Effect of anticonvulsants on spiking activity induced by cortical freezing in cats.

In an attempt to know whether the existing anticonvulsants act on epileptogenic focus, the effect on SA induced by freezing of the visual cortex was examined in gallamine-immobilized cats. The SA was localized in the neighbor or ipsilateral cortex of the freezing area; little epileptiform activity was produced in the contralateral anterior cortex, and ipsilateral thalamus and hippocampus. Spike frequency and its amplitude were stable over 8 hr. Diazepam suppressed SA and decreased spike frequency and its amplitude. Dipropylacetate and acetazolamide also suppressed SA. On the other hand, phenobarbital, carbamazepine, and a high dose of phenytoin enhanced SA and increased the spike frequency. Low doses of phenytoin and trimethadione were without effect in this aspect. Taurine suppressed SA and changed the spikes to wave-like forms. The EEG arousal response was depressed with phenobarbital, carbamazepine, diazepam, and a high dose of phenytoin, but not with the other drugs examined. From these results, it is suggested that diazepam, dipropylacetate, acetazolamide, and taurine depress the epileptogenic focus activity itself without relation to the activating system.