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  1 / 1998 MEDLINE  
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[PMID]:28576940
[Au] Autor:Smith CC; Paton JFR; Chakrabarty S; Ichiyama RM
[Ad] Endereço:School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom, and calvin.smith@ucl.ac.uk.
[Ti] Título:Descending Systems Direct Development of Key Spinal Motor Circuits.
[So] Source:J Neurosci;37(26):6372-6387, 2017 Jun 28.
[Is] ISSN:1529-2401
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:The formation of mature spinal motor circuits is dependent on both activity-dependent and independent mechanisms during postnatal development. During this time, reorganization and refinement of spinal sensorimotor circuits occurs as supraspinal projections are integrated. However, specific features of postnatal spinal circuit development remain poorly understood. This study provides the first detailed characterization of rat spinal sensorimotor circuit development in the presence and absence of descending systems. We show that the development of proprioceptive afferent input to motoneurons (MNs) and Renshaw cells (RCs) is disrupted by thoracic spinal cord transection at postnatal day 5 (P5TX). P5TX also led to malformation of GABApre neuron axo-axonic contacts on Ia afferents and of the recurrent inhibitory circuit between MNs and RCs. Using a novel perfused preparation for studying motor control, we show that malformation of these spinal circuits leads to hyperexcitability of the monosynaptic reflex. Our results demonstrate that removing descending input severely disrupts the development of spinal circuits and identifies key mechanisms contributing to motor dysfunction in conditions such as cerebral palsy and spinal cord injury. Acquisition of mature behavior during postnatal development correlates with the arrival and maturation of supraspinal projections to the spinal cord. However, we know little about the role that descending systems play in the maturation of spinal circuits. Here, we characterize postnatal development of key spinal microcircuits in the presence and absence of descending systems. We show that formation of these circuits is abnormal after early (postnatal day 5) removal of descending systems, inducing hyperexcitability of the monosynaptic reflex. The study is a detailed characterization of spinal circuit development elucidating how these mechanisms contribute to motor dysfunction in conditions such as cerebral palsy and spinal cord injury. Understanding these circuits is crucial to developing new therapeutics and improving existing ones in such conditions.
[Mh] Termos MeSH primário: Envelhecimento/fisiologia
Vias Eferentes/fisiologia
Neurônios Motores/fisiologia
Neurogênese/fisiologia
Reflexo Monosináptico/fisiologia
Medula Espinal/fisiologia
[Mh] Termos MeSH secundário: Animais
Feminino
Masculino
Rede Nervosa/fisiologia
Ratos Wistar
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1708
[Cu] Atualização por classe:170818
[Lr] Data última revisão:
170818
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170604
[St] Status:MEDLINE
[do] DOI:10.1523/JNEUROSCI.0149-17.2017


  2 / 1998 MEDLINE  
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[PMID]:27010723
[Au] Autor:Nito M; Hashizume W; Miyasaka T; Suzuki K; Sato T; Fujii H; Shindo M; Naito A
[Ad] Endereço:Department of Anatomy and Structural Science, Yamagata University School of Medicine, 2-2-2, Iida-nishi, Yamagata, 990-9585, Japan.
[Ti] Título:Facilitation from flexor digitorum superficialis to extensor carpi radialis in humans.
[So] Source:Exp Brain Res;234(8):2235-44, 2016 Aug.
[Is] ISSN:1432-1106
[Cp] País de publicação:Germany
[La] Idioma:eng
[Ab] Resumo:Effects of low-threshold afferents from the flexor digitorum superficialis (FDS) to the extensor carpi radialis (ECR) motoneurons were examined using a post-stimulus time-histogram (PSTH) and electromyogram-averaging (EMG-A) methods in eight healthy human subjects. In the PSTH study in five of the eight subjects, electrical conditioning stimuli (ES) to the median nerve branch innervating FDS with the intensity below the motor threshold induced excitatory effects (facilitation) in 39 out of 92 ECR motor units. In 11 ECR motor units, the central synaptic delay of the facilitation was -0.1 ± 0.3 ms longer than that of the homonymous facilitation of ECR. Mechanical conditioning stimuli (MS) to FDS with the intensity below the threshold of the tendon(T)-wave-induced facilitation in 51 out of 51 ECR motor units. With the EMG-A method, early and significant peaks were produced by ES and MS in all the eight subjects. The difference between latencies of the peaks by ES and MS was almost equivalent to that of the Hoffmann- and T-waves of FDS by ES and MS. The peak was diminished by tonic vibration stimuli to FDS. These findings suggest that a facilitation from FDS to ECR exists in humans and group Ia afferents mediate the facilitation through a monosynaptic path.
[Mh] Termos MeSH primário: Dedos/fisiologia
Antebraço/fisiologia
Neurônios Motores/fisiologia
Músculo Esquelético/fisiologia
Reflexo Monosináptico/fisiologia
[Mh] Termos MeSH secundário: Adulto
Estimulação Elétrica
Eletromiografia
Feminino
Dedos/inervação
Antebraço/inervação
Seres Humanos
Masculino
Estimulação Física
Adulto Jovem
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1709
[Cu] Atualização por classe:170922
[Lr] Data última revisão:
170922
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160325
[St] Status:MEDLINE
[do] DOI:10.1007/s00221-016-4629-1


  3 / 1998 MEDLINE  
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[PMID]:25615850
[Au] Autor:Schomburg ED; Steffens H; Pilyavskii AI; Maisky VA; Brück W; Dibaj P; Sears TA
[Ad] Endereço:Institute of Physiology, University of Göttingen, Germany. Electronic address: eschomb@gwdg.de.
[Ti] Título:Long lasting activity of nociceptive muscular afferents facilitates bilateral flexion reflex pattern in the feline spinal cord.
[So] Source:Neurosci Res;95:51-8, 2015 Jun.
[Is] ISSN:1872-8111
[Cp] País de publicação:Ireland
[La] Idioma:eng
[Ab] Resumo:Chronic muscular limb pain requires the adoption of motor patterns distinct from the classic ipsilateral flexion, crossed extension and corresponding reciprocal inhibitions to acute exteroceptive stimulation. Using selective chemical activation of group III/IV afferents in gastrocnemius-soleus (GS) muscles we investigated bilaterally their reflex responses conditioned by (a) acute 'myositis' induced by intramuscular carrageenan; and (b) sub-acute 'myositis' induced by infusion of complete Freund's adjuvant (CFA). Reflex transmission was detected by monosynaptic testing and c-fos staining used to identify increased neuronal activity. In all control experiments with chemical stimulation of group III/IV afferents, ipsilateral responses conformed to the flexor reflex pattern. However, the expected contralateral facilitation of GS motoneurones occurred in fewer than 50% trials while only 9% of trials induced contralateral inhibition of flexor posterior-biceps-semitendinosus (PBSt) motoneurones. During carrageenan acute myositis contralateral PBSt was transiently facilitated by selective activation of group III/IV afferents. During CFA-induced myositis, contralateral only inhibition of GS motoneurones occurred instead of any facilitation, while bidirectionally a crossed facilitation of PBST dominated. These reflex changes were mirrored in an enhanced number of neurones with enhanced c-fos expression. Muscle pain, particularly if chronically persistent, requires another behavioural response pattern than acute exteroceptive pain.
[Mh] Termos MeSH primário: Mialgia/fisiopatologia
Miosite/fisiopatologia
Nociceptores/fisiologia
Reflexo Anormal/fisiologia
Reflexo Monosináptico
Medula Espinal/fisiopatologia
[Mh] Termos MeSH secundário: Animais
Carragenina/farmacologia
Gatos
Estimulação Elétrica
Adjuvante de Freund/farmacologia
Neurônios Motores/metabolismo
Músculo Esquelético/inervação
Músculo Esquelético/fisiopatologia
Mialgia/induzido quimicamente
Miosite/induzido quimicamente
Proteínas Proto-Oncogênicas c-fos
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Proto-Oncogene Proteins c-fos); 9000-07-1 (Carrageenan); 9007-81-2 (Freund's Adjuvant)
[Em] Mês de entrada:1601
[Cu] Atualização por classe:150427
[Lr] Data última revisão:
150427
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:150124
[St] Status:MEDLINE


  4 / 1998 MEDLINE  
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[PMID]:25469831
[Au] Autor:Mazo I; Roza C; Zamanillo D; Merlos M; Vela JM; Lopez-Garcia JA
[Ad] Endereço:Department of Systems Biology (Division Physiology), Edificio Medicina, Universidad de Alcala, Madrid, Spain.
[Ti] Título:Effects of centrally acting analgesics on spinal segmental reflexes and wind-up.
[So] Source:Eur J Pain;19(7):1012-20, 2015 Aug.
[Is] ISSN:1532-2149
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:BACKGROUND: The spinal cord is a prime site of action for analgesia. Here we characterize the effects of established analgesics on segmental spinal reflexes. The aim of the study was to look for the pattern of action or signature of analgesic effects on these reflexes. METHODS: We used a spinal cord in vitro preparation of neonate mice to record ventral root responses to dorsal root stimulation. Pregabalin, clonidine, morphine and duloxetine and an experimental sigma-1 receptor antagonist (S1RA) were applied to the preparation in a cumulative concentration protocol. Drug effects on the wind-up produced by repetitive stimulation of C-fibres and on responses to single A- and C-fibre intensity stimuli were analysed. RESULTS: All compounds produced a concentration-dependent inhibition of total spikes elicited by repetitive stimulation. Concentrations producing ∼50% reduction in this parameter were (in µM) clonidine (0.01), morphine (0.1), pregabalin (1), duloxetine (10) and S1RA (30). At these concentrations clonidine, pregabalin and S1RA had significant effects on the wind-up index and little depressant effects on responses to single stimuli. Morphine and duloxetine did not depress wind-up index and showed large effects on responses to single stimuli. None of the compounds had strong effects on the amplitude of the non-nociceptive monosynaptic reflex. CONCLUSIONS: morphine and duloxetine had general depressant effects on spinal reflexes, whereas the effects of clonidine, pregabalin and S1RA appeared to be restricted to signals originated by strong repetitive activation of C-fibres. Results are discussed in the context of reported behavioural effects of the compounds studied.
[Mh] Termos MeSH primário: Analgésicos/farmacologia
Nociceptividade/efeitos dos fármacos
Reflexo Monosináptico/efeitos dos fármacos
Medula Espinal/efeitos dos fármacos
[Mh] Termos MeSH secundário: Animais
Animais Recém-Nascidos
Relação Dose-Resposta a Droga
Estimulação Elétrica
Feminino
Masculino
Camundongos
Camundongos Endogâmicos C57BL
Neurônios Motores/efeitos dos fármacos
Fibras Nervosas Mielinizadas/efeitos dos fármacos
Fibras Nervosas Amielínicas/efeitos dos fármacos
Receptores sigma/efeitos dos fármacos
Raízes Nervosas Espinhais/efeitos dos fármacos
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Analgesics); 0 (Receptors, sigma); 0 (sigma-1 receptor)
[Em] Mês de entrada:1608
[Cu] Atualização por classe:150716
[Lr] Data última revisão:
150716
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:141204
[St] Status:MEDLINE
[do] DOI:10.1002/ejp.629


  5 / 1998 MEDLINE  
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[PMID]:24920027
[Au] Autor:Ford TW; Meehan CF; Kirkwood PA
[Ad] Endereço:University of Nottingham School of Health Sciences, Queen's Medical Centre, Nottingham, United Kingdom; and.
[Ti] Título:Absence of synergy for monosynaptic Group I inputs between abdominal and internal intercostal motoneurons.
[So] Source:J Neurophysiol;112(5):1159-68, 2014 Sep 01.
[Is] ISSN:1522-1598
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Internal intercostal and abdominal motoneurons are strongly coactivated during expiration. We investigated whether that synergy was paralleled by synergistic Group I reflex excitation. Intracellular recordings were made from motoneurons of the internal intercostal nerve of T8 in anesthetized cats, and the specificity of the monosynaptic connections from afferents in each of the two main branches of this nerve was investigated. Motoneurons were shown by antidromic excitation to innervate three muscle groups: external abdominal oblique [EO; innervated by the lateral branch (Lat)], the region of the internal intercostal muscle proximal to the branch point (IIm), and muscles innervated from the distal remainder (Dist). Strong specificity was observed, only 2 of 54 motoneurons showing excitatory postsynaptic potentials (EPSPs) from both Lat and Dist. No EO motoneurons showed an EPSP from Dist, and no IIm motoneurons showed one from Lat. Expiratory Dist motoneurons fell into two groups. Those with Dist EPSPs and none from Lat (group A) were assumed to innervate distal internal intercostal muscle. Those with Lat EPSPs (group B) were assumed to innervate abdominal muscle (transversus abdominis or rectus abdominis). Inspiratory Dist motoneurons (assumed to innervate interchondral muscle) showed Dist EPSPs. Stimulation of dorsal ramus nerves gave EPSPs in 12 instances, 9 being in group B Dist motoneurons. The complete absence of heteronymous monosynaptic Group I reflex excitation between muscles that are synergistically activated in expiration leads us to conclude that such connections from muscle spindle afferents of the thoracic nerves have little role in controlling expiratory movements but, where present, support other motor acts.
[Mh] Termos MeSH primário: Músculos Abdominais/inervação
Músculos Intercostais/inervação
Neurônios Motores/fisiologia
Reflexo Monosináptico
[Mh] Termos MeSH secundário: Animais
Gatos
Potenciais Pós-Sinápticos Excitadores
Feminino
Masculino
Fusos Musculares/inervação
Fusos Musculares/fisiologia
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Em] Mês de entrada:1505
[Cu] Atualização por classe:170220
[Lr] Data última revisão:
170220
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:140613
[St] Status:MEDLINE
[do] DOI:10.1152/jn.00245.2014


  6 / 1998 MEDLINE  
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[PMID]:24778886
[Au] Autor:Shu L; Su J; Jing L; Huang Y; Di Y; Peng L; Liu J
[Ad] Endereço:The Department of Neurology, Shanghai Ninth People's Hospital Affiliated Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.
[Ti] Título:Reduced Renshaw recurrent inhibition after neonatal sciatic nerve crush in rats.
[So] Source:Neural Plast;2014:786985, 2014.
[Is] ISSN:1687-5443
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Renshaw recurrent inhibition (RI) plays an important gated role in spinal motion circuit. Peripheral nerve injury is a common disease in clinic. Our current research was designed to investigate the change of the recurrent inhibitory function in the spinal cord after the peripheral nerve crush injury in neonatal rat. Sciatic nerve crush was performed on 5-day-old rat puppies and the recurrent inhibition between lateral gastrocnemius-soleus (LG-S) and medial gastrocnemius (MG) motor pools was assessed by conditioning monosynaptic reflexes (MSR) elicited from the sectioned dorsal roots and recorded either from the LG-S and MG nerves by antidromic stimulation of the synergist muscle nerve. Our results demonstrated that the MSR recorded from both LG-S or MG nerves had larger amplitude and longer latency after neonatal sciatic nerve crush. The RI in both LG-S and MG motoneuron pools was significantly reduced to virtual loss (15-20% of the normal RI size) even after a long recovery period upto 30 weeks after nerve crush. Further, the degree of the RI reduction after tibial nerve crush was much less than that after sciatic nerve crush indicatig that the neuron-muscle disconnection time is vital to the recovery of the spinal neuronal circuit function during reinnervation. In addition, sciatic nerve crush injury did not cause any spinal motor neuron loss but severally damaged peripheral muscle structure and function. In conclusion, our results suggest that peripheral nerve injury during neonatal early development period would cause a more sever spinal cord inhibitory circuit damage, particularly to the Renshaw recurrent inhibition pathway, which might be the target of neuroregeneration therapy.
[Mh] Termos MeSH primário: Animais Recém-Nascidos/fisiologia
Compressão Nervosa
Inibição Neural/fisiologia
Nervo Isquiático/patologia
[Mh] Termos MeSH secundário: Animais
Estimulação Elétrica
Fenômenos Eletrofisiológicos/fisiologia
Membro Posterior/inervação
Peroxidase do Rábano Silvestre
Masculino
Neurônios Motores/fisiologia
Músculo Esquelético/inervação
Músculo Esquelético/fisiologia
Regeneração Nervosa/fisiologia
Ratos
Ratos Wistar
Reflexo Monosináptico/fisiologia
Nervo Tibial/fisiologia
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
EC 1.11.1.- (Horseradish Peroxidase)
[Em] Mês de entrada:1410
[Cu] Atualização por classe:161125
[Lr] Data última revisão:
161125
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:140430
[St] Status:MEDLINE
[do] DOI:10.1155/2014/786985


  7 / 1998 MEDLINE  
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[PMID]:24484172
[Au] Autor:Chopek JW; MacDonell CW; Gardiner K; Gardiner PF
[Ad] Endereço:1 Spinal Cord Research Centre, Department of Physiology and, University of Manitoba , Winnipeg, Manitoba, Canada .
[Ti] Título:Daily passive cycling attenuates the hyperexcitability and restores the responsiveness of the extensor monosynaptic reflex to quipazine in the chronic spinally transected rat.
[So] Source:J Neurotrauma;31(12):1083-7, 2014 Jun 15.
[Is] ISSN:1557-9042
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Activity-based interventions such as locomotor training or passive cycling have a positive influence on the spinal circuitry and recovery following a spinal cord injury (SCI). The use of quipazine in combination with exercise training has demonstrated a greater functional recovery than has exercise training alone. However, the influence of exercise or training on the responsiveness of the spinal cord to quipazine has not been examined following a chronic spinal transection. The purpose of this study was to characterize the flexor and extensor monosynaptic reflex (MSR) response pre- and post-quipazine in chronic complete spinally transected rats that either underwent daily passive cycling for 3 months or did not receive passive cycling. Following a chronic spinal transection, the extensor MSR demonstrated a hyperreflexive response (fivefold increase) to afferent stimuli, and did not respond to quipazine injection. With daily passive cycling, the extensor MSR hyperexcitability was attenuated, and the MSR amplitude increased 72% following quipazine injection (p<0.004), which was comparable to the extensor MSR response (94%) in the control group. For both chronic spinal transection groups, the flexor MSR amplitudes were not altered following quipazine injection, whereas in the control group the flexor MSR amplitude increased 86% in response to quipazine (p<0.004). These results demonstrate that passive cycling attenuates the hyperreflexive response of the extensor MSR following a chronic SCI, and restores the MSR response to quipazine.
[Mh] Termos MeSH primário: Terapia por Exercício/métodos
Quipazina/farmacologia
Recuperação de Função Fisiológica/fisiologia
Reflexo Monosináptico/fisiologia
Agonistas de Receptores de Serotonina/farmacologia
Traumatismos da Medula Espinal/terapia
[Mh] Termos MeSH secundário: Animais
Terapia Combinada
Modelos Animais de Doenças
Feminino
Quipazina/administração & dosagem
Ratos
Ratos Sprague-Dawley
Recuperação de Função Fisiológica/efeitos dos fármacos
Reflexo Monosináptico/efeitos dos fármacos
Agonistas de Receptores de Serotonina/administração & dosagem
Traumatismos da Medula Espinal/tratamento farmacológico
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Serotonin Receptor Agonists); 4WCY05C0SJ (Quipazine)
[Em] Mês de entrada:1502
[Cu] Atualização por classe:140618
[Lr] Data última revisão:
140618
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:140204
[St] Status:MEDLINE
[do] DOI:10.1089/neu.2013.3207


  8 / 1998 MEDLINE  
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[PMID]:23365181
[Au] Autor:Chopek JW; MacDonell CW; Power KE; Gardiner K; Gardiner PF
[Ad] Endereço:Spinal Cord Research Centre, Department of Physiology and Faculty of Kinesiology and Recreation Management, University of Manitoba, Winnipeg, Manitoba, Canada.
[Ti] Título:Removal of supraspinal input reveals a difference in the flexor and extensor monosynaptic reflex response to quipazine independent of motoneuron excitation.
[So] Source:J Neurophysiol;109(8):2056-63, 2013 Apr.
[Is] ISSN:1522-1598
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:The purpose of this study was to determine if quipazine, a serotonergic agonist, differentially modulates flexor and extensor motor output. This was achieved by examining the monosynaptic reflex (MSR) of the tibial (extensor) and peroneal (flexor) nerves, by determining the basic and rhythmic properties of extensor and flexor motoneurons, and by recording extracellular Ia field potentials of the tibial and peroneal nerves in the in vivo adult decerebrate rat in both spinal intact and acute spinalized preparations. In the spinal intact preparation, the tibial and peroneal MSR amplitude significantly increased compared with baseline in response to quipazine, with no difference between nerves (P < 0.05). In the spinalized preparation, the MSR was significantly increased in both the tibial and peroneal nerves with the latter increasing more than the former (5.7 vs. 3.6 times; P < 0.05). Intracellular motoneuron experiments demonstrated that rheobase decreased, while input resistance, afterhyperpolarization amplitude, and the firing rate at a given current injection increased in motoneurons following quipazine administration with no differences between extensor and flexor motoneurons. Both the tibial and peroneal nerve extracellular Ia field potentials increased with the peroneal demonstrating a significantly greater increase (7 vs. 38%; P < 0.05) following quipazine. It is concluded that in the spinal intact preparation quipazine does not have a differential effect on flexor or extensor motor output. However, in the acute spinalized preparation, quipazine preferentially affects the flexor MSR compared with the extensor MSR, likely due to the removal of a descending tonic inhibition on flexor Ia afferents.
[Mh] Termos MeSH primário: Neurônios Motores/fisiologia
Nervo Fibular/fisiologia
Quipazina/farmacologia
Reflexo Monosináptico/efeitos dos fármacos
Agonistas de Receptores de Serotonina/farmacologia
Nervo Tibial/fisiologia
[Mh] Termos MeSH secundário: Potenciais de Ação/efeitos dos fármacos
Animais
Feminino
Músculo Esquelético/inervação
Músculo Esquelético/fisiologia
Ratos
Ratos Sprague-Dawley
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Serotonin Receptor Agonists); 4WCY05C0SJ (Quipazine)
[Em] Mês de entrada:1309
[Cu] Atualização por classe:131121
[Lr] Data última revisão:
131121
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:130201
[St] Status:MEDLINE
[do] DOI:10.1152/jn.00405.2012


  9 / 1998 MEDLINE  
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[PMID]:22917776
[Au] Autor:Bosch KD; Bradbury EJ; Verhaagen J; Fawcett JW; McMahon SB
[Ad] Endereço:Wolfson Centre for Age-Related Diseases, King's College London, Guy's Campus, London Bridge, SE1 1UL, UK. karen.bosch@kcl.ac.uk
[Ti] Título:Chondroitinase ABC promotes plasticity of spinal reflexes following peripheral nerve injury.
[So] Source:Exp Neurol;238(1):64-78, 2012 Nov.
[Is] ISSN:1090-2430
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Peripheral nerve transection, even with optimal repair, can result in an extensive disruption of central connectivity, which can lead to long-lasting impairments in motor and sensory function. We hypothesised that removal of spinal cord chondroitin sulphate proteoglycans (CSPGs) would promote plasticity in the spinal cord, allowing compensation for inaccurate peripheral reinnervation. In adult rats, the median and radial nerves were cut and repaired, either correctly (median to median and radial to radial), or incorrectly (median to radial and vice versa). This produced two levels of inaccuracy of peripheral reinnervation. Whole nerve recordings from a third brachial plexus nerve, the ulnar, were made during median or radial nerve stimulation. Low and high threshold reflexes were characterised in uninjured animals and a clear difference in the pattern of ulnar response to flexor (median) or extensor (radial) stimulation was established. This included the phenomenon of wind-up, where repetitive median nerve stimulation at supramaximal C-fibre threshold leads to a progressive increase in the number of spikes recorded. To achieve digestion of CSPGs a lentiviral vector expressing ChABC was delivered to the spinal cord via intraspinal injection. Following ChABC treatment, we found several indicators of reorganisation of central connections. Firstly, we found that the amplitude of a low threshold, polysynaptic reflex could be increased after nerve injury, only following treatment with ChABC. Secondly, wind-up of motor responses in the ulnar nerve to supramaximal stimulation of afferents in the median nerve, which collapses after nerve injury (to ~25% of uninjured value), could be restored by ChABC after correct repair (to ~90% of uninjured value). Thirdly, wind-up in ulnar motor axons to stimulation of radial nerve afferents, which is minimal in the uninjured state, becomes significantly stronger after nerve injury and ChABC treatment (a 10 fold increase). We propose that application of a plasticity-promoting treatment to the spinal cord allows the amplification of adaptive changes in response to inaccurate wiring in the periphery.
[Mh] Termos MeSH primário: Condroitina ABC Liase/uso terapêutico
Plasticidade Neuronal/fisiologia
Traumatismos dos Nervos Periféricos/fisiopatologia
Reflexo Monosináptico/efeitos dos fármacos
Traumatismos da Medula Espinal/tratamento farmacológico
Traumatismos da Medula Espinal/fisiopatologia
[Mh] Termos MeSH secundário: Animais
Comportamento Animal/fisiologia
Condroitina ABC Liase/genética
Eletrocardiografia
Fenômenos Eletrofisiológicos
Vetores Genéticos
Imuno-Histoquímica
Lentivirus/genética
Neurônios Motores/efeitos dos fármacos
Neurônios Motores/fisiologia
Destreza Motora/efeitos dos fármacos
Destreza Motora/fisiologia
Fibras Nervosas Mielinizadas/efeitos dos fármacos
Fibras Nervosas Mielinizadas/fisiologia
Plasticidade Neuronal/efeitos dos fármacos
Neurônios Aferentes/efeitos dos fármacos
Medição da Dor
Limiar da Dor/fisiologia
Ratos
Reflexo de Estiramento/fisiologia
Sensação
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
EC 4.2.2.20 (Chondroitin ABC Lyase)
[Em] Mês de entrada:1211
[Cu] Atualização por classe:170922
[Lr] Data última revisão:
170922
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:120825
[St] Status:MEDLINE


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[PMID]:22490553
[Au] Autor:Wang Z; Li L; Frank E
[Ad] Endereço:Department of Molecular Physiology and Pharmacology, Tufts University School of Medicine, Boston, MA 02111, USA.
[Ti] Título:The role of muscle spindles in the development of the monosynaptic stretch reflex.
[So] Source:J Neurophysiol;108(1):83-90, 2012 Jul.
[Is] ISSN:1522-1598
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Muscle sensory axons induce the development of specialized intrafusal muscle fibers in muscle spindles during development, but the role that the intrafusal fibers may play in the development of the central projections of these Ia sensory axons is unclear. In the present study, we assessed the influence of intrafusal fibers in muscle spindles on the formation of monosynaptic connections between Ia (muscle spindle) sensory axons and motoneurons (MNs) using two transgenic strains of mice. Deletion of the ErbB2 receptor from developing myotubes disrupts the formation of intrafusal muscle fibers and causes a nearly complete absence of functional synaptic connections between Ia axons and MNs. Monosynaptic connectivity can be fully restored by postnatal administration of neurotrophin-3 (NT-3), and the synaptic connections in NT-3-treated mice are as specific as in wild-type mice. Deletion of the Egr3 transcription factor also impairs the development of intrafusal muscle fibers and disrupts synaptic connectivity between Ia axons and MNs. Postnatal injections of NT-3 restore the normal strengths and specificity of Ia-motoneuronal connections in these mice as well. Severe deficits in intrafusal fiber development, therefore, do not disrupt the establishment of normal, selective patterns of connections between Ia axons and MNs, although these connections require the presence of NT-3, normally supplied by intrafusal fibers, to be functional.
[Mh] Termos MeSH primário: Neurônios Motores/fisiologia
Fusos Musculares/fisiologia
Reflexo Monosináptico/fisiologia
[Mh] Termos MeSH secundário: Actinas/genética
Animais
Animais Recém-Nascidos
Relação Dose-Resposta a Droga
Proteína 3 de Resposta de Crescimento Precoce/genética
Estimulação Elétrica
Seres Humanos
Técnicas In Vitro
Camundongos
Camundongos Transgênicos
Neurônios Motores/efeitos dos fármacos
Fusos Musculares/efeitos dos fármacos
Músculo Esquelético/fisiologia
Fatores de Crescimento Neural/farmacologia
Neurônios Aferentes/fisiologia
Tempo de Reação/efeitos dos fármacos
Tempo de Reação/genética
Receptor ErbB-2/deficiência
Reflexo Monosináptico/efeitos dos fármacos
Reflexo Monosináptico/genética
Medula Espinal/citologia
Potenciais Sinápticos/efeitos dos fármacos
Potenciais Sinápticos/genética
Potenciais Sinápticos/fisiologia
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, N.I.H., EXTRAMURAL
[Nm] Nome de substância:
0 (Actins); 0 (Egr3 protein, mouse); 0 (Nerve Growth Factors); 0 (neurotropin 3, mouse); 144516-98-3 (Early Growth Response Protein 3); EC 2.7.10.1 (Erbb2 protein, mouse); EC 2.7.10.1 (Receptor, ErbB-2)
[Em] Mês de entrada:1211
[Cu] Atualização por classe:170220
[Lr] Data última revisão:
170220
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:120412
[St] Status:MEDLINE
[do] DOI:10.1152/jn.00074.2012



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