THE EFFECTS OF KAINIC ACID IN RATS WITH SPONTANEOUS RECURRENT SEIZURES

1. Rats with spontaneous recurrent seizures (SRS) were obtained by inj ection of kainic acid (KA; 10 mg/kg SC) to drug-naive rats that regula rly developed wet-dog shakes followed by complex partial seizures and status epilepticus. Three to five weeks later, the rats with manifest SRS were selected. 2. The SRS rats were challenged with KA (10 mg/kg S C). The seizures induced in SRS rats by KA were similar to SRS regardi ng their clinical stage and duration (mean duration of seizures: 44 se c and 43 sec, respectively). The frequency of seizures was, however, i ncreased compared with the frequency of SRS in control, vehicle-treate d SRS rats (mean frequency of seizures: 12.9 and 0.4 per 3 hr, respect ively). The KA-induced seizures in SRS rats differ behaviorally from K A-induced seizures in naive rats-namely, neither wet dog shakes nor th e status epilepticus could be induced. 3. Repeated injection of an equ al dose of KA, applied to the SRS rats 1 day after the previous KA cha llenge, did not induce seizures. The loss of seizure susceptibility to KA was only temporary, as shown after a 7-day drug-free period, when the repeated injection of KA regained its seizure-triggering capacity. 4. The results indicate that reactivity to the seizure-inducing agent kainic acid changes in rats with spontaneous recurrent seizures. (C) 1998 Elsevier Science Inc.