Behavioural research and nonconvulsive spontaneous electrocortical seizures in laboratory rats. A note of concern

A proportion of subjects of rat strains and lines commonly used for behavioural research in neurotoxicology, neuropharmacology and related fields show spontaneous generalized nonconvulsive EEG seizures. The seizures have the form of bursts of spike and wave discharges (SWD) reminiscent of human petit-mal epilepsy. Behavioural manifestations of SWD seizures are poor and, therefore, their occurrence is not taken into account either during selection or during grouping of rats for the experiment. This paper comprises a short discussion of literature data which allow one to suspect that the rats with SWD seizures differ from normal nonepileptic ones with respect to behavioural performance in some test situations and behavioural effects of exposure to drugs or other chemicals. Thus, considering the fact that the proportion of subjects with SWD seizures may vary considerably in rat samples, it seems likely that the broad use of rat populations heterogenous with respect to this EEG pathology may be responsible, at least in part, for inconsistent results of similar experiments performed at different laboratories. Therefore, attempts should be made in order to reduce the use of such rat population in behavioural research, particularly those intended to supply data which may consist the basis of hygiene standards of exposure to xenobiotics.