PROGRESSIVE EVALUATION OF CORTICAL HISTOMORPHOLOGY AND HISTOMORPHOMETRIC PARAMETERS IN ADULT WISTAR RATS FOLLOWING LITHIUM-PILOCARPINE-INDUCED TEMPORAL LOBE EPILEPSY

Sanmi Tunde Ogunsanya, Olugbenga Ayodeji Ayannuga, Adegbenga Rotimi Owolabi, Taiwo Olusola Osibogun and Ayodeji Zabdiel Abijo*

ABSTRACT

Introduction: Temporal lobe epilepsy (TLE) the most common form of drug-refractory epilepsy in humans. This study evaluated the histomorphology of the neocortex, subcortical white matter and the timeline dynamics of the above parameters at different epileptogenesis phases following lithium-pilocarpine-induced TLE in Wistar rats. Methods: Sixty Wistar rats were assigned into 3 groups A-C (n=20each). A, B and C; acute, latent and chronic groups. Each group had 3 sub-groups {Control (5), sham (5) and experimental (10)}. Control and sham received 2mL/kg normal saline and diazepam (10mg/kg) intraperitoneally respectively. Experimental sub-group received lithium chloride (127mg/kg) subcutaneously 24hours prior pilocarpine administration. Pilocarpine (30mg/kg) was administered intraperitoneally. After seizure onset (90minutes), the experimental rats received diazepam (10mg/kg). The brains were excised and fixed in 10% neutral buffered formalin. Brain slices were obtained at the optic chiasm for routine paraffin embedding. Neuroarchitecture of the cortex was investigated using Hematoxylin and eosin (H&E) stains, while the morphology of white matter and the corpus callosum was demonstrated using Luxol fast blue. Results: Different layers of the cerebral cortex showed neurodegenerative characteristics in all three groups, with severe neurodegeneration in experimental sub-group compared to control and sham sub-groups. Subcortical white matter displayed non-compactness of the myelin sheath, resulting in greater white matter thickness in the experimental sub-groups compared to the compact myelin sheath found in control and sham. Conclusion: Conclusively, progressive neurodegeneration observed in the cerebral cortex as well as the demylineation dynamics seen in subcortical white matter further explains the scientific basis of epileptogenesis following lithium-pilocarpine-induced TLE.

Keywords: TLE, lithium-pilocarpine, epileptogenesis, demyelination.