Ultrastructural study of hippocampal cortex neurons in an experimental model of valproate encephalopathy

Abstract

Abstract:Valproate (VPA) is a widely used antiepileptic drug. A serious neurological-outcome defined as valproate encephalopathy (VE) may rarely occur during VPA therapy. Structural abnormalities within neurons are postulated as one of the reasons for VE. The aim of this study was to assess the ultrastructure of neurons in the hippocampal cortex during the course of chronic application of VPA to rats. VPA was chronically administered to rats, intragastrically, once daily at a dose of 200 mg/kg b.w. for 1, 3, 6, 9 and 12 months. The samples of hippocampal cortex, after routine laboratory preparation, were examined by electron microscopy. The drug induced pronounced ultrastructural changes in the population of pyramidal neurons within the hippocampal cortex after 9 and 12 months of VPA administration. The most expressed abnormalities were observed within the mitochondria and manifested by fragmentation of crests and almost complete disappearance of intramitochondrial granules. Mitochondria of numerous neurons resembled large vacuolar structures. Widening, shortening and irregular distribution of rough endoplasmic reticulum was also found. A characteristic feature of damaged neurocytes in the last two phases of the experiment was the disintegration of nuclear chromatin and the presence of numerous lipofuscin deposits within hyaloplasm. These cells assumed the look of "dark neurons" and presented the ultrastructural features of apoptosis and necrosis. Our results indicate that long-term VPA administration to rats leads to aponecrosis of hippocampal neurons.

A mathematical model of neuroimmune interactions in epileptogenesis for discovering treatment strategies

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Valproic Acid in Pregnancy Revisited: Neurobehavioral, Biochemical and Molecular Changes Affecting the Embryo and Fetus in Humans and in Animals: A Narrative Review

“…Investigations on the effects of VPA in undermining the functional integrity of mitochondria revealed various outcomes, including the conformational alteration of the inner membrane and transport chain proteins, ATP depletion and increased reactive oxygen species (ROS) [ 212 , 213 ]. A dose-dependent VPA-induced cristae distortion in pyramidal neurons that altered mitochondrial ultrastructure was suggested as a sign of an impairment of synaptic plasticity and neurogenesis in treated rodents [ 214 , 215 ]. It was also observed in pigs that VPA inhibits mitochondrial respiratory chain complexes I, leading to the asymmetrical distribution and fragmentation of cristae, raised oxidative stress and the enlargement of the mitochondrial matrix [ 216 , 217 , 218 ].…”

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“…The main requirements to obtain valuable results are suitable fixation protocol and functional antibody conjugated with an appropriate nanoparticle to be detected. For many years different protocols were developed for structure localisation study [167] based mainly on Tokuyasu technique, HPF followed by FS and low-temperature embedding [169] or conventional chemical fixation [207,218] together with progressive-lowering temperature technique. Nevertheless, this field is still amenable to new solutions, especially for difficultto-fix samples and difficult-to-fix antigens.…”