Effect of acrylamide on neurological recovery following spinal cord injury in rats

Acrylamide (ACR) is a cumulative neurotoxin which causes axonal degeneration in animals and man. Industrial workers exposed to ACR have been reported to suffer from a variety of central and peripheral neuropathological symptoms including numbness of hands and feet, skin peeling and muscular weakness of legs. These reports suggest that the body burden of ACR may be a risk factor in recovery patterns following neurotrauma. The present study was designed to assess the effect of ACR on neurological recovery following spinal cord injury (SCI) in rats. Male Sprague-Dawley rats weighing 200-230 g were anaesthetised with chloral hydrate and laminectomy was performed at T 7-8 level leaving the dura intact. A compression plate (2.2 x 5.0 mm) loaded with a weight of 35 g was placed on the exposed cord for 5 minutes. Animals were divided into seven groups of eight rats each. The animals in Group 1 served as control whereas rats in Group 2 underwent laminectomy alone (sham). The rats in Group 3 to 6 were subjected to SCI as mentioned above. Animals in Groups 4, 5 and 6 also received ACR in the doses of 10 mg/kg, 20 mg/kg and 40 mg/kg, i.p., respectively in addition to SCI, whereas the rats in Group 7 received ACR alone at a dose of 40 mg/kg body weight. The first dose of ACR was given 30 minutes before SCI, followed by daily administration of drug for 7 days. Post traumatic neurological recovery was recorded daily for 10 days using a modified Tarlov score, inclined plane test and sensory and vocal score. Electrophysiological changes were assessed using somatosensory and corticomotor evoked potentials. The animals were sacrificed at different time intervals and the injured site of the spinal cord was analysed for lipid hydroperoxides (LPH), conjugated dienes (CD) and glutathione (GSH). Neuropathological changes in the spinal cord were assessed using light microscopy. The rats exposed to compression injury alone showed a maximum neurological deficit at 24 hr and then a gradual recovery was observed over a period of 10 days. The rats treated with ACR along with SCI showed poor or no recovery over a period of 10 days. Our electrophysiological and histopathological studies also confirmed that concomitant exposure to ACR produces a significant deleterious effect on the recovery from SCI. SCI induced increase in oxidative stress (increase in LPH and CD and decrease in GSH) is also exacerbated by ACR suggesting a role of free radicals. The results of this study suggest that increased body burden of ACR may retard the recovery from neurotrauma or even lead to permanent disability.