Change in bladder contractility associated with bladder overactivity in rats with cerebral infarction

Overactive Bladder Symptoms Within Nervous System: A Focus on Etiology

Overactive bladder (OAB) is a common debilitating condition characterized by urgency symptoms with detrimental effects on the quality of life and survival. The exact etiology of OAB is still enigmatic, and none of therapeutic approaches seems curative. OAB is generally regarded as a separate syndrome, whereas in clinic, OAB symptoms could be found in numerous diseases of other non-urogenital systems, particularly nervous system. The OAB symptoms in neurological diseases are often poorly recognized and inadequately treated. This review provided a comprehensive overview of recent findings related to the neurogenic OAB symptoms. Relevant neurological diseases could be mainly divided into seven kinds as follows: multiple sclerosis and related neuroinflammatory disorders, Parkinson’s diseases, multiple system atrophy, spinal cord injury, dementia, peripheral neuropathy, and others. Concurrently, we also summarized the hypothetical reasonings and available animal models to elucidate the underlying mechanism of neurogenic OAB symptoms. This review highlighted the close association between OAB symptoms and neurological diseases and expanded the current knowledge of pathophysiological basis of OAB. This may increase the awareness of urological complaints in neurological disorders and inspire robust therapies with better outcomes.

Change in the central control of the bladder function of rats with focal cerebral infarction induced by photochemically-induced thrombosis

The photochemically-induced thrombosis (photothrombosis) method can create focal cerebral infarcts anywhere in the relatively superficial layers of the cerebrum; it is easy to implement and minimally invasive. Taking advantage of this versatility, we aimed to establish a new rat model of urinary frequency with focal cerebral infarction, which was characterized by its simplicity, nonlethal nature, and high reproducibility. The prefrontal cortex and the anterior cingulate cortex, which are involved in lower urinary tract control, were targeted for focal cerebral infarction, and urinary parameters were measured by cystometrogram. Cystometric analysis indicated that micturition intervals significantly shortened in photothrombosis-treated rats compared with those in the sham operative group on Days 1 and 7 (P < 0.01), but prolonged after 14 days, with no difference between the two groups. Immunopathological evaluation showed an accumulation of activated microglia, followed by an increase in reactive astrocytes at the peri-infarct zone after photothrombotic stroke. Throughout this study, all postphotothrombosis rats showed cerebral infarction in the prefrontal cortex and anterior cingulate cortex; there were no cases of rats with fatal cerebral infarction. This model corresponded to the clinical presentation, in that the micturition status changed after stroke. In conclusion, this novel model combining nonlethality and high reproducibility may be a suitable model of urinary frequency after focal cerebral infarction.

Electrochemical detection of NGF using a reduced graphene oxide- titanium nitride nanocomposite

There is a correlation between the severity of neurological impairment in patients that have suffered a cerebrovascular accident and the nerve growth factor (NGF) level. This study addressed the fabrication of a titanium nitride (TiN) and reduced graphene oxide (RGO)-based composite with remarkable electrocatalytic activity towards NGF oxidation in a phosphate buffer solution (PB, 0.1 M). The proposed electrochemical sensor was linearly related to the NGF concentration in the range of 10 nM-5 μM with a detection limit of 2.6 nM.

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

PURPOSE

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.

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Traumatic brain injury increases the risk of female urinary incontinence

AIMS

According to our knowledge, no study has attempted to explore the risk of urinary incontinence (UI) after traumatic brain injury (TBI). This study aimed to examine the relationship between TBI in Taiwanese women and their risk of developing UI.

METHODS

The study was based on 2,416 female patients newly diagnosed with TBI together with 12,080 matched enrollees without a history of TBI as a comparison group. All patients were tracked for a 1-year period from their index date to identify those who developed subsequent UI. The stratified Cox proportional hazards models were performed to compute the risk of UI between groups.

RESULTS

Of 14,496 patients, 104 (4.30%) from the TBI group and 192 (1.59%) from the comparison group had a diagnosis of UI during the follow-up period. The incidence rate of UI was 4.50 (95% CI: 3.69-5.43) per 100 person-years in patients with TBI and 1.62 (95% CI: 1.40-1.86) per 100 person-years in patients without TBI. The stratified Cox proportional analysis showed that after adjusting for socioeconomic status, obesity, hypertension, diabetes, and hysterectomy, the increased UI risk of patients with TBI persisted at about the same level as in the unadjusted analysis (hazard ratio = 2.78; 95% CI = 2.16-3.53). In addition, although patients with severe and moderate TBI had higher incidence rates of UI than patients with mild TBI, the difference did not reach a statistically significant level (P = 0.090).

CONCLUSIONS

Our results suggest that an increased risk of UI exists at the first year follow-up in patients with a TBI diagnosis.

Animal models in overactive bladder research

Overactive bladder syndrome (OAB) is a symptom-based diagnosis characterised by the presence of urinary urgency. It is highly prevalent and overlaps with the presence of bladder contractions during urine storage, which characterises the urodynamic diagnosis of detrusor overactivity. Animal models are needed to understand the pathophysiology of OAB, but the subjective nature of the symptom complex means that interpretation of the findings in animals requires caution. Because urinary urgency cannot be ascertained in animals, surrogate markers such as frequency, altered toileting areas, and non-micturition contractions have to be used instead. No model can recapitulate the subjective, objective, and related factors seen in the clinical setting. Models used include partial bladder outlet obstruction, the spontaneous hypertensive rat, the hyperlipidaemic rat, various neurological insults and some gene knock-outs. Strengths and weaknesses of these models are discussed in the context of the inherent difficulties of extrapolating subjective symptoms in animals.

New Unstable Bladder Model in Hypercholesterolemia Rats

OBJECTIVES

To evaluate the voiding function of the new vasculogenic erectile dysfunction (ED) model in hypercholesterolemic rats.

METHODS

We used 14 adult 12-week-old male Sprague-Dawley rats. The cholesterol group received a 1% cholesterol diet for 8 weeks. During the initial 2 weeks, they also drank water containing 3 mg/mL of NG-nitro-L-arginine methyl ester. After 8 weeks, we performed cystometrography, a detrusor strip contraction study, and pathologic examination of the detrusor to confirm voiding dysfunction. The results of the cholesterol and control groups were compared.

RESULTS

Compared with the control group values, the mean serum cholesterol and body weight were significantly elevated in the cholesterol group. The cholesterol group had shorter voiding intervals (377.6 +/- 205.4 versus 121.8 +/- 79.6 seconds, P <0.01) and a smaller functional bladder volume (1.4 +/- 0.7 versus 0.7 +/- 0.3 mL, P <0.05) on cystometrography compared with the control group. In the detrusor strip study, the cholesterol group had greater tension in spontaneous activities and an increase (13.1% +/- 5.6% versus 28.4% +/- 16.2%, P <0.05) in the proportion of purinergic components.

CONCLUSIONS

This vasculogenic ED rat model showed significantly frequent voiding on cystometrography. Considering the many epidemiologic and experimental data, in addition to the data from this model, ED and overactive bladder could share similar pathophysiologic features or be two symptoms of a systemic disorder. This rat model should be useful in evaluating the mechanism of ED and overactive bladder.

Mild brain ischemia produces bladder hyperactivity without brain damage in rats

INTRODUCTION

The influence of brain ischemia without cerebral infarction on voiding function is unknown. To investigate the effects of a reduction in cerebral blood flow on voiding function, the influence of chronic cerebral hypoperfusion (CH) on bladder activity was examined in rats.

MATERIALS AND METHODS

CH was induced in each of 11 female Sprague-Dawley rats by anastomosis between the right external jugular vein and the right common carotid artery with partial obstruction of the left common carotid artery. Twelve intact animals comprised a control group. Voided volume per micturition was assessed in a metabolic cage for 24 h on weeks 2, 4, and 8. Eight weeks after the operation, the rats were tested in a hippocampus-related learning paradigm, the Morris water maze. Bladder activity was monitored in 13 rats with continuous infusion cystometrography (CMG) at 2 weeks. After evaluation, the rats' brains were stained by perfusion with 2% 2,3,5-triphenyltetrazolium chloride (TTC).

RESULTS

Voided volume per micturition was significantly reduced and voiding frequency was significantly increased in CH rats 2 weeks after CH as compared to the control group (p < 0.05). Bladder capacity on CMG of CH rats was significantly reduced 14 days after CH as compared to the controls (p < 0.05). Although TTC staining of the CH rat brain did not show cerebral infarction, CH induced impairment of water maze learning.

CONCLUSIONS

These results indicate that mild forebrain ischemia without infarction results in the development of bladder hyperactivity and impairment of memory. Mild brain ischemia with aging may induce bladder overactivity in humans. Further studies of the nervous system related to bladder hyperactivity using this animal model may lead to pharmacological therapy or prevention of bladder overactivity in the aging individual with an unidentified origin of voiding dysfunction.

ROLE OF CYCLOOXYGENASE-2 IN THE DEVELOPMENT OF BLADDER OVERACTIVITY AFTER CEREBRAL INFARCTION IN THE RAT

PURPOSE

We investigated the role of cyclooxygenase (COX) isoforms in bladder overactivity induced by cerebral infarction (CI) in rats.

MATERIALS AND METHODS

CI was induced by left middle cerebral artery occlusion (MCAO) in female Sprague-Dawley rats. Bladder activity was monitored with continuous infusion cystometrography of conscious rats. Specimens were obtained from the pontine tegmental area (PTA) 1, 3, 5, 12 and 24 hours after CI or sham operation (SO). The effects of MK-801 (0.1 mg/kg intravenously), an NMDA (N-methyl-D-aspartate) glutamatergic receptor antagonist, on bladder activity, and on COX-1 and 2 mRNA expression following MCAO were examined. Real-time quantitative reverse transcriptase-polymerase chain reaction was performed to evaluate the effects of CI on gene expression in the PTA. The effects of the COX-2 inhibitor NS398 (0.01 to 10 mg/kg intravenously) on bladder activity were examined.

RESULTS

The bladder capacity of CI rats was significantly decreased 1 to 24 hours after MCAO compared with that of SO rats (p <0.05 or 0.01). One and 3 hours after MCAO mean COX-2 mRNA expression +/- SE had increased significantly to 22.4 +/- 3.5 in terms of its expression relative to the outer control in a sample obtained immediately after MCAO, in contrast to that in SO rats (p <0.01). The expression level returned to the control level within 12 hours after MCAO. COX-1 expression was not influenced by MCAO. Pretreatment with MK-801 inhibited the development of bladder overactivity and significantly decreased the expression of COX-2 mRNA in the PTA (p <0.01). Treatment with NS398 before MCAO prevented the development of bladder overactivity in a dose dependent manner and did not influence infarct volume.

CONCLUSIONS

These results indicate that the development of bladder overactivity following MCAO is accompanied by an increase in COX-2 mRNA expression in the PTA and is mediated by NMDA receptor activity. COX-2 in the brain may be a new target for the treatment of neurogenic voiding dysfunction after cerebral infarction.

Role of glutamate receptors in the development and maintenance of bladder overactivity after cerebral infarction in the rat

PURPOSE

To investigate the role of glutamate receptors in overactive bladder (OAB) caused by cerebral infarction (CI) we examined the effects of 2 different types of receptors antagonists on OAB induced by left middle cerebral artery (MCA) occlusion.

MATERIALS AND METHODS

Female rats were intravenously injected with dizocilpine, an NMDA (N-methyl-D-aspartate) receptor antagonist, or NBQX (2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo(f)quinoxaline-7-sulfonamide), an AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor antagonist, before or after MCA occlusion. Awake rats were cystometrically examined for 8 hours. Detrusor strips were evaluated for force development in response to dizocilpine and NBQX.

RESULTS

In CI rats without pretreatment bladder capacity (BC) was significantly decreased after MCA occlusion and remained consistently below half that of pre-occlusion capacity. Dizocilpine (0.5 mg/kg intravenously) administered before MCA occlusion blocked the decrease in BC in awake rats 5 to 8 hours after MCA occlusion. In CI rats pretreated with NBQX (10 or 30 mg/kg intravenously) BC was not different from that in rats without pretreatment. Increasing doses of dizocilpine (0.01 to 10 mg/kg) or NBQX (0.1 to 30 mg/kg) increased rat BC 2 hours after MCA occlusion. NBQX did not change the BC of sham operated rats. No differences in the contractile response to dizocilpine or NBQX of detrusor strips from sham operated and CI rats were observed.

CONCLUSIONS

These results indicate that NMDA receptor has an essential role in the development of OAB after CI. AMPA receptor antagonist cannot block the development of OAB. However, AMPA receptor antagonist temporally inhibits OAB after it is established by CI.

Permanent occlusion of the middle cerebral artery upregulates expression of cytokines and neuronal nitric oxide synthase in the spinal cord and urinary bladder in the adult rat

The expression pattern of proinflammatory cytokines, neuronal nitric oxide synthase (nNOS), substance P (SP) and calcitonin gene related peptide (CGRP) in the spinal cord and the bladder in response to permanent middle cerebral artery occlusion (MCAO) was investigated. In this connection, the gene expression of tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta (IL-1beta) and interleukin-6 in the lumbosacral spinal cord and the bladder as determined by real-time polymerase chain reaction was upregulated. In the spinal cord, the immunoreactivity of TNF-alpha and IL-1beta was mainly localized in the ventral horn motoneurons contralateral to MCAO. In the bladder, TNF-alpha was mainly expressed in the inflammatory cells. The expression of nNOS immunoreactivity as well as nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) staining in the spinal cord and bladder was also markedly increased in response to MCAO. Furthermore, the temporal and spatial expression of nNOS paralleled that of TNF-alpha and IL-1beta in the spinal cord. On the other hand, there was no noticeable change in gene expression and immunoreactivity of SP and CGRP. The present results have shown that cytokines and nNOS expression are elevated in areas far removed from the primary site of ischemic infarct, namely, the lumbosacral spinal cord and bladder. This together with some neuronal deaths maybe linked to the dysfunction of the latter in a clinical stroke. On the other hand, the apparent lack of SP and CGRP changes following MCAO suggests that the two neurotransmitters are not directly involved.

Effects of Tramadol on Rat Detrusor Overactivity Induced by Experimental Cerebral Infarction

OBJECTIVE

Cerebrovascular disease, such as stroke, frequently results in incontinence by reducing suprapontine micturition control. Intraluminal occlusion of the middle cerebral artery (MCA), which produces detrusor overactivity, has been introduced as a useful model of stroke-induced lower urinary tract dysfunction. Recently, the effective analgesic tramadol, was found to possess inhibitory actions on normal rat micturition. The current study aimed to examine the potential effect of tramadol on rat detrusor overactivity due to cerebral infarction.

METHODS

In female Sprague-Dawley rats, cerebral ischemia was induced by occlusion of the MCA and the urinary bladder was catheterised. Three days later, continuous cystometry was performed in awake animals and the effects of tramadol given intravenously were studied.

RESULTS

In cerebral infarcted rats, bladder capacity was lower (48+/-9%) and micturition pressure higher (76+/-21%) than in control rats. Tramadol 5 mg x kg(-1) given i.v., increased bladder capacity (59+/-29%) and threshold pressure (47+/-32%) to values similar to those in control rats. However, micturition pressure was not significantly altered. Tramadol induced diuresis in some, but not all, cerebral infarcted rats.

CONCLUSION

Tramadol normalised detrusor overactivity in MCA-occluded rats. The drug might have a treatment potential in patients with detrusor overactivity after stroke.

RNA synthesis in pons necessary for maintenance of bladder overactivity after cerebral infarction in rat

PURPOSE

The maintenance of long lasting bladder overactivity caused by cerebral infarction is believed to require transcription in the pontine micturition center. Therefore, we examined the influence of the RNA synthesis inhibitor actinomycin D (Banyu Pharmaceutical Co., Ltd., Tokyo, Japan) on bladder overactivity induced by left middle cerebral artery occlusion.

MATERIALS AND METHODS

Rats under halothane anesthesia were injected with actinomycin D or vehicle (mannitol) into the bilateral dorsal pontine tegmentum, followed by middle cerebral artery occlusion. Awake rats were cystometrically examined for 12 hours. The expression of c-fos and zif268 mRNA in the dorsal pontine tegmentum was monitored with real-time polymerase chain reaction.

RESULTS

Injection of actinomycin D produced a significant decrease in bladder capacity in sham operated rats but bladder capacity returned to control levels before sham operation within 6 hours. In cerebral infarcted rats pretreated with vehicle bladder capacity was significantly decreased after middle cerebral artery occlusion and it remained consistently below half of pre-occlusion capacity. Actinomycin D blocked the decrease in bladder capacity in cerebral infarcted rats. In actinomycin D treated cerebral infarcted rats bladder capacity gradually recovered and returned to the control level before middle cerebral artery occlusion within 10 hours. Actinomycin D suppressed an increase in c-fos mRNA expression 1 hour after middle cerebral artery occlusion as well as in zif268 3 hours after occlusion. Administering actinomycin D 0.5 or 1 hour after middle cerebral artery occlusion also suppressed bladder overactivity until at least 10 hours after occlusion but injection 3 hours after occlusion did not.

CONCLUSIONS

These results indicate that an RNA synthesis inhibitor can prevent a late stage of bladder overactivity. Transcription in the dorsal pontine tegmentum was found to be necessary to maintain the long lasting bladder overactivity caused by cerebral infarction.

Overactive bladder--experimental aspects

Supra-pontine lesions resulting from neurological disorders such as vascular disease, Parkinson's disease, or Alzheimer type senile dementia lead to an increase in bladder activity. This is due in part to the removal at the cortical inhibitory control of the micturition center in the brain stem - i.e. the pontine micturition center (PMC) - and in part to facilitation of excitatory control. These inhibitory or excitatory controls consist of several neurotransmitter systems, including glutamate, dopamine, gamma-aminobutyric acid (GABA), and acetylcholine. Bladder overactivity caused by cerebral infarction is mediated by upregulation of N-methyl-D-aspartate (NMDA) glutamatergic and D2 dopaminergic excitatory mechanisms, and by downregulation of NMDA glutamatergic and Ml muscarinic inhibitory mechanisms in the brain. Bladder overactivity associated with Parkinson's disease is reportedly induced by a loss of input to the D1 dopaminergic receptor. Furthermore, bladder overactivity caused by Alzheimer type dementia is thought to be mediated by downregulation of M1 muscarinic inhibitory mechanisms. Development of bladder overactivity following cerebral infarction is mediated by activation of the NMDA receptor and accompanied by an increase in c-fos, zif268 and COX-2 mRNA expression in the dorsal pontine tegmentum.

Neurological disorders cerebrovascular disease and parkinsonism

To store and expel urine at appropriate intervals, the lower urinary tract requires extensive input and control from the peripheral autonomic, somatic, and central nervous systems. Neurological disorders, such as cerebrovascular disease and Parkinson's disease, often cause functional disturbances of the lower urinary tract.

Effects of selective beta2 and beta3-adrenoceptor agonists on detrusor hyperreflexia in conscious cerebral infarcted rats

PURPOSE

We evaluated the effects of beta-adrenoceptor agonists on detrusor hyperreflexia in cerebral infarcted rats.

MATERIALS AND METHODS

To produce cerebral infarction in Sprague-Dawley rats the left middle cerebral artery was occluded by introducing a monofilament nylon thread into the artery. In sham operated rats the same artery was exposed but not occluded. After these operations cystometric and cardiovascular experiments were performed with no anesthesia or restraint.

RESULTS

After the operation bladder capacity was significantly decreased and voiding pressure was significantly increased in cerebral infarcted but not in sham operated animals. The difference in cerebral infarcted and sham operated rats was significant for each parameter (p <0.01). Post-void residual urine volume was not affected in either group. In the cerebral infarction group intravenous administration of CL316243 ([R,R]-5-2-[[2-(3-chlorophenyl-2-hydroxyethyl]-amino]propyl] -1,3-benzodioxole-2,2-dicarboxylate) (Kissei Central Laboratories, Hotaka, Japan) a selective beta3-adrenoceptor agonist, significantly increased bladder capacity at 10 and 100 microgram./kg. without affecting voiding pressure or post-void residual urine volume. Procaterol, a selective beta2-adrenoceptor agonist, significantly increased bladder capacity and post-void residual urine volume at 10 microgram/kg. intravenously without affecting voiding pressure. In separate experiments procaterol (1 to 100 microgram./kg. intravenously) decreased mean blood pressure and increased heart rate in a dose dependent manner. In contrast, the effects of CL316243 (0.1 to 100 microgram./kg. intravenously) on mean blood pressure and heart rate were minimal.

CONCLUSIONS

These results indicate that in cerebral infarcted rats detrusor hyperreflexia can be suppressed by the selective beta3-adrenoceptor agonist CL316243 without increasing post-void residual volume and without significant cardiovascular side effects. If the current results hold true in humans, selective beta3-adrenoceptor agonists may prove useful for treating detrusor hyperreflexia associated with cerebral infarction.

Changes in dopaminergic and glutamatergic excitatory mechanisms of micturition reflex after middle cerebral artery occlusion in conscious rats

Previous reports have shown that N-methyl-d-aspartate (NMDA) glutamatergic and D2 dopaminergic mechanisms have independent excitatory effects on bladder activity in normal and cerebral infarcted (CI) rats under urethane anesthesia. The study presented here was undertaken to investigate the interaction between these two mechanisms on bladder activity in conscious Sprague-Dawley female rats with or without cerebral infarction. Occlusion of the left middle cerebral artery or a sham operation (SO) was performed under halothane anesthesia. After recovery from the anesthesia, bladder activity was monitored continuously by means of infusion cystometrography in awake rats. The effects of cumulative intravenous doses of quinpirole (0.001-1 mg/kg), a D2 dopamine receptor agonist, were studied in awake SO and CI rats with or without dizocilpine (10 mg/kg) pretreatment. The effects of dizocilpine (1 or 10 mg/kg) were also examined in other SO or CI rats pretreated with 1 mg/kg of quinpirole. Bladder capacity in CI rats was significantly smaller (0.18 ml) than that in SO rats (0.48 ml). Quinpirole (0.1 and 1 mg/kg) further reduced bladder capacity in both types of rats, an effect blocked by sulpiride (20 mg/kg), a D2 dopamine receptor antagonist. The effect of quinpirole was also antagonized by dizocilpine (1 mg/kg) to a significantly (P < 0.01) greater degree in CI than in SO rats. In SO rats pretreated with 1 mg/kg of quinpirole, dizocilpine significantly increased bladder capacity in a dose-dependent manner. After the maximum dose (10 mg/kg) of dizocilpine, sulpiride did not produce any changes in bladder activity. In CI rats pretreated with 1 mg/kg of quinpirole, 1 mg/kg of dizocilpine increased bladder capacity. After administration of the maximum dose of dizocilpine (10 mg/kg), which did not produce an additional effect, sulpiride (20 mg/kg) increased bladder capacity by 58.3%. These results indicate that in awake rats D2 dopaminergic excitatory effects on the urinary bladder are mediated in part by NMDA glutamatergic mechanisms and in part by non-NMDA mechanisms. The latter type was more prominent in CI rats, indicating that the bladder hyperactivity induced by cerebral infarction may be mediated by an alteration in dopaminergic-glutamatergic interactions in the brain.

Role of the forebrain in bladder overactivity following cerebral infarction in the rat

This study was undertaken to investigate the contribution of the forebrain to bladder overactivity induced by cerebral infarction (CI). CI was induced by left middle cerebral artery (MCA) occlusion in female SD rat. Two and a half hours after CI or a sham operation (SO) decerebration was performed in some animals to eliminate forebrain influences on voiding function. Then bladder activity was monitored during continuous infusion cystometrograms in awake rats for 2.5 h. The effects of cumulative intravenous doses of MK-801 (0.1-1.4 mg/kg), an NMDA (N-methyl-D-aspartate) glutamatergic receptor antagonist, or sulpiride (0.1-41.1 mg/kg), D(2) selective dopaminergic receptor antagonists were studied over a 1.5-h period beginning 5 h after MCA occlusion. Bladder capacity was reduced by 57.5% after CI. In CI rats decerebration increased bladder capacity by 62.5% of predecerebration capacity. In SO rats bladder capacity was reduced by 25% after decerebration. MK-801 (0.4 and 1.4 mg/kg) increased bladder capacity in CI and CI-decerebrate rats, but did not change bladder capacity in SO-decerebrate rats. MK-801 decreased (60.7%) bladder capacity in SO-nondecerebrate rats. Sulpiride (11.1 and 41.1 mg/kg) significantly increased bladder capacity in CI, CI-decerebrate, and SO-decerebrate rats, but had no effect in SO-nondecerebrate rats. These results indicate that CI-induced decrease in bladder capacity is mediated by two mechanisms: (1) upregulation of an excitatory pathway from the forebrain, an effect blocked by decerebration and (2) downregulation of a tonic inhibitory pathway from the forebrain. The latter effect which can be induced by decerebration as well as CI unmasks a D(2) dopaminergic excitatory mechanism. An NMDA excitatory mechanism also contributes to the bladder overactivity after CI, but not after decerebration.

Changes in micturition after spinal cord injury in conscious rats

OBJECTIVES

To determine the feasibility of urodynamic monitoring of voiding function in conscious, female spinal cord-injured (SCI) rats and to compare the voiding function in SCI rats and those with normal spinal cord (NSC).

METHODS

Cystometrograms were performed on conscious, female Sprague-Dawley rats. Parameters measured included voided volume, residual volume, volume threshold for inducing micturition, voiding efficiency, micturition pressure, pressure threshold for inducing micturition, and bladder contraction duration. SCI animals were studied 2 to 3 weeks after T8-T10 spinal cord transection.

RESULTS

Approximately one half of SCI rats exhibited uninhibited bladder contractions before voiding. These contractions were not observed in NSC rats. Compared with NSC rats, SCI rats had larger volume thresholds (1.43 versus 0.34 mL, P <0.001) and voided volumes (0.72 versus 0.31 mL, P <0.01). Although SCI rats had larger micturition pressures (65 versus 35 cm H2O, P <0.001), residual volumes were increased (0.71 versus 0.03 mL, P <0.001) and voiding efficiency was decreased (50% versus 92%, P <0.001) compared with the measurements in NSC rats. The micturition pressure threshold was slightly lower (23%, P <0.05) and the bladder contraction duration was longer (33%, P <0.05) in SCI rats than in NSC rats.

CONCLUSIONS

Cystometric studies in conscious female SCI and NSC rats revealed significant changes in the activity of the lower urinary tract after spinal cord transection. Fifty-five percent of SCI rats exhibited detrusor hyperreflexia during bladder filling and decreased voiding efficiency compared with NSC animals. This method of cystometric evaluation in the conscious animal is likely to be useful for evaluating new pharmacologic treatments for neurogenic bladder dysfunction.