Rectal distention inhibits the spinal micturition reflex via glycinergic or GABAergic mechanisms in rats with spinal cord injury

BACKGROUND: We examined the influence of rectal distention on the spinal micturition reflex and the mechanism underlying its inhibition of bladder contraction. METHODS: Fourteen conscious female Sprague-Dawley rats were used in this study after transection of the lower thoracic cord. Isovolumetric cystometry was performed before and after distention of the rectum by inflation of a rectal balloon, followed by intrathecal injection of strychnine (a selective glycine receptor antagonist) or bicuculline (a GABA(A) receptor antagonist) into the lumbosacral cord. RESULTS: Rectal distention (1.0-3.0 cm(3)) prolonged the interval, decreased the amplitude, and shortened the duration of bladder contraction, and eventually almost abolished bladder activity. After intrathecal injection of strychnine (0.001-10 microg) or bicuculline (0.001-1 microg) in animals with inhibition of bladder activity by rectal distention, the interval, amplitude, and duration of bladder contraction returned to baseline. CONCLUSION: These results suggest that there is an inhibitory rectovesical reflex in the lumbosacral cord of rats with spinal cord injury, which modulates the spinal micturition reflex via glycinergic or GABAergic mechanisms.     

Rectal distention inhibits bladder activity via glycinergic and GABAergic mechanisms in rats

PURPOSE: We examined the influence of rectal distention on the spinobulbospinal micturition reflex and the mechanism underlying the inhibition of bladder contraction. MATERIALS AND METHODS: A total of 22 female Sprague-Dawley rats were used in this study. Using urethane anesthesia isovolumetric cystometry was performed before and after distention of the rectum by inflation of a rectal balloon (0 to 3 cm3), followed by the intrathecal injection of strychnine (a glycine receptor antagonist, 0.001 to 10 microg) and/or bicuculline (a gamma-aminobutyric acid(A) receptor antagonist, 0.001 to 1 microg) at the lumbosacral level of the spinal cord. RESULTS: Rectal distention (1.5 to 3.0 cm3) prolonged the interval, decreased the amplitude and shortened the duration of bladder contraction and finally almost abolished bladder activity. After intrathecal injection of strychnine or bicuculline in animals with inhibition of the bladder by rectal distention the interval and duration of bladder contraction returned to baseline but amplitude only recovered to 47% to 54% of the control level. However, simultaneous intrathecal injection of strychnine and bicuculline (0.001 microg each) restored amplitude to the control level. There were no differences between strychnine and bicuculline with respect to their effects on the interval, amplitude and duration of bladder contraction. CONCLUSIONS: An inhibitory rectovesical reflex exists in the lumbosacral cord of rats. The afferent limb of the spinobulbospinal micturition reflex pathway may be additionally and redundantly inhibited by glycinergic and GABAergic mechanisms, while the efferent limb of this pathway may be synergistically inhibited by these mechanisms.     

Effects of a selective metabotropic glutamate receptor agonist on the micturition reflex pathway in urethane-anesthetized rats

AIMS: To determine a possible role of metabotropic glutamate receptors in the spinobulbospinal micturition reflex pathway in the rat. MATERIALS AND METHODS: A selective metabotropic glutamate receptor agonist, trans-(+/-)-1-amino1,3-cyclopentanedicarboxylic acid (trans-ACPD) was administered to the lumbosacral spinal cord via an intrathecal catheter in urethane anesthetized rats. Amplitude of reflex bladder contractions evoked by bladder distension under isovolumetric condition as well as amplitude of bladder contractions elicited by electrical stimulation of the pontine micturition center (PMC) were examined before and after administration of trans-ACPD. The effect of trans-ACPD on the urethral activity during isovolumetric bladder contractions was also examined by monitoring urethral perfusion pressure and electromyography of the external urethral sphincter (EUS-EMG). RESULTS: Trans-ACPD (3-10 microg) completely inhibited reflex bladder contractions evoked by bladder distension and the duration of inhibition was dose dependent (3 microg: 11.4 +/- 2.8 min, 5 microg: 13.2 +/- 1.3 min, 10 microg: 36.2 +/- 2.4 min). The mean amplitude of bladder contractions evoked by electrical stimulation of the PMC was reduced to 12.6 +/- 2.3% of control by 10 microg of trans-ACPD. In addition, bursting activity of EUS-EMG and corresponding high frequency oscillations of urethral pressure during isovolumetric bladder contractions were completely abolished by 10 microg of trans-ACPD. CONCLUSIONS: These results indicate that intrathecal administration of a selective metabotropic glutamate receptor agonist to the lumbosacral spinal cord has an inhibitory effect on the spinobulbospinal micturition reflex pathway in urethane-anesthetized rats. This pharmacological action is attributed at least to the inhibitory effect on the descending pathway from the PMC to the lumbosacral spinal cord.     

Changes of bladder activity and glycine levels in the lumbosacral cord after partial bladder outlet obstruction in rats

Objectives: We investigated the time course of changes in bladder activity as well as in spinal and serum levels of glutamate and glycine after partial bladder outlet obstruction (BOO) in rats. Methods: A total of 36 female rats were divided into six groups: sham operation (control); 3 days, 14 days, and 28 days after BOO; 3 days and 28 days after relief of BOO. Under urethane anesthesia, isovolumetric cystometry was carried out in each group. Then, spinal and serum levels of glutamate and glycine were measured. Results: The interval between bladder contractions was shorter in all of the groups compared with the control group. The amplitude and duration of bladder contractions was decreased at 3 days, 14 days, and 28 days after BOO, and at 3 days after relief of BOO. Spinal and serum glutamate levels showed no changes. However, the spinal glycine level was decreased at 14 days and 28 days after BOO, and at 28 days after relief of BOO. Serum glycine level was also decreased at 28 days after BOO and 28 days after relief of BOO. Conclusions: Detrusor overactivity during the chronic phase of partial BOO is partly caused by a decrease of glycinergic neuronal activity in the lumbosacral cord. A 3‐day period of BOO produces detrusor overactivity, which might be due to an irreversible decrease of spinal glycinergic neuronal activity.     

Activation of the rostral pontine reticular formation increases the spinal glycine level and inhibits bladder contraction in rats

PURPOSE: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

The effect of intravesical electrical stimulation on bladder function and synaptic neurotransmission in the rat spinal cord after spinal cord injury

OBJECTIVE

To investigate the effects of intravesical electrical stimulation (IVES) on bladder function and synaptic neurotransmission in the lumbosacral spinal cord in the spinalized rat, as the clinical benefits of IVES in patients with increased residual urine or reduced bladder capacity have been reported but studies on the mechanism of IVES have mainly focused on bladder Aδ afferents in central nervous system‐intact rats.

MATERIALS AND METHODS

In all, 30 female Sprague‐Dawley rats were divided equally into three groups: normal control rats, sham‐stimulated spinalized rats and IVES‐treated spinalized rats. IVES was started 5 weeks after spinal cord injury (SCI) and was performed 20 min a day for 5 consecutive days. At 7 days after IVES, conscious filling cystometry was performed. Sections from the L6 and S1 spinal cord segments were examined for n ‐methyl‐d ‐aspartic acid receptor 1 (NMDAR1) subunit and γ‐aminobutyric acid (GABA) immunoactivity.

RESULTS

In IVES‐treated spinalized rats, the number and maximal pressure of nonvoiding detrusor contractions were significantly less than in sham‐stimulated spinalized rats. The mean maximal voiding pressure was also lower in IVES‐treated than in sham‐stimulated spinalized rats. IVES significantly reduced the interval between voiding contractions compared with the untreated spinalized rats. There was an overall increase in NMDAR1 immunoactivity after SCI, which was significantly lower in IVES‐treated spinalized rats. Immunoactivity of GABA after SCI was significantly lower than in the control group and was significantly higher in IVES‐treated spinalized rats.

CONCLUSION

Our results suggest that IVES might affect voiding contractions in addition to inhibiting C‐fibre activity and that IVES seems to have a more complex effect on the bladder control pathway. For synaptic neurotransmission in the spinal cord, IVES could possibly shift the balance between excitation and inhibition towards inhibition.     

Serum amino acids as indicators of cerebrospinal neuronal activity in patients with micturition disorders

OBJECTIVE: Our previous study showed that the spinal glycine level in rats was changed by spinal injury or bladder outlet obstruction, and this change was reflected by serum glycine levels. Therefore, we measured the serum glutamate and glycine levels in healthy volunteers and patients with cerebrospinal damage or benign prostatic hyperplasia (BPH) to confirm whether the change of serum amino acid levels was obtained from these patients as well as the animal experiment. METHODS: We measured the serum glutamate and glycine levels in 170 healthy controls, 57 patients with cerebrovascular disease (CVD), 68 patients with spinal cord injury (SCI), and 70 patients with BPH. Amino acid levels were compared between the controls and patients, according to gender, level of spinal injury and the type of bladder activity. RESULTS: In the healthy controls, glutamate levels were higher and glycine levels were lower in men than in women. On group comparison of each gender, there were no differences of glutamate levels. However, glycine levels were lower in male and female SCI patients and BPH patients than in controls. According to the level of spinal injury or the pattern of bladder activity and amino acid levels, there were no relationships among them. CONCLUSIONS: Serum glutamate and glycine levels were not related to the spinal injury level or bladder activity. However, serum glycine levels changed in patients with SCI or BPH patients, so it may be possible to use it as an indicator of spinal glycinergic neuronal activity.     

5-HT7受体激动剂改善脊髓损伤大鼠排尿障碍

目的:研究五羟色胺-7受体激动剂对慢性脊髓损伤(spinal cord injury,SCI)大鼠排尿障碍的改善作用。方法:体重175～200g之间的SD雌性大鼠,脊髓损伤模型7只,正常对照8只。乌拉坦麻醉下,在正常大鼠和脊髓损伤的模型的大鼠颈静脉和膀胱内置管,连接压力感受器,记录膀胱最大容量、剩余尿量、排尿量和尿道外括约肌的肌电活动。静脉注入5-HT7受体激动剂LP44(3～300μg/kg)得到剂量-效应曲线随后再给予5-HT7受体抑制剂SB269970(100μg/kg)。结果:LP44剂量依赖性的降低SCI大鼠膀胱最大容量,并且增加排尿量、减少剩余尿量从而增加排尿效率。但是不能引起脊髓完好的大鼠排尿的改变。SB269970注入后可以逆转LP44的作用。同时LP44引起脊髓损伤大鼠尿道外括约肌强直收缩中出现阶段性的松弛,而对于脊髓完好的大鼠作用无明显改变。结论:LP44可以剂量依赖性地部分恢复SCI大鼠的尿道外括约肌协调性松弛,从而降低膀胱容量,增加排尿量,减少剩余尿量,结果增加排尿效率,改善排尿障碍。     

A method for producing overactive bladder in the rat and investigation of the effects of GABAergic receptor agonists and glutamatergic receptor antagonists on the cystometrogram

PURPOSE: We induced radio frequency (RF) lesions in the neuronal pathway leading from the forebrain to the pontine micturition center (PMC) to produce a rat model of bladder overactivity. We studied the effects of gamma-aminobutyric acid agonists (diazepam and baclofen) and glutamate receptor antagonists (MK-801 maleate and GYKI52466 [1-(4-aminophenyl-D-4-methyl-7,8 methylenedioxy-5H-2,3-benzodiazepine] hydrochloride) on the cystometrogram and developed a possible explanation of the neuronal mechanisms underlying RF lesion induced bladder overactivity. MATERIALS AND METHOD: Seven-week-old male Sprague-Dawley rats were anesthetized with sodium pentobarbital and RF lesions were produced in the nuclei basalis. Five days later bladder contractions were induced by infusing fluid into the bladder and cystometrograms were measured in conscious rats. RESULTS: The micturition interval (MI) in rats subjected to RF lesioning was significantly shorter than that in sham operated control rats. Diazepam (0.1 and 1 mg/kg intraperitoneally), baclofen (1 mg/kg intravenously) and MK-801 (0.1 and 1 mg/kg intravenously) did not change or shortened MI in control rats but it prolonged MI in lesioned rats. GYKI52466 (0.5 and 1 mg/kg intravenously) weakly prolonged MI in lesioned rats. CONCLUSIONS: We consider that RF lesioning causes interruption of the inhibitory GABAergic neurons that lead from the forebrain to the PMC. This results in the activation of N-methyl-D-aspartate receptors in the PMC that are involved in the facilitation of voiding.     

Intrathecal or dietary glycine inhibits bladder and urethral activity in rats with spinal cord injury

PURPOSE: We examined the influence of intrathecal or dietary glycine on bladder and urethral activity in rats with spinal cord injury. MATERIALS AND METHODS: A total of 20 female Sprague-Dawley rats were used 4 weeks after lower thoracic spinal cord injury. The rats were divided into standard and 1% glycine diet groups. In the standard diet group isovolumetric cystometry and urethral pressure measurement were performed before and after intrathecal injection of glycine. In the 1% glycine diet group bladder and urethral activity were compared with control recordings in the standard diet group. RESULTS: In the standard diet group intrathecal injection of glycine prolonged the interval and decreased the amplitude of bladder contractions, decreased baseline urethral pressure and altered urethral activity during bladder contraction from a pattern of detrusor-sphincter dyssynergia to detrusor-sphincter synergy at 100 mug glycine. In the 1% glycine diet group the interval and amplitude of bladder contractions were prolonged and decreased, respectively, compared with those in the standard diet group. Baseline urethral pressure was lower than in the standard diet group even after intrathecal injection of 100 mug glycine. Urethral pressure did not change during bladder contraction and it was the same as baseline pressure. Residual urine volume was lower than in the standard diet group. CONCLUSIONS: Intrathecal or dietary glycine inhibits bladder and urethral activity, and improves detrusor hyperreflexia and detrusor-sphincter dyssynergia.     

Evidence of a peripheral role of neurokinins in detrusor hyperreflexia: a further study of selective tachykinin antagonists in chronic spinal injured rats

PURPOSE: Spinal cord injury above the sacral micturition center usually leads to detrusor hyperreflexia, increased intravesical pressure and post-void residual urine. Detrusor hyperreflexia is believed to be mediated by afferent C fibers with tachykinins as neurotransmitters. We investigated the selective peptide tachykinin antagonists MEN 11420 and GR 82334 of NK-2 and NK-1 receptors, respectively, in a chronic rat model of detrusor hyperreflexia after suprasacral spinal cord injury. MATERIALS AND METHODS: Adult female Sprague-Dawley rats weighing 200 to 250 gm. were used. The spinal cord was transected at the T10 level. The bladder was evacuated by the Credé maneuver 3 times daily. After 6 weeks the rats were implanted with femoral vein and bladder dome catheters 2 days before filling cystometry. The 5 rats in group 1 received 100 nmol./kg. of the NK-2 antagonist MEN 11420 intravenously. The 5 rats in group 2 received 100 nmol./kg. of the NK-1 antagonist GR 82334 intravenously. The 5 rats in group 3 received a combination of the same dose of each antagonist. Three repetitive micturition cycles were recorded before injection. Three micturition cycles were done 20 minutes after the injection of each antagonist. Mean cystometric parameters were reported, including bladder capacity, micturition pressure, baseline pressure, post-void residual urine and micturition volume, and the number and amplitude of hyperreflexic contractions greater than 15 cm. water. RESULTS: MEN 11420 significantly reduced the frequency of hyperreflexic contractions and baseline bladder pressure (p <0.05). There was no statistically significant effect on the other cystometric parameters. GR 82334 reduced the amplitude of hyperreflexic contractions but not statistically significant. A combination of MEN 11420 and GR 82334 significantly reduced the frequency and amplitude of hyperreflexic contractions (p <0.05) with no significant effects on other cystometric parameters, although there was a tendency toward increased micturition volume and bladder capacity. CONCLUSIONS: These results suggest that at the peripheral level there is an efferent role of tachykinins in detrusor hyperreflexia after spinal cord injury. NK-1 and NK-2 receptor selective antagonists reduced the frequency and amplitude of hyperreflexic contractions as well as baseline bladder pressure. This finding may lead to potential new therapeutic modalities using selective tachykinins antagonists with other pharmacological agents to combat detrusor hyperreflexia.     

The activation of spinal N-methyl-D-aspartate receptors may contribute to degeneration of spinal motor neurons induced by neuraxial morphine after a noninjurious interval of spinal cord ischemia

We investigated the relationship between the degeneration of spinal motor neurons and activation of N-methyl-d-aspartate (NMDA) receptors after neuraxial morphine following a noninjurious interval of aortic occlusion in rats. Spinal cord ischemia was induced by aortic occlusion for 6 min with a balloon catheter. In a microdialysis study, 10 muL of saline (group C; n = 8) or 30 mug of morphine (group M; n = 8) was injected intrathecally (IT) 0.5 h after reflow, and 30 mug of morphine (group SM; n = 8) or 10 muL of saline (group SC; n = 8) was injected IT 0.5 h after sham operation. Microdialysis samples were collected preischemia, before IT injection, and at 2, 4, 8, 24, and 48 h of reperfusion (after IT injection). Second, we investigated the effect of IT MK-801 (30 mug) on the histopathologic changes in the spinal cord after morphine-induced spastic paraparesis. After IT morphine, the cerebrospinal fluid (CSF) glutamate concentration was increased in group M relative to both baseline and group C (P < 0.05). This increase persisted for 8 hrs. IT MK-801 significantly reduced the number of dark-stained alpha-motoneurons after morphine-induced spastic paraparesis compared with the saline group. These data indicate that IT morphine induces spastic paraparesis with a concomitant increase in CSF glutamate, which is involved in NMDA receptor activation. We suggest that opioids may be neurotoxic in the setting of spinal cord ischemia via NMDA receptor activation.     

体神经-内脏神经反射弧建立后脊髓损伤鼠排尿功能的改变以及可能机制

目的 建立新的体神经-内脏神经反射弧,应用尿流动力学方法来检测新反射弧建立后对清醒脊髓损伤(SCI)鼠膀胱功能及逼尿肌-尿道外括约肌协调性的影响以及可能机理。方法成年雄性大鼠(280～300)g在L4～L6的椎管内行L6腹侧根与L4腹侧根神经端端吻合,保留L4背根来传导来自新反射弧的皮肤传入信号。术后3个月行T9～T10椎间脊髓横断,8周后在清醒状态下检测容量诱发性排尿和电刺激新反射弧皮肤感觉传入区诱发排尿的膀胱压力变化图(CMG)和尿道外括约肌肌电图(EUS-EMG)各项参数的变化。结果 新的体神经-内脏神经反射弧建立后,在清醒状态下电刺激L4皮区可以诱发排尿,和不用电刺激的容量诱发性排尿(VEMR)相比排尿量增加、排尿压提高、排尿开放压提高,而残余尿减少,排尿效率明显增加,差异均有显著性(P<0.05)。EUS的肌电频率明显降低。结论 新反射弧建立后使 SCI鼠的排尿功能发生显著改变。电刺激反射弧的皮肤感觉区可以收缩膀胱逼尿肌使膀胱内压升高并同时使尿道外括约肌肌电频率下降,CMG和EUS的多项参数均有改善。逼尿肌-外括约肌不协调得到改善。     

强啡肽对大鼠行为学和脊髓组织学改变的影响及受体机制

目的探明强啡肽(Dyn)对脊髓的损伤效应及其受体机制。方法观测大鼠鞘内注射DynA(1-13)或联合注射Kappa阿片受体拮抗剂nor-BNI或兴奋性氨基酸(EAA)的NMDA受体拮抗剂MK-801后的运动功能和脊髓病理学变化。结果注射30nmolDyn组3d时,Tarlov运动功能评分下降,脊髓前角神经元数目减少,GFAP阳性神经胶质细胞数轻度增生。14d时,Tarlov运动功能评分未恢复,神经胶质细胞增生明显。而鞘内联合注射100nmol nor-BNI、100nmol MK-801后3d时与单纯Dyn组结果相似,14d时Tarlov运动功能评分明显恢复,脊髓前角神经元数目较Dyn组多,GFAP阳性神经胶质细胞增生不明显,nor-BNI组与MK-801组间比较差异不显著。结论Dyn鞘内注射可使大鼠运动功能、脊髓组织损害,而nor-BNI或MK-801有对抗其损害作用。Dyn的病理作用是通过Kappa阿片受体和EAA的NMDA受体两种途径介导的。     

Urinary Bladder Response to Hypogastric Nerve Stimulation After Bilateral Resection of the Pelvic Nerve or Spinal Cord Injury in Rats

Background: We examined the mechanism of urinary bladder motility return after bladder areflexia induced by interruption of the sacral parasympathetic outflow to the urinary bladder following damage to the sacral cord or pelvic nerves in the rat.
Methods: The L6 and SI nerve bundles were resected near the vertebrae, and bilateral pelvic nerve resections (PNR) performed. Spinal cord injury (SCI) was performed by means of a legion generator at the T12 vertebra. Thirty days after PNR and SCI, cystometrograms were recorded under anesthesia.
Results: In all rats subjected to PNR or SCI, overflow incontinence continued, yet some rats subjected to SCI recovered within 2 weeks after the operation. Cystometrograms showed that repetitive bladder contractions appeared in rats subjected to SCI irrespective of hypogastric nerve (HCN) innervation, while bladder contractions did not appear in rats subjected to PNR. Electrical stimulation of the HGN induced higher bladder pressure elevation in rats who underwent PNR than in rats subjected to SCI.
Conclusions: These results suggest that the generation of repetitive bladder contractions induced by bladder distention after bladder areflexia requires the presence of intact pelvic nerves that transmit sacral cord-originating excitatory information to the bladder. However, the HGN system and functioning pelvic nerve ganglia are not involved in this process. Also, the connection from the preganglionic HGN to the postganglionic parasympathetic nerves in the pelvic plexus did not form after PNR.     

Dynamic Bulbocavernosus Reflex: Dyssynergia Evaluation Following SCI

ABSTRACT

High urethral resistance caused by detrusor-sphincter dyssynergia (DSD) occurs following spinal cord injury (SCI) and results in poor voiding. A major pelvic floor reflex that may be involved in DSD is the bulbocavernosus reflex (BC) and evaluation of this reflex during the micturition cycle may provide additional information regarding this role. The periodic BC observed during micturition via cystometry is described as a dynamic bulbocavernosus reflex (DBC).

The DBC was induced in upper motor neuron SCI patients using periodic dorsal penile nerve stimulation; the evoked reflex response was recorded with an anal sphincter pressure sensing balloon. Stimulation of 15–50 mA was applied at the base and dorsal side of the penis with surface electrodes, pulsed at a rate of 0.25 Hz. By applying the stimulation during cystometry, the BC reflex could be evaluated throughout the entire micturition cycle. Results showed that the DBC increased during bladder filling and bladder contractions. These findings indicate that an enhanced BC reflex is a major factor causing increased urethral resistance during micturition. (J Am Paraplegia Soc: 17; 140–145)     

Detrusor-myoplasty,innervated rectus muscle transposition study,and functional effect on the spinal cord injury rat model

The purpose of this investigation was to determine the feasibility of striated muscular augmentation of the urinary bladder (detrusor-myoplasty, DMP). Initial studies, transposition, and bladder wrap using several distinct muscle groups was attempted in laboratory rats, goats, and fresh human cadavers. The rectus abdominus muscle was found to be best suited to completely encompass the bladder with an intact neural and vascular supply. The technique was then applied in a rat model of spinal cord injury (SCI). Modified Tarlov ratings were employed to assess neurologic function 30 days after SCI. The median final neurological score of SCI rats with and without DMP was 4 and 5, respectively. Sham-operated SCI (control) rats, with and without DMP, both had normal final Tarlov scores of 12 (P < 0.05). Muscle blood flow values for the flap and the contralateral undissected rectus muscles were not significantly different (97 ± 34 and 105 ± 40 ml/100 g tissue/min, respectively, P = 0.47). Postoperatively, no bowel or abdominal wall functional deficits were apparent. The rotated muscular flap remained innervated and vascularized. Analysis of 24 hr micturition patterns demonstrated no differences in oral fluid intake/24hr. voided volume/24hr, and ratio of number of micturitions during the night vs. day among the four groups: (1) control (neither SCI nor DMP), (2) DMP only, (3) SCI only, and (4) SCI with DMP. Spinal cord injured rats with and without detrusor-myoplasty demonstrated a significant decrease in the number of micturitions/24hr, an increased volume per micturition, and greater largest and smallest micturition volumes (P < 0.05) when compared to controls. The micturition patterns among SCI rats with and without DMP were similar, as were non-SCI animals with and without DMP. This is the first report of the principle and technique of detrusor-myoplasty. Dissection of rats, goats, and human cadavers revealed that a vascularized and innervated rectus muscle flap can be rotated into the pelvis and wrapped around the bladder without tension. Significant loss of bladder capacity did not occur with skeletal muscle adaptation. Detrusor-myoplasty may be applicable for patients with an areflexic detrusor and non-intact sacral motor roots who are not candidates for sacral anterior root neurostimulation. © 1994 Wiley-Liss, Inc.     

Roles of peripheral and central nicotinic receptors in the micturition reflex in rats

PURPOSE: We investigated the effects of nicotinic acetylcholine receptor activation in the bladder and central nervous system on the micturition reflex in urethane anesthetized rats. MATERIALS AND METHODS: The effects of nicotinic acetylcholine receptor activation on bladder activity were examined during continuous infusion cystometrogram. Nicotine with or without the nicotinic acetylcholine receptor antagonist mecamylamine (Sigma Chemical Co., St. Louis, Missouri) was administered intravesically, intrathecally or intracerebroventricularly in normal or capsaicin pretreated rats. We also examined nicotine induced responses in dissociated bladder afferent neurons from L6 to S1 dorsal root ganglia that were sensitive to capsaicin using whole cell patch clamp recordings. RESULTS: Intravesical nicotine (1 to 10 mM) significantly decreased intercontraction intervals in dose dependent fashion. This excitatory effect was abolished by co-application of mecamylamine (3 mM) as well as by capsaicin pretreatment. On patch clamp recordings 300 muM nicotine evoked rapid inward currents that were antagonized by mecamylamine in capsaicin sensitive bladder afferent neurons. Intrathecal and intracerebroventricular administration of nicotine (10 mug) decreased and increase intercontraction intervals, respectively. Each effect was antagonized by mecamylamine (50 mug) administered intrathecally and intracerebroventricularly. The spinal excitatory effect was significantly inhibited by the N-methyl-D-aspartate receptor antagonist (+)-MK-801 hydrogen maleate (20 mug) given intrathecally or by capsaicin pretreatment, although the effects of capsaicin pretreatment were significantly smaller than those of (+)-MK-801 hydrogen maleate. CONCLUSIONS: These results indicate that nicotinic acetylcholine receptor activation in capsaicin sensitive C-fiber afferents in the bladder can induce detrusor overactivity. In the central nervous system nicotinic acetylcholine receptor activation in the spinal cord and brain has an excitatory and an inhibitory effect on the micturition reflex, respectively. In addition, the nicotine induced spinal excitatory effect may be mediated by the activation of glutamatergic mechanisms.     

Voiding reflex in chronic spinal cord injured cats induced by stimulating and blocking pudendal nerves

AIMS: To induce efficient voiding in chronic spinal cord injured (SCI) cats. METHODS: Voiding reflexes induced by bladder distension or by electrical stimulation and block of pudendal nerves were investigated in chronic SCI cats under alpha-chloralose anesthesia. RESULTS: The voiding efficiency in chronic SCI cats induced by bladder distension was very poor compared to that in spinal intact cats (7.3 +/- 0.9% vs. 93.6 +/- 2.0%, P < 0.05). In chronic SCI cats continuous stimulation of the pudendal nerve on one side at 20 Hz induced large amplitude bladder contractions, but failed to induce voiding. However, continuous pudendal nerve stimulation (20 Hz) combined with high-frequency (10 kHz) distal blockade of the ipsilateral pudendal nerve elicited efficient (73.2 +/- 10.7%) voiding. Blocking the pudendal nerves bilaterally produced voiding efficiency (82.5 +/- 4.8%) comparable to the efficiency during voidings induced by bladder distension in spinal intact cats, indicating that the external urethral sphincter (EUS) contraction was caused not only by direct activation of the pudendal efferent fibers, but also by spinal reflex activation of the EUS through the contralateral pudendal nerve. The maximal bladder pressure and average flow rate induced by stimulation and bilateral pudendal nerve block in chronic SCI cats were also comparable to those in spinal intact cats. CONCLUSIONS: This study shows that after the spinal cord is chronically isolated from the pontine micturition center, bladder distension evokes a transient, inefficient voiding reflex, whereas stimulation of somatic afferent fibers evokes a strong, long duration, spinal bladder reflex that elicits efficient voiding when combined with blockade of somatic efferent fibers in the pudendal nerves.     

Effect of intravesical nitric oxide therapy on cyclophosphamide-induced cystitis

PURPOSE: This study was conducted to examine effects of nitric oxide (NO) donors on bladder hyperactivity induced by cyclophosphamide (CYP)-induced cystitis. MATERIALS AND METHODS: Female Sprague-Dawley rats received a single intraperitoneal injection of CYP (100 mg./kg.), and then their micturition pattern including mean micturition volume and the number of micturitions during 24 hours was recorded in a metabolic cage before and after CYP treatment. Forty-eight hours after CYP injection, bladder function under urethane anesthesia was evaluated by cystometry with continuous saline infusion (0.04 ml. per minute) or under isovolumetric conditions (0.8 ml. bladder volume). NO donors, S-nitroso-N-acetyl-penicillamine (SNAP, 2 mM) or sodium nitroprusside (SNP, 1 mM), and an NO synthase (NOS) inhibitor, N-nitro-L-arginine methyl ester (L-NAME, 20 mM) were administered intravesically. Direct action of SNAP on bladder afferent neurons was also tested in a patch-clamp recording study. RESULTS: The number of micturitions significantly increased during the first 24 hours after CYP injection (19.0 +/- 0.88 versus 92.1 +/- 16.3 micturitions/24 hours, mean +/- SE, n = 25) (p <0.001). There was no significant difference in total micturition volume before (12.3 +/- 1.0 ml./24 hours) and after CYP treatment (15.6 +/- 1.5 ml./24 hours). During continuous infusion cystometry, intercontraction interval (ICI) was smaller in CYP-injected rats than in control rats. In CYP-injected animals, NO donors increased the ICI, but did not change the amplitude of bladder contractions. Continuous intravesical infusion of the NOS inhibitor did not alter the cystometric parameters. During cystometry under isovolumetric conditions, contraction frequency was decreased after NO donor administration. NO donors did not influence bladder activity in control rats. In patch clamp recordings, when SNAP (500 microM) was directly applied to dissociated afferent neurons innervating the urinary bladder, high-voltage-activated Ca2+ channel currents were suppressed by approximately 30%. CONCLUSIONS: Intravesical NO donors can suppress CYP-induced bladder hyperactivity. We hypothesize that the effect of NO donors is not due to smooth muscle relaxation, but rather due to an inhibitory effect on bladder afferent pathways that was manifested by an increase in intercontraction interval without changes in contraction amplitude. NO donors may be considered as a possible treatment of CYP-induced and other types of bladder inflammation.