PubMed1983
To test a convenient and reliable neuronal index that suggests the development of autonomous epileptogenicity, we conducted in acute experiments on rabbits a comparative study of the changes in direct cortical responses (DCRs) in primary and mirror sites during electrically induced primary (PRID) and projected seizure discharges (PROD). It has been assumed that the primary site shows autonomous epileptogenicity during the PRID, whereas the mirror site during the PROD does not. We observed that in the primary site, the dendritic potentials (field EPSPs) were remarkably suppressed in amplitude or disappeared during the PRID and that there was a loss of the after-positivity (field IPSPs); these DCRs recovered gradually after termination of the PRID. Instead of DCRs, "convulsoid responses" (a general term for responses similar to the individual spontaneous waves which occur in all types of seizures discharges) were usually elicited in the primary site during PRID. In the mirror site during PROD, the DCRs showed three different behaviors: they were either unaffected, increased, or suppressed. Convulsoid responses were never elicited. In a few cases, independent seizure discharges were induced in the mirror site. During the independent seizure discharges, the DCRs in the mirror site disappeared and convulsoid responses similar to the individual independent waves were usually elicited, as in the primary site during PRID. We conclude that the convulsoid response was the most reliable indicator of the development of autonomous epileptogenicity, and that suppression or disappearance of DCRs was the supplementary sign of that development. These neuronal indexes may be useful for identification of secondary epileptogenesis.