Post-stimulation inhibitory effect on reflex bladder activity induced by activation of somatic afferent nerves in the foot

Spinal glycinergic and gamma-aminobutyric acid-ergic neurons inhibit the micturition reflex after electrical stimulation of the perineum in rats with pelvic venous congestion

OBJECTIVES

To examine whether electrical stimulation of the perineum inhibited urinary frequency in rats with pelvic venous congestion, and whether electrical stimulation influences spinal glycinergic/gamma-aminobutyric acid-ergic neurons.

METHODS

Bilateral common iliac veins and bilateral uterine veins were ligated to create pelvic venous congestion rats. At 4 weeks after ligation, cystometry was carried out before and after electrical stimulation with/without intrathecal injection of strychnine (a glycine receptor antagonist) and/or bicuculline (a gamma-aminobutyric acid type A receptor antagonist). In addition, measurement of amino acid levels in the lumbosacral cord was carried out with/without electrical stimulation, and cystometry was carried out after oral administration of glycine.

RESULTS

Continuous cystometry showed that the interval between bladder contractions was shorter in pelvic venous congestion rats than in sham rats. Electrical stimulation did not change cystometric parameters in sham rats, but the interval between bladder contractions was increased by electrical stimulation in pelvic venous congestion rats. Electrical stimulation increased the levels of glutamic acid, glycine, gamma-aminobutyric acid, and taurine in the lumbosacral cord of pelvic venous congestion rats. Intrathecal strychnine abolished the effects of electrical stimulation in pelvic venous congestion rats, and intrathecal administration of both strychnine and bicuculline shortened the interval between bladder contractions more than before electrical stimulation. Oral administration of glycine (3%) to pelvic venous congestion rats increased bladder capacity.

CONCLUSIONS

Electrical stimulation of the perineum inhibits urinary frequency mainly through activation of spinal glycinergic neurons, and partly through activation of gamma-aminobutyric acid-ergic neurons in a rat model of pelvic venous congestion.

Repeat periods of electrical stimulation prolong the modulation of the micturition reflex in the rat

AIMS

The aim of this study was to determine if the duration of the micturition reflex modulation could be prolonged by repeated periods of afferent stimulation in the decorticated rat.

METHODS

Eighteen female Sprague-Dawley rats were used for the study, 10 for intravesical electrical stimulation (IVES), and 8 for Ano-genital pudendal afferents stimulation. Repeated constant flow cystometries were performed with body-warm saline (0.06-0.1 mL/min) at about 10 min interval. The selected afferents were stimulated continuously for 5 min at maximal intensity. The same stimulation was repeated six times with a pause of 5 min between the stimulations. The mean threshold volume of cystometries performed during one hour before and each hour after the stimulation were compared.

RESULTS

After six periods of IVES, the micturition threshold volume decreased to its lowest value (62% of control) during the first hour and remained at 80% 4 h later (n = 10, P < 0.01). Ano-genital afferent stimulation produced a corresponding increase in the micturition threshold volume. The long-lasting poststimulation effect was again observed for more than 5 h. During the first hour the mean threshold volume increased to 211% of controls and it remained at about this level for the entire observation period (n = 8, P < 0.01).

CONCLUSIONS

Repeated short periods of stimulation prolonged the modulatory effect well beyond the stimulation period. The findings provide experimental evidence supporting the clinical application of IVES and ano-genital stimulation for treatment of neurogenic urinary bladder dysfunction.

Increasing bladder capacity by foot stimulation in rats with spinal cord injuries

Background

This study was to explore the possibility that foot stimulation increased bladder capacity(BC) in rats with neurogenic bladder secondary to T10 spinal cord injuries.

Methods

In 20 awake rats (stimulation group) with T10 spinal cord injuries, 5 repeat cystometrograms (CMGs) were recorded. The 1st and 2nd CMGs were performed without stimulation. The 3rd, 4th, and 5th CMGs were done separately with 1 T, 2 T, and 4 T stimulation, respectively, through a pair of pad electrodes on the skin of the hind foot. In the control group of 20 rats, 5 repeat CMGs were recorded without foot stimulation. The threshold (T) was the minimal stimulation intensity to induce an observable toe twitch.

Results

In the stimulation group, foot stimulation with 2 T significantly increased the BC an additional 68.9% ± 20.82% (p < 0.05). Foot stimulation with 4 T increased the BC an additional 120.9% ± 24.82% (p < 0.05). Compared with the control group, BC in the 1st, 2nd, and 3rd (1 T) CMG had no significant difference in the stimulation group, but the 4th (2 T) and 5th (4 T) CMGs were significantly increased (p < 0.05).

Conclusions

Electrical stimulation of the foot was effective in inhibiting reflex bladder activity and increasing bladder capacity in spinal cord injury rats.

An excitatory reflex from the superficial peroneal nerve to the bladder in cats

This study in α-chloralose-anesthetized cats discovered an excitatory peroneal nerve-to-bladder reflex. A urethral catheter was used to infuse the bladder with saline and record bladder pressure changes. Electrical stimulation was applied to the superficial peroneal nerve to trigger reflex bladder activity. With the bladder distended at a volume ~90% of bladder capacity, superficial peroneal nerve stimulation (PNS) at 1-3 Hz and threshold (T) intensity for inducing muscle twitching on the posterior thigh induced large-amplitude (40-150 cmH₂O) bladder contractions. PNS (1-3 Hz, 1-2T) applied during cystometrograms (CMGs) when the bladder was slowly (1-3 ml/min) infused with saline significantly (P < 0.01) reduced bladder capacity to ~80% of the control capacity and significantly (P < 0.05) enhanced reflex bladder contractions. To determine the impact of PNS on tibial nerve stimulation (TNS)-induced changes in bladder function, PNS was delivered following TNS. TNS of 30-min duration produced long-lasting poststimulation inhibition and significantly (P < 0.01) increased bladder capacity to 140.5 ± 7.6% of the control capacity. During the post-TNS inhibition period, PNS (1-3 Hz, 1-4T) applied during CMGs completely restored bladder capacity to the control level and significantly (P < 0.05) increased the duration of reflex bladder contractions to ~200% of control. The excitatory peroneal nerve-to-bladder reflex could also be activated by transcutaneous PNS using skin surface electrodes attached to the dorsal surface of the foot. These results raise the possibility of developing novel neuromodulation therapies to treat underactive bladder and nonobstructive urinary retention.

Transcutaneous electrical stimulation of somatic afferent nerves in the foot relieved symptoms related to postoperative bladder spasms

BACKGROUND

Bladder spasm is a common side effect of urological surgery. Main treatment modalities include opioids or anticholinergic medication; however, bladder spasms still occur even after these interventions. Recent studies indicate that transcutaneous stimulation of the foot can result in 50% increase in bladder capacity in healthy adults, and inhibit bladder detrusor overactivity in spinal cord injured patients. In this study, we examined the effects of transcutaneous electrical stimulation of the foot on bladder spasms related symptoms.

METHODS

Sixty-six male patients who underwent prostate or bladder surgeries due to benign prostatic hyperplasia or bladder diseases were randomly divided into two groups: the control group (n = 36) and the treatment group (n = 30). The control group received the routine postoperative care. The treatment group received daily transcutaneous electrical stimulation of the foot during 3 days after surgery; each time lasted for 60 min. All patients were evaluated by the Visual Analogue Scale for pain sensation, frequency of bladder spasm episodes, and a total score of bladder spasms symptoms.

RESULTS

In the control group, the patients with bladder surgery had a higher Visual Analogue Scale score than patients with prostate surgery (P = 0.024). In both treatment and control groups, the Visual Analogue Scale score, spasm frequency, and total score of bladder spasm symptoms decreased from day 1 to day 3 (P <0.001). The Visual Analogue Scale score at day 2, total score of bladder spasm symptoms at day 2 and day 3 were significantly lower in the treatment group than in the control group (P <0.05).

CONCLUSION

These results provided preliminary evidence suggesting beneficial effects of stimulating somatic afferent nerves in the foot on postoperative bladder spasms.

TRIAL REGISTRATION

The study was registered with Chinese Clinical Trial Registry on June 13 2016 ( http://www.chictr.org.cn/ ) (Identifier: ChiCTR-INR-16008635).

Role of the brain stem in tibial inhibition of the micturition reflex in cats

This study examined the role of the brain stem in inhibition of bladder reflexes induced by tibial nerve stimulation (TNS) in α-chloralose-anesthetized decerebrate cats. Repeated cystometrograms (CMGs) were performed by infusing saline or 0.25% acetic acid (AA) to elicit normal or overactive bladder reflexes, respectively. TNS (5 or 30 Hz) at three times the threshold (3T) intensity for inducing toe movement was applied for 30 min between CMGs to induce post-TNS inhibition or applied during the CMGs to induce acute TNS inhibition. Inhibition was evident as an increase in bladder capacity without a change in amplitude of bladder contractions. TNS applied for 30 min between saline CMGs elicited prolonged (>2 h) poststimulation inhibition that significantly (P < 0.05) increased bladder capacity to 30-60% above control; however, TNS did not produce this effect during AA irritation. TNS applied during CMGs at 5 Hz but not 30 Hz significantly (P < 0.01) increased bladder capacity to 127.3 ± 6.1% of saline control or 187.6 ± 5.0% of AA control. During AA irritation, naloxone (an opioid receptor antagonist) administered intravenously (1 mg/kg) or directly to the surface of the rostral brain stem (300-900 μg) eliminated acute TNS inhibition and significantly (P < 0.05) reduced bladder capacity to 62.8 ± 22.6% (intravenously) or 47.6 ± 25.5% (brain stem application). Results of this and previous studies indicate 1) forebrain circuitry rostral to the pons is not essential for TNS inhibition; and 2) opioid receptors in the brain stem have a critical role in TNS inhibition of overactive bladder reflexes but are not involved in inhibition of normal bladder reflexes.

Electrical stimulation of somatic afferent nerves in the foot increases bladder capacity in neurogenic bladder patients after sigmoid cystoplasty

Background

A previous study showed that foot stimulation can delay the bladder filling sensation and increase bladder volume in healthy humans without OAB. The aim of this study was to determine whether or not electrical stimulation of somatic afferent nerves in the foot can increase bladder capacity in neurogenic bladder patients after sigmoid cystoplasty.

Methods

Eleven subjects underwent 30-min foot stimulation using skin surface electrodes connected to a bladder-pelvic stimulator. The electrodes were attached to the bottom of the foot. The subjects completed a 5-day voiding diary, during which time foot stimulation was applied on day 3. The stimulation parameter was a continuous, bi-polar square wave form with a pulse duration of 200 μs and a stimulation frequency of 5 Hz. The stimulation intensity was set by each subject at a maximal level without causing discomfort.

Results

The volume per clean intermittent catheterization (CIC) was 279.4 ± 11.7 ml and 285.4 ± 11.8 ml on the 1st and 2nd days, respectively. On the 3rd day, the average volume per CIC increased to 361.1 ± 18.1 ml after stimulation (p <0.05). The average volume per CIC returned to 295.4 ± 13.4 ml and 275.1 ± 11.5 ml on the 4th and 5th days, respectively.

Conclusions

Foot stimulation can delay the bladder filling sensation and significantly increase bladder capacity in neurogenic bladder patients after sigmoid cystoplasty.

Reflex neuromodulation of bladder function elicited by posterior tibial nerve stimulation in anesthetized rats

Although posterior tibial nerve stimulation (PTNS) has been shown in both clinical and animal studies to elicit bladder-inhibitory reflexes, our understanding of the role of posterior tibial nerve (PTN) afferents that elicit these responses is significantly limited. To this end, we investigated the effects of frequency-dependant PTNS in urethane-anesthetized rats undergoing repeated urodynamic fills. Nerve stimulation trials (10 min) resulted in statistically significant inhibition of the urinary bladder, both during and after nerve stimulation ( P < 0.05). PTNS applied at 5 Hz resulted in both acute and prolonged changes that corresponded to 38.0% and 34.1% reductions in the bladder contraction frequency, respectively. In contrast, PTNS applied at 10 Hz could only elicit an acute decrease (22.9%) in bladder activity. Subsequent electrical activation of individual PTN branches (lateral or medial plantar nerves) confirmed that these bladder reflexes are mediated by specific subsets of the PTN trunk. Both acute and prolonged inhibition of the bladder were achieved by electrical stimulation of the lateral plantar (10 and 20 Hz) and medial plantar (5 and 10 Hz) nerves. Finally, we report a bladder-excitatory reflex that is elicited by electrical activation of either the PTN trunk or lateral plantar nerve at 50 Hz. This study shows that multiple bladder reflexes are tuned to specific subsets of nerve afferents and stimulation frequencies, each of which provide novel insights into the physiological effects of PTNS.

Impact of Bioelectronic Medicine on the Neural Regulation of Pelvic Visceral Function

Neuromodulation elicited by electrical stimulation of peripheral or spinal nerves is a U.S. Food and Drug Administered (FDA)-approved therapy for treating disorders of the pelvic viscera, including urinary urgency, urgency-frequency, nonobstructive urinary retention and fecal incontinence. The technique is also being tested experimentally for its efficacy in treating interstitial cystitis, chronic constipation and pelvic pain. The goal of neuromodulation is to suppress abnormal visceral sensations and involuntary reflexes and restore voluntary control. Although detailed mechanisms underlying the effects of neuromodulation are still to be elucidated, it is generally believed that effects are due to stimulation of action potentials in somatic afferent nerves. Afferent nerves project to the lumbosacral spinal cord, where they release excitatory neurotransmitters that activate ascending pathways to the brain or spinal circuits that modulate visceral sensory and involuntary motor mechanisms. Studies in animals revealed that different types of neuromodulation (for example, stimulation of a sacral spinal root, pudendal nerve or posterior tibial nerve) act by releasing different inhibitory and excitatory neurotransmitters in the central nervous system. In addition, certain types of neuromodulation inhibit visceral smooth muscle by initiating reflex firing in peripheral autonomic nerves or excite striated sphincter muscles by initiating reflex firing in somatic efferent nerves. This report will provide a brief summary of (a) neural control of the lower urinary tract and distal bowel, (b) clinical use of neuromodulation in the treatment of bladder and bowel dysfunctions,

Novel multi-system functional gains via task specific training in spinal cord injured male rats

Locomotor training (LT) after spinal cord injury (SCI) is a rehabilitative therapy used to enhance locomotor recovery. There is evidence, primarily anecdotal, also associating LT with improvements in bladder function and reduction in some types of SCI-related pain. In the present study, we determined if a step training paradigm could improve outcome measures of locomotion, bladder function, and pain/allodynia. After a T10 contusive SCI trained animals (adult male Wistar rats), trained animals began quadrupedal step training beginning 2 weeks post-SCI for 1 h/day. End of study experiments (3 months of training) revealed significant changes in limb kinematics, gait, and hindlimb flexor-extensor bursting patterns relative to non-trained controls. Importantly, micturition function, evaluated with terminal transvesical cystometry, was significantly improved in the step trained group (increased voiding efficiency, intercontraction interval, and contraction amplitude). Because both SCI and LT affect neurotrophin signaling, and neurotrophins are involved with post-SCI plasticity in micturition pathways, we measured bladder neurotrophin mRNA. Training regulated the expression of nerve growth factor (NGF) but not BDNF or NT3. Bladder NGF mRNA levels were inversely related to bladder function in the trained group. Monitoring of overground locomotion and neuropathic pain throughout the study revealed significant improvements, beginning after 3 weeks of training, which in both cases remained consistent for the study duration. These novel findings, improving non-locomotor in addition to locomotor functions, demonstrate that step training post-SCI could contribute to multiple quality of life gains, targeting patient-centered high priority deficits.

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.

Electrical stimulation of somatic afferent nerves in the foot increases bladder capacity in healthy human subjects

PURPOSE

We determined whether electrical stimulation of somatic afferent nerves in the foot could delay bladder filling sensations and increase bladder capacity in healthy humans without overactive bladder.

MATERIALS AND METHODS

Eight subjects underwent 90-minute foot stimulation using skin surface electrodes connected to a transcutaneous electrical nerve stimulator. The electrodes were attached to the bottom of the foot. Subjects completed a 3-day voiding diary, during which foot stimulation was applied on day 2. Stimulation parameters were pulse frequency 5 Hz, rectangular waveform pulse width 0.2 milliseconds and intensity 2 to 6 times the minimal stimulation current necessary to induce toe twitch. Stimulation intensity was set by each subject to a maximal level without causing discomfort. Subjects were provided with 500 to 1,000 ml of water to drink during stimulation.

RESULTS

Average ± SE volume per void was 350 ± 22 ml during the 24 hours before foot stimulation. This voided volume increased to a mean of 547 ± 52 ml for up to 5 hours after stimulation (p <0.01). Average voided volume returned to 363 ± 21 ml within 36 hours after stimulation. There were no adverse events.

CONCLUSIONS

Foot stimulation can delay bladder filling sensations and significantly increase bladder capacity in healthy humans without overactive bladder. Although the study group was small, our results support moving forward with clinical trials of foot neuromodulation in patients with overactive bladder.

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.

Combination of foot stimulation and tramadol treatment reverses irritation induced bladder overactivity in cats

PURPOSE

We determined whether transcutaneous electrical foot stimulation combined with a low dose of tramadol (Sigma-Aldrich®) could completely suppress bladder overactivity.

MATERIALS AND METHODS

Repeat cystometrograms were performed in 18 α-chloralose anesthetized cats by infusing the bladder with saline or 0.25% acetic acid. Transcutaneous electrical stimulation (5 Hz) of the cat hind foot at 2 to 4 times the threshold intensity needed to induce observable toe movement was applied to suppress acetic acid induced bladder overactivity. Tramadol (1 to 3 mg/kg intravenously) was administered to enhance foot inhibition.

RESULTS

Acetic acid irritated the bladder, induced bladder overactivity and significantly decreased bladder capacity to a mean ± SE of 26% ± 5% of saline control capacity (p <0.01). Without tramadol, foot stimulation at 2 and 4 threshold intensity applied during acetic acid cystometrograms significantly increased bladder capacity to a mean of 47% ± 5% and 62% ± 6% of saline control capacity, respectively (p <0.05). Without foot stimulation, tramadol (1 mg/kg) only slightly changed bladder capacity to a mean of 39% ± 2% of saline control capacity (p >0.05), while 3 mg/kg significantly increased capacity to 85% ± 14% that of control (p <0.05). However, 1 mg/kg tramadol combined with foot stimulation increased bladder capacity to a mean of 71% ± 18% (2 threshold intensity) and 84% ± 14% (4 threshold intensity), respectively, which did not significantly differ from saline control capacity. In addition, long lasting (greater than 1.5 to 2 hours) post-stimulation inhibition was induced by foot stimulation combined with 3 mg/kg tramadol treatment.

CONCLUSIONS

This study suggests a new treatment strategy for overactive bladder by combining foot stimulation with a low dose of tramadol, which is noninvasive and has potentially high efficacy and fewer adverse effects.

Involvement of opioid receptors in inhibition of bladder overactivity induced by foot stimulation in cats

PURPOSE

We examined the role of opioid receptors in the inhibition of bladder overactivity induced by electrical stimulation of the foot.

MATERIALS AND METHODS

Experiments were done in 6 cats under α-chloralose anesthesia when the bladder was infused with saline or 0.25% acetic acid. Naloxone (1 mg/kg intravenously) was administered to block opioid receptors. To modulate reflex bladder activity electrical stimulation (5 Hz, 0.2 millisecond pulse width) was applied to the foot via skin surface electrodes at intensities of multiple times the threshold needed to induce observable toe movement.

RESULTS

Acetic acid irritated the bladder, induced bladder overactivity and significantly decreased bladder capacity to a mean ± SE 25.3% ± 5.9% that of saline control capacity (p = 0.0001). Foot stimulation at 4T suppressed acetic acid induced bladder overactivity and significantly increased bladder capacity to 47.1% ± 5.9% of control (p = 0.0007). Naloxone did not significantly change bladder capacity during acetic acid irritation but it completely eliminated the inhibition of bladder overactivity induced by foot stimulation.

CONCLUSIONS

Results indicate that opioid receptors have an important role in foot afferent inhibition of bladder overactivity. This raises the possibility that opioid receptors might be used as a pharmacological target to enhance the efficacy of foot stimulation for inhibiting bladder overactivity.