Physiology of Limbic Hyperexcitability after Experimental Complex Febrile Seizures: Interactions of Seizure-Induced Alterations at Multiple Levels of Neuronal Organization

Publisher Summary This chapter summarizes the findings concerning the electrophysiological basis of the long-term modifications in limbic circuits following experimental complex febrile seizures. The electrophysiological experiments were conducted one week or months after the seizure episode. Data from rats that experienced prolonged hyperthermia-induced seizures were compared to results from their control littermates, which either were maintained normothermic or underwent the same duration and magnitude of hyperthermia but did not sustain seizures because they were pretreated with a short-acting barbiturate. The novel results summarized in this chapter demonstrate that prolonged experimental febrile seizures in the immature rat can lead to robust, long-lasting modifications at the level of channels, synapses, and neuronal networks. In light of the increased knowledge about the long-term modifications in limbic circuits after hyperthermia-induced seizures, it is interesting to consider the question of whether the potentiated inhibition after experimental febrile seizure is primarily pro- or anticonvulsive in its ultimate net effects. The field recording results indicate that the potentiated inhibitory synaptic transmission induced by the hyperthermic seizures can inhibit pyramidal cell discharges to a greater extent than in controls, as long as the incoming excitatory inputs arrive at low frequencies.