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Hao F, Jia F, Hao P, Duan H, Wang Z, Fan Y, Zhao W, Gao Y, Fan OR, Xu F, Yang Z, Sun YE, Li X. Proper wiring of newborn neurons to control bladder function after complete spinal cord injury. Biomaterials 2023; 292:121919. [PMID: 36455486 DOI: 10.1016/j.biomaterials.2022.121919] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 10/14/2022] [Accepted: 11/18/2022] [Indexed: 11/26/2022]
Abstract
Activation of endogenous neurogenesis by bioactive materials enables restoration of sensory/motor function after complete spinal cord injury (SCI) via formation of new relay neural circuits. The underlying wiring logic of newborn neurons in adult central nervous system (CNS) is unknown. Here, we report neurotrophin3-loaded chitosan biomaterial substantially recovered bladder function after SCI. Multiple neuro-circuitry tracing technologies using pseudorabies virus (PRV), rabies virus (RV), and anterograde adeno-associated virus (AAV), demonstrated that newborn neurons were integrated into the micturition neural circuits and reconnected higher brain centers and lower spinal cord centers to control voiding, and participated in the restoration of the lower urinary tract function, even in the absence of long-distance axonal regeneration. Opto- and chemo-genetic studies further supported the notion that the supraspinal control of the lower urinary tract function was partially recovered. Our data demonstrated that regenerated relay neurons could be properly integrated into disrupted long-range neural circuits to restore function of adult CNS.
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Affiliation(s)
- Fei Hao
- Beijing Key Laboratory for Biomaterials and Neural Regeneration, School of Engineering Medicine, Beihang University, Beijing, 100191, China
| | - Fan Jia
- Guangdong Provincial Key Laboratory of Brain Connectome and Behavior, CAS Key Laboratory of Brain Connectome and Manipulation, The Brain Cognition and Brain Disease Institute (BCBDI), Translational Research Center for the Nervous System (TRCNS), Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences; Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, 518055, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Peng Hao
- Department of Neurobiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China
| | - Hongmei Duan
- Department of Neurobiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China
| | - Zijue Wang
- Department of Neurobiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China
| | - Yubo Fan
- Key Laboratory for Biomechanics and Mechanobiology of the Ministry of Education, Beijing Advanced Innovation Centre for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, China; School of Engineering Medicine, Beihang University, Beijing, 100191, China
| | - Wen Zhao
- Department of Neurobiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China
| | - Yudan Gao
- Department of Neurobiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China
| | - Orion R Fan
- Department of Evolution and Ecology, University of California, Davis, CA, 90007, USA
| | - Fuqiang Xu
- Guangdong Provincial Key Laboratory of Brain Connectome and Behavior, CAS Key Laboratory of Brain Connectome and Manipulation, The Brain Cognition and Brain Disease Institute (BCBDI), Translational Research Center for the Nervous System (TRCNS), Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences; Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, 518055, China; University of Chinese Academy of Sciences, Beijing, 100049, China; State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Center for Magnetic Resonance, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, China.
| | - Zhaoyang Yang
- Department of Neurobiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China.
| | - Yi E Sun
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration (Tongji University), Ministry of Education, Shanghai, 200065, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai East Hospital, Tongji University, School of Medicine, Shanghai, 200120, China.
| | - Xiaoguang Li
- Beijing Key Laboratory for Biomaterials and Neural Regeneration, School of Engineering Medicine, Beihang University, Beijing, 100191, China; Department of Neurobiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China.
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Rao Y, Gao Z, Li X, Li X, Li J, Liang S, Li D, Zhai J, Yan J, Yao J, Chen X. Ventrolateral Periaqueductal Gray Neurons Are Active During Urination. Front Cell Neurosci 2022; 16:865186. [PMID: 35813503 PMCID: PMC9259957 DOI: 10.3389/fncel.2022.865186] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Accepted: 05/31/2022] [Indexed: 11/13/2022] Open
Abstract
The ventrolateral periaqueductal gray (VLPAG) is thought to be the main PAG column for bladder control. PAG neurons (especially VLPAG neurons) and neurons in the pontine micturition center (PMC) innervating the bladder detrusor have anatomical and functional synaptic connections. The prevailing viewpoint on neural control of the bladder is that PAG neurons receive information on the decision to void made by upstream brain regions, and consequently activate the PMC through their direct projections to initiate urination reflex. However, the exact location of the PMC-projecting VLPAG neurons, their activity in response to urination, and their whole-brain inputs remain unclear. Here, we identified the distribution of VLPAG neurons that may participate in control of the bladder or project to the PMC through retrograde neural tracing. Population Ca2+ signals of PMC-projecting VLPAG neurons highly correlated with bladder contractions and urination as shown by in vivo recording in freely moving animals. Using a RV-based retrograde trans-synaptic tracing strategy, morphological results showed that urination-related PMC-projecting VLPAG neurons received dense inputs from multiple urination-related higher brain areas, such as the medial preoptic area, medial prefrontal cortex, and lateral hypothalamus. Thus, our findings reveal a novel insight into the VLPAG for control of bladder function and provide a potential therapeutic midbrain node for neurogenic bladder dysfunction.
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Affiliation(s)
- Yu Rao
- Brain Research Center and State Key Laboratory of Trauma, Burns, and Combined Injury, Third Military Medical University, Chongqing, China
| | - Ziyan Gao
- Center for Neurointelligence, School of Medicine, Chongqing University, Chongqing, China
| | - Xianping Li
- Brain Research Center and State Key Laboratory of Trauma, Burns, and Combined Injury, Third Military Medical University, Chongqing, China
| | - Xing Li
- School of Physical Science and Technology, Guangxi University, Nanning, China
| | - Jun Li
- School of Physical Science and Technology, Guangxi University, Nanning, China
| | - Shanshan Liang
- Brain Research Center and State Key Laboratory of Trauma, Burns, and Combined Injury, Third Military Medical University, Chongqing, China
| | - Daihan Li
- Center for Neurointelligence, School of Medicine, Chongqing University, Chongqing, China
| | | | - Junan Yan
- Center for Neurointelligence, School of Medicine, Chongqing University, Chongqing, China
- Department of Urology, Southwest Hospital, Third Military Medical University, Chongqing, China
- Guangyang Bay Laboratory, Chongqing Institute for Brain and Intelligence, Chongqing, China
- *Correspondence: Junan Yan Jiwei Yao Xiaowei Chen
| | - Jiwei Yao
- Center for Neurointelligence, School of Medicine, Chongqing University, Chongqing, China
- *Correspondence: Junan Yan Jiwei Yao Xiaowei Chen
| | - Xiaowei Chen
- Brain Research Center and State Key Laboratory of Trauma, Burns, and Combined Injury, Third Military Medical University, Chongqing, China
- Guangyang Bay Laboratory, Chongqing Institute for Brain and Intelligence, Chongqing, China
- *Correspondence: Junan Yan Jiwei Yao Xiaowei Chen
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Neural circuit control of innate behaviors. SCIENCE CHINA. LIFE SCIENCES 2022; 65:466-499. [PMID: 34985643 DOI: 10.1007/s11427-021-2043-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 12/10/2021] [Indexed: 12/17/2022]
Abstract
All animals possess a plethora of innate behaviors that do not require extensive learning and are fundamental for their survival and propagation. With the advent of newly-developed techniques such as viral tracing and optogenetic and chemogenetic tools, recent studies are gradually unraveling neural circuits underlying different innate behaviors. Here, we summarize current development in our understanding of the neural circuits controlling predation, feeding, male-typical mating, and urination, highlighting the role of genetically defined neurons and their connections in sensory triggering, sensory to motor/motivation transformation, motor/motivation encoding during these different behaviors. Along the way, we discuss possible mechanisms underlying binge-eating disorder and the pro-social effects of the neuropeptide oxytocin, elucidating the clinical relevance of studying neural circuits underlying essential innate functions. Finally, we discuss some exciting brain structures recurrently appearing in the regulation of different behaviors, which suggests both divergence and convergence in the neural encoding of specific innate behaviors. Going forward, we emphasize the importance of multi-angle and cross-species dissections in delineating neural circuits that control innate behaviors.
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Slow development of bladder malfunction parallels spinal cord fiber sprouting and interneurons' loss after spinal cord transection. Exp Neurol 2021; 348:113937. [PMID: 34826427 DOI: 10.1016/j.expneurol.2021.113937] [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: 08/29/2021] [Revised: 11/02/2021] [Accepted: 11/19/2021] [Indexed: 11/23/2022]
Abstract
Neurogenic lower urinary tract dysfunction typically develops after spinal cord injury. We investigated the time course and the anatomical changes in the spinal cord that may be causing lower urinary tract symptoms following injury. Rats were implanted with a bladder catheter and external urethral sphincter electromyography electrodes. Animals underwent a large, incomplete spinal transection at the T8/9 spinal level. At 1, 2-3, and 4 weeks after injury, the animals underwent urodynamic investigations. Urodynamic investigations showed detrusor overactivity and detrusor-sphincter-dyssynergia appearing over time at 3-4 weeks after injury. Lower urinary tract dysfunction was accompanied by an increase in density of C-fiber afferents in the lumbosacral dorsal horn. CRF-positive Barrington's and 5-HT-positive bulbospinal projections drastically decreased after injury, with partial compensation for the CRF fibers at 3-4 weeks. Interestingly, a decrease over time was observed in the number of GABAergic neurons in the lumbosacral dorsal horn and lamina X, and a decrease of glutamatergic cells in the dorsal horn. Detrusor overactivity and detrusor-sphincter-dyssynergia might therefore arise from a discrepancy in inhibitory/excitatory interneuron activity in the lumbosacral cord as well as input changes which develop over time after injury. The processes point to spinal plastic changes leading to malfunction of the important physiological pathway of lower urinary tract control.
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Social isolation uncovers a circuit underlying context-dependent territory-covering micturition. Proc Natl Acad Sci U S A 2021; 118:2018078118. [PMID: 33443190 DOI: 10.1073/pnas.2018078118] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The release of urine, or micturition, serves a fundamental physiological function and, in many species, is critical for social communication. In mice, the pattern of urine release is modulated by external and internal factors and transmitted to the spinal cord via the pontine micturition center (PMC). Here, we exploited a behavioral paradigm in which mice, depending on strain, social experience, and sensory context, either vigorously cover an arena with small urine spots or deposit urine in a few isolated large spots. We refer to these micturition modes as, respectively, high and low territory-covering micturition (TCM) and find that the presence of a urine stimulus robustly induces high TCM in socially isolated mice. Comparison of the brain networks activated by social isolation and by urine stimuli to those upstream of the PMC identified the lateral hypothalamic area as a potential modulator of micturition modes. Indeed, chemogenetic manipulations of the lateral hypothalamus can switch micturition behavior between high and low TCM, overriding the influence of social experience and sensory context. Our results suggest that both inhibitory and excitatory signals arising from a network upstream of the PMC are integrated to determine context- and social-experience-dependent micturition patterns.
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Neurophysiological control of urinary bladder storage and voiding-functional changes through development and pathology. Pediatr Nephrol 2021; 36:1041-1052. [PMID: 32415328 DOI: 10.1007/s00467-020-04594-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 04/24/2020] [Accepted: 04/28/2020] [Indexed: 10/24/2022]
Abstract
The effective storage of urine and its expulsion relies upon the coordinated activity of parasympathetic, sympathetic, and somatic innervations to the lower urinary tract (LUT). At birth, all mammalian neonates lack the ability to voluntary regulate bladder storage or voiding. The ability to control urinary bladder activity is established as connections to the central nervous system (CNS) form through development. The neural regulation of the LUT has been predominantly investigated in adult animal models where comparatively less is known about the neonatal and postnatal neurophysiological development that facilitate urinary continence. Furthermore, congenital neurological or anatomical defects can adversely affect both storage and voiding functions through postnatal development and into adulthood, leading to secondary conditions including vesicoureteral reflux, chronic urinary tract infections, and end-stage renal disease. Therefore, the aim of the review is to provide the current knowledge available on neurophysiological regulation of the LUT through pre- to postnatal development of human and animal models and the consequences of congenital anomalies that can affect LUT neural function.
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Qin H, He W, Yang C, Li J, Jian T, Liang S, Chen T, Feng H, Chen X, Liao X, Zhang K. Monitoring Astrocytic Ca 2+ Activity in Freely Behaving Mice. Front Cell Neurosci 2020; 14:603095. [PMID: 33343304 PMCID: PMC7744696 DOI: 10.3389/fncel.2020.603095] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Accepted: 11/09/2020] [Indexed: 12/24/2022] Open
Abstract
Monitoring astrocytic Ca2+ activity is essential to understand the physiological and pathological roles of astrocytes in the brain. However, previous commonly used methods for studying astrocytic Ca2+ activities can be applied in only anesthetized or head-fixed animals, which significantly affects in vivo astrocytic Ca2+ dynamics. In the current study, we combined optic fiber recordings with genetically encoded Ca2+ indicators (GECIs) to monitor astrocytic activity in freely behaving mice. This approach enabled selective and reliable measurement of astrocytic Ca2+ activity, which was verified by the astrocyte-specific labeling of GECIs and few movement artifacts. Additionally, astrocytic Ca2+ activities induced by locomotion or footshock were stably recorded in the cortices and hippocampi of freely behaving mice. Furthermore, this method allowed for the longitudinal study of astrocytic activities over several weeks. This work provides a powerful approach to record astrocytic activity selectively, stably, and chronically in freely behaving mice.
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Affiliation(s)
- Han Qin
- Brain Research Center and State Key Laboratory of Trauma, Burns, and Combined Injury, Third Military Medical University, Chongqing, China.,Center for Neurointelligence, School of Medicine, Chongqing University, Chongqing, China
| | - Wenjing He
- Brain Research Center and State Key Laboratory of Trauma, Burns, and Combined Injury, Third Military Medical University, Chongqing, China
| | - Chuanyan Yang
- Department of Neurosurgery and Key Laboratory of Neurotrauma, Southwest Hospital, Third Military Medical University, Chongqing, China
| | - Jin Li
- Brain Research Center and State Key Laboratory of Trauma, Burns, and Combined Injury, Third Military Medical University, Chongqing, China
| | - Tingliang Jian
- Brain Research Center and State Key Laboratory of Trauma, Burns, and Combined Injury, Third Military Medical University, Chongqing, China
| | - Shanshan Liang
- Brain Research Center and State Key Laboratory of Trauma, Burns, and Combined Injury, Third Military Medical University, Chongqing, China
| | - Tunan Chen
- Department of Neurosurgery and Key Laboratory of Neurotrauma, Southwest Hospital, Third Military Medical University, Chongqing, China
| | - Hua Feng
- Department of Neurosurgery and Key Laboratory of Neurotrauma, Southwest Hospital, Third Military Medical University, Chongqing, China
| | - Xiaowei Chen
- Brain Research Center and State Key Laboratory of Trauma, Burns, and Combined Injury, Third Military Medical University, Chongqing, China
| | - Xiang Liao
- Center for Neurointelligence, School of Medicine, Chongqing University, Chongqing, China
| | - Kuan Zhang
- Brain Research Center and State Key Laboratory of Trauma, Burns, and Combined Injury, Third Military Medical University, Chongqing, China
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Fan L, Xiang B, Xiong J, He Z, Xiang H. Use of viruses for interrogating viscera-specific projections in central nervous system. J Neurosci Methods 2020; 341:108757. [PMID: 32371062 DOI: 10.1016/j.jneumeth.2020.108757] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 04/28/2020] [Accepted: 04/28/2020] [Indexed: 12/18/2022]
Abstract
Each internal organ may perform many different functions under central regulation, yet how these processes are coordinated is poorly understood. The last three decades have witnessed a renaissance in tract tracing with genetically engineered strains of viruses that rapidly interrogate viscera-specific projections in the CNS. The application of novel methods to study cell type-specific projections through trans-synaptically transmitted virus 'label' highlights projections exclusively originating from neurons expressing a very specific molecular phenotype. This has opened the door to neuroanatomical studies interrogating organ-specific projections in the CNS at an unprecedented scale. In this contribution to the Special Issue we present an overview of the present state and of future opportunities in charting viscera-brain specific connectivity and in linking brain circuits to internal organ function.
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Affiliation(s)
- Li Fan
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, PR China
| | - Boqi Xiang
- University of California-Davis, Davis, CA 95616, USA
| | - Jun Xiong
- Hepatobiliary Surgery Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, PR China
| | - Zhigang He
- Department of Critical Care Medicine, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, PR China
| | - Hongbing Xiang
- Department of Anesthesiology and Pain Medicine, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, PR China.
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Aguiniga LM, Searl TJ, Rahman-Enyart A, Yaggie RE, Yang W, Schaeffer AJ, Klumpp DJ. Acyloxyacyl hydrolase regulates voiding activity. Am J Physiol Renal Physiol 2020; 318:F1006-F1016. [PMID: 32003596 DOI: 10.1152/ajprenal.00442.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Corticotropin-releasing factor (CRF) regulates diverse physiological functions, including bladder control. We recently reported that Crf expression is under genetic control of Aoah, the locus encoding acyloxyacyl hydrolase (AOAH), suggesting that AOAH may also modulate voiding. Here, we examined the role of AOAH in bladder function. AOAH-deficient mice exhibited enlarged bladders relative to wild-type mice and had decreased voiding frequency and increased void volumes. AOAH-deficient mice had increased nonvoiding contractions and increased peak voiding pressure in awake cystometry. AOAH-deficient mice also exhibited increased bladder permeability and higher neuronal firing rates of bladder afferents in response to stretch. In wild-type mice, AOAH was expressed in bladder projecting neurons and colocalized in CRF-expressing neurons in Barrington's nucleus, an important brain area for voiding behavior, and Crf was elevated in Barrington's nucleus of AOAH-deficient mice. We had previously identified aryl hydrocarbon receptor (AhR) and peroxisome proliferator-activated receptor-γ as transcriptional regulators of Crf, and conditional knockout of AhR or peroxisome proliferator-activated receptor-γ in Crf-expressing cells restored normal voiding in AOAH-deficient mice. Finally, an AhR antagonist improved voiding in AOAH-deficient mice. Together, these data demonstrate that AOAH regulates bladder function and that the AOAH-Crf axis is a therapeutic target for treating voiding dysfunction.
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Affiliation(s)
- Lizath M Aguiniga
- Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Timothy J Searl
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Afrida Rahman-Enyart
- Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Ryan E Yaggie
- Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Wenbin Yang
- Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Anthony J Schaeffer
- Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - David J Klumpp
- Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.,Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
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Propriospinal Neurons of L3-L4 Segments Involved in Control of the Rat External Urethral Sphincter. Neuroscience 2019; 425:12-28. [PMID: 31785359 DOI: 10.1016/j.neuroscience.2019.11.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/31/2019] [Accepted: 11/11/2019] [Indexed: 12/17/2022]
Abstract
Coordination of activity of external urethral sphincter (EUS) striated muscle and bladder (BL) smooth muscle is essential for efficient voiding. In this study we examined the morphological and electrophysiological properties of neurons in the L3/L4 spinal cord (SC) that are likely to have an important role in EUS-BL coordination in rats. EUS-related SC neurons were identified by retrograde transsynaptic tracing following injection of pseudorabies virus (PRV) co-expressing fluorescent markers into the EUS of P18-P20 male rats. Tracing revealed not only EUS motoneurons in L6/S1 but also interneurons in lamina X of the L6/S1 and L3/L4 SC. Physiological properties of fluorescently labeled neurons were assessed during whole-cell recordings in SC slices followed by reconstruction of biocytin-filled neurons. Reconstructions of neuronal processes from transverse or longitudinal slices showed that some L3/L4 neurons have axons projecting toward and into the ventro-medial funiculus (VMf) where axons extended caudally. Other neurons had axons projecting within laminae X and VII. Dendrites of L3/L4 neurons were distributed within laminae X and VII. The majority of L3/L4 neurons exhibited tonic firing in response to depolarizing currents. In transverse slices focal electrical stimulation (FES) in the VMf or in laminae X and VII elicited antidromic axonal spikes and/or excitatory synaptic responses in L3/L4 neurons; while in longitudinal slices FES elicited excitatory synaptic inputs from sites up to 400 μm along the central canal. Inhibitory inputs were rarely observed. These data suggest that L3/L4 EUS-related circuitry consists of at least two neuronal populations: segmental interneurons and propriospinal neurons projecting to L6/S1.
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