The effect of indomethacin and substance P on the guinea pig urinary bladder

Purinergic signalling in the urinary tract in health and disease

Purinergic signalling is involved in a number of physiological and pathophysiological activities in the lower urinary tract. In the bladder of laboratory animals there is parasympathetic excitatory cotransmission with the purinergic and cholinergic components being approximately equal, acting via P2X1 and muscarinic receptors, respectively. Purinergic mechanosensory transduction occurs where ATP, released from urothelial cells during distension of bladder and ureter, acts on P2X3 and P2X2/3 receptors on suburothelial sensory nerves to initiate the voiding reflex, via low threshold fibres, and nociception, via high threshold fibres. In human bladder the purinergic component of parasympathetic cotransmission is less than 3 %, but in pathological conditions, such as interstitial cystitis, obstructed and neuropathic bladder, the purinergic component is increased to 40 %. Other pathological conditions of the bladder have been shown to involve purinoceptor-mediated activities, including multiple sclerosis, ischaemia, diabetes, cancer and bacterial infections. In the ureter, P2X7 receptors have been implicated in inflammation and fibrosis. Purinergic therapeutic strategies are being explored that hopefully will be developed and bring benefit and relief to many patients with urinary tract disorders.

The localization of cyclo-oxygenase immuno-reactivity (COX I-IR) to the urothelium and to interstitial cells in the bladder wall

Localized phasic contractions in the bladder wall (autonomous activity) have been hypothesized to be an integral part of a motor/sensory system contributing to bladder sensation. The sites responsible for generating this activity, the mechanisms involved in its propagation and modulation remain unknown. This phasic motor activity is modulated by exogenous prostaglandins. Therefore, analysis of the sites of prostaglandin production and action within the bladder wall may shed light on the mechanisms of generation and modulation of this phasic activity. In this paper we report the localization of immuno-reactivity indicative of the expression of cyclo-oxygenase enzyme type I (COX I-IR) within the bladder wall. Basically, three types of COX I-IR cell were identified: epithelial cells in the basal and intermediate layers of the urothelium, complex vimentin-positive and COX I-IR cells in the lamina propria and vimentin-negative COX I-IR cells in the lamina propria and on the surface of the inner muscle bundles. These vimentin-negative/COX I-IR cells appear to be in close apposition to a continuous network of vimentin-positive cells, which extends from the lamina propria into the inner muscle layers and subsequently into the outer muscle layers. However, the interstitial cells in this region might form a distinctly different sub-type. First, the interstitial cells in this region differ from those in the inner layer by their responsiveness to NO with a rise in cGMP. Two subtypes have been identified: cells on the surface of the muscle bundles and within the muscle bundles. Second, COX I-IR cells are not associated with the interstitial cells in the outer layers. The physiological significance for these apparent differences in the interstitial cell network is not clear. However, such differences are likely to reflect differences in the processes involved in their activation, modulation and control.

The effects of exogenous prostaglandins and the identification of constitutive cyclooxygenase I and II immunoreactivity in the normal guinea pig bladder

OBJECTIVES

To establish the functional consequences of exposing the isolated whole bladder preparation to exogenous prostaglandins (PGE(1), PGE(2), PGF(2alpha)) and to determine which cells express cyclooxygenase (COX) types I and II, to generate PG to effect these changes in vivo.

MATERIALS AND METHODS

Fifteen female guinea pigs (270-350 g) were used, i.e. seven for structural studies and eight for physiological measurement. For the structural study pieces of the lateral wall were incubated separately in Krebs' solution at 36 degrees C, gassed with 95% O(2) and 5% CO(2) with 1 mm isobutyl-methyl-xanthene. Individual pieces were then exposed to 100 microm of the nitric oxide (NO) donor NONOate for 10 min; control tissues remained in Krebs' solution. Tissues were then fixed in 4% paraformaldehyde. For the physiological experiments bladders were isolated and a cannula inserted into the urethra to monitor intravesical pressure. The bladders were suspended in a chamber containing carboxygenated physiological solution at 33-36 degrees C. All drugs were added to the abluminal bladder surface.

RESULTS

In the resting bladder there were small spontaneous transient rises in pressure, i.e. autonomous activity. Exposure to PGE(2) (3-300 nM) resulted in an increase in basal pressure on which were superimposed autonomous activity, which was increased both in amplitude and frequency. The changes in the amplitude and frequency depended on the concentration of PGE(2). After a brief exposure (240 s) to PGE(2) the augmentation of the autonomous activity continued for >60 min despite regular washing. The responses were similar with PGE(1) but the responses to PGF(2alpha) and arachidonic acid were reduced. The augmented activity was reduced by the EP1/EP2 receptor blocking agent AH6809 (10 microm). Using an antibody to the 70 kDa constitutive form (COX I), COX I immunoreactivity (COX I-IR) was located in cells in the basal urothelium, in lamina propria and cells on the surface of the inner muscle bundles. There were few COX I-IR cells associated with the outer muscle bundles. The COX I-IR cells lying within the lamina propria were distinct from the suburothelial cells which respond to NO with an increase in cGMP. The lamina propria COX I-IR cells appeared to form a network surrounding muscle trabeculae within the inner muscle layer. COX II-IR was associated with the nuclei of cells in the urothelium, lamina propria and muscle.

CONCLUSIONS

These data show that PGs regulate autonomous activity. Potential sources of endogenous PG were identified. It is unclear how the PGs produced by these cells alter autonomous activity. There might be a direct activation of the muscle by PGs released by the network of superficial muscle interstitial cells, or PG released from the urothelium might influence phasic contractile activity via networks of COX I-IR interstitial cells. The possible roles and importance of this mechanism for bladder physiology and pathology are discussed.

NK2 tachykinin receptors mediate contraction of the pig intravesical ureter: tachykinin-induced enhancement of non-adrenergic non-cholinergic excitatory neurotransmission

The current study was designed to characterize the functionally active tachykinin receptors involved in tachykinin-elicited contractions in the pig intravesical ureter, and to investigate the possible modulation exerted by the natural tachykinins substance P (SP) and neurokinin A (NKA) on the non-adrenergic non-cholinergic (NANC) excitatory ureteral neurotransmission. In pig intravesical ureteral strips pretreated with phosphoramidon (10(-5) mol/L) to block the endopeptidase activities, isometric force recordings showed that SP, NKA, and the NK2 receptor selective agonist [beta-Ala(8)]-NKA (4-10), all three induced contractions, with the following potency order: NKA > [beta-Ala(8) ]-NKA (4-10) > SP. [Sar(9), Met(O(2))(11)]-SP and senktide, selective agonists of the NK1 and NK3 receptors, respectively, failed to modify the ureteral tone. Urothelium removal and incubation with tetrodotoxin (10(-6) mol/L), phentolamine (10(-7) mol/L), propranolol (3 x 10(-6) mol/L), atropine (10(-7) mol/L) and indomethacin (3 x 10(-6) mol/L), did not alter the contraction induced by a submaximal (10(-7) mol/L) dose of [beta-Ala(8)]-NKA (4-10). MEN 10,376 (10(-8)-10(-7) mol/L), a NK2 receptor antagonist, reduced the contraction to 3 x 10(-8) mol/L NKA. GR 82334 (10(-6) -10(-5) mol/L) and SR 142801 (10(-8)-10(-7) mol/L), selective antagonists of the NK1 and NK3 receptors, respectively, did not modify that contraction. In pig intravesical ureteral strips in NANC conditions, SP and NKA induced a potentiation of the contractions to electrical field stimulation (EFS) and to exogenous ATP. The results suggest that the tachykinins evoke a direct contraction of pig intravesical ureteral strips through NK2 receptors located in the smooth muscle. SP and NKA exert an enhancement of the NANC excitatory neurotransmission of the pig intravesical ureter.

Evaluation of the role of neurolinins and urecholine hypersensitivity in an animal model of infravesical outflow obstruction

OBJECTIVES

To determine whether detrusor muscle strips from a male rat with infravesical outflow obstruction model demonstrate supersensitivity to parasympathomimetic and neurokinin NK-1 and NK-2 selective agonists.

METHODS

Bladder instability developed after 6 weeks of partial urethral obstruction. The micturition frequency and voided volume were determined in unanesthetized animals. Detrusor hypertrophy was confirmed by evaluation of bladder weight. In vitro organ bath was used to compare the affinity and maximal activity of bethanechol and neurokinin NK-1 and NK-2 selective agonists on strips from the detrusor muscle of sham and obstructed rats. Bethanechol, N-Ac[Arg6, Sar9, Met(O2)]-SP(6-11), and [beta-Ala8]-NKA(4-10) were used to characterize cholinergic muscarinic, neurokinin NK-1 and NK-2 receptors. Results. No significant differences in affinities and maximal responses were found using 10-mg detrusor muscle strips with each of the three agonists.

CONCLUSIONS

Bladder instability produced by outlet obstruction does not involve changes in the affinity or maximal activity of cholinergic muscarinic, neurokinin NK-1 and NK-2 receptors. Furthermore, detrusor supersensitivity to neurokinins or bethanechol was not seen. This suggests that bladder instability is not due to an increased affinity or maximal response to neurokinins or parasympathomimetics.

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.

Capsaicin-induced bladder hyperactivity in normal conscious rats

Capsaicin, instilled intravesically in normal, unanesthetized rats induced a concentration-dependent bladder hyperactivity, which could be abolished by hexamethonium, given intra-arterially near the bladder, or by morphine administered intrathecally. The effect was reversible and could be repeated. The NK-2 receptor selective antagonist SR 48,968 and the nonselective NK receptor antagonist spantide, given intra-arterially near the bladder, which by themselves, in the concentrations used, did not affect cystometric parameters, both counteracted the capsaicin-induced hyperactivity, whereas the NK-1 receptor selective antagonist RP 67,580 failed to do so. Blockade of tachykinin receptors in the urinary bladder does not seem to produce changes of the micturition reflex associated with bladder filling in the conscious rat. However, tachykinins released from capsaicin-sensitive nerves by various stimuli may, through stimulation of NK-2 receptors, lower the threshold for initiation of the micturition reflex. In the rat, intravesical capsaicin may be a suitable model for studies of afferent activity caused by stimuli releasing peptides from sensory nerves in the bladder, thereby provoking bladder hyperactivity.

Muscarinic supersensitivity in the rat urinary bladder after capsaicin pretreatment

The effects of capsaicin on urinary bladder function have been investigated in adult rats. Ten days after capsaicin treatment immunocytochemical investigations showed a nearly complete disappearance of substance P (SP) and calcitonin gene-related peptide (CGRP) in all parts of the bladder. Recordings of micturition patterns and cytometrical investigations in conscious animals revealed no functional effects of capsaicin treatment. In-vitro experiments showed that the contractile response to substance P was similar before and after capsaicin treatment and CGRP exerted no contractile effects on the urinary bladder in either group of rats. The concentration-response curve to carbachol as well as the frequency-response curve to electrical stimulation were significantly shifted to the left in bladder muscle after capsaicin treatment. However, the maximal responses were similar in control and capsaicin-treated bladders. In the presence of scopolamine the maximal response to electrical stimulation was clearly lower in bladders subjected to capsaicin treatment than in controls. In conclusion, depletion of substance P and CGRP in the rat urinary bladder by capsaicin induced no supersensitivity to these peptides. However, the increased sensitivity to carbachol and to electrical stimulation seen after capsaicin treatment indicates the development of a supersensitivity to muscarinic receptor stimulation. Despite this supersensitivity in vitro no functional effects of capsaicin treatment were found in vivo.

The effects of purine nucleotides on transmission in vesical parasympathetic ganglia of the cat

1. In adult cats, postganglionic nerve fibres on the surface of the bladder were isolated and multiunit activity of these fibres was recorded. In these cats, the urinary bladder was cannulated and intravesical pressure was also recorded. 2. ATP, APPCP, ADP, AMP and adenosine depress transmission in vesical parasympathetic ganglia equipotently; however, 2-chloroadenosine was 10-fold more potent than ATP. 3. 2-chloroadenosine, ATP, ADP, AMP, adenosine and APPCP inhibit neurally evoked bladder contractions in the same order or potency with which they depress pelvic ganglionic transmission; however, adenine, inosine, IMP and ITP were ineffective. 4. 3',5'-cyclic AMP and dibutyryl cAMP produced little or no effect on bladder activity. 5. ATP and APPCP produced a transient rise in intravesical pressure at doses 2 to 50 times the dose needed for inhibition, presumably through ATP (P2) receptors. APPCP was 10 to 20 times more potent in exciting the bladder than ATP. 6. Theophylline and caffeine effectively antagonized purinergic effects mediated through adenosine (P1) receptors on both pelvic ganglia and bladder smooth muscle. 7. ATP inhibition of TMA-evoked bladder contractions and postganglionic nerve firing suggests that purinergic inhibition occurs, at least in part, at a postsynaptic site in the ganglia.

Dual capsaicin effects on ureteric motility: low dose inhibition mediated by calcitonin gene-related peptide and high dose stimulation by tachykinins?

The effects of capsaicin, in relation to substance P (SP), neurokinin A (NKA), neuropeptide K (NPK) and calcitonin gene-related peptide (CGRP) which coexist in local sensory nerves, on the motility of the guinea-pig ureter were studied in vivo and in vitro. Capsaicin in a low dose (10 nmol kg-1) given i.v. inhibited spontaneous, peristaltic contractions, as revealed by perfusion-pressure changes of the constantly perfused ureter in vivo. This action was independent of autonomic reflexes and prostaglandin formation. Capsaicin stimulated ureteric motility at higher doses (100 and 500 nmol kg-1). The dual effects of capsaicin on the ureteric contractility were absent 2 weeks after systemic capsaicin treatment, which depletes sensory neuropeptides. Both NKA and NPK initiated, as well as increased, the magnitude of the peristaltic contractions of the ureter, while SP only caused a minor excitatory effect. The CGRP inhibited spontaneous, as well as NKA- and NPK-induced ureteric peristaltic contractions. In vitro experiments on the ureter revealed that capsaicin (10(-6) M) induced phasic circular muscle contractions in 60% of the experiments. Neurokinin A, NPK and SP consistently increased the contractile activity. The NKA tachyphylaxis inhibited the contractile response to other tachykinins and capsaicin. The SP analogue Spantide (/D-Arg1, D-Trp7,9, Leu11/-SP) inhibited the contractile responses to SP, NKA and NPK. The CGRP also inhibited the NKA- and NPK-induced contractions of the ureter in vitro. In conclusion, capsaicin, which induces the release of mediators from sensory nerves within the ureter, has either stimulatory or inhibitory effects on ureteric smooth muscle, depending on the in vivo dose administered. The inhibitory response at a low capsaicin dose is similar to the effect of CGRP, while the contractile effects at higher doses resemble the response to tachykinins.

Intramural neurons of the guinea-pig urinary bladder: histochemical localization of putative neurotransmitters in cultures and newborn animals

Histochemical methods have been used to study the distribution of putative neurotransmitters in the urinary bladder of newborn guinea-pigs and in cultures of intramural ganglia. Following the nicotinamide adenine dinucleotide (NADH)-diaphorase reaction which specifically labels nerve cell bodies, up to 66 ganglia were observed in stretch preparations of the newborn urinary bladder. Each ganglion contained 2-50 nerve cell bodies. Vasoactive intestinal polypeptide was localized in a few nerve cell bodies of intramural ganglia both in in situ and culture preparations. In the in situ preparations it was widely distributed in nerve fibres to the muscle, being most dense at the base of the bladder, and in some mucosal epithelial cells. Somatostatin was contained in numerous neuronal cell bodies in the detrusor muscle both in situ and in culture. Extensively distributed varicose fibres were found in culture and in the muscle, submucous and mucosal layers in situ. Substance P immunofluorescence was demonstrated in a few neuronal cell bodies in ganglia both in situ and in vitro, particularly in those of the mucosa at the base of the bladder. In the in situ preparations varicose nerve fibres containing substance P were seen in the muscle coats with greatest density in the bladder base. Met-enkephalin-immunoreactive nerve cell bodies were not seen either in situ or in culture. Nerve fibres in in situ preparations were found largely enveloping neuronal cell bodies within the ganglia. Neither serotonin-immunoreactive nor catecholamine-containing neuronal cell bodies were seen in the in situ bladder preparation. However, some nerve cell bodies in culture showed positive staining, possibly as a result of selective uptake of serotonin and catecholamine known to be contained in foetal calf serum in the culture medium or possibly as the result of increased synthetic activity in certain neurones in the culture situation. In whole-mount stretch preparations, no serotonin-immunoreactive nerve fibres were seen, but catecholamine-containing small intensely fluorescent cells and nerve fibres were observed. Acetylcholinesterase-positive nerve cell bodies and nerve fibres were observed both in in situ and culture preparations of the bladder. Quinacrine-positive nerve cell bodies (as an indicator of purinergic neurones) were found in numerous intramural neurones examined. in situ; however, under the culture conditions used, non-selective staining of all cell types occurred.

Three-dimensional distribution of substance P-like immunoreactivity in the urinary bladder of rat

The overall distribution of substance P-like immunoreactive (SPI) fibers in the rat urinary bladder was examined by means of frozen sections and whole mount preparations. Two types of SPI fibers entered the urinary bladder from the neck; one forming thick fiber bundles and the other around the blood vessels. These SPI fiber bundles branched into several thinner segments which often project many collaterals to the smooth muscle and submucosal layers. In the smooth muscle layer, single SPI fibers were seen running parallel to both longitudinal and circular muscle bundles. They appeared to be evenly distributed in the smooth muscle layer. SPI fiber bundles located in the circular muscle layer dissociated SPI fibers which entered the submucosal layer, where they directed to the epithelium and formed a meshwork just beneath it. SPI fibers often left the meshwork to enter the epithelium where abundant arborization of fine SPI fibers was seen. The density of SPI fibers in the submucosal layer and epithelium was not even. The highest density was identified in the neck and the trigonum area.

A comparative study of electrical field stimulation of the guinea-pig, ferret and marmoset urinary bladder

The spontaneous and electrically evoked activity was examined in guinea-pig, ferret and marmoset urinary bladder. Electrical field stimulation of detrusor strips in vitro induced a rapid, frequency-dependent contraction with a maximum response at 40 Hz. This contraction was partly decreased by either atropine (0.29 microM) or desensitisation to alpha, beta-methylene ATP (alpha, beta-MeATP) (5 microM), and was totally blocked by a combination of the two. Atropine blocked responses to carbachol (30 microM) but not to ATP (80 microM), whereas desensitisation to alpha, beta-MeATP blocked those to ATP but not to carbachol. The nature of the excitatory neurotransmission mechanism in the bladder of those species examined in the present experiments was shown to be similar to that of other species described previously.

Evidence against VIP or substance P being the transmitter in non-cholinergic excitatory nerves supplying the guinea-pig bladder

In the guinea-pig bladder, contractile responses to substance P (0.3 microM) and VIP (3 microM) were unaffected by P2-purinoceptor desensitization with alpha,beta-methylene ATP (3 X 10(-6) M), while the responses to stimulation of the non-cholinergic excitatory nerves (4-16 Hz) were abolished. The evidence presented suggests that ATP or a related purine nucleotide, and not VIP or substance P, is responsible for the non-cholinergic excitatory component of the nerve-mediated response.

Interaction of tachykinins with an adrenergic receptor in the rat urinary bladder

The rat urinary bladder was examined as a model for studying tachykinin receptors. The order of potency, the maximal effect and the slope of the dose-response curve were examined with six tachykinins - substance P (SP), physalaemin, phyllomedusin, uperolein, eledoisin, kassinin - and several substance P fragments - SP-(2-11), SP-(3-11), SP-(4-11) and SP-(6-11). The tachykinin receptor on the rat urinary bladder was shown to bind preferentially tachykinins having a hydrophilic amino acid residue in position 5-6, as occurs with physalaemin, phyllomedusin, eledoisin and kassinin. The N-terminal of the tachykinins and in particular substance P is suggested to play a major role in regulating affinity, intrinsic activity and the slope of the dose-response curve. The tachykinins are thought to exert a direct action on smooth muscle. An accessory binding site associated with the tachykinin receptor on rat urinary bladder was also identified. This accessory site binds the N-terminal amino acids of the tachykinins as well as some alpha-adrenergic compounds (phentolamine, prazosin, noradrenaline or adrenaline in the presence of propranolol). When the accessory binding site is occupied by adrenergic compounds, the affinity of the tachykinins is markedly reduced. This observation is interpreted to mean that catecholamines may have a modulatory influence on tachykinin activity on the rat urinary bladder.

The effects of topical capsaicin on rat urinary bladder motility in vivo

The effects of topical capsaicin on urinary bladder motility were investigated following saline-induced distension of the bladder wall in urethane-anaesthetized rats and compared to the effects of topical substance P and acetylcholine. Capsaicin and substance P produced similar excitatory effects in both quiescent and rhythmically contracting bladders, i.e., a TTX resistant tonic contraction followed by a series of rhythmic, TTX sensitive, phasic contractions. Acetylcholine, in doses equieffective in producing TTX resistant contractions was less effective than capsaicin or substance P in triggering neurogenic rhythmic contractions of bladder muscle. Atropine pretreatment prevented the neurogenic component of the excitatory effect of both capsaicin and substance P. Repeated applications of capsaicin but not of substance P led to desensitization. Bladders of animals pretreated (4 days before) with a large dose of s.c. capsaicin developed insensitivity to topical capsaicin and a larger volume of saline was required to trigger neurogenic rhythmic contractions of the detrusor muscle. These results suggest that capsaicin acts by interfering with the mechanism(s) regulating the threshold for the micturition reflex to occur.

A study of [D-Pro2, D-Phe7, D-Trp9]-substance P and [D-Trp7,9]-substance P as tachykinin partial agonists in the rat colon

Two substance P (SP) analogues, [D-Pro2, D-Phe7, D-Trp9]-SP (DPDPDT) and [D-Trp7,9]-SP (DT79), previously described as tachykinin antagonists, have been shown to contract the rat colon muscularis mucosae preparation. The maximum response exhibited by these analogues was about 30% that of the SP maximum, suggesting that they were acting as partial agonists relative to SP. The responses to DPDPDT were unaffected by pretreatment with mepyramine, methysergide or [Sar1, Ile5, Ala8]-angiotensin II, which abolished the responses to histamine, 5-hydroxytryptamine (5-HT) and angiotensin II, respectively. Methysergide also did not affect the responses to DT79; the other antagonists were not tested against this analogue. Indomethacin and cimetidine also had no inhibitory effect. Atropine (2 microM) was present in all experiments to prevent indirect muscarinic effects. Phenoxybenzamine did not affect the dose-response curves to SP, eledoisin-related peptide (ERP), kassinin, eledoisin or physalaemin, nor did it affect the responses to individual doses of DPDPDT or DT79. However, in the absence of atropine, it shifted the carbachol dose-response curve markedly to the right, and reduced its maximum. The tachykinin antagonist [D-Pro4, D-Trp7,9,10]-SP4-11 reduced the responses to individual matched doses of DPDPDT, DT79 and SP to the same degree, whilst leaving responses to 5-HT or angiotensin II unaffected. This suggested that DPDPDT and DT79 were acting at the same receptor as SP. The inhibitory effects of DPDPDT on responses to SP, ERP and kassinin, and that of DT79 on responses to SP, were analysed. All four combinations yielded data compatible with an interaction at only one receptor, although DPDPDT appeared slightly more potent at inhibiting responses to kassinin. The results are discussed in the light of the proposed existence of multiple tachykinin receptor subtypes. The possible influence of differential metabolism of tachykinin analogues is also considered.

A study of the atropine-resistant component of the neurogenic response of the rabbit urinary bladder

Rabbit bladder body was stimulated to contract by a number of agonists, of which bradykinin was the most potent, and ATP one of the least potent substances tested. The atropine-resistant component of the neurogenic response was unaffected by 2 X 10(-5) M chlorpheniramine or 10(-6) M methysergide, doses which suppressed responses to histamine or 5HT. Indomethacin 10(-5) M, or 10(-5) M capsaicin both reduced the atropine-resistant component. Following treatment with 10(-6) M atropine and 10(-5) M prazosin, 10(-4) M ANAPP3 produced a further suppression of the response, but did not antagonize the response to ATP. In the bladder body, the transmitter(s) responsible for the neurogenic response may be acetylcholine and prostaglandins and possibly ATP and substance P.

Sensory substance P-innervation of the urinary bladder: possible site of action of capsaicin in causing urine retention in rats

In rats treated neonatally with capsaicin there is, in later life, a tendency tendency towards urine retention. Since capsaicin is known to cause irreversible loss of certain primary sensory neurons, notably those containing substance P, we have studied the sensory innervation of the bladder in capsaicin-treated and control rats using retrograde tracing methods and immunohistochemistry; in addition, the motor function of the bladder was assessed in in vitro experiments, using electrical field stimulation. Five days after injection of the fluorescent tracer True Blue into the wall of the bladder, numerous labelled cells were identified in dorsal root ganglia T13, L1, L2, L6, and S1 and smaller numbers of cells were found in T12 and L3. In capsaicin-treated rats the numbers of labelled cells were reduced by over 50% in L1, L6 and S1. In control rats, 10-16% of True Blue labelled cells also contained substance P as demonstrated by indirect immunofluorescence, but in capsaicin-treated rats substance P cells were virtually absent. In in vitro studies, contractions of the detrusor muscle to electrical field stimulation, both before and after atropine, were similar in control and capsaicin-treated rats. We suggest that capsaicin causes urine retention in rats due to an impairment of sensory transmission from the bladder (that could involve substance P) and a consequent failure in the normal micturition reflexes.

The substance P content of peripheral tissues in several mammals

Levels of substance P immunoreactivity (SPI) were determined in several skin and mucosal areas, in parts of the sympathetic nervous system, the urinary, biliary and respiratory systems of cats, rabbits and guinea-pigs, and in various skin and mucosal areas of humans by radioimmunoassay. Salient findings are (1) The general distribution pattern of SPI in rabbits was similar to that in rodents. (2) The highest SPI tissue levels were found in the sympathetic nervous system, notably in guinea-pigs. (3) The guinea-pig also had the highest SPI levels in ureter, urinary bladder and bile duct. (4) The aorta, pulmonary artery and portal vein of the rabbit contained very low amounts of SPI, the concentration in the carotid sinus being several fold higher. (5) Skin SPI content was generally highest in the cat, especially in the hindpaw-pad, and lowest in abdominal and back skin. (6) SPI levels found in postmortem human skin and mucosal samples are comparable to those found in other mammals. The observations are discussed in view of the sensory innervation of the various tissues.