Injections of kainic acid into the raphe dorsal nucleus in freely moving cats: electroencephalographic, behavioral and histopathological consequences.

Results are presented concerning the functional and morphological changes occurring after kainic acid injections into raphe dorsal nucleus in freely moving cats. The effects of kainic acid at two doses, 4 and 12 nmol, on electroencephalographic activity, behavior and cell morphology were examined on the day of injection, and on the 1st, 3rd, 6th, 15th, 30th and 65th day. A well-pronounced dose-dependent effect of kainic acid was established: in 50% of the animals injected with 4 nmol of kainic acid and in 85.7% of the animals injected with 12 nmol electroencephalographic and behavioral seizures appeared. The strength of the seizures in the animals receiving 12 nmol of kainic acid was different--from focal single epileptiform patterns first in raphe dorsal nucleus and then in other brain regions to generalized high-voltage ictal activity and in some animals to epileptic state. In all animals receiving 4 nmol of kainic acid and in 75% of the animals receiving 12 nmol of kainic acid, the electrical activity and behavior returned to normal several hours after or within two days following the kainic acid injection. The histopathological data obtained by light microscopy showed a dose-dependent cytoarchitectural disorganization (mainly chromatolytic changes) not only at the injection site but also in many other brain structures. The present results confirm our previous studies on cats in acute conditions showing enhancement of brain excitability level up to hyperexcitation (seizures) after kainic acid injection into the raphe dorsal nucleus.