Mechanical properties of rat soleus after long-term spinal cord transection.
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 approximately 44 and approximately 25% at 3 and 6 mo post-ST, respectively. Similarly, maximum twitch force was reduced by approximately 29% in 3-mo and approximately 17% in 6-mo ST rats. ST resulted in faster twitch properties as evidenced by shorter time to peak tension (approximately 45%) and half-relaxation time (approximately 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 (approximately 25%) and 6 mo (approximately 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.
Talmadge
Robert J
RJ
Department of Biological Sciences, California State Polytechnic University, Pomona 91768, California, USA. rjtalmadge@csupomona.edu
Roy
Roland R
RR
Caiozzo
Vincent J
VJ
Edgerton
V Reggie
VR
D000818:Animals; D001835:Body Weight; D005260:Female; D007537:Isometric Contraction; D009119:Muscle Contraction; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D009929:Organ Size; D051381:Rats; D017207:Rats, Sprague-Dawley; D013119:Spinal Cord Injuries / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D013997:Time Factors
D018995:Myosin Heavy Chains