Fig. 8.

Decrease of extracellular Ca²⁺concentrations ([Ca²⁺]_out) during SW seizures. A, Simultaneous intracellular recording of a neuron in the suprasylvian gyrus and of neighboring DC field potentials and [Ca²⁺]_out. SW seizures are accompanied by a persistent drop of ∼0.6 mmof the extracellular Ca²⁺ concentration and by phasic oscillations of the [Ca²⁺]_outduring the SW complexes (B). The WTAs (n = 40) were triggered by the maximum slope of the neuronal depolarization (vertical dotted line) and depict the relationship between the neuronal paroxysmal depolarization, the field potential and the Ca²⁺ concentration. Extracellular Ca²⁺ increases during the hyperpolarizing phase foregoing the onset of the ictal discharge and decreases during the subsequent neuronal depolarization.