Dynamic variations of local cerebral blood flow in maximal electroshock seizures in the rat

Purpose: Measurement of cerebral blood flow is routinely used to locate the areas involved in generation and spread of seizures in epilepsy patients. Because the nature of the hyperperfused regions varies with the timing of injection of tracer, in this study, we used a rat model of maximal electroshock seizures to follow up the time-dependent changes in the distribution of seizure-induced cerebral blood flow (CBF) changes. Methods: CBF was measured by the quantitative autoradiographic [C-14] iodoantipyrine technique over a 30-s duration. The tracer was injected either at 15 s before seizure induction, simultaneous with the application of the electroshock (tonic phase), at the onset of the clonic phase, or at 3 and 6 min after the seizure (postictal phase). Results: Rates of CBF underwent dynamic changes during the different phases of seizure activity and largely increased over control levels (less than or equal to400%) in the 45 regions studied during all phases of the seizure (first 3 times). CBF remained higher than control levels in 35 and 15 areas at 3 and 6 min after the seizure, respectively. Conclusions: The distribution of maximal CBF increases showed a good correlation with their known involvement in the circuits underlying the clinical expression of the different types of seizure activity, tonic versus clonic.