Mechanical properties of rat soleus after long-term spinal cord transection

• Published in: Journal of applied physiology (1985) Vol. 93; no. 4; pp. 1487 - 1497
• Main Authors: Talmadge, Robert J, Roy, Roland R, Caiozzo, Vincent J, Edgerton, V. Reggie
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.10.2002; American Physiological Society
• Subjects: Animals; Biological and medical sciences; Body Weight; Fatigue; Female; Isometric Contraction; Medical sciences; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal - metabolism; Muscle, Skeletal - pathology; Muscle, Skeletal - physiopathology; Muscular system; Myosin Heavy Chains - metabolism; Nervous system (semeiology, syndromes); Nervous system as a whole; Neurology; Organ Size; Paralysis; Rats; Rats, Sprague-Dawley; Space life sciences; Spinal cord injuries; Spinal Cord Injuries - metabolism; Spinal Cord Injuries - pathology; Spinal Cord Injuries - physiopathology; Time Factors; Animal model; Myosin heavy chain; Spinal cord; Rat; Rodentia; Central nervous system; Contractility; Contractile protein; Mechanical properties; Fatigue; Striated muscle; Soleus muscle; Long term; Biomechanics; Vertebrata; Mammalia; Animal; Lesion; Paralysis; Spinal cord disease; Adaptation; Non-programmatic
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00053.2002

1  Department of Biological Sciences, California State Polytechnic University, Pomona 91768; 2  Brain Research Institute, University of California, Los Angeles 90095; 3  Department of Physiology and Biophysics and Department of Orthopaedics, College of Medicine, University of California, Irvine 92717; and 4  Physiological Science Department, University of California, Los Angeles, California 90095 The effects of a complete spinal cord transection (ST) on the mechanical properties of the rat soleus were assessed 3 and 6 mo post-ST and compared with age-matched controls. Maximal tetanic force was reduced by ~44 and ~25% at 3 and 6 mo post-ST, respectively. Similarly, maximum twitch force was reduced by ~29% in 3-mo and ~17% in 6-mo ST rats. ST resulted in faster twitch properties as evidenced by shorter time to peak tension (~45%) and half-relaxation time (~55%) at both time points. Maximum shortening velocity was significantly increased in ST rats whether measured by extrapolation from the force-velocity curve (approximately twofold at both time points) or by slack-test measurements (over twofold at both time points). A significant reduction in fatigue resistance of the soleus was observed at 3 (~25%) and 6 mo (~45%) post-ST. For the majority of the speed-related properties, no significant differences were detected between 3- and 6-mo ST rats. However, the fatigue resistance of the soleus was significantly lower in 6- vs. 3-mo ST rats. These data suggest that, between 3 and 6 mo post-ST, force-related properties tended to recover, speed-related properties plateaued, and fatigue-related properties continued to decline. Thus some specific functional properties of the rat soleus related to contractile force, speed, and fatigue adapted independently after ST. adaptation; contractile function; fatigue; myosin heavy chain; paralysis; plasticity