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Doelman AW, Streijger F, Majerus SJA, Damaser MS, Kwon BK. Assessing Neurogenic Lower Urinary Tract Dysfunction after Spinal Cord Injury: Animal Models in Preclinical Neuro-Urology Research. Biomedicines 2023; 11:1539. [PMID: 37371634 DOI: 10.3390/biomedicines11061539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 05/20/2023] [Accepted: 05/21/2023] [Indexed: 06/29/2023] Open
Abstract
Neurogenic bladder dysfunction is a condition that affects both bladder storage and voiding function and remains one of the leading causes of morbidity after spinal cord injury (SCI). The vast majority of individuals with severe SCI develop neurogenic lower urinary tract dysfunction (NLUTD), with symptoms ranging from neurogenic detrusor overactivity, detrusor sphincter dyssynergia, or sphincter underactivity depending on the location and extent of the spinal lesion. Animal models are critical to our fundamental understanding of lower urinary tract function and its dysfunction after SCI, in addition to providing a platform for the assessment of potential therapies. Given the need to develop and evaluate novel assessment tools, as well as therapeutic approaches in animal models of SCI prior to human translation, urodynamics assessment techniques have been implemented to measure NLUTD function in a variety of animals, including rats, mice, cats, dogs and pigs. In this narrative review, we summarize the literature on the use of animal models for cystometry testing in the assessment of SCI-related NLUTD. We also discuss the advantages and disadvantages of various animal models, and opportunities for future research.
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Affiliation(s)
- Adam W Doelman
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
| | - Femke Streijger
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
| | - Steve J A Majerus
- Department of Electrical, Computer and Systems Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
- Advanced Platform Technology Center, Louis Stokes Cleveland VA Medical Center, Cleveland, OH 44106, USA
| | - Margot S Damaser
- Advanced Platform Technology Center, Louis Stokes Cleveland VA Medical Center, Cleveland, OH 44106, USA
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Brian K Kwon
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
- Department of Orthopaedics, Vancouver Spine Surgery Institute, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
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Coolen RL, Emmer KM, Spantidea PI, van Asselt E, Scheepe JR, Serdijn WA, Blok BFM. Kilohertz alternating current neuromodulation of the pudendal nerves: effects on the anal canal and anal sphincter in rats. J Appl Biomed 2022; 20:56-69. [PMID: 35727123 DOI: 10.32725/jab.2022.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 06/21/2022] [Indexed: 11/05/2022] Open
Abstract
The first two objectives were to establish which stimulation parameters of kilohertz frequency alternating current (KHFAC) neuromodulation influence the effectiveness of pudendal nerve block and its safety. The third aim was to determine whether KHFAC neuromodulation of the pudendal nerve can relax the pelvic musculature, including the anal sphincter. Simulation experiments were conducted to establish which parameters can be adjusted to improve the effectiveness and safety of the nerve block. The outcome measures were block threshold (measure of effectiveness) and block threshold charge per phase (measure of safety). In vivo, the pudendal nerves in 11 male and 2 female anesthetized Sprague Dawley rats were stimulated in the range of 10 Hz to 40 kHz, and the effect on anal pressure was measured. The simulations showed that block threshold and block threshold charge per phase depend on waveform, interphase delay, electrode-to-axon distance, interpolar distance, and electrode array orientation. In vivo, the average anal pressure during unilateral KHFAC stimulation was significantly lower than the average peak anal pressure during low-frequency stimulation (p < 0.001). Stimulation with 20 kHz and 40 kHz (square wave, 10 V amplitude, 50% duty cycle, no interphase delay) induced the largest anal pressure decrease during both unilateral and bilateral stimulation. However, no statistically significant differences were detected between the different frequencies. This study showed that waveform, interphase delay and the alignment of the electrode along the nerve affect the effectiveness and safety of KHFAC stimulation. Additionally, we showed that KHFAC neuromodulation of the pudendal nerves with an electrode array effectively reduces anal pressure in rats.
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Affiliation(s)
- Rosa L Coolen
- Erasmus Medical Center, Department of Urology, Rotterdam, Zuid-Holland, Netherlands
| | - Koen M Emmer
- Delft University of Technology, Section Bioelectronics, Delft, Zuid-Holland, Netherlands
| | | | - Els van Asselt
- Erasmus Medical Center, Department of Urology, Rotterdam, Zuid-Holland, Netherlands
| | - Jeroen R Scheepe
- Erasmus Medical Center, Department of Urology, Rotterdam, Zuid-Holland, Netherlands
| | - Wouter A Serdijn
- Delft University of Technology, Section Bioelectronics, Delft, Zuid-Holland, Netherlands
| | - Bertil F M Blok
- Erasmus Medical Center, Department of Urology, Rotterdam, Zuid-Holland, Netherlands
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Chen J, Jian J, Wang J, Shen Z, Shen B, Wang W, Beckel J, de Groat WC, Chermansky C, Tai C. Low pressure voiding induced by stimulation and 1 kHz post-stimulation block of the pudendal nerves in cats. Exp Neurol 2021; 346:113860. [PMID: 34487735 DOI: 10.1016/j.expneurol.2021.113860] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 08/27/2021] [Accepted: 09/01/2021] [Indexed: 11/28/2022]
Abstract
The goal of this study is to induce low-pressure voiding by stimulation and bilateral 1 kHz post-stimulation block of the pudendal nerves. In anesthetized cats, wire hook electrodes were placed on the left and/or right pudendal nerves. Stimulus pulses (30 Hz, 0.2 ms) were applied to one pudendal nerve to induce a reflex bladder contraction and to produce contractions of the external urethral sphincter (EUS). High frequency (1 kHz) biphasic stimulation was applied to block axonal conduction in both pudendal nerves and block EUS activity. In 4 cats, a catheter was inserted into the distal urethra to perfuse and measure the back pressure caused by the EUS contraction. In another 5 cats, a catheter was inserted into the bladder dome and the urethra was left open to allow voiding. The 1 kHz stimulation (30-60 s, 0.5-5 mA) delivered via a wire hook electrode completely blocked pudendal nerve conduction for ≥2 min after terminating the stimulation, i.e., a post-stimulation block. The block gradually disappeared in 6-18 min. The block duration increased with increasing amplitude or duration of the 1 kHz stimulation. Without the 1 kHz block, 30 Hz stimulation alone induced high-pressure (90 cmH2O) voiding. When combined with the 1 kHz block, the 30 Hz stimulation induced low-pressure (≤50 cmH2O) voiding with a high voiding efficiency (80%). In summary, a minimally invasive surgical approach might be developed to restore voiding function after spinal cord injury by stimulation and block of the pudendal nerves using lead electrodes.
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Affiliation(s)
- Jialiang Chen
- Department of Urology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Urology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, PR China
| | - Jianan Jian
- Department of Urology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Jicheng Wang
- Department of Urology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Zhijun Shen
- Department of Urology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Bing Shen
- Department of Urology, University of Pittsburgh, Pittsburgh, PA, USA
| | - William Wang
- Department of Urology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Jonathan Beckel
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA
| | - William C de Groat
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA
| | | | - Changfeng Tai
- Department of Urology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
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Restoring both continence and micturition after chronic spinal cord injury by pudendal neuromodulation. Exp Neurol 2021; 340:113658. [PMID: 33639209 DOI: 10.1016/j.expneurol.2021.113658] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 01/23/2021] [Accepted: 02/22/2021] [Indexed: 01/23/2023]
Abstract
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.
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Yousefpour A, Erfanian A. A general framework for automatic closed-loop control of bladder voiding induced by intraspinal microstimulation in rats. Sci Rep 2021; 11:3424. [PMID: 33564019 PMCID: PMC7873267 DOI: 10.1038/s41598-021-82933-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Accepted: 01/27/2021] [Indexed: 12/13/2022] Open
Abstract
Individuals with spinal cord injury or neurological disorders have problems in voiding function due to the dyssynergic contraction of the urethral sphincter. Here, we introduce a closed-loop control of intraspinal microstimulation (ISMS) for efficient bladder voiding. The strategy is based on asynchronous two-electrode ISMS with combined pulse-amplitude and pulse-frequency modulation without requiring rhizotomy, neurotomy, or high-frequency blocking. Intermittent stimulation is alternately applied to the two electrodes that are implanted in the S2 lateral ventral horn and S1 dorsal gray commissure, to excite the bladder motoneurons and to inhibit the urethral sphincter motoneurons. Asynchronous stimulation would lead to reduce the net electric field and to maximize the selective stimulation. The proposed closed-loop system attains a highly voiding efficiency of 77.2-100%, with an average of 91.28 ± 8.4%. This work represents a promising approach to the development of a natural and robust motor neuroprosthesis device for restoring bladder functions.
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Affiliation(s)
- Abolhasan Yousefpour
- Department of Biomedical Engineering, School of Electrical Engineering, Iran Neural Technology Research Center, Iran University of Science and Technology (IUST), Tehran, Iran
| | - Abbas Erfanian
- Department of Biomedical Engineering, School of Electrical Engineering, Iran Neural Technology Research Center, Iran University of Science and Technology (IUST), Tehran, Iran.
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Li S, Browning J, Theisen K, Yecies T, Shen B, Wang J, Roppolo JR, de Groat WC, Tai C. Prolonged nonobstructive urinary retention induced by tibial nerve stimulation in cats. Am J Physiol Regul Integr Comp Physiol 2020; 318:R428-R434. [PMID: 31913685 DOI: 10.1152/ajpregu.00277.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
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.
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Affiliation(s)
- Shun Li
- Department of Urology, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Urology, The First Affiliated Hospital of Shandong First Medical University, Jinan, People's Republic of China
| | - Jeffery Browning
- Department of Urology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Katherine Theisen
- Department of Urology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Todd Yecies
- Department of Urology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Bing Shen
- Department of Urology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Jicheng Wang
- Department of Urology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - James R Roppolo
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - William C de Groat
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Changfeng Tai
- Department of Urology, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania
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Estimation of Bladder Pressure and Volume from the Neural Activity of Lumbosacral Dorsal Horn Using a Long-Short-Term-Memory-based Deep Neural Network. Sci Rep 2019; 9:18128. [PMID: 31792247 PMCID: PMC6889392 DOI: 10.1038/s41598-019-54144-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 11/09/2019] [Indexed: 12/30/2022] Open
Abstract
In this paper, we propose a deep recurrent neural network (DRNN) for the estimation of bladder pressure and volume from neural activity recorded directly from spinal cord gray matter neurons. The model was based on the Long Short-Term Memory (LSTM) architecture, which has emerged as a general and effective model for capturing long-term temporal dependencies with good generalization performance. In this way, training the network with the data recorded from one rat could lead to estimating the bladder status of different rats. We combined modeling of spiking and local field potential (LFP) activity into a unified framework to estimate the pressure and volume of the bladder. Moreover, we investigated the effect of two-electrode recording on decoding performance. The results show that the two-electrode recordings significantly improve the decoding performance compared to single-electrode recordings. The proposed framework could estimate bladder pressure and volume with an average normalized root-mean-squared (NRMS) error of 14.9 ± 4.8% and 19.7 ± 4.7% and a correlation coefficient (CC) of 83.2 ± 3.2% and 74.2 ± 6.2%, respectively. This work represents a promising approach to the real-time estimation of bladder pressure/volume in the closed-loop control of bladder function using functional electrical stimulation.
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Cai H, Morgan T, Pace N, Shen B, Wang J, Roppolo JR, Horlen K, Khanwilkar P, Groat WC, Tai C. Low pressure voiding induced by a novel implantable pudendal nerve stimulator. Neurourol Urodyn 2019; 38:1241-1249. [DOI: 10.1002/nau.23994] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 02/01/2019] [Accepted: 03/18/2019] [Indexed: 11/10/2022]
Affiliation(s)
- Haotian Cai
- Department of Urology University of Pittsburgh Pittsburgh Pennsylvania
- School of Health and Rehabilitation Science University of Pittsburgh Pittsburgh Pennsylvania
| | - Tara Morgan
- Department of Urology University of Pittsburgh Pittsburgh Pennsylvania
| | - Natalie Pace
- Department of Urology University of Pittsburgh Pittsburgh Pennsylvania
| | - Bing Shen
- Department of Urology University of Pittsburgh Pittsburgh Pennsylvania
| | - Jicheng Wang
- Department of Urology University of Pittsburgh Pittsburgh Pennsylvania
| | - James R. Roppolo
- Department of Pharmacology and Chemical Biology University of Pittsburgh Pittsburgh Pennsylvania
| | | | | | - William C. Groat
- Department of Pharmacology and Chemical Biology University of Pittsburgh Pittsburgh Pennsylvania
| | - Changfeng Tai
- Department of Urology University of Pittsburgh Pittsburgh Pennsylvania
- Department of Pharmacology and Chemical Biology University of Pittsburgh Pittsburgh Pennsylvania
- Department of Bioengineering University of Pittsburgh Pittsburgh Pennsylvania
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Peh WYX, Raczkowska MN, Teh Y, Alam M, Thakor NV, Yen SC. Closed-loop stimulation of the pelvic nerve for optimal micturition. J Neural Eng 2018; 15:066009. [PMID: 30181427 DOI: 10.1088/1741-2552/aadee9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
OBJECTIVE Neural stimulation to restore bladder function has traditionally relied on open-loop approaches that used pre-set parameters, which do not adapt to suboptimal outcomes. The goal of this study was to examine the effectiveness of a novel closed-loop stimulation paradigm for improving micturition or bladder voiding. APPROACH We compared the voiding efficiency obtained with this closed-loop framework against open-loop stimulation paradigms in anesthetized rats. The bladder pressures that preceded voiding, and the minimum current amplitudes for stimulating the pelvic nerves to evoke bladder contractions, were first calibrated for each animal. An automated closed-loop system was used to initiate voiding upon bladder fullness, adapt the stimulation current by using real-time bladder pressure changes to classify voiding outcomes, and halt stimulation when the bladder had been emptied or when the safe stimulation limit was reached. MAIN RESULTS In vivo testing demonstrated that the closed-loop system achieved high voiding efficiency or VE (75.7% ± 3.07%, mean ± standard error of the mean) and outperformed open-loop systems with either conserved number of stimulation epochs (63.2% ± 4.90% VE) or conserved charge injected (32.0% ± 1.70% VE). Post-hoc analyses suggest that the classification algorithm can be further improved with data from additional closed-loop experiments. SIGNIFICANCE This novel approach may be applied to an implantable device for treating underactive bladder (<60% VE), especially in cases where under- or over-stimulation of the nerve is a concern.
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Affiliation(s)
- Wendy Yen Xian Peh
- Singapore Institute for Neurotechnology, National University of Singapore, 28 Medical Drive, #05-02, Singapore 117456, Singapore
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Creasey GH. Restoration of Bladder and Bowel Control After Spinal Cord Injury. Neuromodulation 2018. [DOI: 10.1016/b978-0-12-805353-9.00124-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Prochazka A. Neurophysiology and neural engineering: a review. J Neurophysiol 2017; 118:1292-1309. [PMID: 28566462 PMCID: PMC5558026 DOI: 10.1152/jn.00149.2017] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 05/30/2017] [Accepted: 05/30/2017] [Indexed: 12/19/2022] Open
Abstract
Neurophysiology is the branch of physiology concerned with understanding the function of neural systems. Neural engineering (also known as neuroengineering) is a discipline within biomedical engineering that uses engineering techniques to understand, repair, replace, enhance, or otherwise exploit the properties and functions of neural systems. In most cases neural engineering involves the development of an interface between electronic devices and living neural tissue. This review describes the origins of neural engineering, the explosive development of methods and devices commencing in the late 1950s, and the present-day devices that have resulted. The barriers to interfacing electronic devices with living neural tissues are many and varied, and consequently there have been numerous stops and starts along the way. Representative examples are discussed. None of this could have happened without a basic understanding of the relevant neurophysiology. I also consider examples of how neural engineering is repaying the debt to basic neurophysiology with new knowledge and insight.
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Affiliation(s)
- Arthur Prochazka
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
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Effects of Acute Sacral Neuromodulation at Different Frequencies on Bladder Overactivity in Pigs. Int Neurourol J 2017; 21:102-108. [PMID: 28673064 PMCID: PMC5497198 DOI: 10.5213/inj.1732754.377] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2016] [Accepted: 11/28/2016] [Indexed: 01/23/2023] Open
Abstract
Purpose We investigated the effects of different stimulation frequencies on the inhibition of bladder overactivity by sacral neuromodulation (SNM) in pigs. Methods Implant-driven stimulators were used to stimulate the S3 spinal nerve in 13 pigs. Cystometry was performed by infusing normal saline (NS) or acetic acid (AA). SNM (pulse width, 210 µsec) at frequencies ranging from 5 to 50 Hz was conducted at the intensity threshold at which observable perianal and/or tail movement was induced. Multiple cystometrograms were performed to determine the effects of different frequencies on the micturition reflex. Results AA-induced bladder overactivity significantly reduced the bladder capacity (BC) to 34.4%±4.7% of the NS control level (354.4±35.9 mL) (P<0.05). During AA infusion, SNM at 5 Hz did not significantly change the BC (48.1%±6.9% of the NS control level) (P>0.05), but SNM at 15, 30, and 50 Hz significantly increased the BC to 54.5%±7.1%, 55.2%±6.5%, and 57.2%±6.1% of the NS control level (P<0.05), respectively. No significant differences were found among the results obtained using frequencies of 15, 30, and 50 Hz (P>0.05). Conclusions This study demonstrated that 15 Hz was an appropriate frequency for SNM and that frequencies higher than 15 Hz did not lead to better surgical outcomes.
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Effects of pudendal neuromodulation on bladder function in chronic spinal cord-injured rats. J Formos Med Assoc 2016; 115:703-13. [DOI: 10.1016/j.jfma.2015.07.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2014] [Revised: 07/02/2015] [Accepted: 07/02/2015] [Indexed: 02/02/2023] Open
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Ju YH, Liao LM. Electrical stimulation of dog pudendal nerve regulates the excitatory pudendal-to-bladder reflex. Neural Regen Res 2016; 11:676-81. [PMID: 27212934 PMCID: PMC4870930 DOI: 10.4103/1673-5374.180757] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Pudendal nerve plays an important role in urine storage and voiding. Our hypothesis is that a neuroprosthetic device placed in the pudendal nerve trunk can modulate bladder function after suprasacral spinal cord injury. We had confirmed the inhibitory pudendal-to-bladder reflex by stimulating either the branch or the trunk of the pudendal nerve. This study explored the excitatory pudendal-to-bladder reflex in beagle dogs, with intact or injured spinal cord, by electrical stimulation of the pudendal nerve trunk. The optimal stimulation frequency was approximately 15-25 Hz. This excitatory effect was dependent to some extent on the bladder volume. We conclude that stimulation of the pudendal nerve trunk is a promising method to modulate bladder function.
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Affiliation(s)
- Yan-He Ju
- Department of Urology, China Rehabilitation Research Center, Beijing, China; School of Rahabilitation Medicine, Capital Medical University, Beijing, China; Center of Neural Injury and Repair, Beijing Institute for Brain Disorders, Beijing, China
| | - Li-Min Liao
- Department of Urology, China Rehabilitation Research Center, Beijing, China; School of Rahabilitation Medicine, Capital Medical University, Beijing, China; Center of Neural Injury and Repair, Beijing Institute for Brain Disorders, Beijing, China
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de Groat WC, Tai C. Impact of Bioelectronic Medicine on the Neural Regulation of Pelvic Visceral Function. Bioelectron Med 2015; 2015:25-36. [PMID: 26491706 PMCID: PMC4610375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023] Open
Abstract
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,
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Affiliation(s)
- William C de Groat
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania, United States of America
| | - Changfeng Tai
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania, United States of America
- Department of Urology, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania, United States of America
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de Groat WC, Tai C. Impact of Bioelectronic Medicine on the Neural Regulation of Pelvic Visceral Function. Bioelectron Med 2015. [DOI: 10.15424/bioelectronmed.2015.00003] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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Yang G, Wang J, Shen B, Roppolo JR, de Groat WC, Tai C. Pudendal nerve stimulation and block by a wireless-controlled implantable stimulator in cats. Neuromodulation 2013; 17:490-6; discussion 496. [PMID: 24320615 DOI: 10.1111/ner.12136] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Revised: 09/20/2013] [Accepted: 10/25/2013] [Indexed: 11/27/2022]
Abstract
OBJECTIVE The study aims to determine the functionality of a wireless-controlled implantable stimulator designed for stimulation and block of the pudendal nerve. MATERIALS AND METHODS In five cats under α-chloralose anesthesia, the stimulator was implanted underneath the skin on the left side in the lower back along the sacral spine. Two tripolar cuff electrodes were implanted bilaterally on the pudendal nerves in addition to one bipolar cuff electrode that was implanted on the left side central to the tripolar cuff electrode. The stimulator provided high-frequency (5-20 kHz) biphasic stimulation waveforms to the two tripolar electrodes and low-frequency (1-100 Hz) rectangular pulses to the bipolar electrode. Bladder and urethral pressures were measured to determine the effects of pudendal nerve stimulation (PNS) or block. RESULTS The maximal (70-100 cmH2O) urethral pressure generated by 20-Hz PNS applied via the bipolar electrode was completely eliminated by the pudendal nerve block induced by the high-frequency stimulation (6-15 kHz, 6-10 V) applied via the two tripolar electrodes. In a partially filled bladder, 20-30 Hz PNS (2-8 V, 0.2 ms) but not 5 Hz stimulation applied via the bipolar electrode elicited a large sustained bladder contraction (45.9 ± 13.4 to 52.0 ± 22 cmH2O). During cystometry, the 5 Hz PNS significantly (p < 0.05) increased bladder capacity to 176.5 ± 27.1% of control capacity. CONCLUSIONS The wireless-controlled implantable stimulator successfully generated the required waveforms for stimulation and block of pudendal nerve, which will be useful for restoring bladder functions after spinal cord injury.
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Affiliation(s)
- Guangning Yang
- Department of Urology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Biomedical Engineering, Beijing Jiaotong University, China
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Boger A, Bhadra N, Gustafson KJ. Different clinical electrodes achieve similar electrical nerve conduction block. J Neural Eng 2013; 10:056016. [PMID: 23986089 DOI: 10.1088/1741-2560/10/5/056016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE We aim to evaluate the suitability of four electrodes previously used in clinical experiments for peripheral nerve electrical block applications. APPROACH We evaluated peripheral nerve electrical block using three such clinical nerve cuff electrodes (the Huntington helix, the Case self-sizing Spiral and the flat interface nerve electrode) and one clinical intramuscular electrode (the Memberg electrode) in five cats. Amplitude thresholds for the block using 12 or 25 kHz voltage-controlled stimulation, onset response, and stimulation thresholds before and after block testing were determined. MAIN RESULTS Complete nerve block was achieved reliably and the onset response to blocking stimulation was similar for all electrodes. Amplitude thresholds for the block were lowest for the Case Spiral electrode (4 ± 1 Vpp) and lower for the nerve cuff electrodes (7 ± 3 Vpp) than for the intramuscular electrode (26 ± 10 Vpp). A minor elevation in stimulation threshold and reduction in stimulus-evoked urethral pressure was observed during testing, but the effect was temporary and did not vary between electrodes. SIGNIFICANCE Multiple clinical electrodes appear suitable for neuroprostheses using peripheral nerve electrical block. The freedom to choose electrodes based on secondary criteria such as ease of implantation or cost should ease translation of electrical nerve block to clinical practice.
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Affiliation(s)
- Adam Boger
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
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Collinger JL, Foldes S, Bruns TM, Wodlinger B, Gaunt R, Weber DJ. Neuroprosthetic technology for individuals with spinal cord injury. J Spinal Cord Med 2013; 36:258-72. [PMID: 23820142 PMCID: PMC3758523 DOI: 10.1179/2045772313y.0000000128] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
CONTEXT Spinal cord injury (SCI) results in a loss of function and sensation below the level of the lesion. Neuroprosthetic technology has been developed to help restore motor and autonomic functions as well as to provide sensory feedback. FINDINGS This paper provides an overview of neuroprosthetic technology that aims to address the priorities for functional restoration as defined by individuals with SCI. We describe neuroprostheses that are in various stages of preclinical development, clinical testing, and commercialization including functional electrical stimulators, epidural and intraspinal microstimulation, bladder neuroprosthesis, and cortical stimulation for restoring sensation. We also discuss neural recording technologies that may provide command or feedback signals for neuroprosthetic devices. CONCLUSION/CLINICAL RELEVANCE Neuroprostheses have begun to address the priorities of individuals with SCI, although there remains room for improvement. In addition to continued technological improvements, closing the loop between the technology and the user may help provide intuitive device control with high levels of performance.
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Liu H, Zhu L, Sheng S, Sun L, Zhou H, Tang H, Qiu T. Post stimulus effects of high frequency biphasic electrical current on a fibre's conductibility in isolated frog nerves. J Neural Eng 2013; 10:036024. [PMID: 23676976 DOI: 10.1088/1741-2560/10/3/036024] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
OBJECTIVE High frequency biphasic (HFB) electrical currents are widely used in nerve blocking studies. Their safety margins largely remain unknown and need to be investigated. APPROACH This study, exploring the post stimulus effects of HFB electrical currents on a nerve's conductibility, was performed on bullfrog sciatic nerves. Both compound action potentials (CAPs) and differential CAPs (DCAPs, i.e. control CAPs subtracted by CAPs following HFB currents) were obtained, and N1 and N2 components, which were the first and second upward components of DCAPs, were used for analyses of the effects introduced by HFB electrical stimulation. MAIN RESULTS First, HFB currents of 10 kHz at a completely blocking threshold were applied for 5 s. The maximum amplitudes and conducting velocities of the CAPs were significantly (P < 0.02) decreased within the observed period (60 s) following HFB currents. The DCAPs displayed clear N1 and N2 components, demonstrating respectively the losses of the fibres' normal conductibility and the appearances of new delayed conductions. Decreases of N1 amplitudes along time, regarded as the recovery of the nerve's conductibility, exhibited two distinct phases: a fast one lasting several seconds and a slow one lasting longer than 5 min. Further tests showed a linear relationship between the HFB stimulation durations and recovering periods of N1 amplitudes. Supra-threshold blocking did not cause higher N1 amplitudes. SIGNIFICANCE This study indicates that HFB electrical currents lead to long lasting post stimulus reduction of a nerve's conductibility, which might relate to potential nerve injuries. A possible mechanism, focusing on changes in intracellular and periaxonal ionic concentrations, was proposed to underlie the reduction of the nerve's conductibility and potential nerve injuries. Greater caution and stimulation protocols with greater safety margins should be explored when utilizing HFB electrical current to block nerve conductions.
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Affiliation(s)
- Hailong Liu
- Department of Biomedical Engineering, Dalian University of Technology, Dalian, Liaoning, People's Republic of China.
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Chen SC, Lai CH, Fan WJ, Peng CW. Pudendal neuromodulation improves voiding efficiency in diabetic rats. Neurourol Urodyn 2012; 32:293-300. [PMID: 22674809 DOI: 10.1002/nau.22280] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 05/15/2012] [Indexed: 12/22/2022]
Abstract
AIMS Diabetic cystopathy is typically manifested as bladder voiding dysfunction, and numerous patients are refractory to standard therapy. In this study, we determined whether electrical stimulation (ES) of the sensory branch of the pudendal nerve could engage an augmenting reflex and thereby improve bladder emptying in a diabetic animal model with cystopathy. METHODS The efficiency of bladder emptying with ES of the sensory branch of the pudendal nerve at different stimulation intensities was measured in rats at 8 or 18 weeks after the induction of diabetes with streptozotocin. RESULTS The voiding efficiency (VE) was reduced from 74 ± 4% to 30 ± 8% in rats with diabetes for 8 weeks and from 73 ± 6% to 20 ± 6% in rats with diabetes for 18 weeks. ES at lower intensities (0.025-0.05 mA) applied to the pudendal sensory nerve did not affect the VE in rats with diabetes for 18 weeks but increased the VE in rats with diabetes for 8 weeks. Subsequently, when the stimulation intensity was elevated to 0.1-0.3 mA, the VEs in rats with diabetes for both 8 and 18 weeks increased to 40-50%. CONCLUSIONS The results of the present study are consistent with the essential role for pudendal sensory feedback in efficient bladder emptying, and electrical activation of the sensory branch of the pudendal nerve was efficient restoring the voiding function in diabetic animals with cystopathy. This could provide an approach to improve bladder emptying in diabetic patients with voiding dysfunction.
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Affiliation(s)
- Shih-Ching Chen
- Department of Physical Medicine and Rehabilitation, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
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Boger AS, Bhadra N, Gustafson KJ. High frequency sacral root nerve block allows bladder voiding. Neurourol Urodyn 2012; 31:677-82. [PMID: 22473837 DOI: 10.1002/nau.21075] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Accepted: 01/24/2011] [Indexed: 11/08/2022]
Abstract
AIMS Dyssynergic reflexive external urethral sphincter (EUS) activity following spinal cord injury can prevent bladder voiding, resulting in significant medical complications. Irreversible sphincterotomies or neurotomies can prevent EUS activation and allow bladder voiding, but may cause incontinence or loss of sacral reflexes. We investigated whether kilohertz frequency (KF) electrical conduction block of the sacral roots could prevent EUS activation and allow bladder voiding. METHODS The S2 sacral nerve roots were stimulated bilaterally to generate bladder pressure in six cats. One S1 nerve root was stimulated proximally (20 Hz biphasic pulse trains) to evoke EUS pressure, simulating worst-case dyssynergic EUS reflexes. KF waveforms (12.5 kHz biphasic square wave) applied to an electrode implanted distally on the S1 nerve root blocked nerve conduction, preventing the increase in EUS pressure and allowing voiding. RESULTS Applying KF waveforms increased bladder voiding in single, limited-duration trials from 3 ± 6% to 59 ± 12%. Voiding could be increased to 82 ± 9% of the initial bladder volume by repeating or increasing the duration of the trials. CONCLUSIONS Sacral nerve block can prevent EUS activation and allow complete bladder voiding, potentially eliminating the need for a neurotomy. Eliminating neurotomy requirements could increase patient acceptance of bladder voiding neuroprostheses, increasing patient quality of life and reducing the cost of patient care.
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Affiliation(s)
- Adam S Boger
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA
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25
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Snellings AE, Yoo PB, Grill WM. Urethral flow-responsive afferents in the cat sacral dorsal root ganglia. Neurosci Lett 2012; 516:34-8. [PMID: 22480694 DOI: 10.1016/j.neulet.2012.03.045] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Revised: 03/01/2012] [Accepted: 03/16/2012] [Indexed: 11/25/2022]
Abstract
Although sensory feedback from the urethra plays an integral role in the regulation of lower urinary tract function, little is known about the properties of flow-responsive primary afferent neurons. The purpose of this study was to characterize the activity of sacral afferents that responded to fluid flow through the urethra. Single neuron action potentials were recorded extracellularly from the S1 and S2 dorsal root ganglia in eight cats anesthetized with α-chloralose. 21 of 116 cells responded to urethral flow but not to mechanical palpation of the perineum, 22 responded to both urethral flow and palpation, and 27 responded to palpation only. 34 of the 43 flow-responsive cells exhibited a firing response to 10 ml flow boluses that could be fit using a power function: FR(t)=a×(t)(b)+c, where FR is firing rate, t is time, and a, b and c are constants. In all 34 cells the 'b' term was negative, indicating that the firing rate slowed over the time course of the urethral flow. In 16 of the 24 cells that were recorded during at least four different flow rates, a power function provided a good fit of the relationship between firing rate and flow rate: FR(flow)=k×(flow)(p)+q, where k, p and q are constants. In each of these 16 cells the 'p' term was positive, indicating that the firing rate tended to increase with increases in flow rate. These are the first data to characterize the properties of flow-responsive afferents in the cat, and reveal properties that parallel those of other afferents.
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Affiliation(s)
- Andre' E Snellings
- Department of Biomedical Engineering, Duke University, Durham, NC 27708-0281, USA
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26
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Su X, Nickles A, Nelson DE. Neuromodulation in a rat model of the bladder micturition reflex. Am J Physiol Renal Physiol 2011; 302:F477-86. [PMID: 22049401 DOI: 10.1152/ajprenal.00515.2011] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A rat model of bladder reflex contraction (BRC) was used to determine the optimal frequency and intensity of spinal nerve (SN) stimulation to produce neuromodulation of bladder activity and to assess the therapeutic mechanisms of this neuromodulation. In anesthetized female rats (urethane 1.2 g/kg ip), a wire electrode was used to produce bilateral stimulation of the L6 SN. A cannula was placed into the bladder via the urethra, and the urethra was ligated to ensure an isovolumetric bladder. Saline infusion induced BRC. Electrical stimulation of the SN produced a frequency- and intensity-dependent attenuation of the frequency of bladder contractions. Ten-herz stimulation produced maximal inhibition; lower and higher stimulation frequency produced less attenuation of BRC. Attenuation of bladder contraction frequency was directly proportional to the current intensity. At 10 Hz, stimulation using motor threshold pulses (T(mot)) produced a delayed inhibition of the frequency of bladder contractions to 34 ± 11% of control. Maximal bladder inhibition appeared at 10 min poststimulation. High current intensity at 0.6 mA (∼6 * T(mot)) abolished bladder contraction during stimulation, and the inhibition was sustained for 10 min poststimulation (prolonged inhibition). Furthermore, in rats pretreated with capsaicin (125 mg/kg sc), stimulation produced a stronger inhibition of BRC. The inhibitory effects on bladder contraction may be mediated by both afferent and efferent mechanisms. Lower intensities of stimulation may activate large, fast-conducting fibers and actions through the afferent limb of the micturition reflex arc in SN neuromodulation. Higher intensities may additionally act through the efferent limb.
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Affiliation(s)
- Xin Su
- Medtronic, Inc., Neuromodulation Research, 7000 Central Ave. NE, RCE470, Minneapolis, MN 55432, USA.
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27
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Tai C, Chen M, Shen B, Wang J, Liu H, Roppolo JR, de Groat WC. Plasticity of urinary bladder reflexes evoked by stimulation of pudendal afferent nerves after chronic spinal cord injury in cats. Exp Neurol 2010; 228:109-17. [PMID: 21192927 DOI: 10.1016/j.expneurol.2010.12.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Revised: 12/13/2010] [Accepted: 12/15/2010] [Indexed: 01/23/2023]
Abstract
Bladder reflexes evoked by stimulation of pudendal afferent nerves (PudA-to-Bladder reflex) were studied in normal and chronic spinal cord injured (SCI) adult cats to examine the reflex plasticity. Physiological activation of pudendal afferent nerves by tactile stimulation of the perigenital skin elicits an inhibitory PudA-to-Bladder reflex in normal cats, but activates an excitatory reflex in chronic SCI cats. However, in both normal and chronic SCI cats electrical stimulation applied to the perigenital skin or directly to the pudendal nerve induces either inhibitory or excitatory PudA-to-Bladder reflexes depending on stimulation frequency. An inhibitory response occurs at 3-10 Hz stimulation, but becomes excitatory at 20-30 Hz. The inhibitory reflex activated by electrical stimulation significantly (P<0.05) increases the bladder capacity to about 180% of control capacity in normal and chronic SCI cats. The excitatory reflex significantly (P<0.05) reduces bladder capacity to about 40% of control capacity in chronic SCI cats, but does not change bladder capacity in normal cats. Electrical stimulation of pudendal afferent nerves during slow bladder filling elicits a large amplitude bladder contraction comparable to the contraction induced by distension alone. A bladder volume about 60% of bladder capacity was required to elicit this excitatory reflex in normal cats; however, in chronic SCI cats a volume less than 20% of bladder capacity was sufficient to unmask an excitatory response. This study revealed the co-existence of both inhibitory and excitatory PudA-to-Bladder reflex pathways in cats before and after chronic SCI. However our data combined with published electrophysiological data strongly indicates that the spinal circuitry for both the excitatory and inhibitory PudA-to-Bladder reflexes undergoes a marked reorganization after SCI.
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Affiliation(s)
- Changfeng Tai
- Department of Urology, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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28
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Durand DM, Park EH, Jensen AL. Potassium diffusive coupling in neural networks. Philos Trans R Soc Lond B Biol Sci 2010; 365:2347-62. [PMID: 20603356 DOI: 10.1098/rstb.2010.0050] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Conventional neural networks are characterized by many neurons coupled together through synapses. The activity, synchronization, plasticity and excitability of the network are then controlled by its synaptic connectivity. Neurons are surrounded by an extracellular space whereby fluctuations in specific ionic concentration can modulate neuronal excitability. Extracellular concentrations of potassium ([K(+)](o)) can generate neuronal hyperexcitability. Yet, after many years of research, it is still unknown whether an elevation of potassium is the cause or the result of the generation, propagation and synchronization of epileptiform activity. An elevation of potassium in neural tissue can be characterized by dispersion (global elevation of potassium) and lateral diffusion (local spatial gradients). Both experimental and computational studies have shown that lateral diffusion is involved in the generation and the propagation of neural activity in diffusively coupled networks. Therefore, diffusion-based coupling by potassium can play an important role in neural networks and it is reviewed in four sections. Section 2 shows that potassium diffusion is responsible for the synchronization of activity across a mechanical cut in the tissue. A computer model of diffusive coupling shows that potassium diffusion can mediate communication between cells and generate abnormal and/or periodic activity in small (section sign 3) and in large networks of cells (section sign 4). Finally, in section sign 5, a study of the role of extracellular potassium in the propagation of axonal signals shows that elevated potassium concentration can block the propagation of neural activity in axonal pathways. Taken together, these results indicate that potassium accumulation and diffusion can interfere with normal activity and generate abnormal activity in neural networks.
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Affiliation(s)
- Dominique M Durand
- Department of Biomedical Engineering, Neural Engineering Center, Case Western Reserve University, Cleveland, OH 44106, USA.
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29
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Horvath EE, Yoo PB, Amundsen CL, Webster GD, Grill WM. Conditional and continuous electrical stimulation increase cystometric capacity in persons with spinal cord injury. Neurourol Urodyn 2010; 29:401-7. [PMID: 19634166 DOI: 10.1002/nau.20766] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
AIMS Individuals with spinal cord injury (SCI) exhibit neurogenic detrusor overactivity (NDO) causing high intravesicle pressures and incontinence. The first aim was to measure changes in maximum cystometric capacity (MCC) evoked by electrical stimulation of the dorsal genital nerve (DGN) delivered either continuously or conditionally (only during bladder contractions) in persons with SCI. The second aim was to use the external anal sphincter electromyogram (EMG(EAS)) for real-time control of conditional stimulation. METHODS Serial filling cystometries were performed in nine volunteers with complete or incomplete supra-sacral SCI. Conditional stimulation was delivered automatically when detrusor pressure increased to 8-12 cmH(2)O above baseline. MCCs were measured for each treatment (continuous, conditional, and no stimulation) and compared using post-ANOVA Tukey HSD paired comparisons. Additional treatments in two subjects used the EMG(EAS) for automatic control of conditional stimulation. RESULTS Continuous and conditional stimulation increased MCC by 63 +/- 73 ml (36 +/- 24%) and 74 +/- 71 ml (51 +/- 37%), respectively (P < 0.05), compared to no stimulation. There was no significant difference between MCCs for conditional and continuous stimulation, but conditional stimulation significantly reduced stimulation time (174 +/- 154 sec, or 27 +/- 17% of total time) as compared to continuous stimulation (469 +/- 269 sec, 100% of total time, P < 0.001). The EMG(EAS) algorithm provided reliable detection of bladder contractions (six of six contractions over four trials) and reduced stimulation time (21 +/- 8% of total time). CONCLUSIONS Conditional stimulation generates increases in bladder capacity while substantially reducing stimulation time. Furthermore, EMG(EAS) was successfully used as a real-time feedback signal to control conditional electrical stimulation in a laboratory setting.
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Affiliation(s)
- Eric E Horvath
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708-0281, USA
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30
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Fry C, Daneshgari F, Thor K, Drake M, Eccles R, Kanai A, Birder L. Animal models and their use in understanding lower urinary tract dysfunction. Neurourol Urodyn 2010; 29:603-8. [DOI: 10.1002/nau.20903] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Bruns TM, Bhadra N, Gustafson KJ. Bursting stimulation of proximal urethral afferents improves bladder pressures and voiding. J Neural Eng 2009; 6:066006. [PMID: 19901447 DOI: 10.1088/1741-2560/6/6/066006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Reflex bladder excitation has been evoked via pudendal nerve, pudendal nerve branch and intraurethral stimulation; however, afferent-evoked bladder emptying has been less efficient than direct activation of the bladder via sacral root stimulation. A stimulation method that improves activation of the urethra-bladder excitatory reflex with minimal sphincter recruitment may lead to improved bladder emptying. Fine wire electrodes were placed in the wall of the urethra in five cats. Placement of electrodes near the proximal urethra evoked bladder contractions with minimal sphincter activation. On these electrodes, lower frequency burst-patterned stimuli evoked greater bladder voiding efficiencies (71.2 +/- 27.8%) than other stimulus patterns on the same electrodes (50.4 +/- 41.5%, p > 0.05) or any stimulus pattern on electrodes that elicited urethral closure (16.5 +/- 12.7%, p < 0.05). Fine wire electrodes specifically targeted afferent fibers in the urethra, indicating the feasibility of clinical evaluations using the same method. This work may improve the translation of next generation neuroprostheses for bladder control.
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Affiliation(s)
- Tim M Bruns
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA. Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH, USA. Cleveland Functional Electrical Stimulation Center, Cleveland, OH, USA
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TAI C, ROPPOLO JR. Bladder and Sphincter Control after Spinal Cord Injury. Low Urin Tract Symptoms 2009. [DOI: 10.1111/j.1757-5672.2009.00038.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Gaunt RA, Prochazka A. Transcutaneously coupled, high-frequency electrical stimulation of the pudendal nerve blocks external urethral sphincter contractions. Neurorehabil Neural Repair 2008; 23:615-26. [PMID: 19109445 DOI: 10.1177/1545968308328723] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Detrusor-sphincter dyssynergia is a condition in which reflexive contractions of the external urethral sphincter occur during bladder contractions, preventing the expulsion of urine. High-frequency stimulation (kHz range) has been shown to elicit a fast-acting and reversible block of action potential propagation in peripheral nerves, which may be a useful technique in the management of this condition. OBJECTIVE The aim of these experiments was to see if a newly developed stimulus delivery system, capable of transmitting current transcutaneously to remote peripheral nerves using a passive implanted conductor, was an effective way to transmit high-frequency waveforms to the pudendal nerve to block ongoing sphincter contractions. METHODS High-frequency waveforms were delivered through the skin to the pudendal nerve using a passive implanted conductor in 6 adult cats anesthetized with isoflurane. Five of the experiments were acute, terminal procedures, and the remaining cat was implanted with a permanent electrode system allowing evaluation for 6 months. Typical stimulation parameters were in the range of 1 to 10 kHz and 1 to 10 mA. RESULTS Complete blocking of external urethral sphincter contractions was achieved in 5 of the 6 animals. High-frequency stimulation was also tested in the chronically implanted animal without anesthesia, and the stimulation was tolerated with minimal aversive reactions. CONCLUSIONS The transcutaneous passive implanted conductor stimulus delivery system is an effective way to stimulate the pudendal nerve at high frequency, leading to sphincter relaxation. This system may provide a simple means to implement this stimulation paradigm in people with detrusor-sphincter dyssynergia.
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Affiliation(s)
- Robert A Gaunt
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
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Influence of temperature on pudendal nerve block induced by high frequency biphasic electrical current. J Urol 2008; 180:1173-8. [PMID: 18639276 DOI: 10.1016/j.juro.2008.04.138] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Indexed: 11/24/2022]
Abstract
PURPOSE We determined the influence of temperature on the minimal stimulation frequency required to block pudendal nerve conduction. MATERIALS AND METHODS The pudendal nerve block induced by high frequency, biphasic electrical current was investigated at different temperatures using cats under alpha-chloralose anesthesia. Urethral pressure was measured to indicate pudendal nerve activation or block. RESULTS As stimulation frequency was increased above a frequency threshold, the urethral pressure response was decreased and the pudendal nerve was blocked. The minimal stimulation frequency required to block the pudendal nerve was decreased from 6 to 4 kHz as the temperature was decreased from 37C to 15C. At a 4 kHz frequency the maximal temperature below which the pudendal nerve could be blocked was 24.5C. CONCLUSIONS To block pudendal nerve conduction at body temperature (37C) the stimulation frequency must be greater than 6 kHz. This study provides a practical guide for blocking the pudendal nerves to restore efficient voiding after spinal cord injury.
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Woock JP, Yoo PB, Grill WM. Activation and inhibition of the micturition reflex by penile afferents in the cat. Am J Physiol Regul Integr Comp Physiol 2008; 294:R1880-9. [PMID: 18434446 DOI: 10.1152/ajpregu.00029.2008] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Coordination of the urinary bladder and the external urethral sphincter is controlled by descending projections from the pons and is also subject to modulation by segmental afferents. We quantified the effects on the micturition reflex of sensory inputs from genital afferents traveling in the penile component of the somatic pudendal nerve by electrical stimulation of the dorsal nerve of the penis (DNP) in alpha-chloralose anesthetized male cats. Depending on the frequency of stimulation (range, 1-40 Hz), activation of penile afferents either inhibited contractions of the bladder and promoted urine storage or activated the bladder and produced micturition. Stimulation of the DNP at 5-10 Hz inhibited distension-evoked contractions and increased the maximum bladder capacity before incontinence. Conversely, stimulation at 33 and 40 Hz augmented distension-evoked contractions. When the bladder was filled above a threshold volume (70% of the volume necessary for distension-evoked contractions), stimulation at 20-40 Hz activated de novo the micturition reflex and elicited detrusor contractions that increased voiding efficiency compared with distension-evoked voiding. Electrical stimulation of the DNP with a cuff electrode or percutaneous wire electrode produced similar results. The ability to evoke detrusor contractions by activation of the DNP was preserved following acute spinal cord transection. These results demonstrate a clear role of genital afferents in modulating the micturition reflex and suggest the DNP as a potential target for functional restoration of bladder control using electrical stimulation.
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Affiliation(s)
- John P Woock
- Department of Biomedical Engineering, Duke University, Durham, NC 27708-0281, USA
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36
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Boger A, Bhadra N, Gustafson KJ. Bladder voiding by combined high frequency electrical pudendal nerve block and sacral root stimulation. Neurourol Urodyn 2008; 27:435-9. [DOI: 10.1002/nau.20538] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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