Progressive changes in hippocampal cytoarchitecture in a neurodevelopmental rat model of epilepsy: implications for understanding presymptomatic epileptogenesis, predictive diagnosis, and targeted treatments

Abstract

Epilepsies affect about 4% of the population and are frequently characterized by a prolonged Bsilent^period before the onset of spontaneous seizures. Most current animal models of epilepsy either involve acute seizure induction or kindling protocols that induce repetitive seizures. We have developed a rat model of epilepsy that is characterized by a slowly progressing series of behavioral abnormalities prior to the onset of behavioral seizures. In the current study, we further describe an accompanying progression of cytoarchitectural changes in the hippocampal formation. Groups of male and female SD rats received serial injections of a low dose of domoic acid (0.020 mg/kg) (or vehicle) throughout the second week of life. Postmortem hippocampal tissue was obtained on postnatal days 29, 64, and 90 and processed for glial fibrillary acidic protein (GFAP), NeuN, and calbindin expression. The data revealed no significant changes on postnatal day (PND) 29 but a significant increase in hilar NeuN-positive cells in some regions on PND 64 and 90 that were identified as ectopic granule cells. Further, an increase in GFAP positive cell counts and evidence of reactive astrogliosis was found on PND 90 but not at earlier time points. We conclude that changes in cellular expression, possibly due to on-going non-convulsive seizures, develop slowly in this model and may contribute to progressive brain dysfunction that culminates in a seizure-prone phenotype.

Diverse Effects of an Acetylcholinesterase Inhibitor, Donepezil, on Hippocampal Neuronal Death after Pilocarpine-Induced Seizure

“…NeuN staining was performed to observe live neurons to confirm that donepezil administration for one week affected neuronal death after the pilocarpine-induced seizure. NeuN staining is widely used as a method for specifically detecting live neurons [ 26 , 27 , 28 ]. One week after seizure induction, the rats were sacrificed and the number of live neurons quantified.…”

A Systematic, Open-Science Framework for Quantification of Cell-Types in Mouse Brain Sections Using Fluorescence Microscopy

“…Analysis of cell types provides important information on neurodevelopmental processes and neurological disease states. There is a narrow range of acceptable variance in cell type density and distribution, outside of which is associated with neurological and neuropsychiatric disorders ( Stoner et al, 2014 ; Bernard et al, 2017 ; DeTure and Dickson, 2019 ; Briscoe and Marín, 2020 ). Studies of this kind stemmed from the influential work of neuroscientists such as Ramon y Cajal, Golgi, del Rio-Hortega, and others, who provided the initial morphological descriptions of neurons and glial cells ( Glickstein, 2006 ; Garcia-Lopez et al, 2010 ; Sierra et al, 2016 ).…”