Alterações na junção neuromuscular e ventre muscular de ratos Wistar submetidos ao alongamento estático associado às modalidades de escada vertical
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Data
2021-06-01
Autores
Barbosa, Gabriela Klein [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A contração do músculo estriado esquelético depende da relação entre a junção neuromuscular (JNM) e o músculo alvo. A morfologia da JNM e as características do ventre e das fibras musculares apresentam plasticidade tecidual derivada do estímulo. Com o protocolo proposto ocorreram adaptações na JNM e no ventre muscular. O objetivo do presente estudo consistiu em descrever as alterações morfológicas na JNM e ventre do músculo gastrocnêmio de ratos Wistar submetidos ao alongamento estático prévio às modalidades de escada vertical. Foram utilizados ratos Wistar com 60 dias de idade (n = 10): Sedentário (S); Alongado (A); Escada vertical sem carga extra (EC); Escada vertical com sobrecarga (ES); Alongado e escada vertical sem carga extra (AEC); e Alongado e escada vertical com sobrecarga (AES). Os animais foram submetidos aos protocolos 3x por semana por oito semanas. A relação das massas do S, EC, ES e A não demonstraram diferença, enquanto que AEC e AES resultaram em menores valores. Os grupos EC e ES apresentaram aumento da placa motora e redução da compacidade, com destaque para o grupo EC e, ainda, revelaram maior número de clusters e fragmentação. O grupo A apresentou redução da placa motora, com aumento da compacidade e manutenção do número de clusters e fragmentação. Os grupos de alongamento prévio às modalidades de escada vertical (AEC e AES) revelaram aumento da placa motora, com destaque para AES, menor número de clusters e menor índice de fragmentação; entretanto, a compacidade apresentou aumento para AEC e redução para AES. Houve aumento da área de secção transversa das miofibras Tipo IIa para EC e ES, e do Tipo IIx para AES, e redução dos tipos miofibrilares para A e AEC. Houve predominância do Tipo IIx nos grupos EC, A, AEC e AES, e de IIa no grupo ES. Além disso, os grupos AEC e AES apresentaram aumento da quantidade total de miofibras. Os grupos ES e AEC apresentaram maior complexidade mionuclear, os grupos EC e AES revelaram menor complexidade intersticial, e o grupo A mostrou redução das complexidades mionuclear e intersticial. Nos grupos EC, ES, A, AEC e AES houve redução da área intersticial. A análise funcional mostrou a redução do tempo para EC, ES, AEC e AES, e dos movimentos para EC, ES e AEC. O teste de carga máxima carrega (TCMC) revelou aumento de trabalho para ES e AES, com destaque para ES. Concluímos que o alongamento estático prévio às modalidades de escada vertical apresentou aumento da placa motora e menor fragmentação; no entanto, a ocupação dos clusters de receptores de acetilcolina demonstrou diferentes adaptações frente à AEC e AES. Em ambos, ocorre o aumento da quantidade total de miofibras. O alongamento prévio à escada vertical sem carga extra reduz o diâmetro miofibrilar, acarreta maior complexidade mionuclear e reduz a área intersticial. Por outro lado, a modalidade com sobrecarga propicia o aumento do diâmetro miofibrilar do Tipo IIx, menor complexidade e área intersticiais, e apresenta aumento da capacidade de carga.
Skeletal muscle contraction depends on the proper communication between the neuromuscular junction (NMJ) and the muscle. The NMJ morphology and the characteristics of the belly muscle and the myofibers exhibit plasticities stimulus-derived. The protocols proposed in this study promoted adaptations in the NMJ and the belly muscle elements. This study aimed to describe the morphological changes in the NMJ and the belly muscle of the gastrocnemius muscle of Wistar male rats submitted to previous static stretching to vertical ladder modalities. Wistar male rats with 60-days-old (n = 10) were divided into (S) Sedentary, (A) Stretched, (EC) Vertical ladder without overload, (ES) Vertical ladder with overload, (AEC) Stretched and vertical ladder without overload, and (AES) Stretched and vertical ladder with overload. The animals were submitted to the protocols 3x/week for eight weeks. The training session data were used for functional analysis and the samples were processed for light microscopy and immunofluorescence techniques. The mass ratio of S, EC, ES, and A groups showed no difference, while AEC and AES groups resulted in lower values. The EC and ES groups demonstrated an increase in motor endplate and reduced compactness, highlighting the EC group, and showed a greater number of clusters and fragmentation. The A group showed a reduction in motor endplate, increased compactness, and maintenance of the number of clusters and fragmentation. Previous static stretching to vertical ladder modalities (AEC and AES groups) revealed an increase in motor endplate, highlighting the AES group, and lower number of clusters and fragmentation index, though the compactness increased for AEC and decreased for AES. The cross-sectional area (CSA) of myofibers Type IIa increased in the EC and ES groups, Type IIx increased in the AES group, and the myofibrillar types (Type I, IIa, and IIx) reduced in the A and AEC groups. The EC, A, AEC, and AES groups demonstrated Type IIx predominance, while the ES group showed Type IIa predominance. Furthermore, the AEC and AES groups demonstrated an increase in the myofibers’ total quantity. The ES and AEC groups demonstrated higher myonuclear complexity, the EC and AES groups revealed lower interstitial complexity, and the A group showed a reduction in the myonuclear and interstitial complexities. Moreover, there was a reduction of the interstitial area in the EC, ES, A, AEC, and AES groups. Functional analysis showed a reduction in time for EC, ES, AEC, and AES groups, and a reduction in movements for EC, ES, and AEC groups. The maximum loaded carrying test (MLCT) revealed an increase in work for ES and AES, highlighting the ES group. We concluded that the previous static stretching to vertical ladders modalities demonstrated an increase in the motor endplate and a reduction in fragmentation, but the AEC and AES groups demonstrated different adaptations in the percentage of acetylcholine receptor clusters in the motor endplate. There was an increase in the myofibers’ total quantity in both groups (AEC and AES). Previous static stretching to the vertical ladder without overload reduced the myofibrillar diameter, triggered an increase in the myonuclear complexity, and reduced the interstitial area. In contrast, the previous static stretching to the vertical ladder with overload increased the myofiber Type IIx diameter, reduced the interstitium’ area and complexity, and demonstrated an increase in load capacity.
Skeletal muscle contraction depends on the proper communication between the neuromuscular junction (NMJ) and the muscle. The NMJ morphology and the characteristics of the belly muscle and the myofibers exhibit plasticities stimulus-derived. The protocols proposed in this study promoted adaptations in the NMJ and the belly muscle elements. This study aimed to describe the morphological changes in the NMJ and the belly muscle of the gastrocnemius muscle of Wistar male rats submitted to previous static stretching to vertical ladder modalities. Wistar male rats with 60-days-old (n = 10) were divided into (S) Sedentary, (A) Stretched, (EC) Vertical ladder without overload, (ES) Vertical ladder with overload, (AEC) Stretched and vertical ladder without overload, and (AES) Stretched and vertical ladder with overload. The animals were submitted to the protocols 3x/week for eight weeks. The training session data were used for functional analysis and the samples were processed for light microscopy and immunofluorescence techniques. The mass ratio of S, EC, ES, and A groups showed no difference, while AEC and AES groups resulted in lower values. The EC and ES groups demonstrated an increase in motor endplate and reduced compactness, highlighting the EC group, and showed a greater number of clusters and fragmentation. The A group showed a reduction in motor endplate, increased compactness, and maintenance of the number of clusters and fragmentation. Previous static stretching to vertical ladder modalities (AEC and AES groups) revealed an increase in motor endplate, highlighting the AES group, and lower number of clusters and fragmentation index, though the compactness increased for AEC and decreased for AES. The cross-sectional area (CSA) of myofibers Type IIa increased in the EC and ES groups, Type IIx increased in the AES group, and the myofibrillar types (Type I, IIa, and IIx) reduced in the A and AEC groups. The EC, A, AEC, and AES groups demonstrated Type IIx predominance, while the ES group showed Type IIa predominance. Furthermore, the AEC and AES groups demonstrated an increase in the myofibers’ total quantity. The ES and AEC groups demonstrated higher myonuclear complexity, the EC and AES groups revealed lower interstitial complexity, and the A group showed a reduction in the myonuclear and interstitial complexities. Moreover, there was a reduction of the interstitial area in the EC, ES, A, AEC, and AES groups. Functional analysis showed a reduction in time for EC, ES, AEC, and AES groups, and a reduction in movements for EC, ES, and AEC groups. The maximum loaded carrying test (MLCT) revealed an increase in work for ES and AES, highlighting the ES group. We concluded that the previous static stretching to vertical ladders modalities demonstrated an increase in the motor endplate and a reduction in fragmentation, but the AEC and AES groups demonstrated different adaptations in the percentage of acetylcholine receptor clusters in the motor endplate. There was an increase in the myofibers’ total quantity in both groups (AEC and AES). Previous static stretching to the vertical ladder without overload reduced the myofibrillar diameter, triggered an increase in the myonuclear complexity, and reduced the interstitial area. In contrast, the previous static stretching to the vertical ladder with overload increased the myofiber Type IIx diameter, reduced the interstitium’ area and complexity, and demonstrated an increase in load capacity.
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Palavras-chave
Placa motora, Receptores colinérgicos, Plasticidade adaptativa, Músculo estriado esquelético, Tecido conjuntivo, Motor endplate, Cholinergic receptors, Physiological adaptation, Skeletal muscle, Connective tissue