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Recently a hyperthermic rat hippocampal slice model system has been used to investigate febrile seizure pathophysiology. Our previous data indicates that heating immature rat hippocampal slices from 34 to 41 degrees C in an interface chamber induced epileptiform-like population spikes accompanied by a spreading depression (SD). This may serve as an in vitro model of febrile seizures.In this study, we further investigate cellular mechanisms of hyperthermia-induced initial population spike activity. We hypothesized that GABA(A) receptor-mediated 30-100 Hz gamma oscillations underlie some aspects of the hyperthermic population spike activity. In 24 rat hippocampal slices, the hyperthermic population spike activity occurred at an average frequency of 45.9 +/- 14.9 Hz (Mean +/- SE, range = 21-79 Hz, n = 24), which does not differ significantly from the frequency of post-tetanic gamma oscillations (47.1 +/- 14.9 Hz, n = 34) in the same system. High intensity tetanic stimulation induces hippocampal neuronal discharges followed by a slow SD that has the magnitude and time course of the SD, which resembles hyperthermic responses. Both post-tetanic gamma oscillations and hyperthermic population spike activity can be blocked completely by a specific GABA(A) receptor blocker, bicuculline (5-20 microM). Bath-apply kynurenic acid (7 mM) blocks synaptic transmission, but fails to prevent hyperthermic population spikes, while intracellular diffusion of QX-314 (30 mM) abolishes spikes and produces a smooth depolarization in intracellular recording.These results suggest that the GABA(A) receptor-governed gamma oscillations underlie the hyperthermic population spike activity in immature hippocampal slices.
View details for Web of Science ID 000207529000001
View details for PubMedID 11747470
View details for PubMedCentralID PMC61040