Enhanced D1 and D2 Inhibitions Induced by Low-Frequency Trains of Conditioning Stimuli: Differential Effects on H- and T-Reflexes and Possible Mechanisms

Autor(es)

Mezzarane, Rinaldo Andre ^{[1, 2]} ; Magalhaes, Fernando Henrique ^{[1, 3]} ; Chaud, Vitor Martins ^{[1, 4]} ; Elias, Leonardo Abdala ^{[1, 5]} ; Kohn, Andre Fabio ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, PTC, Escola Politecn, Biomed Engn Lab, Sao Paulo - Brazil

^[2] Univ Brasilia, UnB, Coll Phys Educ, Lab Signal Proc & Motor Control, Brasilia, DF - Brazil

^[3] Univ Sao Paulo, EACH, Sch Arts Sci & Humanities, Sao Paulo - Brazil

^[4] Univ Fed Triangulo Mineiro, Dept Elect Engn, Uberaba - Brazil

^[5] Univ Estadual Campinas, UNICAMP, Sch Elect & Comp Engn, Dept Biomed Engn, Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: PLoS One; v. 10, n. 3 MAR 25 2015.
• Citações Web of Science: 7

Resumo

Mechanically evoked reflexes have been postulated to be less sensitive to presynaptic inhibition (PSI) than the H-reflex. This has implications on investigations of spinal cord neurophysiology that are based on the T-reflex. Preceding studies have shown an enhanced effect of PSI on the H-reflex when a train of similar to 10 conditioning stimuli at 1 Hz was applied to the nerve of the antagonist muscle. The main questions to be addressed in the present study are if indeed T-reflexes are less sensitive to PSI and whether (and to what extent and by what possible mechanisms) the effect of low frequency conditioning, found previously for the H-reflex, can be reproduced on T-reflexes from the soleus muscle. We explored two different conditioning-to-test (C-T) intervals: 15 and 100 ms (corresponding to D1 and D2 inhibitions, respectively). Test stimuli consisted of either electrical pulses applied to the posterior tibial nerve to elicit H-reflexes or mechanical percussion to the Achilles tendon to elicit T-reflexes. The 1 Hz train of conditioning electrical stimuli delivered to the common peroneal nerve induced a stronger effect of PSI as compared to a single conditioning pulse, for both reflexes (T and H), regardless of C-T-intervals. Moreover, the conditioning train of pulses (with respect to a single conditioning pulse) was proportionally more effective for T-reflexes as compared to H-reflexes (irrespective of the C-T interval), which might be associated with the differential contingent of Ia afferents activated by mechanical and electrical test stimuli. A conceivable explanation for the enhanced PSI effect in response to a train of stimuli is the occurrence of homosynaptic depression at synapses on inhibitory interneurons interposed within the PSI pathway. The present results add to the discussion of the sensitivity of the stretch reflex pathway to PSI and its functional role. (AU)

• Processo FAPESP: 10/15522-4 - Proposta de utilização de estimulador mecânico para estudo de flutuações síncronas na excitabilidade de reflexos bilaterais em humanos
• Beneficiário: Rinaldo André Mezzarane
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 13/10433-1 - Estudo das propriedades de disparo de unidades motoras dos músculos extensores e flexores do tornozelo durante modulações senoidais do torque e de ângulo articulares
• Beneficiário: Leonardo Abdala Elias
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 11/13222-6 - Avaliação de vias inibitórias e do efeito de estimulações com ruído elétrico sobre o controle neuromuscular de flexão plantar
• Beneficiário: Fernando Henrique Magalhães
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 09/15802-0 - Modelagem e simulação de sistema de controle neuronal de torque por realimentação proprioceptiva: aplicação ao controle postural
• Beneficiário: Leonardo Abdala Elias
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 11/17193-0 - Respostas reflexas, encefálicas e comportamentais a estímulos mecânicos e elétricos no estudo da propriocepção e da medula espinhal em seres humanos
• Beneficiário: André Fábio Kohn
• Modalidade de apoio: Auxílio à Pesquisa - Regular