Hyperthermic Spreading Depressions In The Immature Rat Hippocampal Slice
Febrile seizures are the most common seizure type in children (6 mo to 5 yr). The pathophysiology of febrile seizures is unknown. Current genetic studies show that some febrile seizures result from channelopathies. We have performed electrophysiological experiments in in vitro hippocampal slices to test a novel hypothesis that a disordered regulation of ionic homeostasis underlies the genesis of febrile seizures. In transverse hippocampal CA1 slices from 104 rats, temperature increase from 34Â°to 40Â°C produced a series of spreading depressions (SDs), called hyperthermic SDs. The hyperthermic SDs were age-dependent, occurring in only 1/17 8-16 day-old animals, 44/49 17-60 day-old animals, and 11/20 rats older than than 60 days. The hyperthermic SDs usually occurred on the rising phase of the temperature. The mean temperature to trigger a first hyperthermic SD was 38.8 Â± 1.3Â°C (mean Â± SD, n = 44). The hyperthermic SDs induced a reversible loss of evoked synaptic potentials and a dramatic decrease of input resistance. Neuronal and field epileptiform bursting occurred in the early phases of the hyperthermic SD. During hyperthermic SDs, pyramidal cell membrane potential depolarized by 38.3 Â± 4.9 mV (n = 20), extracellular field shifted negative 18.5 Â± 3.9 mV (n = 44), and extracellular K + rose reversibly to 43.8 Â± 10.9 mM (n = 6). Similar SDs could be evoked by ouabain or transient hypoxia with normal temperature. Tetrodotoxin could block initial epileptiform bursting, without blocking SDs. Hyperthermia-induced SDs should be investigated as possible contributing factors to febrile seizures.
Journal of Neurophysiology
Wu, Jie and Fisher, Robert S., "Hyperthermic Spreading Depressions In The Immature Rat Hippocampal Slice" (2000). Neurobiology. 433.