not altered when tissues were treated with 42.1 microM Mergetpa, a carboxypeptidase N inhibitor. While the relaxant and contractile effects elicited by BK were significantly inhibited in the presence of Hoe 140 (0.7 microM), a selective B2 receptor antagonist, those induced by the selective B1 receptor agonist desArg9-BK were not. Furthermore, [Leu8]-desArg9-BK (2.6 microM), which is both a pure and selective B1 receptor antagonist, acted as an agonist on the rat duodenum, inducing a biphasic relaxant and contractile effect. These relaxant and contractile effects were not altered by drugs that inhibit or stimulate NO production, such as L-NAME (200 microM), a combination of L-NAME (200 microM) and indomethacin (2.5 microM), L-arginine (1 mM), or superoxide dismutase (20 U/ml). However, the contractile effect was significantly reduced when tissues were preincubated with methylene blue (100 microM), which inhibits activation of guanylate cyclase. We conclude that 1) BK and its analogues selectively activate a B2 receptor, producing a biphasic effect (relaxation and contraction); 2) DesArg9-BK may either acts via a different receptor which might be another B1 receptor subtype or a typical B1 receptor where [Leu8]-desArg9-BK acts as a partial agonist; and 3) neither NO nor the prostaglandin pathway mediates BK-induced relaxation in the isolated rat duodenum.

The regulatory effect of bradykinin on the actions of sensory nerves in the perfused rat mesentery is mediated by nitric oxide

In the perfused rat mesentery, when adrenergic nerves were blocked with guanethidine and vascular smooth muscle tone was increased with methoxamine, transmural field stimulation caused a dilator response. Bradykinin significantly suppressed vasodilator responses to a transmural field stimulation in a concentration-dependent manner. After pretreatment with saponin to damage endothelial cells, bradykinin still suppressed vasodilator responses to transmural field stimulation. The effect of bradykinin was unaltered by indomethacin. N omega-Nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthesis, abolished the inhibition of vasodilator responses to transmural field stimulation elicited by bradykinin. However, in the presence of L-arginine and L-NAME the inhibitory effect of bradykinin reappeared. Furthermore, methylene blue itself caused potentiation of vasodilator responses to transmural field stimulation and reversed the effect of bradykinin. These findings suggest that bradykinin can produce an inhibitory modulation of the actions of sensory nerves in the perfused rat mesentery and that the effect of bradykinin may be mediated by nitric oxide released from non-adrenergic, non-cholinergic nerves.

Effect of bradykinin and tachykinin receptor antagonist on xylene-induced cystitis in rats

The effects of the bradykinin receptor selective antagonist, Hoe 140, and of the tachykinin NK-1 receptor antagonist (+/-)CP 96,345 were investigated in a rat model of chemically-induced cystitis (intravesical instillation of xylene in female rats). Intravenous injection of bradykinin (1 mumol./kg.) or substance P (3 nmol./kg.) produced plasma protein extravasation (PPE) in the rat urinary bladder. Bradykinin response was prevented by Hoe 140 (100 nmol./kg. intravenously) and unaffected by (+/-)CP 96,345 (10 mumol./kg. intravenously). Plasma protein extravasation produced by substance P was inhibited by (+/-)CP 96,345 but unchanged by Hoe 140. Catheterization required for intravesical xylene instillation into the female rat bladder produced per se an inflammatory response which was abolished by either Hoe 140 or (+/-)CP 96,345. Intravesical instillation of xylene produced a large PPE response which was reduced by about 65% by Hoe 140 or (+/-)CP 96,345. Combined administration of the two antagonists produced an additive effect on the PPE response to xylene. We conclude that both bradykinin and tachykinins are involved in the inflammatory reaction of the rat urinary bladder to catheterization and xylene irritation.

Sensory neuropeptide release by bradykinin: mechanisms and pathophysiological implications

Bradykinin (BK) and related kinins excite primary sensory neurons, thus leading to the activation of sensory impulses. More recently, both functional and neurochemical evidence have been accumulated that BK evokes release of neuropeptides, including calcitonin gene-related peptide and the tachykinins substance P and neurokinin A, from peripheral terminals of capsaicin-sensitive primary afferents. The present article will review the mechanisms and the pathophysiological implications of the ability of BK to release sensory neuropeptides at the peripheral level. An account of the clinical studies performed on this subject will be also given.

Effects of cromakalim on bradykinin-, histamine- and substance P-induced airway microvascular leakage in the guinea-pig

The effects of cromakalim on the increase in microvascular permeability induced by histamine, substance P or bradykinin in guinea-pig airways were studied in vivo. Extravasation of i.v. injected Evans blue dye was used as an index of permeability. We also studied the effects of cromakalim on the contractile effect of substance P, histamine or bradykinin on the isolated guinea-pig main bronchus and on the contractile response of isolated guinea-pig main bronchi to electrical field stimulation. Cromakalim (30 to 300 micrograms.kg-1) did not inhibit the increase in microvascular permeability induced by histamine (30 micrograms.kg-1) in guinea-pig airways and potentiated (30 and 100 micrograms.kg-1) the effects of substance P (0.3 microgram.kg-1) in trachea, main bronchi and proximal intrapulmonary airways. In contrast, cromakalim (30 and 300 micrograms.kg-1) reduced the increase in microvascular permeability induced by bradykinin (0.3 microgram.kg-1). However, a significant potentiation of the effects of bradykinin was observed with cromakalim (100 micrograms.kg-1) in main bronchi and intrapulmonary airways. In the isolated guinea-pig main bronchus, the contractile effects of bradykinin, histamine and substance P were not modified by cromakalim (10(-5) M). Conversely, cromakalim (10(-5) M) significantly reduced both cholinergic and noncholinergic contractile responses induced by electrical field stimulation of the isolated guinea-pig main bronchus. In conclusion, cromakalim can partially inhibit the increase in microvascular permeability induced by i.v. bradykinin. It is suggested that this effect might occur through inhibition of the nonadrenergic noncholinergic excitatory (NANC) nerves preventing release by bradykinin of inflammatory neuropeptides such as substance P.

Evidence for the involvement of bradykinin in chemically-evoked cystitis in anaesthetized rats

The effect of Hoe 140, a potent bradykinin B2 receptor antagonist, on the micturition reflex and detrusor hyperreflexia induced by chemical cystitis has been investigated in anaesthetized rats. Hoe 140 (1-100 nmol/kg i.v.) produced a dose-dependent blockade of the contraction of the rat urinary bladder induced by i.v. administration of bradykinin (100 nmol/kg) without affecting the response produced by the selective tachykinin NK-1 receptor agonist, [Sar9] substance P (SP) sulfone (1 nmol/kg i.v.). At doses which produce selective and long-lasting blockade of bradykinin receptors in the urinary bladder, Hoe 140 did not modify urodynamic parameters in normal rats. Intravesical instillation of xylene in female rats decreased bladder capacity and increased micturition frequency. These effects also occurred in rats pretreated with capsaicin as adults. Hoe 140 did not modify xylene-induced cystitis. Intraperitoneal administration of cyclophosphamide (150 mg/kg, 48 h before) decreased bladder capacity and increased micturition frequency. These effects of cyclophosphamide were abolished in rats pretreated with capsaicin as adults. Hoe 140 increased bladder capacity and decreased micturition frequency in rats pretreated with cyclophosphamide. Addition of bradykinin (10 mumol/l) to the medium in the superfused rat urinary bladder preparation evoked a prompt increase in the outflow of calcitonin gene-related peptide like immunoreactivity (CGRP-LI). Hoe 140 (3 mumol/l) inhibited (by about 50%) the CGRP-LI out-flow stimulated by bradykinin. These findings demonstrate the participation of bradykinin, through B2 receptors, in the genesis of detrusor hyperreflexia during cyclophosphamide-induced cystitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Local motor responses to bradykinin and bacterial chemotactic peptide formyl-methionyl-leucyl-phenylalanine (FMLP) in the guinea-pig isolated renal pelvis and ureter

The local motor response to bradykinin and the bacterial chemotactic peptide, formyl-methionyl-leucyl-phenylalanine (FMLP) was investigated in the guinea-pig isolated renal pelvis and ureter in relation to possible activation of capsaicin-sensitive primary afferent nerves and release of sensory neuropeptides. Both bradykinin (1 nM-10 microM) and FMLP (10 nM-10 microM) produced a concentration-dependent positive inotropic effect in the isolated renal pelvis which was unaffected by in vitro capsaicin desensitization. The response to bradykinin was antagonized by HOE 140, a bradykinin receptor antagonist, while it was unaffected by MEN 10,376, a tachykinin receptor antagonist, hCGRP(8-37) a calcitonin gene-related peptide (CGRP) receptor antagonist and N-t-BOC-Phe-DLeu-Phe-DLeu-Phe (BPLPLP), an FMLP antagonist. The response to FMLP was blocked by BPLPLP while it was unaffected by HOE 140, MEN 10,376 or hCGRP(8-37). Indomethacin (10 microM) enhanced the response to both bradykinin and FMLP. Bradykinin transiently activated rhythmic contractions in the isolated ureter. The response to bradykinin was blocked by HOE 140 and was unaffected by in vitro capsaicin desensitization, indomethacin, MEN 10,376 or BPLPLP. FMLP had no motor effect on the resting ureter but when rhythmic background contractions were evoked by the addition of 100 nM endothelin 1, it produced a transient suppression of ureteral motility. This inhibitory effect was unchanged by in vitro capsaicin desensitization or HOE 140 while it was abolished by indomethacin or BPLPLP pretreatment. Both bradykinin and FMLP evoked the release of CGRP-like immunoreactivity in the renal pelvis. The effect of bradykinin but not that of FMLP was abolished by indomethacin. By contrast neither bradykinin nor FMLP did evoke a significant CGRP-LI release in the ureter. It is concluded that bradykinin and FMLP affect pyeloureteral motility through specific and independent pathways. The local motor responses produced by these chemical stimulants are independent from the release of sensory neuropeptides from capsaicin-sensitive primary afferent neurons. Direct neurochemical evidence was obtained for activation of capsaicin-sensitive primary afferents in the renal pelvis: such a mechanism could be involved in the genesis of ureteral pain whenever bradykinin or FMLP come into contact with sensory nerves in the pyeloureteral wall.

Bradykinin receptors: pharmacological properties and biological roles

Kinins contribute to the acute inflammatory response and are implicated in the pathophysiology of inflammatory disease. The development of therapeutically viable agents that counteract the effects of kinins is, therefore, potentially very rewarding. Since kinin actions are generally mediated via an interaction with cell-surface receptors, one approach is the development of site-specific receptor antagonists. The emphasis in this review is to outline our current understanding of the properties of bradykinin receptors and the potential therapeutic applications for drugs acting at these sites. As a result of the recent introduction of potent bradykinin receptor antagonists and the cloning of bradykinin receptor genes, considerable advances in kinin research can now be confidently anticipated.

Haemodynamic effects of the calcium facilitator Bay K-8644 in rats following vascular calcium overload

1. The haemodynamic effects of the Ca2+ facilitator Bay K-8644 (Bay) were studied in a model of calcinosis induced by acute treatment with vitamin D3 and nicotine administration over 4 days with 13 days of recovery. 2. Calcium content of the left ventricular myocardium increased 8-9 fold, while aortic Ca2+ levels increased up to 12-fold in treated animals. There were minimal changes in the ECG and no change in the level of plasma alpha-hydroxy-butyrate-dehydrogenase, a cardiac specific enzyme which increases during ischaemia. Significant increases in pulse pressure (PP) were seen in anaesthetized and conscious calcinotic rats, with no increase in cardiac output index (DABF) or systemic vascular resistance. However, aortic rigidity (AORI) was significantly elevated in the calcinotic group under anaesthesia. 3. In both control and calcinotic rats, pressor responses to i.v. Bay were exclusively mediated by an increase in aortic blood flow (DABF) as lower body vascular resistance (TLBVR) did not change. The increase in DABF at low doses (0.1-1 microgram kg-1) of Bay probably resulted from an increase in venous return induced by the agonist, as Bay had little effect on cardiac contractility over this dose range (as estimated by left ventricular dp/dtmax) and did not cause tachycardia. At higher doses (10-1000 micrograms kg-1), Bay significantly increased LV dp/dt. Bay caused dose-related increases in AORI in pithed calcinotic rats, but a decrease in AORI in control animals. 4. The calcinosis model, which incorporates a recovery period to obviate the acute effects of nicotine and/or vitamin D3 treatment, results in long-term tissue calcium accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Non-adrenergic non-cholinergic excitatory innervation of the guinea-pig isolated renal pelvis: involvement of capsaicin-sensitive primary afferent neurons

Circular muscle strips from the guinea-pig renal pelvis exhibit a spontaneous activity averaging about 50% of maximal contractile response at a frequency of about six contractions/min. This spontaneous activity is tetrodotoxin resistant. Acetylcholine and noradrenaline (one to 100 microM) produce a positive inotropic effect which was abolished or strongly inhibited by atropine and phentolamine, respectively. Electrical field stimulation (five to 10 Hz, 0.5 ms pulse width for 10 s, 60 V, maximal voltage) produces a transient positive inotropic response which is tetrodotoxin-sensitive but unaffected by atropine and phentolamine alone or in combination, as well as by atropine plus guanethidine. Application of capsaicin produced a large positive inotropic response which was not reproduced upon a second application of the drug (desensitization). After in vitro capsaicin desensitization, the response to electrical field stimulation was abolished, indicating its dependence on activation of peripheral endings of sensory nerves. These findings demonstrate the existence of a non-adrenergic non-cholinergic functional innervation of the guinea-pig renal pelvis which is entirely dependent on sensory nerve activation.

A possible role for urinary bladder epithelium in bradykinin-induced contraction in diabetic rats

Diabetes provokes a greater responsiveness of rat urinary bladder preparations to bradykinin and a greater formation and release of prostaglandin F2 alpha, without affecting prostaglandin E2 release significantly. Inhibition of cyclooxygenase by indomethacin (1 microM) inhibits the contraction elicited by bradykinin and leads to identical contractile responses of control and diabetic urinary bladder strips. Removal of the urinary bladder epithelium does not modify the contractile response evoked by bradykinin in control preparations but significantly decreases the contraction of preparations of diabetic tissues. Quantitatively, the activity of control urinary bladder strips with epithelium and the activity of diabetic preparations without epithelium are the same. More prostaglandin F2 alpha is released into the medium by urinary bladder strips devoid of epithelium in both control and in diabetic rats. These results indicate a role for epithelial cells in the smooth muscle contraction evoked by bradykinin in diabetic rats.

Bradykinin receptors in the guinea-pig taenia caeci are similar to proposed BK3 receptors in the guinea-pig trachea, and are blocked by HOE 140

1. Bradykinin (BK) receptors of the guinea-pig taenia caeci were compared with those of the guinea-pig trachea, a preparation proposed to possess novel BK3 receptors. 2. Bradykinin-evoked contractile responses were unaffected in both preparations by the selective BK1 receptor antagonist [des-Arg9,Leu8]-BK (1 microM-10 microM). The BK2 receptor antagonists, D-Arg-[Hyp3,D-Phe7]-BK and D-Arg-[Hyp3,Thi5,8,D-Phe7]-BK, both had low affinities (apparent pKB estimates less than 6) which did not differ significantly between the two preparations (P greater than 0.05). In contrast, the novel bradykinin receptor antagonist D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]-BK (HOE 140) potently antagonized responses to bradykinin with relatively high affinity (apparent pKB = 8.42 +/- 0.15 and 8.94 +/- 0.16 in the taenia caeci, and trachea, respectively). 3. We conclude that the bradykinin receptors in the guinea-pig taenia caeci have similar recognition properties to those present in the guinea-pig trachea, and in this respect the taenia caeci represents a useful preparation for the further study of proposed novel BK3 receptors.

Putative novel bradykinin B3 receptors in the smooth muscle of the guinea-pig taenia caeci and trachea

The bradykinin receptors mediating contraction in smooth muscle of the guinea-pig taenia caeci were compared with the proposed novel B3 receptors of the guinea-pig trachea. The activities of several antagonists in functional and binding studies were found to be very similar between these two guinea-pig preparations, but pKBs were markedly lower than in a number of typical B2 preparations from other species, suggesting that the characteristics of the proposed B3 receptor may be in part species-related.

Mechanical irritation induces neurogenic inflammation in the rat urethra

A catheter was inserted into the urethral meatus of urethane-anaesthetized rats and rotated (30 rotations/minute) during a three minute period. One hour later, microvascular permeability in the distal urethra was evaluated by means of the Evans Blue leakage technique. Dye extravasation increased significantly (74 +/- 12 ng./mg. of wet tissue weight, p less than 0.05), as compared to control values (18 +/- 2 ng./mg.). The effect of catheterism was prevented by about 50% by systemic pretreatment with capsaicin performed in either adult or newborn rats, as well as by bilateral removal of pelvic ganglia. Furthermore, pretreatment with capsaicin of adult rats, combined to pelvic ganglionectomy, virtually abolished the inflammatory response produced by mechanical irritation of the urethra. These results indicate that: 1) the increase of vascular permeability produced by mechanical irritation is nerve-mediated, 2) capsaicin-sensitive afferents participate in the inflammatory process and 3) capsaicin-insensitive nerves, which pass through the pelvic ganglia, contribute to the overall response.

Bradykinin B2 receptor evoked K+ permeability increase mediates relaxation in the rat duodenum

We have investigated the receptors and associated coupling mechanisms that mediate the smooth muscle relaxant response to bradykinin (BK) in the rat duodenum in vitro. Relaxation in response to BK seems due to a direct action on the longitudinal smooth muscle since effects were demonstrable in the presence of ibuprofen, mepyramine, atropine, guanethidine (all 1 microM), hexamethonium (10 microM) and TTX (0.3 microM). Receptors involved are of the B2 subtype since agonists and antagonists active at B1 receptors were essentially inactive, and the B2 receptor antagonist Lys,Lys-[Hyp3,Thi5,8,D-Phe7]BK was a potent competitive antagonist of BK-induced relaxation (pKB of 7.2 +/- 0.1). The activity of both BK and the antagonist were unchanged by the presence of peptidase inhibitors including the carboxypeptidase inhibitor DL-2-mercaptomethyl-3-guanidinoethylthiopropanoic acid (mergetpa, 10 microM), which prevents conversion of BK analogues to des-Arg9-B1-active products. In high-K+ solution, BK (0.1-10 microM) produced concentration-related increases in 86Rb efflux. Both this permeability increase in high-K+ solution, and the relaxant responses in Krebs solution, were inhibited by low concentrations (10-100 nM) of apamin, as well as the B2 receptor antagonist Lys,Lys-[Hyp3,Thi5,8,D-Phe7]BK (1 microM). These results are compatable with the proposal that BK-evoked relaxation of the rat duodenum is mediated via a subset of B2 receptors for which the antagonist Lys,Lys-[Hyp3,Thi5,8,D-Phe7]BK has a high affinity, and results from stabilisation of the smooth muscle membrane through the opening of apamin-sensitive 86Rb-permeable calcium-activated K+ channels.

Effect of thiorphan on the response of guinea-pig isolated urinary bladder to exogenous and endogenous tachykinins

Thiorphan, a well known inhibitor of 'enkephalinase' (endopeptidase 24.11) potentiated and prolonged the contractile response to substance P (SP) and neurokinin A (NKA) on strips of the guinea-pig isolated urinary bladder and this effect was evident both in presence and absence of the mucosal layer. Thiorphan also enhanced and prolonged the capsaicin-induced contraction in strips from the bladder dome which is thought to be mediated by release of endogenous tachykinins. Exposure to capsaicin produced simultaneous release of SP- and tachykinin-like immunoreactivity both in presence and absence of mucosa. This effect of capsaicin was potentiated by thiorphan. Endopeptidase 24.11 activity was detected in the guinea-pig urinary bladder, being more concentrated in the mucosal than the muscular layer. These findings indicate that endopeptidase 24.11 terminates the activity of tachykinins in the guinea-pig urinary bladder and modulates the intensity of the biological response produced after their release from peripheral endings of sensory nerves.

Bradykinin-induced release of calcitonin gene-related peptide from capsaicin-sensitive nerves in guinea-pig atria: mechanism of action and calcium requirements

The mechanism of neuropeptide secretion induced by bradykinin from capsaicin-sensitive afferents was studied in guinea-pig atria. Both the inotropic response induced by bradykinin (0.1 microM) in the electrically driven isolated guinea-pig left atria and the bradykinin (10 microM)-induced release of calcitonin gene-related peptide calcitonin gene-related peptide-like immunoreactivity from slices of guinea-pig atria were abolished in vitro by capsaicin pretreatment or in the presence of indomethacin. Bradykinin-induced calcitonin gene-related peptide-like immunoreactive release was unaffected by tetrodotoxin (0.3 microM), the protein kinase C inhibitor, 1-(5-isoquinolinesulphonyl)-2-methylpiperazine (30 microM), nefedipine (1 microM) or Ruthenium Red (10 microM). It was significantly reduced by 79% in a Ca2(+)-free medium and by 52% in the presence of 0.1 microM omega-conotoxin (fraction GVIA). It is proposed that bradykinin releases calcitonin gene-related peptide from capsaicin-sensitive afferents in guinea-pig atria, via prostanoid generation. This mode of activation of the "efferent" function of capsaicin-sensitive nerves appears to be distinct from those produced by capsaicin or electrical field stimulation as they have been characterized in previous works. In fact, the bradykinin activation of capsaicin-sensitive afferents is not affected by tetrodotoxin and Ruthenium Red, but is partially sensitive to the selective blocker of N-type Ca2(+)-channels, omega-conotoxin.