Tension- and afferent input-associated responses of neuromuscular system of rats to hindlimb unloading and/or tenotomy.
Am J Physiol Regul Integr Comp Physiol
; 287(1): R76-86, 2004 Jul.
Article
em En
| MEDLINE
| ID: mdl-15031139
ABSTRACT
Responses of electromyogram (EMG) in soleus muscle and both afferent and efferent neurograms at the fifth lumbar (L(5)) segmental level of spinal cord were investigated during acute and chronic unloading induced by hindlimb suspension and/or tenotomy in adult rats. The soleus EMG and afferent neurogram decreased 88 and 37%, respectively, relative to those at quadrupedal posture on the floor after acute hindlimb suspension that causes passive shortening of soleus due to ankle plantarflexion. However, the afferent neurogram (P < 0.05) and soleus EMG (P > 0.05) recorded on the floor increased after tenotomy of synergists. Furthermore, the afferent input was inhibited when the soleus EMG disappeared after tenotomy of soleus. The afferent neurogram and EMG of the soleus showed correlated responses to a variety of treatments, suggesting that the afferent neurogram recorded at the L(5) segmental level reflects the neural input associated with the activity level of the soleus predominantly. The level of efferent neurogram decreased after acute hindlimb suspension but was not influenced significantly by tenotomy of synergists and/or soleus itself. The EMG and afferent neurograms remained low up to the 4th day but recovered to the preexperimental levels within 14 days, due to reorganization of sarcomere number and length, as well as the shortening of muscle fiber length and recovery of tension development. It is suggested that the levels of EMG and afferent neurogram associated with antigravity muscle are closely related to the tension development of the muscle.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Nervos Periféricos
/
Músculo Esquelético
/
Elevação dos Membros Posteriores
Tipo de estudo:
Risk_factors_studies
Limite:
Animals
Idioma:
En
Revista:
Am J Physiol Regul Integr Comp Physiol
Assunto da revista:
FISIOLOGIA
Ano de publicação:
2004
Tipo de documento:
Article
País de afiliação:
Japão
País de publicação:
EEUU
/
ESTADOS UNIDOS
/
ESTADOS UNIDOS DA AMERICA
/
EUA
/
UNITED STATES
/
UNITED STATES OF AMERICA
/
US
/
USA