title: Differential effects of low versus high amounts of weight supported treadmill training in spinally transected rats.
abstract: Intensive weight-supported treadmill training (WSTT) improves locomotor function following spinal cord injury. Because of a number of factors, undergoing intensive sessions of training may not be feasible. Whether reduced amounts of training are sufficient to enhance spinal plasticity to a level that is necessary for improving function is not known. The focus of the present study was to assess differences in recovery of locomotor function and spinal plasticity as a function of the amount of steps taken during WSTT in a rodent model of spinal cord injury. Rats were spinally transected at 5 days of age. When they reached 28 days of age, a robotic system was used to implement a weight-supported treadmill training program of either 100 or 1000 steps/training session daily for 4 weeks. Antibodies for brain-derived neurotrophic factor (BDNF), TrkB, and the pre-synaptic marker, synaptophysin, were used to examine the expression of these proteins in the ventral horn of the lumbar spinal cord. Rats that received weight-supported treadmill training performed better stepping relative to untrained rats, but only the rats that received 1000 steps/training session recovered locomotor function that resembled normal patterns. Only the rats that received 1000 steps/training session recovered normal levels of synaptophysin immunoreactivity around motor neurons. Weight-supported treadmill training consisting of either 100 or 1000 steps/training session increased BDNF immunoreactivity in the ventral horn of the lumbar spinal cord. TrkB expression in the ventral horn was not affected by spinal cord transection or weight-supported treadmill training. Synaptophysin expression, but not BDNF or TrkB expression was correlated with the recovery of stepping function. These findings suggested that a large amount of weight-supported treadmill training was necessary for restoring synaptic connections to motor neurons within the locomotor generating circuitry. Although a large amount of training was best for recovery, small amounts of training were associated with incremental gains in function and increased BDNF levels.
authors.affiliation: School of Kinesiology and Nutritional Science, California State University, Los Angeles, California 90032-8162, USA. rdeleon@calstatela.edu
authors.forename: Ray D
authors.initials: RD
authors.lastname: de Leon
authors.forename: Pamela A
authors.initials: PA
authors.lastname: See
authors.forename: Cheryl H T
authors.initials: CH
authors.lastname: Chow
mesh_terms: D000818:Animals; D001835:Body Weight / Q000502:physiology*; D004195:Disease Models, Animal; D005080:Exercise Test / Q000379:methods*; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D010264:Paraplegia / Q000534:rehabilitation*; D010805:Physical Conditioning, Animal / Q000379:methods* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013119:Spinal Cord Injuries / Q000534:rehabilitation*