Brief Successive Temporal Observational Sampling as a Possible Indicator of Daily Overt Seizure Activity in Epileptic Rats

Chronic, limbic epilepsy was induced in male rats by a single systemic injection of lithium and pilocarpine. In two separate experiments, each 6 mo. in duration, the proportion of the population that displayed an overt motor seizure (head nodding, rearing, and forelimb clonus) within 10 min. each day after delivery of food pellets (despite food provided ad libitum) was recorded. Cumulative records for the numbers of rats in each population that displayed overt seizure for the first time during the observation period were plotted as a function of time. The occurrence of the saturated (approaching 100%) asymptote at about five months was interpreted to indicate that brief (10 min.) sampling over the 144 successive days that would compose a single 24-hr. period could serve as an estimate of the average probability of an overt seizure during an average 24-hr. period. If this assumption is correct, then these rats would have displayed about one overt seizure per day.