The model of spinal cord lateral hemisection. Part II. State of the neuromuscular system, syndrome of post-injury spasticity and chronic pain syndrome

Abstract

Relevance of the topic: Spinal cord function recovery upon spinal cord injury is associated with the progress of neuroengineering and robot bionics. The effectiveness is advanced by the development of syndrome of spasticity and chronic pain. The study of their passing under the condition of neuroengineering interventions requires the involvement of appropriate models of spinal injury. Objective: To examine changes in the neuromuscular system, peculiarities of development of spasticity syndrome and chronic pain syndrome on the model of lower thoracic left-side rat’s spinal cord hemisection ( LHS ). Materials and methods: Eleсtroneuromyography (ENMG): direct stimulation of the spinal cord (M- waves amplitude), registration of Hoffmann-reflex (the ratio of H-wave amplitude to M-wave amplitude — N/M, percent); verification of spasticity according to Ashworth scale; exteroceptive sensitivity — the method of von Frey in the modification of Weinstein ; hindlimb function — Basso–Beattie–Bresnahan ( ВВВ ) scale. Results. The average value of the maximum amplitude of M-wave in the examined ipsilateral hindlimb ( IH ) muscle on the seventh week after LHS is equal to the indicator of intact animals with the dissociation of values of the function indicator ( 2.5 versus 21 points under the BBB scale ); up to the 23rd week a reliable reduction of the indicator is observed. N/M for hindlimbs of intact animals ( n=14 ) is 34,14±3,17 percent, for IH ( n=10 ) is 52,44±7,27 percent ( p<0.05 ). In young animals ( LHS at the age of 3 weeks; n=8 ) spasticity during 2–16 weeks is within 2,2–2,5 points according to Ashworth ( with a reliable decrease to 1,44±0,15 points at 28th week ), in mature animals ( LHS at the age of 3–6 months; n=16 ) spasticity during 9–26 weeks is 2,3–2,6 points. Exteroceptive IH sensitivity is reliably reduced at least to the 6th week after LHS, pain syndrome with IH autophagy have ~15 percent of animals, more frequently, mature ones. Conclusion . LHS model allows to reproduce the spasticity syndrome and chronic pain syndrome, to study the dynamics of the neuromuscular system.