Ultrastructural Analysis of the Large Neuronal Perikarya in an Injured Dentate Nucleus Using an Experimental Model of Hyperthermia-Induced Convulsions: the First Qualitative and Quantitative Study

Background: Febrile seizures are a common form of convulsions in childhood, with poorly known cellular mechanisms. The objective of this pioneering study was to provide qualitative and quantitative ultrastructural research on the large neuronal perikarya in the cerebellar dentate nucleus (DN), using an experimental model of hyperthermia-induced seizures (HSs), comparable to febrile seizures in children. Methods: The study used young male Wistar rats, divided into experimental and control groups. The HSs were evoked by a hyperthermic water bath at 45 °C for 4 min for four consecutive days. Specimens (1 mm3) collected from the DN were routinely processed for transmission electron microscopy studies. Results: The ultrastructure of the large neurons in the DN affected by hyperthermic stress showed variously pronounced lesions in the perikarya, including total cell disintegration. The most pronounced neuronal lesions exhibited specific morphological signs of aponecrosis, i.e., dark cell degeneration (‘dark neurons’). In close vicinity to the ‘dark neurons’, the aponecrotic bodies were found. The findings of this qualitative ultrastructural study correspond with the results of the morphometric analysis of the neuronal perikarya. Conclusions: Our results may constitute interesting comparative material for similar submicroscopic observations on large DN neurons in HS morphogenesis and, in the future, may help to find potential treatment targets to prevent febrile seizures or reduce recurrent seizures in children.