Biomedical subjects

William C De Groat

Publications and source records attributed to William C De Groat.

9 recordsLinked to original sources

PubMed2004

Sustained intravesical drug delivery using thermosensitive hydrogel.

PURPOSE: Direct instillation of drug solutions into the bladder through a urethral catheter (i.e., intravesical therapy) evades systemic adverse effects of drugs used for bladder diseases. However, conventional vehicles for these drugs fail to extend duration of drug exposure in the bladder beyond the first voiding of urine postinstillation. The current study seeks to overcome the aforementioned inherent limitation of intravesical drug administration by using thermosensitive hydrogel as a matrix for sustained intravesical drug delivery. METHODS: Under halothane anesthesia, normal adult female Sprague-Dawley rats were catheterized with PE-50 tubing to instill either 0.02% w/v solution of fluorescein isothiocyanate (FITC) or the same amount of FITC in a 30% w/v dispersion of thermosensitive [Poly(ethylene glycol)-Poly[lactic acid-co-glycolic acid]-Poly(ethylene glycol)) (PEG-PLGA-PEG) polymer in a 0.1 M phosphate buffer. After instillations, rats were kept in metabolic cages for urine collection. Fluorescence emanating from FITC was measured in the urine at various time points up to 24 h after instillation. A rat model of cyclophosphamide-induced cystitis was chosen for the efficacy study using misoprostol as a model drug entrapped in the thermosensitive hydrogel in place of FITC. Efficacy of hydrogel containing misoprostol was compared against rat groups instilled with saline, hydrogel, and misoprostol independently. RESULTS: Prolonged drug exposure to the bladder afforded by hydrogel was evident from the time course of FITC elimination in the urine and by the green fluorescence of FITC seen at the bladder surface when isolated 24 h after instillation. Rats instilled with free FITC voided almost all of the fluorescence in the urine within the first 8 h, whereas rats instilled with hydrogel encapsulated FITC showed sustained release up to 24 h after instillation. Using a cyclophosphamide-induced cystitis model, rats instilled with misoprostol, a synthetic PGE1 analog, showed significantly reduced frequency of urine voiding (p < 0.05) as compared to the rats instilled with saline. Histological examination of the urothelium showed near normal morphology in rats instilled with misoprostol in hydrogel, whereas extensive tissue damage was observed in rats instilled with saline. CONCLUSION: Our study showed that PEG-PLGA-PEG polymer could be used as a viable sustained drug delivery system for intravesical therapy of diseases of the bladder such as cystitis using misoprostol.

Animals↗

PubMed2004

Suppression of detrusor-sphincter dyssynergia by immunoneutralization of nerve growth factor in lumbosacral spinal cord in spinal cord injured rats.

PURPOSE: We investigated the effects of intrathecal application of nerve growth factor (NGF) antibodies (NGF-Abs) and desensitization of C-fiber afferent pathways by capsaicin treatment on detrusor-sphincter dyssynergia (DSD) after spinal cord injury (SCI). MATERIALS AND METHODS: In adult female rats SCI was induced by complete transection of the spinal cord at Th8 to 9. Ten days after spinalization vehicle or NGF-Ab (10 microg daily) was continuously administered at the level of the L6-S1 spinal cord through an implanted intrathecal catheter connected to an osmotic pump for 2 weeks. Another group of spinalized rats was treated with capsaicin (125 mg/kg subcutaneously) 3 weeks after spinalization and 5 days before experiments. Simultaneous recordings of intravesical pressure and urethral perfusion pressure were then performed. NGF levels in the L6 spinal cord were measured in vehicle or NGF-Ab treated spinalized rats using enzyme-linked immunosorbent assay. RESULTS: DSD was observed in all vehicle treated spinalized rats. The average urethral pressure increase at the peak bladder contraction was significantly lower by 84% and 78% in NGF-Ab and capsaicin treated spinalized rats, respectively, than in vehicle treated rats. After NGF-Ab treatment NGF levels were significantly decreased by 38% in the L6 spinal cord compared with vehicle treated spinalized rats, in which NGF levels in the L6 spinal cord were 7 times higher than in spinal intact rats. CONCLUSIONS: Increased levels of NGF in the spinal cord could contribute to the emergence of DSD that is at least in part mediated by C-fiber bladder afferents after SCI. Thus suppression of NGF levels in afferent pathways could be useful for treating DSD following SCI.

Afferent Pathways↗

PubMed2004

Urodynamic and immunohistochemical evaluation of intravesical capsaicin delivery using thermosensitive hydrogel and liposomes.

PURPOSE: Aqueous insolubility of the vanilloids such as capsaicin is a major disincentive in their intravesical therapy of detrusor hyperreflexia. We sought to overcome the delivery of this hydrophobic neurotoxin by entrapping it in a lipid bilayer of positively charged multilamellar lipid vesicles (liposomes) or in a hydrophobic polymer matrix of thermosensitive hydrogel. MATERIALS AND METHODS: Liposomes, hydrogel and 30% ethanol/normal saline were prepared with or without 1 mM capsaicin (0.5 ml) and administered intravesically for 30 minutes to 7 groups of age matched, normal female adult Sprague-Dawley rats under halothane anesthesia. At 48 hours after intravesical instillation cystometric studies were performed using urethane anesthesia (0.04 ml per minute). The animals were subsequently sacrificed and whole bladders were harvested for histology and immunohistochemistry. RESULTS: In normal urethane anaesthetized rats capsaicin in 30% ethanol and liposomes completely blocked micturition reflexes. Capsaicin in hydrogel did not completely block the micturition reflex but it significantly decreased bladder contraction frequency compared with vehicle controls. The results of cystometry with capsaicin in liposomes and capsaicin in 30% ethanol correlated with a significant decrease in calcitonin gene-related peptide staining of afferent nerves in the bladder wall. Photographs taken after hematoxylin and eosin staining of the bladder treated with liposomes and hydrogel in the absence of capsaicin did not reveal any adverse histological changes. There were significant histological changes in bladders treated with 30% ethanol alone. CONCLUSIONS: In comparison with 30% ethanol liposomes are a superior vehicle for the intravesical administration of capsaicin, producing comparable efficacy with less tissue damage. Hydrogel can also serve as safe alternative option for capsaicin delivery.

Administration, Intravesical↗

PubMed2004

Urethral dysfunction in diabetic rats.

PURPOSE: We investigated the effects of diabetes mellitus (DM) on urethral relaxation mechanisms during reflex bladder contractions in rats. MATERIALS AND METHODS: Five weeks after streptozotocin injection (65 mg/kg intraperitoneally) the effects of DM on urethral relaxation mechanisms were evaluated by simultaneous recordings of intravesical pressure under isovolumetric conditions and urethral perfusion pressure (UPP) using urethane anesthesia. RESULTS: In diabetic rats the UPP nadir during urethral relaxation and intravesical pressure thresholds for inducing urethral relaxation were significantly higher (199% and 92%, respectively) than in normal rats, while baseline UPPs were not significantly different. The mean rate and amplitude of high frequency oscillations of urethral striated muscle in diabetic rats were also significantly lower (17% and 64%, respectively) compared with normal rats. Following alpha-bungarotoxin treatment to eliminate striated muscle sphincter contractions intravenous administration of L-arginine (200 mg/kg) [corrected] , the substrate of nitric oxide (NO) synthase, decreased the UPP nadir (36% and 22%, in diabetic and normal rats) as well as intravesical pressure thresholds (49% and 22%, respectively). The effect was greater (61% to 126%) in diabetic rats than in normal rats. In each group of rats the effect of L-arginine was inhibited by Nomega-nitro-L-arginine (100 mg/kg intravenously) [corrected], a NO synthase inhibitor. CONCLUSIONS: During reflex bladder contractions streptozotocin induced diabetic rats exhibited smooth and striated muscle dysfunctions of the urethral outlet. L-arginine therapy, which could augment urethral smooth muscle relaxation by increasing NO production, may be useful for partially restoring the urethral relaxation mechanism in DM.

Animals↗

PubMed2003

Development of an experimental system for the study of urethral biomechanical function.

Despite its principal mechanical function in the storage and release of urine, the biomechanical properties of the urethra have remained largely unexplored. The purpose of this study was to develop and validate an experimental model that can be used for evaluating whole urethral tissue in such a manner. Bladder-urethral specimens were excised from halothane-anesthetized female rats and mounted at in vivo length within the experimental apparatus consisting of a tissue perfusion chamber, an adjustable fluid column, and a laser micrometer. Outer diameter measurements were made at proximal, mid, and distal axial locations in response to increases in intraluminal pressure and after addition of various muscle-responsive agents. Basal smooth muscle tone and regional variations in compliance were detected through pressure-diameter responses. Chemically evoked contractile responses were measured and correspond to regional compositions of intrinsic smooth and striated muscle components. The results presented illustrate the utility of this system, which should permit a more thorough characterization of structure-function relationships and urethral biomechanical function in relation to normal and dysfunctional tissue states.

Acetylcholine↗

PubMed2003

Intravesical protamine sulfate and potassium chloride as a model for bladder hyperactivity.

OBJECTIVES: An acute animal model for hyperactive bladder in rats was developed using intravesical infusion of protamine sulfate (PS), an agent thought to break down urothelial barrier function, and physiologic concentrations of potassium chloride (KCl). METHODS: Continuous cystometrograms (CMGs) were performed in urethane-anesthetized female rats by filling the bladder (0.04 mL/min) with normal saline followed by intravesical infusion of a test solution consisting of either KCl (100 or 500 mM) or PS (10 or 30 mg/mL) for 60 minutes. Subsequently, the 10 mg/mL PS-treated animals were infused intravesically with 100, 300, or 500 mM KCl. Some animals were pretreated with capsaicin (125 mg/kg subcutaneously) 4 days before the experiments. RESULTS: Unlike KCl (100 or 500 mM) or a low concentration of PS (10 mg/mL) alone, the intravesical administration of a high concentration of PS (30 mg/mL) produced irritative effects with a decreased intercontraction interval (by 80.6%). After infusion of a low concentration of PS, infusion of 300 or 500 mM KCl produced irritative effects (intercontraction interval decreased by 76.9% or 82.9%, respectively). The onset of irritation occurred more rapidly after 500 mM KCl (10 to 15 minutes) than after 300 mM KCl (20 to 30 minutes). Capsaicin pretreatment delayed the onset (approximately 60 minutes) and reduced the magnitude (intercontraction interval decreased by 35.5%) of irritative effects. CONCLUSIONS: Intravesical administration of KCl after PS treatment activates capsaicin-sensitive afferents and detrusor muscle and presumably capsaicin-resistant afferents. Modest, noncytotoxic affronts to urothelial barrier function can result in dramatic irritative responses. This model may be useful in the study of bladder irritation and hyperactivity.

Administration, Intravesical↗

PubMed2003

Intravesical liposome administration--a novel treatment for hyperactive bladder in the rat.

OBJECTIVES: To examine the effect of intravesical administration of liposomes (LPs) on chemically induced bladder hyperactivity in the rat. It has been suggested that interstitial cystitis (IC) is associated with a dysfunctional or leaky epithelium. Thus, enhancement of epithelial barrier function might be useful in the treatment of IC. LPs are vesicles that are concentric phospholipid bilayers separated by an aqueous compartment and can fuse with cells to provide a molecular film that can promote wound healing. METHODS: The intravesical pressure was recorded using a transurethral catheter in adult female Sprague-Dawley rats anesthetized with urethane (1.2 g/kg subcutaneously). Some animals were pretreated with capsaicin (125 mg/kg subcutaneously) 4 days before the experiments. Continuous cystometrograms were performed by slowly filling the bladder (0.04 mL/min) with solutions of varying compositions, including saline, acetic acid (AA, 0.1%), potassium chloride (KCl, 500 mM), protamine sulfate (PS, 10 mg/mL), LPs, PS/KCl, or LPs/KCl. The parameters measured included the intercontraction interval (ICI), amplitude of bladder contractions, compliance, and micturition pressure threshold. RESULTS: The ICI was decreased after exposure to AA (79.8% decrease) or PS/KCl (81% decrease); however, the ICI was not changed after LPs, PS, or KCl alone. The decreased ICI was partially reversed after infusion of LPs (172.8% increase) or LPs/KCl (63% increase), but was not significantly changed after switching to saline or KCl administration. Pretreatment with capsaicin delayed the onset of the irritative effects of AA by approximately 30 to 60 minutes, but had not changed the magnitude after 2 hours of infusion. CONCLUSIONS: Intravesical administration of PS/KCl or AA activates capsaicin-sensitive and capsaicin-resistant afferents in a time-dependent sequence that is partially reversed by LP infusion. We hypothesize that LPs might enhance the barrier properties of a dysfunctional uroepithelium and increase resistance to irritant penetration. Thus, intravesical LP administration could be a novel treatment of patients with IC.

Administration, Intravesical↗

PubMed2003

Dopaminergic mechanisms underlying bladder hyperactivity in rats with a unilateral 6-hydroxydopamine (6-OHDA) lesion of the nigrostriatal pathway.

1. This study was undertaken to elucidate dopaminergic mechanisms underlying bladder hyperactivity in a rat model of Parkinson's disease (PD) induced by a unilateral 6-OHDA injection into the substantia nigra pars compacta. 2. In 6-OHDA-lesioned rats, voided volume per micturition (0.41+/-0.04 ml, mean+/-s.e.m.) measured during 24 h in a metabolic cage was significantly smaller than in sham-operated rats (0.67+/-0.07 ml). 3. Cystrometrograms (CMG) in conscious animals revealed significantly smaller bladder capacity (BC) (0.46+/-0.03 ml) in 6-OHDA-lesioned rats than in sham rats (0.72+/-0.06 ml). 4. SKF38393 (D1/D5 receptor agonist, i.v.) significantly increased BC in 6-OHDA rats without apparent effects in sham rats. SKF38393 applied intracerebroventricularly (i.c.v.) under urethane anesthesia also increased BC in 6-OHDA-lesioned rats and by a smaller increment in sham rats. 5. In contrast, quinpirole (D2/D3/D4 receptor agonist, i.v.) significantly reduced BC in sham and 6-OHDA-lesioned rats. Intrathecal injection of quinpirole similarly reduced BC in sham and 6-OHDA-lesioned rats. 6. PD128907 (D(3)-receptor agonist) did not have significant effects on BC in 6-OHDA-lesioned rats. 7. These results indicate that a rat model of PD exhibited bladder hyperactivity as observed in patients with PD, and that stimulation of D1/D5 dopamine receptors at a supraspinal site can suppress bladder hyperactivity in PD, whereas stimulation of D2/D4, but not D3, dopamine receptors had the opposite effect to reduce bladder capacity. Thus, D1/D5 dopamine receptor agonists might be effective in treating neurogenic bladder hyperactivity in PD.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed2003

Excitatory synaptic currents in lumbosacral parasympathetic preganglionic neurons evoked by stimulation of the dorsal commissure.

Excitatory pathways from the dorsal commissure (DCM) to L(6)-S(1) parasympathetic preganglionic neurons (PGN) were examined using whole-cell patch-clamp recording techniques in spinal cord slices from neonatal rats. PGN were identified by retrograde axonal transport of a fluorescent dye injected into the intraperitoneal space. Excitatory postsynaptic currents (EPSCs) were evoked in PGN by stimulation of DCM in the presence of bicuculline methiodide (10 microM) and strychnine (1 microM) to block inhibitory pathways. Electrical stimulation of DCM evoked two types of inward currents. In the majority of PGN (n = 66), currents (mean amplitude, 47.9 +/- 4.7 pA) occurred at a short and relatively constant latency (3.8 +/- 0.1 ms) and presumably represent monosynaptic EPSCs (Type 1). However, in other neurons (n = 20), a different type of EPSC (Type 2) was noted, consisting of a fast monosynaptic component followed by a prolonged inward current with superimposed fast transients presumably representing excitatory inputs mediated by polysynaptic pathways. Type 1 EPSCs were pharmacologically dissected into two components. A fast component was blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 5 microM) and a slowly decaying component was blocked by 2-amino-5-phosphonovalerate (APV, 50 microM). The fast component of Type 1 EPSCs had a linear current-voltage relationship and reversed at a membrane potential of -7.6 +/- 1.3 mV (n = 5). The fast component of Type 2 EPSCs was also blocked by 5 microM CNQX and the remaining slower component was blocked by 50 microM APV. When the DCM was stimulated in the presence of 50 microM APV, the time to peak and decay time constant in Type 1 EPSCs were 1.9 +/- 0.2 and 4.1 +/- 0.8 ms, respectively. Examination of the NMDA receptor-mediated component of the EPSCs in the presence of 5 microM CNQX revealed a current-voltage relationship that had a region of negative slope conductance (from -20 to -80 mV), which was abolished in Mg(2+)-free external solution. The time to peak and decay time constant of this component were 14.2 +/- 2.0 and 91.0 +/- 12.4 ms, respectively. Type 1 EPSCs in some PGN responded in an all-or-none manner and presumably represented unitary synaptic responses; whereas Type 2 EPSCs always exhibited a graded stimulus intensity-response relationship. Paired-pulse facilitation (50-ms interstimulus intervals; 141 +/- 5.6% increase, n = 8) of EPSCs was observed. These results indicate that PGN receive monosynaptic and polysynaptic glutamatergic excitatory inputs from neurons and/or axonal pathways in the DCM.

Animals↗