Spinal cord injury and its underlying mechanism in rats with temporal lobe epilepsy

Protocol paper: kainic acid excitotoxicity-induced spinal cord injury paraplegia in Sprague-Dawley rats

BACKGROUND

Excitotoxicity-induced in vivo injury models are vital to reflect the pathophysiological features of acute spinal cord injury (SCI) in humans. The duration and concentration of chemical treatment controls the extent of neuronal cell damage. The extent of injury is explained in relation to locomotor and behavioural activity. Several SCI in vivo methods have been reported and studied extensively, particularly contusion, compression, and transection models. These models depict similar pathophysiology to that in humans but are extremely expensive (contusion) and require expertise (compression). Chemical excitotoxicity-induced SCI models are simple and easy while producing similar clinical manifestations. The kainic acid (KA) excitotoxicity model is a convenient, low-cost, and highly reproducible animal model of SCI in the laboratory. The basic impactor approximately cost between 10,000 and 20,000 USD, while the kainic acid only cost between 300 and 500 USD, which is quite cheap as compared to traditional SCI method.

METHODS

In this study, 0.05 mM KA was administered at dose of 10 µL/100 g body weight, at a rate of 10 µL/min, to induce spinal injury by intra-spinal injection between the T12 and T13 thoracic vertebrae. In this protocol, detailed description of a dorsal laminectomy was explained to expose the spinal cord, following intra-spinal kainic acid administration at desired location. The dose, rate and technique to administer kainic acid were explained extensively to reflect a successful paraplegia and spinal cord injury in rats. The postoperative care and complication post injury of paraplegic laboratory animals were also explained, and necessary requirements to overcome these complications were also described to help researcher.

RESULTS

This injury model produced impaired hind limb locomotor function with mild seizure. Hence this protocol will help researchers to induce spinal cord injury in laboratories at extremely low cost and also will help to determine the necessary supplies, methods for producing SCI in rats and treatments designed to mitigate post-injury impairment.

CONCLUSIONS

Kainic acid intra-spinal injection at the concentration of 0.05 mM, and rate 10 µL/min, is an effective method create spinal injury in rats, however more potent concentrations of kainic acid need to be studied in order to create severe spinal injuries.

Pannexin-1 Contributes to the Apoptosis of Spinal Neurocytes in Spinal Cord Injury

Currently, the role of Pannexin-1, a homomeric membrane hemichannel on the neuron cell membrane, in the development of spinal cord injury (SCI) is largely unknown. Herein, we assessed the contribution of Panx1 in the development of SCI. The SCI in vitro model was established using rat primary spinal neurocytes treated with hydrogen peroxide (H₂O₂). Effects of Panx1 overexpression or depletion in spinal neurocytes were analyzed by lentivirus-mediated transfection of Panx1 and interference sh-Panx1. Decreased cell viability was seen in SCI cells, which was further enhanced under Panx1 overexpression and mitigated by Panx1 deficiency. H₂O₂ induced an increase of intracellular Ca²⁺ signal and upregulated level of the proapoptotic protein Bax, and apoptosis pathway proteins including cleaved Caspase-3 and PARP1, which was enhanced by Panx1 overexpression or attenuated by Panx1 depletion. On the other hand, H₂O₂ treatment suppressed the level of antiapoptotic protein Bcl-2, which was further decreased by Panx1 overexpression or mitigated by Panx1 depletion. The results indicate that Panx1 was involved in the intracellular Ca²⁺ overload of SCI cells by accelerating extracellular Ca²⁺ influx, which promoted the apoptosis of spinal neurocytes through Ca²⁺ dependent pathways, thus aggravating the secondary injury of SCI.