Bladder Activity In Rats Research Articles

Effects of a selective androgen receptor modulator (SARM), GSK2849466A, on stress urinary incontinence and bladder activity in rats with ovariectomy-induced oestrogen deficiency.

To report the effect of a selective androgen receptor modulators (SARMs) on the urethral continence mechanisms in a rat model of stress urinary incontinence (SUI) induced by bilateral ovariectomy (OVX). Female Sprague-Dawley rats with bilateral OVX were used. Rats were divided into five groups; sham operated, vehicle-treated OVX, low-dose SARM-treated OVX (GSK2849466A: 0.005mg/kg/day, per os [p.o.]), high-dose SARM-treated OVX (GSK2849466A: 0.03mg/kg/day, p.o.) and dihydrotestosterone (DHT)-treated OVX (1mg/kg/day, subcutaneous) groups. After 4weeks of SARM treatments or 3weeks of DHT treatment (6weeks after OVX), rats were subjected to evaluation of the sneeze-induced continence reflex using microtransducer-tipped catheter methods, sneeze-induced leak-point pressure, and continuous cystometry measurements, followed by histological analyses of urethral tissues. (i) OVX significantly impaired urethral continence function after 6weeks to induce SUI during sneezing. (ii) Low-dose SARM treatment restored urethral baseline pressure (UBP) without affecting the amplitude of urethral response during sneezing (A-URS), partially reversing OVX-induced SUI during sneezing. (iii) High-dose SARM treatment reversed decreases in both UBP and A-URS, more effectively preventing SUI during sneezing. (iv) DHT treatment only restored A-URS without affecting UBP, partially preventing OVX-induced SUI during sneezing. (v) The high-dose SARM treatment induced hypertrophy of the striated and smooth muscle around the urethra. (vi) SARM treatment did not affect bladder function in sham or OVX rats. Treatment with SARMs could be a more effective modality for the treatment of SUI than DHT, without affecting bladder function, by enhancing smooth- and striated muscle-mediated urethral function under stress conditions such as sneezing.

Mechanisms underlying the effects of propiverine on bladder activity in rats with pelvic venous congestion and urinary frequency.

We investigated the mechanisms by which propiverine hydrochloride influenced bladder activity in rats with pelvic venous congestion (PC) and urinary frequency. To create PC rats, female rats were anesthetized with isoflurane and the bilateral common iliac veins and bilateral uterine veins were ligated. At 4 weeks after ligation, we assessed voiding behaviour, locomotor activity, and urinary 8-hydroxydeoxyguanosine (8-OHdG) and nitric oxide metabolites (NOx). We also performed cystometry and measured mRNAs for nitric oxide synthase (NOS) and several receptors in the bladder wall. PC rats showed a decrease in locomotor activity and an increased frequency of urination. There was a decrease in endothelial NOS (eNOS), M3, and TRPV1 mRNA expression in the bladder wall, as well as an increase in inducible NOS (iNOS) mRNA. Administration of propiverine to PC rats increased locomotor activity to the level in sham rats, improved bladder function, decreased urinary 8-OHdG excretion, and increased urinary NOx excretion. In addition, propiverine increased neuronal NOS (nNOS) mRNA expression, and decreased expression of iNOS, M3 and TRPV1 mRNA in the bladder wall. Therefore, propiverine not only improved bladder dysfunction through its previously reported actions (anti-muscarinic effect, Ca antagonist effect, and inhibition of noradrenaline re-uptake), but also by reducing inflammation.

Injecting RNA interference lentiviruses targeting the muscarinic 3 receptor gene into the bladder wall inhibits neurogenic detrusor overactivity in rats with spinal cord injury.

To investigate the effects of injecting RNA interference (RNAi) lentiviruses targeting the muscarinic 3 (M3 ) receptor gene into the bladder wall on bladder activity in rats with spinal cord injury (SCI). Four M3 RNAi lentiviruses were constructed and used to infect primary cultured bladder smooth muscle cells (BSMCs). Western blotting and quantitative reverse transcription polymerase chain reaction (qRT-PCR) were performed to determine the optimal RNAi lentivirus with the highest interference efficiency. Female Wistar rats were subjected spinal cord transection at T9-10 and randomly divided into three groups (n = 8), namely, blank control, negative control, and experimental groups, and injected into the bladder wall with saline, negative control shRNA, and M3 RNAi lentiviruses, respectively, 1 week after spinal cord transection. The normal rats were used as normal control group. Urodynamic parameters and bladder tissues were evaluated in the different groups. An M3 RNAi lentivirus with the highest interference efficiency (78.9%) was constructed and identified. Three weeks after injecting M3 RNAi lentiviruses into the bladder wall, Western blotting and qRT-PCR showed that the M3 receptor was significantly downregulated in the experimental group. Cystometric evaluation suggested that downregulating M3 receptor expression could substantially decrease basal pressure, residual volume, and non-voiding contraction number, increase intercontraction interval, and significantly improve bladder compliance in rats with SCI. Injecting RNAi lentiviruses targeting the M3 receptor gene into the bladder wall could effectively inhibit neurogenic detrusor overactivity (NDO) due to SCI. Thus, this approach may be a potential treatment for NDO in SCI.

Effects of silodosin on bladder activity in rats with frequent urination induced by pelvic venous congestion.

To examine the effects of silodosin on bladder activity using female rats with frequent urination induced by pelvic venous congestion. A total of 24 female rats were divided into three groups: sham, pelvic venous congestion and pelvic venous congestion/silodosin group. Rats in the pelvic venous congestion and pelvic venous congestion/silodosin groups were anesthetized with isoflurane, after which the bilateral common iliac veins and uterine veins were ligated. In the pelvic venous congestion/silodosin group, silodosin (0.3 mg/kg/day) was given using an osmotic pump implanted into the subcutaneous space of the back. After 5-6 weeks, analysis of voiding behavior, measurements of urinary 8-hydroxydeoxyguanosine and nitric oxide metabolites, continuous cystometry under urethane anesthesia, and Evans blue dye extravasation test of the bladder were carried out. In comparison with sham rats, pelvic venous congestion rats showed an increase in urination frequency with a concomitant increase in urine volume, a shorter interval between bladder contractions on continuous cystometry, an increase in urinary 8-hydroxydeoxyguanosine, a decrease in urinary nitric oxide metabolites and an increase in vesical vascular permeability. In comparison with pelvic venous congestion rats, pelvic venous congestion/silodosin rats showed a decrease in urination frequency with a concomitant decrease in urine volume, a lower maximum bladder contraction pressure, a longer interval between bladder contractions, an increase in urinary nitric oxide metabolites and a decrease in vascular permeability. Silodosin might improve both bladder dysfunction caused by pelvic venous congestion, and the pelvic venous congestion itself.

Effect of Ethanol Root Extract of <i>Equisetum arvense</i> (L) on Urinary Bladder Activity in Rats and Analysis of Principal Plant Constituents

Purpose : To investigate the mechanism of action by which ethanol root extract of Equisetum arvense influences urinary bladder activity in rats, and to characterize the major compounds of the extract. Methods: Ethanol (95 %) was used for hot extraction for 3 h in a Soxhlet extraction apparatus. A total of 36 female rats were divided into Equisetum arvense root extract-treated group (EA) and control group. Rats in EA group were treated with a standard diet containing 0.2 % of the extract, while rats in the control group were fed with the diet only. After 3 weeks, 12 rats underwent cystometry with 0.2 % acetic acid solution and bladder activity was recorded. In another 12 rats, blood pressure, body weight and adenosine triphosphate were measured. In the remaining 12 rats, 0.2 % acetic acid solution was infused into the bladder and urinary adenosine triphosphate determined before and after the stimulation. Results: The results showed that during cystometry with acetic acid, the time interval between urinary bladder contractions was shorter and maximum bladder contraction pressure was much greater in rats in the control group, but in the Equisetum arvense group, the changes were much lower. Also in the Equisetum arvense group, plasma adrenaline and noradrenaline levels were lower than for the control group. Furthermore, increase in the levels of urinary adenosine triphosphate was smaller in Equisetum arvense group than in control group. Conclusion: This study suggests that Equisetum arvense ethanol root extract influences urinary bladder activity by decreasing adenosine triphosphate release, and is therefore a potential therapeutic agent against bladder disorder. However, there is need for further investigation of its exact mechanism of action.

Effects of Duloxetine on Urethral Continence Reflex and Bladder Activity in Rats with Cerebral Infarction

We investigated the effect of duloxetine, a norepinephrine and serotonin reuptake inhibitor, on the sneeze induced continence reflex and on bladder function in rats with cerebral infarction. Using urethane anesthesia the effect of duloxetine (1 mg/kg intravenously) on the amplitude of urethral responses during sneezing as well as urethral baseline pressure at the mid urethra was evaluated in normal female adult rats and cerebral infarction rats. Tilt leak point pressure was also measured. In normal and cerebral infarction rats continuous cystometry was evaluated before and after duloxetine injection. In cerebral infarction rats urethral baseline pressure was 43% lower than in normal rats but the amplitude of urethral responses during sneezing did not differ in the 2 groups. Duloxetine increased the amplitude of urethral responses during sneezing and urethral baseline pressure by 31% and 21%, respectively, in normal rats but did not affect either in cerebral infarction rats. Also, in cerebral infarction rats leak point pressure was 29% lower compared with normal rats. Duloxetine increased leak point pressure in normal rats but not in cerebral infarction rats. Cerebral infarction reduced intercontraction intervals without affecting the amplitude of bladder contractions compared with normal rats. Duloxetine prolonged intercontraction intervals in cerebral infarction rats but not in normal rats. These results suggest that cerebral infarction induces not only bladder overactivity but also stress urinary incontinence, which may account for mixed incontinence in patients with cerebral infarction. After cerebral infarction duloxetine reduced bladder overactivity but failed to enhance active urethral closure mechanisms during sneezing, suggesting that disorganization of the brain network after cerebral infarction might influence the effect of duloxetine on lower urinary tract function.

Roles of adenosine A1 and A2A receptors in the control of micturition in rats

Adenosine is a neurotransmitter that exerts numerous physiological effects in many organs. However, few studies have focused on the role of adenosine receptors in the control of micturition. Therefore, we examined the role of adenosine A1 and A2A receptors in the control of bladder activity in rats with normal or acetic acid (AA) irritated bladders. Cystometrograms during saline or 0.2% AA infusion were recorded under urethane anesthesia in female Sprague-Dawley rats. After a stabilization period, CCPA (A1 receptor agonist) and/or ZM24138 (A2A receptor antagonist) were administered intravenously (i.v.), intrathecally (i.t.), intracerebroventricularly (i.c.v.), or intravesically. Micturition parameters were recorded and compared before and after drug administration. I.v., i.t., or i.c.v. administration of CCPA or ZM24138 significantly increased intercontraction intervals (ICIs) in both saline and AA infusion groups. During AA infusion, the inhibitory effects induced by i.c.v. CCPA or i.t. ZM24138 were significantly greater than those by i.t. or i.c.v. administration, respectively. Intravesical administration of CCPA, but not ZM24138, significantly increased ICI. These results indicated that: (1) when nociceptive signals from the bladder increase, adenosine A1 receptor-mediated inhibition of micturition is enhanced in the brain, compared to the normal condition, (2) A1 receptor activation also exerts a peripheral inhibitory effect on micturition, and (3) adenosine A2A receptor-mediated excitatory mechanisms are enhanced in the spinal cord following C-fiber bladder afferent stimulation. Thus adenosine A1 receptor agonists and A2A receptor antagonists might be effective for the treatment of overactive bladder and/or bladder hypersensitive disorders, in which C-fiber afferent function is enhanced.

Improvement by Phytotherapeutic Agent of Detrusor Overactivity, Down-Regulation of Pharmacological Receptors and Urinary Cytokines in Rats with Cyclophosphamide Induced Cystitis

We characterized pharmacological effects of the phytotherapeutic agent Eviprostat® on urodynamic parameters, bladder muscarinic and purinergic receptors, and urinary cytokines in rats with cyclophosphamide induced cystitis. Urodynamic parameters in cyclophosphamide (150 mg/kg intraperitoneally) treated rats were measured by a cystometric method. Muscarinic and purinergic receptors in the bladder and other tissues were measured by radioreceptor assays using [N-methyl-(3)H]scopolamine methyl chloride and [(3)H]αβ-MeATP, respectively. The urinary cytokines interleukin-1β, 6 and 17 were measured with enzyme-linked immunoassay kits. Eviprostat (36 mg/kg per day twice daily for 7 days) was orally administered. On cystometry the micturition interval and micturition volume were significantly decreased in cyclophosphamide vs sham treated rats, while micturition frequency, basal pressure and post-void residual urine volume were significantly increased. Repeat oral administration of Eviprostat in cyclophosphamide treated rats significantly increased the micturition interval and micturition volume, and decreased micturition frequency, basal pressure and post-void residual urine volume. The maximal number of binding sites for [N-methyl-(3)H]scopolamine methyl chloride and [(3)H]αβ-MeATP was significantly decreased in the bladder of cyclophosphamide vs sham treated rats. Such decreases were significantly attenuated by repeat Eviprostat treatment. Increased urinary cytokine levels in cyclophosphamide treated rats were also effectively attenuated by Eviprostat. Repeat Eviprostat treatment significantly improved detrusor overactivity, down-regulated the expression of bladder pharmacological receptors and increased urinary cytokine levels in rats with cyclophosphamide induced cystitis. Therefore, Eviprostat may be a pharmacologically useful phytotherapeutic agent for cystitis.

Effect of Chemical Stimulation of the Medial Frontal Lobe on the Micturition Reflex in Rats

We assessed the influence of the medial frontal lobe on micturition after chemical stimulation. We also examined the relation between the medial frontal lobe and the rostral pontine reticular formation, which has a strong inhibitory effect on micturition. A total of 35 female rats underwent continuous cystometry. Bladder activity changes were examined after physiological saline, glutamate, the glutamate receptor antagonist MK-801, noradrenaline or the adrenergic α-1 receptor antagonist naftopidil was injected in the medial frontal lobe. When glutamate was injected in the medial frontal lobe, MK-801 was also injected in the rostral pontine reticular formation. Glutamate injection in the medial frontal lobe prolonged the interval between bladder contractions while injection of the glutamate antagonist MK-801 shortened the interval. Glutamate injection in the medial frontal lobe just after MK-801 injection in the ipsilateral rostral pontine reticular formation also prolonged the interval between bladder contractions. However, after prior injection of MK-801 in the bilateral rostral pontine reticular formation glutamate injection in the medial frontal lobe did not influence cystometric parameters. Noradrenaline injection in the medial frontal lobe shortened the interval between bladder contractions while injection of its antagonist naftopidil prolonged the interval. Medial frontal lobe neurons excited by glutamate inhibited the micturition reflex via activation of the rostral pontine reticular formation by glutamatergic projection while medial frontal lobe neurons excited by noradrenaline facilitated the micturition reflex. Thus, the medial frontal lobe may be an important integration center for the initiation of micturition and urine storage mechanisms.

Effect of distigmine combined with propiverine on bladder activity in rats with spinal cord injury

It is not uncommon for patients with spinal cord injury to have both detrusor overactivity during the storage phase and detrusor underactivity during the voiding phase. However, there has been no information about the efficacy of combined treatment with cholinesterase inhibitors and anti-muscarinic agents for this condition. Therefore, the effect of co-administration of distigmine bromide (a cholinesterase inhibitor) and propiverine hydrochloride (an anti-muscarinic agent) on bladder activity was examined in rats with spinal cord injury. Rats were anesthetized with isoflurane and the lower thoracic spinal cord was transected. The bladder was emptied by abdominal compression twice a day for 14 days after surgery. A total of 4 weeks after surgery, the animals were anesthetized with urethane, and the effect of intravenous injection of distigmine (0.01-1 mg/kg) followed by propiverine (1 mg/kg) on continuous cystometry parameters was examined. After injection of distigmine (0.1 and 1 mg/kg), the maximum bladder contraction pressure was significantly increased, and the duration of bladder contraction and the interval between bladder contractions were significantly prolonged. The baseline bladder pressure was not changed by injection of distigmine. After the addition of propiverine, the interval between bladder contractions was significantly further prolonged without any change of the maximum contraction pressure, baseline pressure or duration of bladder contraction. The residual volume after voiding bladder contraction was less than 0.1 mL in all animals. In conclusion, co-administration of distigmine with propiverine might improve both bladder underactivity during the voiding phase and bladder overactivity during the storage phase.

Synergistic Effect by Co-Administration of Tamsulosin and Solifenacin on Bladder Activity in Rats.

We examined the effects of alpha1-adrenoceptor antagonist (tamsulosin hydrochloride) and antimuscarinic agent (solifenacin succinate) alone or in combination on the urinary adenosine triphosphate (ATP) level and cystometric parameters before and after bladder stimulation. Female rats were administered tamsulosin hydrochloride (0.5 or 3 µg/kg/h) and/or solifenacin succinate (20 or 100 µg/kg/h) via a subcutaneously implanted osmotic minipump. Rats receiving distilled water were used as control. After 2 weeks, continuous cystometry with physiological saline or 0.1% acetic acid solution was performed. Urinary ATP level was also measured before and after stimulation by 0.1% acetic acid solution. During cystometry with bladder stimulation, the interval between voiding became shorter and the maximum voiding pressure (MVP) became higher in the control group. In the high-dose tamsulosin and solifenacin groups, the inhibition of urinary frequency was observed. The MVP also became higher in the high-dose tamsulosin group, but such a change was not seen in the high-dose solifenacin group. In case of low-dose administration, either agent alone did not inhibit the increase of urinary frequency and MVP due to bladder stimulation. However, co-administration of these ineffective low doses of tamsulosin and solifenacin resulted in the inhibition of urinary frequency. The high-dose or low-dose solifenacin group and the co-administration group showed similar inhibition of the increase of urinary ATP after bladder stimulation. Tamsulosin may have a different effect on the bladder and/or the neuronal pathways that is unrelated to ATP, so the combination of tamsulosin and solifenacin may synergistically inhibit urinary frequency after bladder stimulation.

Muscarinic receptor activation in the lumbosacral spinal cord ameliorates bladder irritation in rat cystitis models

To investigate whether activation of spinal cholinergic pathways affects bladder activity in rats with chemical cystitis induced by acetic acid (AA) and cyclophosphamide (CYP). The effects of intrathecal (i.t.) application of neostigmine as an acetylcholine esterase (AChE) inhibitor, oxotremorine-M (OXO-M) as a muscarinic ACh receptor (mAChR) agonist or epibatidine as a nicotinic AChR (nACHR) agonist with or without atropine as a mAChR antagonist or mecamylamine (MEC) as a nAChR antagonist at the level of L6-S1 spinal cord on C-fibre mediated bladder irritation were examined by using continuous-infusion cystometry (0.1 mL/min) in urethane-anaesthetized female Spraque-Dawley rats. Bladder irritation was induced by intravesical AA (0.25%) or pretreatment with intraperitoneal injection of CYP (150 mg/kg) 24 h before cystometry. In control rats during intravesical saline, the effects of above drugs on the bladder activity were also examined. The intercontraction intervals (ICI) in AA- and CYP-treated rats were significantly shorter than those in control rats. Neostigmine (i.t.) significantly increased ICI dose-dependently without changing maximum voiding pressure in all groups. The mean (sem) maximal percentage increases in ICI after i.t. neostigmine as compared with the pretreatment value in control, AA- and CYP-treated rats were 93.2 (18.5)%, 117.5 (20.2)% and 200.7 (19.6)%, respectively. The percentage increases of ICI in the CYP-treated group were significantly (P < 0.05) higher than those in the AA-treated or control groups. In all groups, pretreatment with atropine, but not MEC, almost completely antagonized the inhibitory effects of neostigmine. OXO-M produced almost the same effects as that of neostigmine in all groups. Conversely, i.t. epibatidine decreased the ICI in all groups and these excitatory effects were completely antagonized by pretreatment with MEC and significantly inhibited by pretreatment with MK-801(noncompetitive n-methyl-d-aspartate receptor antagonist). These results indicate that accumulation of ACh by AChE inhibition in the spinal cord can ameliorate frequent urination in chemical cystitis via mAChRs, but not nAChRs.

Excitatory and Inhibitory Influence of Pathways in the Pelvic Nerve on Bladder Activity in Rats with Bladder Outlet Obstruction

OBJECTIVES: This study was undertaken to investigate whether chronic bladder outlet obstruction (BOO) in female rats influences the tonic parasympathetic excitatory or inhibitory reflex control of bladder activity. METHODS: Bladder activity during isovolumetric cystometry (1.5-12 mL) was examined after transection of dorsal and ventral lumbosacral spinal roots (L4-S4) and administration of hexamethonium, a ganglionic blocking agent, in urethane anesthetized female rats with sympathectomy and BOO. RESULTS: Lumbosacral dorsal root transection abolished reflex bladder contractions, but did not influence intravesical baseline pressure. However, ventral root transection after dorsal root transection decreased baseline intravesical pressure (y: % change) at low bladder volumes (x) and increased pressure at high volumes. The calculated (y = 1.9x - 16.5) transition volume was 9 mL. Administration of hexamethonium (100 mg/kg, intraperitoneally) after dorsal and ventral root transection increased the amplitude and decreased the frequency of myogenic bladder contractions. CONCLUSION: The bladder is tonically excited or inhibited depending upon bladder volume by the interactions between a parasympathetic preganglionic pathway in the pelvic nerve and a peripheral reflex. However, in rats with BOO, the volume at which the response shifts from excitation to inhibition was very large, and tonic function of the parasympathetic preganglionic pathway was weak compared to previously reported results in rats without BOO. The persistence of reflex tonic excitatory control of bladder tone over a broad range of bladder volumes may be one of the reasons for overactivity of the bladder with outlet obstruction.

Mechanisms by Which a Phytotherapeutic Drug Influences Bladder Activity in Rats

We investigated the mechanisms by which Eviprostat, a phytotherapeutic drug for benign prostatic hyperplasia, influences bladder activity in rats. A total of 42 female rats were divided into a control group and an Eviprostat group. Rats in the control group were fed a standard diet, while animals in the Eviprostat group were fed a diet containing 0.1% Eviprostat. After 2 weeks 14 rats (7 rats per group) underwent continuous cystometry with physiological saline or 0.1% acetic acid solution and bladder activity was recorded. Body weight, blood pressure, plasma monoamines and adenosine triphosphate were measured in another 14 rats (7 per group). In the remaining 14 rats (7 per group) 0.1% acetic acid solution was infused into the bladder and urinary adenosine triphosphate was measured before and after stimulation. During cystometry with acetic acid the interval between bladder contractions was shorter and maximum bladder contraction pressure was higher in the control group compared with results obtained using physiological saline but such differences were not seen in the Eviprostat group. Plasma adrenaline and noradrenaline were lower in the Eviprostat group than the control group but no difference in blood pressure was observed. Urinary adenosine triphosphate was higher in the 2 groups than before stimulation but the increase was smaller in the Eviprostat group than in the control group. These results suggest that Eviprostat acts to maintain low catecholamine and also inhibit pathological bladder activity by decreasing adenosine triphosphate release from the bladder.

The effects of a type 4 phosphodiesterase inhibitor and the muscarinic cholinergic antagonist tolterodine tartrate on detrusor overactivity in female rats with bladder outlet obstruction

To investigate the effects of the selective phosphodiesterase (PDE) type 4 inhibitor IC485 and the widely used antimuscarinic drug tolterodine tartrate on bladder activity in rats with bladder outlet obstruction (BOO), as inhibition of PDE4 leads to elevation of intracellular cAMP levels and relaxation of smooth muscle. BOO was induced in female Sprague-Dawley rats by tying a silk ligature around the urethra. Six weeks after inducing BOO, conscious rats were assessed by cystometry with the urethral ligature intact. The effects of IC485 (5, 10 and 50 mg/kg intravenous, i.v.) were examined and compared with those of tolterodine (0.01, 0.1 and 1 mg/kg i.v.). IC485 (5-50 mg/kg i.v.) decreased the number and amplitude of non-voiding contractions during the storage phase by 63-88% and 49-83%, respectively; IC485 also increased bladder capacity by 28-37%. There was no change in blood pressure after applying IC485. Tolterodine tartrate (0.1 and 1.0 mg/kg) significantly decreased the number and amplitude of non-voiding contractions by 38-74% and 29-44%, respectively, and increased bladder capacity by 19-51%. Whereas voiding efficiency and maximum voiding pressure were not altered by IC485 at any dose, tolterodine significantly reduced both, by 35-67% and 19-34%, respectively. Both IC485 and tolterodine tartrate reduced detrusor overactivity in rats with BOO. In addition, doses of IC485 that suppressed non-voiding contractions had no effect on voiding function. Therefore, selective PDE4 inhibitors deserve further study as potential agents for treating detrusor overactivity in patients with BOO.

Characterization and restoration of altered inhibitory and excitatory control of micturition reflex in experimental autoimmune encephalomyelitis in rats

Multiple sclerosis (MS) is characterized by inflammatory lesions throughout the central nervous system. Spinal cord inflammation correlates with many neurological defecits. Most MS patients suffer from micturition dysfunction with urinary incontinence and difficulty in emptying the bladder. In experimental autoimmune encephalomyelitis (EAE) induced in female Lewis rats, a model of MS, we investigated at distinct clinical severity scores the micturition reflex by cystometrograms. All rats presenting symptomatic EAE suffered from micturition reflex alterations with either detrusor areflexia or hyperactivity. During pre-symptomatic EAE, a majority of rats presented with detrusor areflexia, whereas at onset of clinical EAE, detrusor hyperactivity was predominant. During progression of EAE, detrusor areflexia and hyperactivity were equally expressed. Bladder hyperactivity was suppressed by activation of glycine and GABA receptors in the lumbosacral spinal cord with an order of potency: glycine > GABA(B) > GABA(A). Detrusor areflexia was transformed into detrusor hyperactivity by blocking glycine and GABA receptors. Spinalization abolished bladder activity in rats presenting detrusor hyperactivity and failed to induce activity in detrusor areflexia. Altogether, the results reveal an exaggerated descending excitatory control in both detrusor reflex alterations. In detrusor areflexia, a strong segmental inhibition dominates this excitatory control. As in treatment of MS, electrical stimulation of sacral roots reduced detrusor hyperactivity in EAE. Blockade of glycine receptors in the lumbosacral spinal cord suppressed the stimulation-induced inhibitory effect. Our data help to better understand bladder dysfunction and treatment mechanisms to suppress detrusor hyperactivity in MS.

Effect of Gosha-Jinki-Gan, a Blended Herbal Medicine, on Bladder Activity in Rats

We investigated the effect of the blended herbal medicine Gosha-jinki-gan on bladder activity and the autonomic nervous system in rats. A total of 42 female rats were divided into a control diet group of 21 and a Gosha-jinki-gan diet group of 21. Rats in the control diet group were fed a standard diet, while animals in the Gosha-jinki-gan were fed a special diet containing 1.08% Gosha-jinki-gan (TJ107, Tsumura Co., Tokyo, Japan). After 4 weeks 28 rats, including 14 in the control and 14 in the Gosha-jinki-gan group, underwent continuous cystometry with physiological saline or 0.1% acetic acid solution and bladder activity was recorded. The remaining 14 rats were anesthetized with halothane, and body weight, serum amino acid (glutamate and glycine) and plasma monoamine (noradrenaline, adrenaline, dopamine and serotonin) levels were measured. The amplitude of bladder contraction on continuous cystometry with physiological saline was lower in the Gosha-jinki-gan diet group than in the control diet group, and plasma dopamine and serotonin levels were also lower in the Gosha-jinki-gan group. When cystometry was done with 0.1% acetic acid, the interval between bladder contractions was shortened in the control and Gosha-jinki-gan groups. However, the interval and duration of bladder contractions were longer in the Gosha-jinki-gan than in the control group. These results suggest that Gosha-jinki-gan inhibits bladder activity by maintaining the balance of the sympathetic and parasympathetic nervous systems at a low level.

Bladder volume-dependent excitatory and inhibitory influence of lumbosacral dorsal and ventral roots on bladder activity in rats

This study was undertaken to examine the role of the afferent and efferent pathways of the lumbosacral spinal nerve roots in the tonic control of bladder activity. Changes of isovolumetric bladder activity were recorded in 21 sympathectomized female rats under urethane anesthesia following transection of the dorsal (DRT) and ventral (VRT) lumbosacral spinal roots, and after intraperitoneal administration of hexamethonium. DRT altered the baseline intravesical pressure in a bladder volume-dependent manner in each animal. The percent change of baseline pressure after VRT following DRT was also dependent upon bladder volume. The percent change of baseline pressure after VRT alone was similarly dependent on bladder volume, but not after VRT followed by DRT. The percent change of baseline intravesical pressure (y)(-9 to +8 cm H(2)O, -56 to +46%) after DRT and VRT depended upon bladder volume (x)(y = 44.7 x -40.4) in all rats. Hexamethonium increased the amplitude of small myogenic bladder contractions after DRT and VRT. In conclusion, the bladder is tonically excited or inhibited by a local reflex pathway and by a parasympathetic reflex pathway that depends on connections with the lumbosacral spinal cord and the pelvic nerves. Both reflex mechanisms are influenced by bladder volume.

ACTIVATION OF THE ROSTRAL PONTINE RETICULAR FORMATION INCREASES THE SPINAL GLYCINE LEVEL AND INHIBITS BLADDER CONTRACTION IN RATS

We examined the mechanism involved in the inhibition of bladder activity in rats by stimulating the rostral pontine reticular formation (RPRF) using carbachol, flavoxate and propiverine, and by analysis of amino acid levels in the lumbosacral cord. A total of 82 female rats were anesthetized with urethane. Under isovolumetric conditions physiological saline, carbachol, flavoxate or propiverine was injected into the RPRF or intravenously. Changes in bladder activity and amino acid levels in the lumbosacral cord were examined. Injection of carbachol or flavoxate (0.3 microM each) into the RPRF abolished bladder contraction but there was no change after injection of physiological saline or propiverine. Intravenous injection of flavoxate or propiverine (0.1 to 10 mg/kg each) inhibited bladder contraction. Amino acid analysis revealed that injection of carbachol into the RPRF increased glutamate and glycine levels in the lumbosacral cord, while injection of flavoxate into the RPRF or intravenously caused an increase in glycine the lumbosacral cord. Injection of propiverine into the RPRF or intravenously did not influence lumbosacral cord amino acid levels. These results suggest that the RPRF has an important role in the inhibition of bladder contraction and carbachol or flavoxate can activate descending RPRF neurons and inhibit bladder contraction via spinal glycinergic neurons.

DIETARY GLYCINE INHIBITS BLADDER ACTIVITY IN NORMAL RATS AND RATS WITH SPINAL CORD INJURY

The influence of dietary glycine on bladder activity, and on glutamate and glycine levels in the serum and lumbosacral cord was examined in rats with or without spinal cord injury (SCI). A total of 84 female rats were divided into an intact and an SCI group. Each group of rats was divided into 7 subgroups. Two intact and 2 SCI subgroups were fed a standard diet and the remaining subgroups were fed diets containing 0.1% to 3% glycine. After 4 weeks isovolumetric cystometry was performed with rats under urethane anesthesia. Following cystometry glutamate and glycine levels in the serum and lumbosacral cord were measured as well as the glycine receptor alpha1 mRNA level in the lumbosacral cord. Dietary glycine (1% to 3%) prolonged the interval between bladder contractions in intact rats but did not change the amplitude of contractions. On the other hand, dietary glycine (1% to 3%) prolonged the interval and decreased the amplitude of bladder contractions in SCI rats. The glycine levels in the serum and lumbosacral cord of SCI rats on the standard diet were respectively 43% and 45% lower than those in intact rats on the standard diet. Dietary glycine (1% to 3%) increased the serum glycine level in intact and SCI rats but the glycine receptor alpha1 mRNA level in the lumbosacral cord was unchanged. Dietary glycine crosses the blood-brain barrier and inhibits the micturition reflex pathway in the lumbosacral cord but SCI and/or dietary glycine do not influence glycine receptor expression.