Electrophysiological responses in vivo of hippocampal CA1 pyramidal neurons in an animal model of neuronal migration disorders

Cortical dysgenesis arising from neuronal migration disorders is closely associated with intractable epilepsy in humans. We used extracellular field potential and conventional intracellular recordings from the dorsal hippocampus of intact adult rats to determine if the excitability of CA1 pyramidal cells was enhanced in rats with experimentally induced hippocampal dysplasia. Electrical stimulation of afferent fibers resulted in more robust population responses in the CA1 region of irradiated rats versus controls. Synaptic inhibition of pyramidal cells was also reduced in these animals. These results suggest that the excitability of the CA1 region in rats with hippocampal dysplasia is greater than in control animals.