Sacral neuromodulation of bladder underactivity induced by prolonged pudendal afferent firing in cats.

This study examined the effect of sacral neuromodulation on persistent bladder underactivity induced by prolonged pudendal nerve stimulation (PudNS). In 10 α-chloralose-anesthetized cats, repetitive application of 30-min PudNS induced bladder underactivity evident as an increase in bladder capacity during a cystometrogram (CMG). S1 or S2 dorsal root stimulation (15 or 30 Hz) at 1 or 1.5 times threshold intensity (T) for inducing reflex hindlimb movement (S1) or anal sphincter twitch (S2) was applied during a CMG to determine if the stimulation can reverse the bladder underactivity. Persistent (>3 h) bladder underactivity consisting of a significant increase in bladder capacity to 163.1 ± 11.3% of control was induced after repetitive (1-10 times) application of 30-min PudNS. S2 but not S1 dorsal root stimulation at 15 Hz and 1 T intensity reversed the PudNS-induced bladder underactivity by significantly reducing the large bladder capacity to 124.3 ± 12.9% of control. Other stimulation parameters were not effective. After the induction of persistent underactivity, recordings of reflex bladder activity under isovolumetric conditions revealed that S2 dorsal root stimulation consistently induced the largest bladder contraction at 15 Hz and 1 T when compared with other frequencies (5-40 Hz) or intensities (0.25-1.5 T). This study provides basic science evidence consistent with the hypothesis that abnormal pudendal afferent activity contributes to the bladder underactivity in Fowler's syndrome and that sacral neuromodulation treats this disorder by reversing the bladder inhibition induced by pudendal nerve afferent activity.

Superficial peroneal neuromodulation of nonobstructive urinary retention induced by prolonged pudendal afferent activity in cats.

The purpose of this study is to determine whether superficial peroneal nerve stimulation (SPNS) can improve nonobstructive urinary retention (NOUR) induced by prolonged pudendal nerve stimulation (PNS). In this exploratory acute study using eight cats under anesthesia, PNS and SPNS were applied by nerve cuff electrodes. Skin surface electrodes were also used for SPNS. A double lumen catheter was inserted via the bladder dome for bladder infusion and pressure measurement and to allow voiding without a physical urethral outlet obstruction. The voided and postvoid residual (PVR) volumes were also recorded. NOUR induced by repetitive (4-13 times) application of 30-min PNS significantly (P < 0.05) reduced voiding efficiency by 49.5 ± 16.8% of control (78.3 ± 7.9%), with a large PVR volume at 208.2 ± 82.6% of control bladder capacity. SPNS (1 Hz, 0.2 ms) at 1.5-2 times threshold intensity (T) for inducing posterior thigh muscle contractions was applied either continuously (SPNSc) or intermittently (SPNSi) during cystometrograms to improve the PNS-induced NOUR. SPNSc and SPNSi applied by nerve cuff electrodes significantly (P < 0.05) increased voiding efficiency to 74.5 ± 18.9% and 67.0 ± 15.3%, respectively, and reduced PVR volume to 54.5 ± 39.0% and 88.3 ± 56.0%, respectively. SPNSc and SPNSi applied noninvasively by skin surface electrodes also improved NOUR similar to the stimulation applied by a cuff electrode. This study indicates that abnormal pudendal afferent activity could be a pathophysiological cause for the NOUR occurring in Fowler's syndrome and a noninvasive superficial peroneal neuromodulation therapy might be developed to treat NOUR in patients with Fowler's syndrome.

Superficial peroneal neuromodulation of persistent bladder underactivity induced by prolonged pudendal afferent nerve stimulation in cats.

The purpose of this study is to determine whether superficial peroneal nerve stimulation (SPNS) can reverse persistent bladder underactivity induced by prolonged pudendal nerve stimulation (PNS). In 16 α-chloralose-anesthetized cats, PNS and SPNS were applied by nerve cuff electrodes. Skin surface electrodes were also used for SPNS. Bladder underactivity consisting of a significant increase in bladder capacity to 157.8 ± 10.9% of control and a significant reduction in bladder contraction amplitude to 56.0 ± 5.0% of control was induced by repetitive (4-16 times) application of 30-min PNS. SPNS (1 Hz, 0.2 ms) at 1.5-2 times threshold intensity (T) for inducing posterior thigh muscle contractions was applied either continuously (SPNSc) or intermittently (SPNSi) during a cystometrogram (CMG) to determine whether the stimulation can reverse the PNS-induced bladder underactivity. SPNSc or SPNSi applied by nerve cuff electrodes during the prolonged PNS inhibition significantly reduced bladder capacity to 124.4 ± 10.7% and 132.4 ± 14.2% of control, respectively, and increased contraction amplitude to 85.3 ± 6.2% and 75.8 ± 4.7%, respectively. Transcutaneous SPNSc and SPNSi also significantly reduced bladder capacity and increased contraction amplitude. Additional PNS applied during the bladder underactivity further increased bladder capacity, whereas SPNSc applied simultaneously with the PNS reversed the increase in bladder capacity. This study indicates that a noninvasive superficial peroneal neuromodulation therapy might be developed to treat bladder underactivity caused by abnormal pudendal nerve somatic afferent activation that is hypothesized to occur in patients with Fowler's syndrome.

Restoring both continence and micturition after chronic spinal cord injury by pudendal neuromodulation.

Neurogenic bladder management after spinal cord injury (SCI) is very challenging. Daily urethral catheterization is most commonly used to empty the bladder, which causes frequent infections of the lower urinary tract. This study reports a novel idea to restore both continence and micturition after SCI by an implantable pudendal nerve stimulator (PNS). The PNS was surgically implanted in four cats with complete SCI at T9-T10 spinal level and tested weekly for 13-14 weeks under awake conditions. These chronic SCI cats consistently exhibited large residual bladder volumes (average 40-50 ml) due to their inability to void efficiently, while urine leakage also occurred frequently. The PNS which consisted of stimulating the pudendal nerve at 20-30 Hz to trigger a spinal reflex bladder contraction and at the same time blocking the pudendal nerves bilaterally with 10 kHz stimulation to relax the external urethral sphincter and reduce the urethral outlet resistance successfully induced highly efficient (average 80-100%), low pressure (<50 cmH2O) voiding. The PNS at 5 Hz also promoted urine storage by inhibiting reflex bladder activity and increasing bladder capacity. At the end of 14-week chronic testing, low pressure efficient voiding induced by PNS was further confirmed under anesthesia by directly measuring voiding pressure using a bladder catheter inserted through the bladder dome. This study demonstrated the efficacy and safety of the PNS in awake chronic SCI cats, suggesting that a novel neuroprosthesis can be developed for humans to restore bladder function after SCI by stimulating and/or blocking the pudendal nerves.

Superficial peroneal neuromodulation of nonobstructive urinary retention in cats.

AIMS: To determine if superficial peroneal nerve stimulation (SPNS) can improve nonobstructive urinary retention (NOUR). METHODS: In α-chloralose anesthetized cats, NOUR was induced by repetitive application (4-16 times) of 30-minute tibial nerve stimulation (TNS: 5 Hz frequency, 0.2 ms pulse width) at 4 to 6 times threshold intensity (T) for inducing toe twitches. SPNS (1 Hz, 0.2 ms) at 2 to 4 times threshold intensity (T) for inducing posterior thigh muscle contractions was applied either continuously (SPNSc) during a cystometrogram (CMG) or during voiding (SPNSv) by a surgically implanted cuff electrode or by skin surface electrodes to determine if the stimulation reduced NOUR induced by prolonged TNS. RESULTS: During control CMGs, efficient (86.4% ± 5.5%) voiding occurred with a postvoid residual (PVR) volume equal to 14.9% ± 6.2% of control bladder capacity. NOUR elicited by prolonged TNS significantly (P < .05) increased bladder capacity to 168.6% ± 15.5% of control, reduced voiding efficiency to 30.4% ± 4.8%, and increased PVR to 109% ± 9.2% of control. Using the implanted cuff electrode, SPNSc and SPNSv significantly (P < .05) increased voiding efficiency to 66.7% ± 7.4% and 65.0% ± 5.9%, respectively, and reduced PVR to 52.2% ± 11.4% and 64.3% ± 11.6%, respectively. SPNSc but not SPNSv significantly (P < .05) reduced bladder capacity to 133.4% ± 15% of control. Transcutaneous SPNSv but not SPNSc also significantly (P < .05) reversed the TNS-induced NOUR responses. CONCLUSIONS: This study shows that SPNS is effective in reversing NOUR induced by prolonged TNS. Transcutaneous SPNS provides the opportunity to develop a noninvasive neuromodulation therapy for NOUR to treat more patients than current sacral neuromodulation therapy.

Characterization of potentially probiotic lactic acid bacteria and bifidobacteria isolated from human colostrum.

Breast milk is the main source of nutrition for infants; it contains considerable microflora that can be transmitted to the infant endogenously or by breastfeeding, and it plays an important role in the maturation and development of the immune system. In this study, we isolated and identified lactic acid bacteria (LAB) from human colostrum, and screened 2 strains with probiotic potential. The LAB isolated from 40 human colostrum samples belonged to 5 genera: Lactobacillus, Bifidobacterium, Streptococcus, Enterococcus, and Staphylococcus. We also isolated Propionibacterium and Actinomyces. We identified a total of 197 strains of LAB derived from human colostrum based on their morphology and 16S rRNA sequence, among them 8 strains of Bifidobacterium and 10 strains of Lactobacillus, including 3 Bifidobacterium species and 4 Lactobacillus species. The physiological and biochemical characteristics of strains with good probiotic characteristics were evaluated. The tolerances of some of the Bifidobacterium and Lactobacillus strains to gastrointestinal fluid and bile salts were evaluated in vitro, using the probiotic strains Bifidobacterium lactis BB12 and Lactobacillus rhamnosus GG as controls. Among them, B. lactis Probio-M8 and L. rhamnosus Probio-M9 showed survival rates of 97.25 and 78.33% after digestion for 11 h in artificial gastrointestinal juice, and they exhibited growth delays of 0.95 and 1.87 h, respectively, in 0.3% bile salts. These two strains have the potential for application as probiotics and will facilitate functional studies of probiotics in breast milk and the development of human milk-derived probiotics.

Prolonged nonobstructive urinary retention induced by tibial nerve stimulation in cats.

Nonobstructive urinary retention (NOUR) is a medical condition without an effective drug treatment, but few basic science studies have focused on this condition. In α-chloralose-anesthetized cats, the bladder was cannulated via the dome and infused with saline to induce voiding that could occur without urethral outlet obstruction. A nerve cuff electrode was implanted for tibial nerve stimulation (TNS). The threshold (T) intensity for TNS to induce toe twitch was determined initially. Repeated (6 times) application of 30-min TNS (5 Hz, 0.2 ms, 4-6T) significantly (P < 0.05) increased bladder capacity to 180% of control and reduced the duration of the micturition contraction to 30% of control with a small decrease in contraction amplitude (80% of control), which resulted in urinary retention with a low-voiding efficiency of 30% and a large amount of residual volume equivalent to 130% of control bladder capacity. This NOUR condition persisted for >2 h after the end of repeated TNS. However, lower frequency TNS (1 Hz, 0.2 ms, 4T) applied during voiding partially reversed the NOUR by significantly (P < 0.05) increasing voiding efficiency to 60% and reducing residual volume to 70% of control bladder capacity without changing bladder capacity. These results revealed that tibial nerve afferent input can activate either an excitatory or an inhibitory central nervous system mechanism depending on afferent firing frequencies (1 vs. 5 Hz). This study established the first NOUR animal model that will be useful for basic science research aimed at developing new treatments for NOUR.

Frequency Dependent Tibial Neuromodulation of Bladder Underactivity and Overactivity in Cats.

OBJECTIVE: This study is aimed at determining if tibial nerve stimulation (TNS) can modulate both bladder underactivity and overactivity. METHODS: In α-chloralose anesthetized cats, tripolar cuff electrodes were implanted on both tibial nerves and TNS threshold (T) for inducing toe twitching was determined for each nerve. Normal bladder activity was elicited by slow intravesical infusion of saline; while bladder overactivity was induced by infusion of 0.25% acetic acid to irritate the bladder. Bladder underactivity was induced during saline infusion by repeated application (2-6 times) of 30-min TNS (5 Hz, 4-8T, 0.2 msec) to the left tibial nerve, while TNS (1 Hz, 4T, 0.2 msec) was applied to the right tibial nerve to reverse the bladder underactivity. RESULTS: Prolonged 5-Hz TNS induced bladder underactivity by significantly increasing bladder capacity to 173.8% ± 10.4% of control and reducing the contraction amplitude to 40.1% ± 15.3% of control, while 1 Hz TNS normalized the contraction amplitude and significantly reduced the bladder capacity to 130%-140% of control. TNS at 1 Hz in normal bladders did not change contraction amplitude and only slightly changed the capacity, but in both normal and underactive bladders significantly increased contraction duration. The effects of 1 Hz TNS did not persist following stimulation. Under isovolumetric conditions when the bladder was underactive, TNS (0.5-3 Hz; 1-4T) induced large amplitude and sustained bladder contractions. In overactive bladders, TNS during cystometry inhibited bladder overactivity at 5 Hz but not at 1 Hz. CONCLUSIONS: This study indicates that TNS at different frequencies might be used to treat bladder underactivity and overactivity.

Sacral neuromodulation blocks pudendal inhibition of reflex bladder activity in cats: insight into the efficacy of sacral neuromodulation in Fowler's syndrome.

This study tested the hypothesis that sacral neuromodulation, i.e., electrical stimulation of afferent axons in sacral spinal root, can block pudendal afferent inhibition of the micturition reflex. In α-chloralose-anesthetized cats, pudendal nerve stimulation (PNS) at 3-5 Hz was used to inhibit bladder reflex activity while the sacral S1 or S2 dorsal root was stimulated at 15-30 Hz to mimic sacral neuromodulation and to block the bladder inhibition induced by PNS. The intensity threshold (T) for PNS or S1/S2 dorsal root stimulation (DRS) to induce muscle twitch of anal sphincter or toe was determined. PNS at 1.5-2T intensity inhibited the micturition reflex by significantly ( P < 0.01) increasing bladder capacity to 150-170% of control capacity. S1 DRS alone at 1-1.5T intensity did not inhibit bladder activity but completely blocked PNS inhibition and restored bladder capacity to control level. At higher intensity (1.5-2T), S1 DRS alone inhibited the micturition reflex and significantly increased bladder capacity to 135.8 ± 6.6% of control capacity. However, the same higher intensity S1 DRS applied simultaneously with PNS, suppressed PNS inhibition and significantly ( P < 0.01) reduced bladder capacity to 126.8 ± 9.7% of control capacity. S2 DRS at both low (1T) and high (1.5-2T) intensity failed to significantly reduce PNS inhibition. PNS and S1 DRS did not change the amplitude and duration of micturition reflex contractions, but S2 DRS at 1.5-2T intensity doubled the duration of the contractions and increased bladder capacity. These results are important for understanding the mechanisms underlying sacral neuromodulation of nonobstructive urinary retention in Fowler's syndrome.

Saphenous nerve stimulation normalizes bladder underactivity induced by tibial nerve stimulation in cats.

This study in α-chloralose-anesthetized cats aimed at investigating the bladder responses to saphenous nerve stimulation (SNS). A urethral catheter was used to infuse the bladder with saline and to record changes in bladder pressure. With the bladder fully distended, SNS at 1-Hz frequency and an intensity slightly below the threshold (T) for inducing an observable motor response of the hindlimb muscles induced large amplitude (40-150 cmH2O) bladder contractions. Application of SNS (1 Hz, 2-4T) during cystometrograms (CMGs), when the bladder was slowly (1-3 ml/min) infused with saline, significantly ( P < 0.05) increased the duration of the micturition contraction to >200% of the control without changing bladder capacity or contraction amplitude. Repeated application (1-8 times) of intense (4-8T intensity) 30-min tibial nerve stimulation (TNS) produced prolonged post-TNS inhibition that significantly ( P < 0.01) increased bladder capacity to 135.9 ± 7.6% and decreased the contraction amplitude to 44.1 ± 16.5% of the pre-TNS control level. During the period of post-TNS inhibition, SNS (1 Hz, 2-4T) applied during CMGs completely restored the bladder capacity and the contraction amplitude to the pre-TNS control level and almost doubled the duration of the micturition contraction. These results indicate that SNS at 1 Hz can facilitate the normal micturition reflex and normalize the reflex when it is suppressed during post-TNS inhibition. This study provides an opportunity to develop a novel neuromodulation therapy for underactive bladder using SNS.

Sex difference in the contribution of GABAB receptors to tibial neuromodulation of bladder overactivity in cats.

This study investigated the role of γ-aminobutyric acid subtype B (GABAB) receptors in tibial and pudendal neuromodulation of bladder overactivity induced by intravesical administration of dilute (0.5%) acetic acid (AA) in α-chloralose-anesthetized cats. To inhibit bladder overactivity, tibial or pudendal nerve stimulation (TNS or PNS) was applied at 5 Hz and two or four times threshold (T) intensity for inducing toe or anal sphincter twitch. TNS at 2T or 4T intensity significantly (P < 0.05) increased the bladder capacity to 173.8 ± 16.2 or 198.5 ± 24.1%, respectively, of control capacity. Meanwhile, PNS at 2T or 4T intensity significantly (P < 0.05) increased the bladder capacity to 217 ± 18.8 and 221.3 ± 22.3% of control capacity, respectively. CGP52432 (a GABAB receptor antagonist) at intravenous dosages of 0.1-1 mg/kg completely removed the TNS inhibition in female cats but had no effect in male cats. CGP52432 administered intravenously also had no effect on control bladder capacity or the pudendal inhibition of bladder overactivity. These results reveal a sex difference in the role of GABAB receptors in tibial neuromodulation of bladder overactivity in cats and that GABAB receptors are not involved in either pudendal neuromodulation or irritation-induced bladder overactivity.

Role of cannabinoid receptor type 1 in tibial and pudendal neuromodulation of bladder overactivity in cats.

The role of cannabinoid type 1 (CB1) receptors in tibial and pudendal neuromodulation of bladder overactivity induced by intravesical infusion of 0.5% acetic acid (AA) was determined in α-chloralose anesthetized cats. AA irritation significantly (P < 0.01) reduced bladder capacity to 36.6 ± 4.8% of saline control capacity. Tibial nerve stimulation (TNS) at two or four times threshold (2T or 4T) intensity for inducing toe movement inhibited bladder overactivity and significantly (P < 0.01) increased bladder capacity to 69.2 ± 9.7 and 79.5 ± 7.2% of saline control, respectively. AM 251 (a CB1 receptor antagonist) administered intravenously at 0.03 or 0.1 mg/kg significantly (P < 0.05) reduced the inhibition induced by 2T or 4T TNS, respectively, without changing the prestimulation bladder capacity. However, intrathecal administration of AM 251 (0.03 mg) to L7 spinal segment had no effect on TNS inhibition. Pudendal nerve stimulation (PNS) also inhibited bladder overactivity induced by AA irritation, but AM 251 at 0.01-1 mg/kg iv had no effect on PNS inhibition or the prestimulation bladder capacity. These results indicate that CB1 receptors play an important role in tibial but not pudendal neuromodulation of bladder overactivity and the site of action is not within the lumbar L7 spinal cord. Identification of neurotransmitters involved in TNS or PNS inhibition of bladder overactivity is important for understanding the mechanisms of action underlying clinical application of neuromodulation therapies for bladder disorders.

Sacral neuromodulation of nociceptive bladder overactivity in cats.

AIMS: To investigate the effects of electrical stimulation of sacral dorsal/ventral roots on irritation-induced bladder overactivity, reveal possible different mechanisms under nociceptive bladder conditions, and establish a large animal model of sacral neuromodulation. METHODS: Intravesical infusion of 0.5% acetic acid (AA) was used to irritate the bladder and induce bladder overactivity in cats under α-chloralose anesthesia. Electrical stimulation (5, 15, or 30 Hz) was applied to individual S1-S3 dorsal or ventral roots at or below motor threshold intensity. Repeated cystometrograms (CMGs) were performed with/without the stimulation to determine the inhibition of bladder overactivity. RESULTS: AA irritation induced bladder overactivity and significantly (P < 0.05) reduced the bladder capacity to 62.6 ± 11.7% of control capacity measured during saline CMGs. At threshold intensity for inducing reflex twitching of the anal sphincter or toe, S1/S2 dorsal root stimulation at 5 Hz but not at 15 or 30 Hz inhibited bladder overactivity and significantly (P < 0.05) increased bladder capacity to 187.3 ± 41.6% and 155.5 ± 9.7% respectively, of AA control capacity. Stimulation of S3 dorsal root or S1-S3 ventral roots was not effective. Repeated stimulation of S1-S3 dorsal root did not induced a post-stimulation inhibition. CONCLUSIONS: This study established a cat model of sacral neuromodualation of nociceptive bladder overactivity. The results revealed that the mechanisms underlying sacral neuromodulation are different for nociceptive and non-nociceptive bladder activity.

Post-stimulation block of frog sciatic nerve by high-frequency (kHz) biphasic stimulation.

This study determined if high-frequency biphasic stimulation can induce nerve conduction block that persists after the stimulation is terminated, i.e., post-stimulation block. The frog sciatic nerve-muscle preparation was used in the study. Muscle contraction force induced by low-frequency (0.5 Hz) nerve stimulation was recorded to indicate the occurrence and recovery of nerve block induced by the high-frequency (5 or 10 kHz) biphasic stimulation. Nerve block was observed during high-frequency stimulation and after termination of the stimulation. The recovery from post-stimulation block occurred in two distinct phases. During the first phase, the complete block induced during high-frequency stimulation was maintained. The average maximal duration for the first phase was 107 ± 50 s. During the second phase, the block gradually or abruptly reversed. The duration of both first and second phases was dependent on stimulation intensity and duration but not frequency. Stimulation of higher intensity (1.4-2 times block threshold) and longer duration (5 min) produced the longest period (249 ± 58 s) for a complete recovery. Post-stimulation block can be induced by high-frequency biphasic stimulation, which is important for future investigations of the blocking mechanisms and for optimizing the stimulation parameters or protocols in clinical applications.

A graphene-based Fabry-Pérot spectrometer in mid-infrared region.

Mid-infrared spectroscopy is of great importance in many areas and its integration with thin-film technology can economically enrich the functionalities of many existing devices. In this paper we propose a graphene-based ultra-compact spectrometer (several micrometers in size) that is compatible with complementary metal-oxide-semiconductor (CMOS) processing. The proposed structure uses a monolayer graphene as a mid-infrared surface waveguide, whose optical response is spatially modulated using electric fields to form a Fabry-Pérot cavity. By varying the voltage acting on the cavity, we can control the transmitted wavelength of the spectrometer at room temperature. This design has potential applications in the graphene-silicon-based optoelectronic devices as it offers new possibilities for developing new ultra-compact spectrometers and low-cost hyperspectral imaging sensors in mid-infrared region.

Role of µ, κ, and δ opioid receptors in tibial inhibition of bladder overactivity in cats.

In α-chloralose anesthetized cats, we examined the role of opioid receptor (OR) subtypes (µ, κ, and δ) in tibial nerve stimulation (TNS)-induced inhibition of bladder overactivity elicited by intravesical infusion of 0.25% acetic acid (AA). The sensitivity of TNS inhibition to cumulative i.v. doses of selective OR antagonists (cyprodime for µ, nor-binaltorphimine for κ, or naltrindole for δ ORs) was tested. Naloxone (1 mg/kg, i.v., an antagonist for µ, κ, and δ ORs) was administered at the end of each experiment. AA caused bladder overactivity and significantly (P < 0.01) reduced bladder capacity to 21.1% ± 2.6% of the saline control. TNS at 2 or 4 times threshold (T) intensity for inducing toe movement significantly (P < 0.01) restored bladder capacity to 52.9% ± 3.6% or 57.4% ± 4.6% of control, respectively. Cyprodime (0.3-1.0 mg/kg) completely removed TNS inhibition without changing AA control capacity. Nor-binaltorphimine (3-10 mg/kg) also completely reversed TNS inhibition and significantly (P < 0.05) increased AA control capacity. Naltrindole (1-10 mg/kg) reduced (P < 0.05) TNS inhibition but significantly (P < 0.05) increased AA control capacity. Naloxone (1 mg/kg) had no effect in cyprodime pretreated cats, but it reversed the nor-binaltorphimine-induced increase in bladder capacity and eliminated the TNS inhibition remaining in naltrindole pretreated cats. These results indicate a major role of µ and κ ORs in TNS inhibition, whereas δ ORs play a minor role. Meanwhile, κ and δ ORs also have an excitatory role in irritation-induced bladder overactivity.

Combination of foot stimulation and tolterodine treatment eliminates bladder overactivity in cats.

AIMS: To determine whether transcutaneous foot stimulation combined with a lower dose tolterodine would inhibit bladder overactivity more effectively than either treatment alone. METHODS: Cystometrograms were performed on α-chloralose anesthetized cats (N = 6) by infusing 0.25% acetic acid (AA) to induce bladder overactivity. Foot stimulation (5 Hz) was applied at 2 and 4 times the threshold (T) intensity in volts (i.e., 2T or 4T) for inducing toe movement to inhibit bladder overactivity. Cumulative doses of tolterodine (0.003-0.3 mg/kg, i.v.) were also administered to determine the effect of combination treatment. RESULTS: AA irritation of the bladder significantly (P < 0.0001) reduced bladder capacity to 23.6 ± 7.1% of saline control capacity. Foot stimulation alone at 2T and 4T inhibited bladder overactivity and significantly (P < 0.0001) increased bladder capacity to 50.7 ± 6.8% and 79.0 ± 11.6% of saline control, respectively. Tolterodine alone at 0.3 mg/kg significantly (P < 0.05) increased bladder capacity to 65.6 ± 15.5% of saline control. However, when tolterodine at a threshold dose (0.3 mg/kg) was combined with foot stimulation, the bladder capacity was significantly (P < 0.05) increased to 86.2 ± 6.2% and 107.9 ± 10.6% by 2T and 4T stimulation, respectively. Complete inhibition of bladder overactivity could be achieved at a lower tolterodine dose (0.1 mg/kg) when combined with 4T stimulation (97.0 ± 11.2% of saline control). The amplitude of micturition contraction was not changed by tolterodine treatment. CONCLUSIONS: This study suggests a novel, efficacious, non-invasive therapy by combining foot stimulation with a lower dose tolterodine to treat bladder overactivity. It also provides the first objective evidence supporting an additive therapeutic benefit of neuromodulation and antimuscarinic combination treatment.

Inhibition of bladder overactivity by duloxetine in combination with foot stimulation or WAY-100635 treatment in cats.

The purpose of this study was to determine whether duloxetine [a serotonin (5-HT)-norepinephrine reuptake inhibitor] combined with transcutaneous foot stimulation or WAY-100635 (a 5-HT1A antagonist) can enhance inhibition of bladder overactivity in cats. Cystometrograms were performed on eight cats under α-chloralose anesthesia by infusing saline and then 0.25% acetic acid (AA) to induce bladder overactivity. To inhibit bladder overactivity, foot stimulation (5 Hz) was applied via transcutaneous pad electrodes to the right hindfoot at two and four times the threshold intensity for inducing a toe twitch. Duloxetine (0.003-3 mg/kg) was administered intravenously to determine the effect of combination treatment. After the 3 mg/kg dose of duloxetine, WAY-100635 (0.5 mg/kg) was given intravenously. AA irritation significantly (P < 0.0001) reduced bladder capacity to 42.7 ± 7.4% of the saline control capacity. Foot stimulation alone at both two and four times the threshold intensity significantly (P < 0.0001) inhibited bladder overactivity and increased bladder capacity to 66.7 ± 6.3% and 85.7 ± 6.5% of the saline control, respectively. Duloxetine alone dose dependently inhibited bladder overactivity and completely restored bladder capacity to the saline control (109 ± 15.5%) at 3 mg/kg. Although duloxetine combined with foot stimulation did not further enhance inhibition, WAY-100635 (0.5 mg/kg) given after 3 mg/kg duloxetine further increased (P = 0.008) bladder capacity to 162.2 ± 22.5% of the saline control. Although duloxetine and foot stimulation independently inhibited bladder overactivity, combined treatment did not enhance inhibition. Duloxetine combined with WAY-100635, however, synergistically enhanced bladder inhibition, indicating a potential novel treatment for overactive bladder if duloxetine is combined with a 5-HT1A receptor antagonist drug.

Contribution of opioid and metabotropic glutamate receptor mechanisms to inhibition of bladder overactivity by tibial nerve stimulation.

The contribution of metabotropic glutamate receptors (mGluR) and opioid receptors to inhibition of bladder overactivity by tibial nerve stimulation (TNS) was investigated in cats under α-chloralose anesthesia using LY341495 (a group II mGluR antagonist) and naloxone (an opioid receptor antagonist). Slow infusion cystometry was used to measure the volume threshold (i.e., bladder capacity) for inducing a large bladder contraction. After measuring the bladder capacity during saline infusion, 0.25% acetic acid (AA) was infused to irritate the bladder, activate the nociceptive C-fiber bladder afferents, and induce bladder overactivity. AA significantly (P < 0.0001) reduced bladder capacity to 26.6 ± 4.7% of saline control capacity. TNS (5 Hz, 0.2 ms) at 2 and 4 times the threshold (T) intensity for inducing an observable toe movement significantly increased bladder capacity to 62.2 ± 8.3% at 2T (P < 0.01) and 80.8 ± 9.2% at 4T (P = 0.0001) of saline control capacity. LY341495 (0.1-5 mg/kg iv) did not change bladder overactivity, but completely suppressed the inhibition induced by TNS at a low stimulus intensity (2T) and partially suppressed the inhibition at high intensity (4T). Following administration of LY341495, naloxone (0.01 mg/kg iv) completely eliminated the high-intensity TNS-induced inhibition. However, without LY341495 treatment a 10 times higher dose (0.1 mg/kg) of naloxone was required to completely block TNS inhibition. These results indicate that interactions between group II mGluR and opioid receptor mechanisms contribute to TNS inhibition of AA-induced bladder overactivity. Understanding neurotransmitter mechanisms underlying TNS inhibition of bladder overactivity is important for the development of new treatments for bladder disorders.

Neural pathways involved in sacral neuromodulation of reflex bladder activity in cats.

This study examined the mechanisms underlying the effects of sacral neuromodulation on reflex bladder activity in chloralose-anesthetized cats. Bladder activity was recorded during cystometrograms (CMGs) or under isovolumetric conditions. An S1-S3 dorsal (DRT) or ventral root (VRT) was electrically stimulated at a range of frequencies (1-30 Hz) and at intensities relative to threshold (0.25-2T) for evoking anal/toe twitches. Stimulation of DRTs but not VRTs at 1T intensity and frequencies of 1-30 Hz inhibited isovolumetric rhythmic bladder contractions. A 5-Hz DRT stimulation during CMGs was optimal for increasing (P < 0.05) bladder capacity (BC), but stimulation at 15 and 30 Hz was ineffective. Stimulation of the S1 DRT was more effective (increases BC to 144% and 164% of control at 1T and 2T, respectively) than S2 DRT stimulation (increases BC to 132% and 150% of control). Bilateral transection of the hypogastric or pudendal nerves did not change the inhibitory effect induced by S1 DRT stimulation. Repeated stimulation of S1 and S2 DRTs during multiple CMGs elicited a significant (P < 0.05) increase in BC (to 155 ± 11% of control) that persisted after termination of the stimulation. These results in cats suggest that the inhibition of reflex bladder activity by sacral neuromodulation occurs primarily in the central nervous system by inhibiting the ascending or descending pathways of the spinobulbospinal micturition reflex.