Chronic spinal hemisection in rats induces a progressive decline in transmission in uninjured fibers to motoneurons

Abstract

Although most spinal cord injuries are anatomically incomplete, only limited functional recovery has been observed in people and rats with partial lesions. To address why surviving fibers cannot mediate more complete recovery, we evaluated the physiological and anatomical status of spared fibers after unilateral hemisection (HX) of thoracic spinal cord in adult rats. We made intracellular and extracellular recordings at L5 (below HX) in response to electrical stimulation of contralateral white matter above (T6) and below (L1) HX. Responses from T6 displayed reduced amplitude, increased latency and elevated stimulus threshold in the fibers across from HX, beginning 1–2 weeks after HX. Ultrastructural analysis revealed demyelination of intact axons contralateral to the HX, with a time course similar to the conduction changes. Behavioral studies indicated partial recovery which arrested when conduction deficits began. In conclusion, this study is the first demonstration of the delayed decline of transmission through surviving axons to individual lumbar motoneurons during chronic stage of incomplete spinal cord injury in adult rats. These findings suggest a chronic pathological state in intact fibers and necessity for prompt treatment to minimize it.

Chondroitinase ABC Combined with Neurotrophin NT-3 Secretion and NR2D Expression Promotes Axonal Plasticity and Functional Recovery in Rats with Lateral Hemisection of the Spinal Cord

“…The animals were deeply anesthetized and the spinal cords were exposed. L5 motoneurons were impaled with a sharp glass micropipette electrode and a tungsten sharp electrode was introduced at a depth of 1.3 mm, first in the right and then in the left LWM at T6 to stimulate descending spinal axons, as in previous experiments (Arvanian et al, 2009;Hunanyan et al, 2010).…”

“…We usually recorded from 5-6 motoneurons per rat, each one tested with lateral white matter stimulation on each side. After completion of electrophysiological recording, the rats were perfused, spinal cords were removed and the injury was verified by reconstruction (Arvanian et al, 2009). …”

“…Lateral hemisection of the thoracic spinal cord leads to transient severe impairment of hindlimb function ipsilateral to the injury (Hains et al, 2001;Ballermann and Fouad, 2006;Arvanian et al, 2009) with milder effects on the contralateral hindlimb. All the animals tested showed a similar pattern of recovery in the 2 weeks after injury.…”

G-CSF promotes autophagy and reduces neural tissue damage after spinal cord injury in mice

“…22,23 Briefly, mice were anesthetized with 10% chloral hydrate. Dorsal laminectomy was performed to expose spinal cord segments T9-T11 using a superficial vein at T5-T6 as a landmark.…”

Potential variables affecting the quality of animal studies regarding pathophysiology of traumatic spinal cord injuries

“…26 It is worth noting that, in some studies, weight of animals at the beginning of study is used as a reflection of age. [27][28][29] Housing The housing conditions are specified in the ethical approval. The exact values for temperature, humidity, lighting, noise and amount of food and water should be within a certain range.…”