Tail muscle parvalbumin content is decreased in chronic sacral spinal cord injured rats with spasticity

• Published in: Experimental physiology 2011-12, Vol.96 (12), p.1311-1320
• Main Authors: Harris, R. Luke, Bennett, David J., Levine, Max A., Putman, Charles T.
• Format: Article
• Language: English
• Subjects: Animals; Ca super(2+)-transporting ATPase; Chronic Disease; Citrate (si)-Synthase - metabolism; Citric acid; EMG; Enzymes; Fatigue; Female; Glyceraldehyde; Glyceraldehyde-3-phosphate dehydrogenase; Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating) - metabolism; Motor neurons; Muscle Spasticity - metabolism; Muscles; Paralysis; Parvalbumin; Parvalbumins - metabolism; Phosphate; Rats; Sacrum; Sarcoplasmic Reticulum Calcium-Transporting ATPases - metabolism; Sensory neurons; spasticity; Spinal Cord - metabolism; Spinal Cord Injuries - physiopathology; Spinal cord injury; Tail - metabolism; Tails; Transformation; Western blotting
• ISSN: 0958-0670; 1469-445X
• DOI: 10.1113/expphysiol.2011.061614

In rats, chronic sacral spinal isolation eliminates both descending and afferent inputs to motoneurons supplying the segmental tail muscles, eliminating daily tail muscle EMG activity. In contrast, chronic sacral spinal cord transection preserves afferent inputs, causing tail muscle spasticity that generates quantitatively normal daily EMG. Compared with normal rats, rats with spinal isolation and transection/spasticity provide a chronic model of progressive neuromuscular injury. Using normal, spinal isolated and spastic rats, we characterized the activity dependence of calcium‐handling protein expression for parvalbumin, fast sarco(endo)plasmic reticulum Ca2+‐ATPase (SERCA1) and slow SERCA2. As these proteins may influence fatigue resistance, we also assayed the activities of oxidative (citrate synthase; CS) and glycolytic enzymes (glyceraldehyde phosphate dehydrogenase; GAPDH). We hypothesized that, compared with normal rats, chronic isolation would cause decreased parvalbumin, SERCA1 and SERCA2 expression and CS and GAPDH activities. We further hypothesized that chronic spasticity would promote recovery of parvalbumin, SERCA1 and SERCA2 expression and of CS and GAPDH activities. Parvalbumin, SERCA1 and SERCA2 were quantified with Western blotting. Citrate synthase and GAPDH activities were quantified photometrically. Compared with normal rats, spinal isolation caused large decreases in parvalbumin (95%), SERCA1 (70%) and SERCA2 (68%). Compared with spinal isolation, spasticity promoted parvalbumin recovery (ninefold increase) and a SERCA2‐to‐SERCA1 transformation (84% increase in the ratio of SERCA1 to SERCA2). Compared with normal values, CS and GAPDH activities decreased in isolated and spastic muscles. In conclusion, with complete paralysis due to spinal isolation, parvalbumin expression is nearly eliminated, but with muscle spasticity after spinal cord transection, parvalbumin expression partly recovers. Additionally, spasticity after transection causes a slow‐to‐fast SERCA isoform transformation that may be compensatory for decreased parvalbumin content.