1
|
Nicolozakes CP, Sohn MH, Baillargeon EM, Lipps DB, Perreault EJ. Stretch reflex gain scaling at the shoulder varies with synergistic muscle activity. J Neurophysiol 2022; 128:1244-1257. [PMID: 36224165 PMCID: PMC9662809 DOI: 10.1152/jn.00259.2022] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 10/07/2022] [Accepted: 10/12/2022] [Indexed: 11/22/2022] Open
Abstract
The unique anatomy of the shoulder allows for expansive mobility but also sometimes precarious stability. It has long been suggested that stretch-sensitive reflexes contribute to maintaining joint stability through feedback control, but little is known about how stretch-sensitive reflexes are coordinated between the muscles of the shoulder. The purpose of this study was to investigate the coordination of stretch reflexes in shoulder muscles elicited by rotations of the glenohumeral joint. We hypothesized that stretch reflexes are sensitive to not only a given muscle's background activity but also the aggregate activity of all muscles crossing the shoulder based on the different groupings of muscles required to actuate the shoulder in three rotational degrees of freedom. We examined the relationship between a muscle's background activity and its reflex response in eight shoulder muscles by applying rotational perturbations while participants produced voluntary isometric torques. We found that this relationship, defined as gain scaling, differed at both short and long latencies based on the direction of voluntary torque generated by the participant. Therefore, gain scaling differed based on the aggregate of muscles that were active, not just the background activity in the muscle within which the reflex was measured. Across all muscles, the consideration of torque-dependent gain scaling improved model fits (ΔR2) by 0.17 ± 0.12. Modulation was most evident when volitional torques and perturbation directions were aligned along the same measurement axis, suggesting a functional role in resisting perturbations among synergists while maintaining task performance.NEW & NOTEWORTHY Careful coordination of muscles crossing the shoulder is needed to maintain the delicate balance between the joint's mobility and stability. We provide experimental evidence that stretch reflexes within shoulder muscles are modulated based on the aggregate activity of muscles crossing the joint, not just the activity of the muscle in which the reflex is elicited. Our results reflect coordination through neural coupling that may help maintain shoulder stability during encounters with environmental perturbations.
Collapse
Affiliation(s)
- Constantine P Nicolozakes
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois
- Shirley Ryan AbilityLab, Chicago, Illinois
- Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - M Hongchul Sohn
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois
- Shirley Ryan AbilityLab, Chicago, Illinois
- Department of Physical Therapy & Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Emma M Baillargeon
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois
- Shirley Ryan AbilityLab, Chicago, Illinois
- Department of Physical Therapy & Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
- Department of Epidemiology, School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - David B Lipps
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan
- Biomedical Engineering, University of Michigan, Ann Arbor, Michigan
| | - Eric J Perreault
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois
- Shirley Ryan AbilityLab, Chicago, Illinois
- Department of Physical Medicine & Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| |
Collapse
|
2
|
Côté MP, Murray LM, Knikou M. Spinal Control of Locomotion: Individual Neurons, Their Circuits and Functions. Front Physiol 2018; 9:784. [PMID: 29988534 PMCID: PMC6026662 DOI: 10.3389/fphys.2018.00784] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 06/05/2018] [Indexed: 12/31/2022] Open
Abstract
Systematic research on the physiological and anatomical characteristics of spinal cord interneurons along with their functional output has evolved for more than one century. Despite significant progress in our understanding of these networks and their role in generating and modulating movement, it has remained a challenge to elucidate the properties of the locomotor rhythm across species. Neurophysiological experimental evidence indicates similarities in the function of interneurons mediating afferent information regarding muscle stretch and loading, being affected by motor axon collaterals and those mediating presynaptic inhibition in animals and humans when their function is assessed at rest. However, significantly different muscle activation profiles are observed during locomotion across species. This difference may potentially be driven by a modified distribution of muscle afferents at multiple segmental levels in humans, resulting in an altered interaction between different classes of spinal interneurons. Further, different classes of spinal interneurons are likely activated or silent to some extent simultaneously in all species. Regardless of these limitations, continuous efforts on the function of spinal interneuronal circuits during mammalian locomotion will assist in delineating the neural mechanisms underlying locomotor control, and help develop novel targeted rehabilitation strategies in cases of impaired bipedal gait in humans. These rehabilitation strategies will include activity-based therapies and targeted neuromodulation of spinal interneuronal circuits via repetitive stimulation delivered to the brain and/or spinal cord.
Collapse
Affiliation(s)
- Marie-Pascale Côté
- CÔTÉ Lab, Spinal Cord Research Center, Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Lynda M. Murray
- Motor Control and NeuroRecovery Research Laboratory (Klab4Recovery), Department of Physical Therapy, College of Staten Island, City University of New York, New York, NY, United States
- Graduate Center, Ph.D. Program in Biology, City University of New York, New York, NY, United States
| | - Maria Knikou
- Motor Control and NeuroRecovery Research Laboratory (Klab4Recovery), Department of Physical Therapy, College of Staten Island, City University of New York, New York, NY, United States
- Graduate Center, Ph.D. Program in Biology, City University of New York, New York, NY, United States
| |
Collapse
|
3
|
Smith AC, Knikou M. A Review on Locomotor Training after Spinal Cord Injury: Reorganization of Spinal Neuronal Circuits and Recovery of Motor Function. Neural Plast 2016; 2016:1216258. [PMID: 27293901 PMCID: PMC4879237 DOI: 10.1155/2016/1216258] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 04/20/2016] [Indexed: 01/01/2023] Open
Abstract
Locomotor training is a classic rehabilitation approach utilized with the aim of improving sensorimotor function and walking ability in people with spinal cord injury (SCI). Recent studies have provided strong evidence that locomotor training of persons with clinically complete, motor complete, or motor incomplete SCI induces functional reorganization of spinal neuronal networks at multisegmental levels at rest and during assisted stepping. This neuronal reorganization coincides with improvements in motor function and decreased muscle cocontractions. In this review, we will discuss the manner in which spinal neuronal circuits are impaired and the evidence surrounding plasticity of neuronal activity after locomotor training in people with SCI. We conclude that we need to better understand the physiological changes underlying locomotor training, use physiological signals to probe recovery over the course of training, and utilize established and contemporary interventions simultaneously in larger scale research studies. Furthermore, the focus of our research questions needs to change from feasibility and efficacy to the following: what are the physiological mechanisms that make it work and for whom? The aforementioned will enable the scientific and clinical community to develop more effective rehabilitation protocols maximizing sensorimotor function recovery in people with SCI.
Collapse
Affiliation(s)
- Andrew C. Smith
- Interdepartmental Neuroscience Program, Northwestern University, Chicago, IL 60611, USA
| | - Maria Knikou
- The Graduate Center, City University of New York, New York, NY 10016, USA
- Department of Physical Therapy, College of Staten Island, City University of New York, Staten Island, NY 10314, USA
| |
Collapse
|
4
|
Obata H, Ogawa T, Kitamura T, Masugi Y, Takahashi M, Kawashima N, Nakazawa K. Short-term effect of electrical nerve stimulation on spinal reciprocal inhibition during robot-assisted passive stepping in humans. Eur J Neurosci 2015; 42:2283-8. [PMID: 26108136 DOI: 10.1111/ejn.13000] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 06/11/2015] [Accepted: 06/22/2015] [Indexed: 11/27/2022]
Abstract
The purpose of this study was to investigate the effect of electrical stimulation to the common peroneal nerve (CPN) on the spinal reflex and reciprocal inhibition (RI) during robot-assisted passive ground stepping (PGS) in healthy subjects. Five interventions were applied for 30 min in healthy subjects: PGS alone; strong CPN stimulation [50% of the maximal tibialis anterior (TA) M-wave, functional electrical stimulation (FES)] alone; weak CPN stimulation [just above the MT for the TA muscle, therapeutic electrical stimulation (TES)] alone; PGS with FES; and PGS with TES. FES and TES were applied intermittently to the CPN at 25 Hz. The soleus (Sol) H-reflex and RI, which was assessed by conditioning the Sol H-reflex with CPN stimulation, were investigated before (baseline), and 5, 15 and 30 min after each intervention. The amplitudes of the Sol H-reflex were not significantly different after each intervention as compared with the baseline values. The amounts of RI were significantly decreased 5 min after PGS with FES as compared with the baseline values, whereas they were significantly increased 5 and 15 min after PGS with TES. The other interventions did not affect the amount of RI. These results suggest that interventions that combined PGS with CPN stimulation changed the spinal RI in an intensity-dependent manner.
Collapse
Affiliation(s)
- Hiroki Obata
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Tetsuya Ogawa
- Faculty of Sport Sciences, Waseda University, Waseda, Japan.,Japan Society for the Promotion of Science, Tokyo, Japan
| | - Taku Kitamura
- Department of Motor Dysfunction, Research Institute of the National Rehabilitation Center for Persons with Disabilities, Saitama, Japan
| | - Yohei Masugi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Miho Takahashi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Noritaka Kawashima
- Department of Motor Dysfunction, Research Institute of the National Rehabilitation Center for Persons with Disabilities, Saitama, Japan
| | - Kimitaka Nakazawa
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
| |
Collapse
|
5
|
Hanna-Boutros B, Sangari S, Giboin LS, El Mendili MM, Lackmy-Vallée A, Marchand-Pauvert V, Knikou M. Corticospinal and reciprocal inhibition actions on human soleus motoneuron activity during standing and walking. Physiol Rep 2015; 3:3/2/e12276. [PMID: 25825912 PMCID: PMC4393188 DOI: 10.14814/phy2.12276] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Reciprocal Ia inhibition constitutes a key segmental neuronal pathway for coordination of antagonist muscles. In this study, we investigated the soleus H-reflex and reciprocal inhibition exerted from flexor group Ia afferents on soleus motoneurons during standing and walking in 15 healthy subjects following transcranial magnetic stimulation (TMS). The effects of separate TMS or deep peroneal nerve (DPN) stimulation and the effects of combined (TMS + DPN) stimuli on the soleus H-reflex were assessed during standing and at mid- and late stance phases of walking. Subthreshold TMS induced short-latency facilitation on the soleus H-reflex that was present during standing and at midstance but not at late stance of walking. Reciprocal inhibition was increased during standing and at late stance but not at the midstance phase of walking. The effects of combined TMS and DPN stimuli on the soleus H-reflex significantly changed between tasks, resulting in an extra facilitation of the soleus H-reflex during standing and not during walking. Our findings indicate that corticospinal inputs and Ia inhibitory interneurons interact at the spinal level in a task-dependent manner, and that corticospinal modulation of reciprocal Ia inhibition is stronger during standing than during walking.
Collapse
Affiliation(s)
- Berthe Hanna-Boutros
- Sorbonne Universités, UPMC Univ Paris 06, UMR 7371, UMR_S 1146, LIB, Paris, France CNRS, UMR 7371, LIB, Paris, France INSERM, UMR_S 1146, LIB, Paris, France
| | - Sina Sangari
- Sorbonne Universités, UPMC Univ Paris 06, UMR 7371, UMR_S 1146, LIB, Paris, France CNRS, UMR 7371, LIB, Paris, France INSERM, UMR_S 1146, LIB, Paris, France
| | - Louis-Solal Giboin
- Sensorimotor Performance Laboratory, Konstanz University, Konstanz, Germany
| | - Mohamed-Mounir El Mendili
- Sorbonne Universités, UPMC Univ Paris 06, UMR 7371, UMR_S 1146, LIB, Paris, France CNRS, UMR 7371, LIB, Paris, France INSERM, UMR_S 1146, LIB, Paris, France
| | - Alexandra Lackmy-Vallée
- Sorbonne Universités, UPMC Univ Paris 06, UMR 7371, UMR_S 1146, LIB, Paris, France CNRS, UMR 7371, LIB, Paris, France INSERM, UMR_S 1146, LIB, Paris, France
| | - Véronique Marchand-Pauvert
- Sorbonne Universités, UPMC Univ Paris 06, UMR 7371, UMR_S 1146, LIB, Paris, France CNRS, UMR 7371, LIB, Paris, France INSERM, UMR_S 1146, LIB, Paris, France
| | - Maria Knikou
- The Graduate Center, City University of New York, New York, New York Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, Illinois
| |
Collapse
|
6
|
Knikou M, Smith AC, Mummidisetty CK. Locomotor training improves reciprocal and nonreciprocal inhibitory control of soleus motoneurons in human spinal cord injury. J Neurophysiol 2015; 113:2447-60. [PMID: 25609110 DOI: 10.1152/jn.00872.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 01/20/2015] [Indexed: 12/19/2022] Open
Abstract
Pathologic reorganization of spinal networks and activity-dependent plasticity are common neuronal adaptations after spinal cord injury (SCI) in humans. In this work, we examined changes of reciprocal Ia and nonreciprocal Ib inhibition after locomotor training in 16 people with chronic SCI. The soleus H-reflex depression following common peroneal nerve (CPN) and medial gastrocnemius (MG) nerve stimulation at short conditioning-test (C-T) intervals was assessed before and after training in the seated position and during stepping. The conditioned H reflexes were normalized to the unconditioned H reflex recorded during seated. During stepping, both H reflexes were normalized to the maximal M wave evoked at each bin of the step cycle. In the seated position, locomotor training replaced reciprocal facilitation with reciprocal inhibition in all subjects, and Ib facilitation was replaced by Ib inhibition in 13 out of 14 subjects. During stepping, reciprocal inhibition was decreased at early stance and increased at midswing in American Spinal Injury Association Impairment Scale C (AIS C) and was decreased at midstance and midswing phases in AIS D after training. Ib inhibition was decreased at early swing and increased at late swing in AIS C and was decreased at early stance phase in AIS D after training. The results of this study support that locomotor training alters postsynaptic actions of Ia and Ib inhibitory interneurons on soleus motoneurons at rest and during stepping and that such changes occur in cases with limited or absent supraspinal inputs.
Collapse
Affiliation(s)
- Maria Knikou
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois; Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg Medical School, Chicago, Illinois; Graduate Center/The City University of New York, New York, New York; and Department of Physical Therapy, College of Staten Island, Staten Island, New York
| | - Andrew C Smith
- Northwestern University Interdepartmental Neuroscience Program, Chicago, Illinois
| | | |
Collapse
|
7
|
Abstract
Abstract
Collapse
|
8
|
Mummidisetty CK, Smith AC, Knikou M. Modulation of reciprocal and presynaptic inhibition during robotic-assisted stepping in humans. Clin Neurophysiol 2012; 124:557-64. [PMID: 23046639 DOI: 10.1016/j.clinph.2012.09.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 09/11/2012] [Accepted: 09/13/2012] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To establish the modulation pattern of reciprocal inhibition and presynaptic inhibition of soleus Ia afferents during robot-assisted stepping in healthy subjects. METHODS During stepping, the soleus H-reflex was conditioned by percutaneous stimulation of the ipsilateral common peroneal nerve with a single pulse at stimulation intensities that ranged from 0.9 to 1.2 TA M-wave motor thresholds across subjects. To control for movement of recording and stimulating electrodes, a supramaximal stimulus 80ms after the conditioned and/or unconditioned H-reflexes was delivered to the posterior tibial nerve. The short (2, 3, 4ms) and long (60-80ms) conditioning-test intervals at which the largest amount of reflex depression was observed with the subjects seated were utilized during stepping. Stimuli were randomly dispersed across the step cycle which was divided into 16 equal bins. RESULTS Reciprocal inhibition exerted from flexor group I afferents onto soleus motoneurons was decreased at mid-stance and increased and late-stance and throughout the swing phase. Presynaptic inhibition of soleus Ia afferents was increased at heel strike and decreased at late-stance and early swing phases. CONCLUSION Reciprocal inhibition between ankle antagonistic muscles and presynaptic inhibition of soleus Ia afferents are modulated in a similar pattern to that reported during walking on a treadmill with full weight bearing and without robot-assisted leg movement. SIGNIFICANCE The activity of spinal interneuronal circuits engaged in patterned locomotor activity supports a reciprocal gait pattern during robot-assisted stepping in healthy humans.
Collapse
Affiliation(s)
- Chaithanya K Mummidisetty
- Electrophysiological Analysis of Gait & Posture Laboratory, Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA
| | | | | |
Collapse
|
9
|
Baudry S, Duchateau J. Age-related influence of vision and proprioception on Ia presynaptic inhibition in soleus muscle during upright stance. J Physiol 2012; 590:5541-54. [PMID: 22946095 DOI: 10.1113/jphysiol.2012.228932] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
This study investigated the modulation of Ia afferent input in young and elderly adults during quiet upright stance in normal and modified visual and proprioceptive conditions. The surface EMG of leg muscles, recruitment curve of the soleus (SOL) Hoffmann (H) reflex and presynaptic inhibition of Ia afferents from SOL, assessed with the D1 inhibition and single motor unit methods, were recorded when young and elderly adults stood with eyes open or closed on two surfaces (rigid vs. foam) placed over a force platform. The results showed that elderly adults had a longer path length for the centre of pressure and larger antero-posterior body sway across balance conditions (P < 0.05). Muscle EMG activities were greater in elderly compared with young adults (P < 0.05), whereas the H(max) expressed as a percentage of the H(max) was lower (P = 0.048) in elderly (38 ± 16%) than young adults (58 ± 16%). The conditioned H reflex/test H reflex ratio (D1 inhibition method) increased with eye closure and when standing on foam (P < 0.05), with greater increases for elderly adults (P = 0.019). These changes were accompanied by a reduced peak motor unit discharge probability when standing on rigid and foam surfaces (P 0.001), with a greater effect for elderly adults (P = 0.026). Based on these latter results, the increased conditioned H reflex/test H reflex ratio in similar sensory conditions is likely to reflect occlusion at the level of presynaptic inhibitory interneurones. Together, these findings indicate that elderly adults exhibit greater modulation of Ia presynaptic inhibition than young adults with variation in the sensory conditions during upright standing.
Collapse
Affiliation(s)
- Stéphane Baudry
- Laboratory of Applied Biology, Faculty for Motor Sciences, Université Libre de Bruxelles, 808, route de Lennik, CP 640, 1070 Brussels, Belgium.
| | | |
Collapse
|
10
|
Knikou M, Mummidisetty CK. Reduced reciprocal inhibition during assisted stepping in human spinal cord injury. Exp Neurol 2011; 231:104-12. [PMID: 21684274 DOI: 10.1016/j.expneurol.2011.05.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 05/20/2011] [Accepted: 05/26/2011] [Indexed: 10/18/2022]
Abstract
The aim of this study was to establish the modulation pattern of the reciprocal inhibition exerted from tibialis anterior (TA) group I afferents onto soleus motoneurons during body weight support (BWS) assisted stepping in people with spinal cord injury (SCI). During assisted stepping, the soleus H-reflex was conditioned by percutaneous stimulation of the ipsilateral common peroneal nerve at one fold TA M-wave motor threshold with a single pulse delivered at a short conditioning-test interval. To counteract movement of recording and stimulating electrodes, a supramaximal stimulus at 80-100 ms after the test H-reflex was delivered. Stimuli were randomly dispersed across the step cycle which was divided into 16 equal bins. The conditioned soleus H-reflex was significantly facilitated throughout the stance phase, while during swing no significant changes on the conditioned H-reflex were observed when compared to the unconditioned soleus H-reflex recorded during stepping. Spontaneous clonic activity in triceps surae muscle occurred in multiple phases of the step cycle at a mean frequency of 7 Hz for steps with and without stimulation. This suggests that electrical excitation of TA and soleus group Ia afferents did not contribute to manifestation of ankle clonus. Absent reciprocal inhibition is likely responsible for lack of soleus H-reflex depression in swing phase observed in these patients. The pronounced reduced reciprocal inhibition in stance phase may contribute to impaired levels of co-contraction of antagonistic ankle muscles. Based on these findings, we suggest that rehabilitation should selectively target to transform reciprocal facilitation to inhibition through computer controlled reflex conditioning protocols.
Collapse
Affiliation(s)
- Maria Knikou
- The Graduate Center, City University of New York/College of Staten Island, Staten Island, NY 10314, USA.
| | | |
Collapse
|
11
|
Soleus H-reflex phase-dependent modulation during one-legged foot reaching and withdrawal in standing humans. Neurosci Lett 2011; 487:305-9. [DOI: 10.1016/j.neulet.2010.10.044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 09/30/2010] [Accepted: 10/18/2010] [Indexed: 11/23/2022]
|
12
|
Lewis GN, MacKinnon CD, Trumbower R, Perreault EJ. Co-contraction modifies the stretch reflex elicited in muscles shortened by a joint perturbation. Exp Brain Res 2010; 207:39-48. [PMID: 20878148 DOI: 10.1007/s00221-010-2426-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Accepted: 09/09/2010] [Indexed: 10/19/2022]
Abstract
Simultaneous contraction of agonist and antagonist muscles acting about a joint influences joint stiffness and stability. Although several studies have shown that reflexes in the muscle lengthened by a joint perturbation are modulated during co-contraction, little attention has been given to reflex regulation in the antagonist (shortened) muscle. The goal of the present study was to determine whether co-contraction gives rise to altered reflex regulation across the joint by examining reflexes in the muscle shortened by a joint perturbation. Reflexes were recorded from electromyographic activity in elbow flexors and extensors while positional perturbations to the elbow joint were applied. Perturbations were delivered during isolated activation of the flexor or extensor muscles as well as during flexor and extensor co-contraction. Across the group, the shortening reflex in the elbow extensor switched from suppression during isolated extensor muscle activation to facilitation during co-contraction. The shortening reflex in the elbow flexor remained suppressive during co-contraction but was significantly smaller compared to the response obtained during isolated elbow flexor activation. This response in the shortened muscle was graded by the level of activation in the lengthened muscle. The lengthening reflex did not change during co-contraction. These results support the idea that reflexes are regulated across multiple muscles around a joint. We speculate that the facilitatory response in the shortened muscle arises through a fast-conducting oligosynaptic pathway involving Ib interneurons.
Collapse
Affiliation(s)
- Gwyn N Lewis
- Health and Rehabilitation Research Institute, AUT University, Private Bag 92006, Auckland 1142, New Zealand.
| | | | | | | |
Collapse
|
13
|
Roche N, Lackmy A, Achache V, Bussel B, Katz R. Impact of transcranial direct current stimulation on spinal network excitability in humans. J Physiol 2009; 587:5653-64. [PMID: 19805746 DOI: 10.1113/jphysiol.2009.177550] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Transcranial direct current stimulation (tDCS) when applied over the motor cortex, modulates excitability dependent on the current polarity. The impact of this cortical modulation on spinal cord network excitability has rarely been studied. In this series of experiments, performed in healthy subjects, we show that anodal tDCS increases disynaptic inhibition directed from extensor carpi radialis (ECR) to flexor carpi radialis (FCR) with no modification of presynaptic inhibition of FCR Ia terminals and FCR H-reflex recruitment curves. We also show that cathodal tDCS does not modify spinal network excitability. Our results suggest that the increase of disynaptic inhibition observed during anodal tDCS relies on an increase of disynaptic interneuron excitability and that tDCS over the motor cortex in human subjects induces effects on spinal network excitability. Our results highlight the fact that the effects of tDCS should be considered in regard to spinal motor circuits and not only to cortical circuits.
Collapse
Affiliation(s)
- N Roche
- UPMC, Service de Médecine Physique et Réadaptation Hôpital Pitié Salpêtrière 75013 Paris, France
| | | | | | | | | |
Collapse
|
14
|
Knikou M. The H-reflex as a probe: pathways and pitfalls. J Neurosci Methods 2008; 171:1-12. [PMID: 18394711 DOI: 10.1016/j.jneumeth.2008.02.012] [Citation(s) in RCA: 273] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Revised: 02/21/2008] [Accepted: 02/26/2008] [Indexed: 11/30/2022]
Abstract
The Hoffmann (or H) reflex is considered a major probe for non-invasive study of sensorimotor integration and plasticity of the central nervous system in humans. The first section of this paper reviews the neurophysiological properties of the H-reflex, which if ignored create serious pitfalls in human experimental studies. The second section reviews the spinal inhibitory circuits and neuronal pathways that can be indirectly assessed in humans using the H-reflex. The most confounding factor is that reciprocal, presynaptic, and Ib inhibition do not act in isolation during movement. Therefore, characterization of these spinal circuits should be more comprehensive, especially in cases of a neurological injury because neurophysiological findings are critical for the development of successful rehabilitation protocols. To conclude, the H-reflex is a highly sensitive reflex with an amplitude that is the result of complex neural mechanisms that act synchronously. If these limitations are recognized and addressed, the H-reflex constitutes one of the major probes to assess excitability of interneuronal circuits at rest and during movement in humans.
Collapse
Affiliation(s)
- Maria Knikou
- Health Sciences Doctoral Programs, City University of New York, Staten Island, NY 10314, USA.
| |
Collapse
|
15
|
Windhorst U. Muscle proprioceptive feedback and spinal networks. Brain Res Bull 2007; 73:155-202. [PMID: 17562384 DOI: 10.1016/j.brainresbull.2007.03.010] [Citation(s) in RCA: 197] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2007] [Accepted: 03/15/2007] [Indexed: 12/19/2022]
Abstract
This review revolves primarily around segmental feedback systems established by muscle spindle and Golgi tendon organ afferents, as well as spinal recurrent inhibition via Renshaw cells. These networks are considered as to their potential contributions to the following functions: (i) generation of anti-gravity thrust during quiet upright stance and the stance phase of locomotion; (ii) timing of locomotor phases; (iii) linearization and correction for muscle nonlinearities; (iv) compensation for muscle lever-arm variations; (v) stabilization of inherently unstable systems; (vi) compensation for muscle fatigue; (vii) synergy formation; (viii) selection of appropriate responses to perturbations; (ix) correction for intersegmental interaction forces; (x) sensory-motor transformations; (xi) plasticity and motor learning. The scope will at times extend beyond the narrow confines of spinal circuits in order to integrate them into wider contexts and concepts.
Collapse
Affiliation(s)
- U Windhorst
- Center for Physiology and Pathophysiology, University of Goettingen, Humboldtallee 23, D-37073 Goettingen, Germany.
| |
Collapse
|
16
|
Courtine G, Harkema SJ, Dy CJ, Gerasimenko YP, Dyhre-Poulsen P. Modulation of multisegmental monosynaptic responses in a variety of leg muscles during walking and running in humans. J Physiol 2007; 582:1125-39. [PMID: 17446226 PMCID: PMC2075265 DOI: 10.1113/jphysiol.2007.128447] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Motor responses evoked by stimulating the spinal cord percutaneously between the T11 and T12 spinous processes were studied in eight human subjects during walking and running. Stimulation elicited responses bilaterally in the biceps femoris, vastus lateralis, rectus femoris, medial gastrocnemius, soleus, tibialis anterior, extensor digitorum brevis and flexor digitorum brevis. The evoked responses were consistent with activation of Ia afferent fibres through monosynaptic neural circuits since they were inhibited when a prior stimulus was given and during tendon vibration. Furthermore, the soleus motor responses were inhibited during the swing phase of walking as observed for the soleus H-reflex elicited by tibial nerve stimulation. Due to the anatomical site and the fibre composition of the peripheral nerves it is difficult to elicit H-reflex in leg muscles other than the soleus, especially during movement. In turn, the multisegmental monosynaptic responses (MMR) technique provides the opportunity to study modulation of monosynaptic reflexes for multiple muscles simultaneously. Phase-dependent modulation of the MMR amplitude throughout the duration of the gait cycle period was observed in all muscles studied. The MMR amplitude was large when the muscle was activated whereas it was generally reduced, or even suppressed, when the muscle was quiescent. However, during running, there was a systematic anticipatory increase in the amplitude of the MMR at the end of swing in all proximal and distal extensor muscles. The present findings therefore suggest that there is a general control scheme by which the transmission in the monosynaptic neural circuits is modulated in all leg muscles during stepping so as to meet the requirement of the motor task.
Collapse
Affiliation(s)
- Grégoire Courtine
- Physiological Science, University of California, Los Angeles, CA, USA
| | | | | | | | | |
Collapse
|
17
|
Knikou M, Chaudhuri D, Kay E, Schmit BD. Pre- and post-alpha motoneuronal control of the soleus H-reflex during sinusoidal hip movements in human spinal cord injury. Brain Res 2006; 1103:123-39. [PMID: 16782072 PMCID: PMC1540994 DOI: 10.1016/j.brainres.2006.05.036] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Revised: 05/10/2006] [Accepted: 05/12/2006] [Indexed: 11/16/2022]
Abstract
The aim of this study was to establish the contribution of hip-mediated sensory feedback to spinal interneuronal circuits during dynamic conditions in people with incomplete spinal cord injury (SCI). Specifically, we investigated the effects of synergistic and antagonistic group I afferents on the soleus H-reflex during imposed sinusoidal hip movements. The soleus H-reflex was conditioned by stimulating the common peroneal nerve (CPN) at short (2, 3, and 4 ms) and long (80, 100, and 120 ms) conditioning test (C-T) intervals to assess the reciprocal and pre-synaptic inhibition of the soleus H-reflex, respectively. The soleus H-reflex was also conditioned by medial gastrocnemius (MG) nerve stimulation at C-T intervals ranging from 4 to 7 ms to assess changes in autogenic Ib inhibition during hip movement. Sinusoidal hip movements were imposed to the right hip joint at 0.2 Hz by the Biodex system while subjects were supine. The effects of sinusoidal hip movement on five leg muscles along with hip, knee, and ankle joint torques were also established during sensorimotor conditioning of the reflex. Phase-dependent modulation of antagonistic and synergistic muscle afferents was present during hip movement, with the reciprocal, pre-synaptic, and Ib inhibition to be significantly reduced during hip extension and reinforced during hip flexion. Reflexive muscle and joint torque responses--induced by the hip movement--were entrained to specific phases of hip movement. This study provides evidence that hip-mediated input acts as a controlling signal of pre- and post-alpha motoneuronal control of the soleus H-reflex. The expression of these spinal interneuronal circuits during imposed sinusoidal hip movements is discussed with respect to motor recovery in humans after SCI.
Collapse
Key Words
- hip movement
- reciprocal pre-synaptic autogenic
- inhibition
- paraplegia
- rehabilitation. spasms
- cpn, common peroneal nerve
- emg, electromyographic
- hohomonymous, control soleus
- h-reflex recorded during hip
- flexion or extension without any conditioning stimulation and used to normalize the size of the conditioned reflexes recorded in the same orientation of hip movement
- ho, control soleus h-reflex recorded with subjects supine
- mg, medial gastrocnemius
- mh, medial hamstrings
- ptn, posterior tibial nerve
- sci, spinal cord injury
- sem, standard error of mean
- sol, soleus
- ta, tibialis anterior
- vl, vastus lateralis
- vm, vastus medialis
Collapse
Affiliation(s)
- Maria Knikou
- Department of Biology & Physical Therapy, City University of New York, Staten Island, NY 10314, USA.
| | | | | | | |
Collapse
|
18
|
Jackson A, Baker SN, Fetz EE. Tests for presynaptic modulation of corticospinal terminals from peripheral afferents and pyramidal tract in the macaque. J Physiol 2006; 573:107-20. [PMID: 16556658 PMCID: PMC1779692 DOI: 10.1113/jphysiol.2005.100537] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2005] [Accepted: 03/20/2006] [Indexed: 11/08/2022] Open
Abstract
The efficacy of sensory input to the spinal cord can be modulated presynaptically during voluntary movement by mechanisms that depolarize afferent terminals and reduce transmitter release. It remains unclear whether similar influences are exerted on the terminals of descending fibres in the corticospinal pathway of Old World primates and man. We investigated two signatures of presynaptic inhibition of the macaque corticospinal pathway following stimulation of the peripheral nerves of the arm (median, radial and ulnar) and the pyramidal tract: (1) increased excitability of corticospinal axon terminals as revealed by changes in antidromically evoked cortical potentials, and (2) changes in the size of the corticospinal monosynaptic field potential in the spinal cord. Conditioning stimulation of the pyramidal tract increased both the terminal excitability and monosynaptic fields with similar time courses. Excitability was maximal between 7.5 and 10 ms following stimulation and returned to baseline within 40 ms. Conditioning stimulation of peripheral nerves produced no statistically significant effect in either measure. We conclude that peripheral afferents do not exert a presynaptic influence on the corticospinal pathway, and that descending volleys may produce autogenic terminal depolarization that is correlated with enhanced transmitter release. Presynaptic inhibition of afferent terminals by descending pathways and the absence of a reciprocal influence of peripheral input on corticospinal efficacy would help to preserve the fidelity of motor commands during centrally initiated movement.
Collapse
Affiliation(s)
- A Jackson
- Department of Physiology and Biophysics, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195-7290, USA
| | | | | |
Collapse
|
19
|
Abstract
Locomotion results from intricate dynamic interactions between a central program and feedback mechanisms. The central program relies fundamentally on a genetically determined spinal circuitry (central pattern generator) capable of generating the basic locomotor pattern and on various descending pathways that can trigger, stop, and steer locomotion. The feedback originates from muscles and skin afferents as well as from special senses (vision, audition, vestibular) and dynamically adapts the locomotor pattern to the requirements of the environment. The dynamic interactions are ensured by modulating transmission in locomotor pathways in a state- and phase-dependent manner. For instance, proprioceptive inputs from extensors can, during stance, adjust the timing and amplitude of muscle activities of the limbs to the speed of locomotion but be silenced during the opposite phase of the cycle. Similarly, skin afferents participate predominantly in the correction of limb and foot placement during stance on uneven terrain, but skin stimuli can evoke different types of responses depending on when they occur within the step cycle. Similarly, stimulation of descending pathways may affect the locomotor pattern in only certain phases of the step cycle. Section ii reviews dynamic sensorimotor interactions mainly through spinal pathways. Section iii describes how similar sensory inputs from the spinal or supraspinal levels can modify locomotion through descending pathways. The sensorimotor interactions occur obviously at several levels of the nervous system. Section iv summarizes presynaptic, interneuronal, and motoneuronal mechanisms that are common at these various levels. Together these mechanisms contribute to the continuous dynamic adjustment of sensorimotor interactions, ensuring that the central program and feedback mechanisms are congruous during locomotion.
Collapse
Affiliation(s)
- Serge Rossignol
- Department of Physiology, Centre for Research in Neurological Sciences, Faculty of Medicine, Université de Montréal, PO Box 6128, Station Centre-Ville, Montreal, Quebec, Canada H3C 3J7.
| | | | | |
Collapse
|
20
|
Nafati G, Schmied A, Rossi-Durand C. Changes in the Inhibitory Control Exerted by the Antagonist Ia Afferents on Human Wrist Extensor Motor Units During an Attention-Demanding Motor Task. J Neurophysiol 2005; 93:2350-3. [PMID: 15563550 DOI: 10.1152/jn.00996.2004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aim of this study was to determine the extent to which an attention-demanding visuomotor task affects the strength of the inhibitory control exerted by the wrist flexor group Ia afferents on the wrist extensor motoneurons. Effects of median nerve stimulation on the tonic activity of wrist extensor single motor units were analyzed in terms of the interspike interval (ISI) lengthening. Results show that the inhibitory effects exerted by the antagonistic group Ia afferents were significantly enhanced when the wrist extensor motoneurons were involved in an attention-demanding task. Enhanced inhibition from antagonist afferents may reflect task-related changes in the excitability of the di- and/or polysynaptic pathways mediating reciprocal inhibition due to either the action of descending inputs and/or an increase in the efficiency of the Ia inputs to the premotoneuronal inhibitory interneurons. Modulation of the inhibition exerted by proprioceptive antagonist afferents may be one of the processes which contribute to the fine adjustment of the wrist muscle force output required in fine handling tasks.
Collapse
Affiliation(s)
- Gilel Nafati
- Laboratoire de Plasticité et PhysioPathologie de la Motricité (P3M), Unité Mixte Recherche 6196, Centre National de la Recherche Scientifique/Université de la Méditerranée, 31, chemin Joseph-Aiguier, 13402 Marseille Cedex 20, France
| | | | | |
Collapse
|
21
|
Repetitive Sensory Input Increases Reciprocal Ia Inhibition In Individuals With Incomplete Spinal Cord Injury. J Neurol Phys Ther 2004. [DOI: 10.1097/01253086-200409000-00003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
22
|
Pyndt HS, Laursen M, Nielsen JB. Changes in reciprocal inhibition across the ankle joint with changes in external load and pedaling rate during bicycling. J Neurophysiol 2003; 90:3168-77. [PMID: 12878714 DOI: 10.1152/jn.00444.2003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to investigate the role of reciprocal inhibition in the regulation of antagonistic ankle muscles during bicycling. A total of 20 subjects participated in the study. Reciprocal inhibition was induced by stimulation of the peroneal nerve (PN) at 1.2 times threshold for the M-response in the tibialis anterior muscle (TA) and recorded as a depression of the rectified soleus (SOL) EMG. Recordings were made during tonic plantar flexion and during bicycling on an ergometer bicycle. During tonic contraction, the amount of inhibition in the SOL EMG was linearly correlated to the amount of background EMG. This linear relation was used to calculate the expected amount of reciprocal inhibition at corresponding EMG levels during bicycling. During the early phase of down-stroke of bicycling at 60 revolutions per minute (RPM) and an external load of 1.0 kg, the amount of recorded reciprocal inhibition was significantly smaller than that calculated from the linear relation during tonic contraction. In nine subjects, the SOL H-reflex was used to evaluate the amount of inhibition. At a short conditioning test interval (2-3 ms), the PN stimulation depressed the SOL H-reflex when the subjects were at rest. This short latency inhibition was absent during downstroke, but appeared during upstroke just prior to and during TA activation. A positive linear relation was found between the level of SOL background EMG in early downstroke and the external load (0.5-2.5 kg) as well as the rate of pedaling (30-90 RPM at 1.0 kg external load). The amount of inhibition in the SOL EMG when expressed as a percentage of the background EMG activity decreased significantly with increasing load. During increased pedaling rate, a similar decrease was seen, but it did not reach a statistically significant level. The data illustrate that reciprocal inhibition of the soleus muscle is modulated during bicycling being small in downstroke when the SOL muscle is active and large in upstroke where the muscle is inactive and its antagonist becomes active. The depression of the inhibition in relation to increased load and pedaling rate likely reflects the need of reducing inhibition of the SOL motoneurons to ensure a sufficient activation of the muscle.
Collapse
Affiliation(s)
- H S Pyndt
- Department of Medical Physiology, The Panum Institute, University of Copenhagen, DK-2200 N Copenhagen, Denmark
| | | | | |
Collapse
|
23
|
Enríquez-Denton M, Morita H, Christensen LOD, Petersen N, Sinkjaer T, Nielsen JB. Interaction between peripheral afferent activity and presynaptic inhibition of ia afferents in the cat. J Neurophysiol 2002; 88:1664-74. [PMID: 12364496 DOI: 10.1152/jn.2002.88.4.1664] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It has been demonstrated in man that the H-reflex is more depressed by presynaptic inhibition than the stretch reflex. Here we investigated this finding further in the alpha-chloralose-anesthetized cat. Soleus monosynaptic reflexes were evoked by electrical stimulation of the tibial nerve or by stretch of the triceps surae muscle. Conditioning stimulation of the posterior biceps and semitendinosus nerve (PBSt) produced a significantly stronger depression of the electrically than the mechanically evoked reflexes. The depression of the reflexes has been shown to be caused by presynaptic inhibition of triceps surae Ia afferents. We investigated the hypothesis that repetitive activation of peripheral afferents may reduce their sensitivity to presynaptic inhibition. In triceps surae motoneurones, we measured the effect of presynaptic inhibition on excitatory postsynaptic potentials (EPSPs) produced by repetitive activation of the peripheral afferents or by fast and slow muscle stretch. EPSPs evoked by single electrical stimulation of the tibial nerve or by fast muscle stretch were significantly depressed by PBSt stimulation. However, the last EPSP in a series of EPSPs evoked by a train of electrical stimuli (5-6 shocks, 150-200 Hz) was significantly less depressed by the conditioning stimulation than the first EPSP. In addition, the last part of the long-lasting EPSPs evoked by a slow muscle stretch was also less depressed than the first part. A single EPSP evoked by stimulation of the medial gastrocnemius nerve was less depressed when preceded by a train of stimuli applied to the same nerve than when the same train of stimuli was applied to a synergistic nerve. The decreased sensitivity of the test EPSP to presynaptic inhibition was maximal when it was evoked within 20 ms after the train of EPSPs. It was not observed at intervals longer than 30 ms. These findings suggest that afferent activity may decrease the efficiency of presynaptic inhibition. We propose that the described interaction between afferent nerve activity and presynaptic inhibition may partly explain why electrically and mechanically evoked reflexes are differently sensitive to presynaptic inhibition.
Collapse
Affiliation(s)
- M Enríquez-Denton
- Division of Neurophysiology, Department of Medical Physiology, The Panum Institute. University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark.
| | | | | | | | | | | |
Collapse
|
24
|
Tresch MC, Saltiel P, d'Avella A, Bizzi E. Coordination and localization in spinal motor systems. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2002; 40:66-79. [PMID: 12589907 DOI: 10.1016/s0165-0173(02)00189-3] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We review here experiments examining the hypothesis that vertebrate spinal motor systems produce movement through the flexible combination of a small number of units of motor output. Using a variety of preparations and techniques, these experiments provide evidence for such spinally generated units and for the localization of the networks responsible for producing them within different regions of the spinal cord. Such an organization might help to simplify the production of movement, reducing the degrees of freedom that need to be specified by providing a set of units involved in regulating features common to a range of behaviors.
Collapse
Affiliation(s)
- Matthew C Tresch
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | | | | |
Collapse
|
25
|
Spencer NJ, Smith TK. Simultaneous intracellular recordings from longitudinal and circular muscle during the peristaltic reflex in guinea-pig distal colon. J Physiol 2001; 533:787-99. [PMID: 11410635 PMCID: PMC2278663 DOI: 10.1111/j.1469-7793.2001.00787.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2000] [Accepted: 02/05/2001] [Indexed: 11/29/2022] Open
Abstract
1. Simultaneous intracellular recordings were made from longitudinal muscle (LM) and circular muscle (CM) cells of guinea-pig distal colon during the peristaltic reflex. 2. Spontaneous rhythmical depolarizations with superimposed action potentials (mean amplitude: 19 +/- 2 mV) were regularly recorded from the LM (mean interval: 7 +/- 1 s). In contrast, in the CM layer, spontaneous action potentials occurred with an irregular frequency. Although spontaneous action potentials in LM were rarely correlated in time with those in CM, spontaneous inhibitory junction potentials (sIJPs) were found to occur synchronously in both muscles (5 out of 27 animals; 19 %). 3. Graded inflation of an intra-luminal balloon or mucosal stimulation oral to the recording electrodes elicited gradeable compound IJPs synchronously in both LM (mean amplitude: 6 +/- 1 mV) and CM (mean amplitude: 9 +/- 1 mV) (descending inhibitory reflex). Evoked IJPs were often followed by action potentials in both muscle layers. 4. Mucosal stimuli applied anal to the recording electrodes elicited compound excitatory junction potentials (EJPs) synchronously in both muscles layers that were often associated with the generation of action potentials. In the LM, evoked EJP amplitudes ranged from 3 mV (subthreshold) to 31 mV (including the action potential) and in the CM from 4 mV (subthreshold) to 44 mV (including the action potential). 5. Apamin (500 nM) reduced the evoked IJP in the CM by 55 % (from 11 +/- 2 to 5 +/- 1 mV), but caused no significant reduction in the LM layer (from 8 +/- 1 to 6 +/- 1 mV). Apamin-resistant IJPs in both muscle layers were likely to be due to nitric oxide, since they were abolished by L-NA (100 microM). 6. Atropine (1 microM) abolished the ascending excitatory reflex in both muscles. 7. Injection of neurobiotin into the LM and CM confirmed that simultaneous intracellular recordings were made from different muscle layers. 8. In conclusion, during the peristaltic reflex, the LM and CM layers receive synchronous inhibitory neuromuscular inputs during descending inhibition and synchronous excitatory neuromuscular inputs during ascending excitation. No evidence was found to support reciprocal innervation.
Collapse
Affiliation(s)
- N J Spencer
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
| | | |
Collapse
|