Effect of dosage and timing of administration of naloxone on outcome in the rat ventral compression model of spinal cord injury

What is the optimal sequence of decompression for multilevel noncontinuous spinal cord compression injuries in rabbits?

Background

In recent years, multilevel spinal cord injuries (SCIs) have gained a substantial amount of attention from clinicians and researchers. Multilevel noncontinuous SCI patients cannot undergo the multiple steps of a one-stage operation because of a poor general condition or a lack of proper surgical approaches. The surgeon subsequently faces the decision of whether to initially relieve the rostral or caudal compression. In this study, we established a spinal cord compression model involving two noncontinuous segments in rabbits to evaluate the effects of differences in decompression order on the functional recovery of the spinal cord.

Methods

A Fogarty catheter was inserted into the epidural space through a hole in T6-7 and advanced 3 cm rostrally or caudally. Following successful model establishment, which was demonstrated by an evaluation of evoked potentials, balloons of different volumes (40 μl or 50 μl) were inflated in the experimental groups, whereas no balloons were inflated in the control group. The experimental groups underwent the first decompression in the rostral or caudal area at 1 week post-injury; the second decompression was performed at 2 weeks post-injury. For 6 weeks post-injury, the animals were tested to determine behavioral scores, somatosensory evoked potentials (SEPs) and radiographic imaging changes; histological and apoptosis assay results were subsequently analyzed.

Results

The behavioral test results and onset latency of the SEPs indicated that there were significant differences between priority rostral decompression (PRD) and priority caudal decompression (PCD) in the 50-μl compression group at 6 weeks post-injury; however, there were no significant differences between the two procedures in the 40-μl group at the same time point. Moreover, there were no significant peak-to-peak amplitude differences between the two procedures in the 50-μl compression group.

Conclusions

The findings of this study suggested that preferential rostral decompression was more beneficial than priority caudal decompression with respect to facilitating spinal cord functional recovery in rabbits with severe paraplegia and may provide clinicians with a reference for the clinical treatment of multiple-segment spinal cord compression injuries.

Improved rat spinal cord injury model using spinal cord compression by percutaneous method

Here, percutaneous spinal cord injury (SCI) methods using a balloon catheter in adult rats are described. A balloon catheter was inserted into the epidural space through the lumbosacral junction and then inflated between T9-T10 for 10min under fluoroscopic guidance. Animals were divided into three groups with respect to inflation volume: 20 µL (n = 18), 50 µL (n = 18) and control (Fogarty catheter inserted but not inflated; n = 10). Neurological assessments were then made based on BBB score, magnetic resonance imaging and histopathology. Both inflation volumes produced complete paralysis. Gradual recovery of motor function occurred when 20 µL was used, but not after 50 µL was applied. In the 50 µL group, all gray and white matter was lost from the center of the lesion. In addition, supramaximal damage was noted, which likely prevented spontaneous recovery. This percutaneous spinal cord compression injury model is simple, rapid with high reproducibility and the potential to serve as a useful tool for investigation of pathophysiology and possible protective treatments of SCI in vivo.

A simple and reproducible model of spinal cord injury induced by epidural balloon inflation in the rat

This paper describes a modification of a balloon-compression technique to produce spinal cord injury in adult rats. A 2-French Fogarty catheter is inserted into the dorsal epidural space through a small hole made in T10 vertebral arch, advanced cranially to T8-9 spinal level, and inflated for 5 min. Spinal cord damage is graded by increasing the volume of saline used to inflate the balloon. Quantitative neurological and histopathological outcomes are presented with three different volumes (10, 15, and 20 microl of saline) to characterize the gradation of injury. Volume of 15 microl produced complete paraplegia followed by gradual recovery, finally reaching approximately the middle of the scale used to quantitate the locomotor performance. With these animals, after 4 weeks, the center of the lesion shows complete loss of grey matter and partial sparing of the white matter. We conclude that 15 microl volume produced submaximal injury that will be useful for studying the pathophysiology and effects of protective therapies with this compression-injury model.

The effects of naloxone on retinal ischemia in rats

The efficacy of naloxone (NL), a broad spectrum opioid antagonist, on retinal ischemia, was evaluated in a rat model of retinal ischemia with histopathologic and morphometric criteria. Two intraperitoneal injections of naloxone 3 mg/kg given immediately and 6 hr after reperfusion showed beneficial effects to the retina as evaluated at 2, 7, and 14 days after reperfusion. Morphologically, the naloxone-treated group showed better-preserved ganglion cells, nerve fiber layer, and inner nuclear layer. Morphometrically, in the treated groups, inner retinal thickness at all three time points and ganglion cell counts at 7 days showed higher values than vehicle controls. This beneficial effect of naloxone was dose-dependent with a minimal effective total dose of 6 mg/kg. A possible role of opiate receptors in retinal ischemia is suggested.