Differences in spike-wave discharges in two rat selection lines characterized by opposite dopaminergic activities

In the present study, 48 h electroencephalographic recordings were made in order to examine the incidence and duration of spike-wave discharges in apomorphine-susceptible (APO-SUS) and apomorphine-unsusceptible (APO-UNSUS) lines of an outbred strain of Wistar rats. In comparison with APO-UNSUS rats APO-SUS rats showed significantly more spike-wave discharges, especially during the dark period: both the mesor and the amplitude of the optimal cosine fitted to the data were significantly increased, whereas neither the acrophase nor the period length (24 h) differed. It is suggested that both the relatively low dopaminergic activity of the nigrostriatal fibres and the relatively high dopaminergic activity of the mesolimbic fibres, i.e. two well characterized features of the APO-SUS rats, significantly contribute to the high incidence of spike-wave discharges in these APO-SUS rats.