AGE-DEPENDENT COGNITIVE AND BEHAVIORAL DEFICITS AFTER KAINIC ACID SEIZURES

The long-term behavioral and cognitive effects of seizures at different ages were studied using the kainic acid (KA) seizure model. Rats of postnatal (P) ages (in days) 5, 10, 20, 30, and 60 were administered KA intraperitoneally (i.p.), which induced status epilepticus for several hours, or an equivalent volume of saline. Occurrence of spontaneous recurrent seizures (SRS) was then monitored for 3 months by a closed-circuit videotaping system. Rats began behavioral testing on P80; a separate group of rats that received KA on P60 began testing on P120. Behavioral tests included the Morris water maze (visuospatial learning and memory), the open field test (response to a novel environment), and the handling test (emotionality). When tested on P80, KA-treated P5 and P10 rats had no demonstrable deficits on any test as compared with controls. KA-Treated P20 rats differed from controls only on the water maze spatial bias test. KA-Treated P30 rats had deficits in spatial bias, were more active in the open field, and were more aggressive when handled. KA-Treated P60 rats, whether tested on P80 or P120, had deficits in learning platform position and spatial bias in the water maze, were more active in the open field, and were more aggressive when handled. P60 rats with SRS performed poorer in water maze place learning and spatial bias testing, although the number of SRS did not correlate with overall task acquisition. Our findings suggest age-related behavioral and cognitive deficits after KA-induced seizures. Pubescents and adults had alterations in learning, memory, exploratory behavior, and response to handling, whereas younger animals had no obvious behavioral or cognitive deficits.