[Petit-mal epilepsy in laboratory rats, issues that an experimenter should be remember]

A certain proportion of laboratory rats of various strains is characterized with a heritable, abnormally high propensity for spontaneous, nonconvulsive electrocortical seizures. The seizures have form of bursts of spike-wave discharges (SWD) reminiscent of the human petit-mal epilepsy. The experimenter is usually unaware of this fact. The paper concerns the question of reliability of results obtained on rats samples derived from populations nonhomogenous with respect to the high propensity for SWD seizures.