Electrophysiological and pharmacological characteristics of two types of spike-wave discharges in WAG/Rij rats.

Rats of the WAG/Rij strain are commonly seen as a genetic model for generalised absence epilepsy in man. Interestingly, generalised absence epilepsy shows, in addition to the fully generalised spike-wave discharges, a second type of spike-wave discharge, which lasts for a shorter time, has a lower frequency, and a lower incidence. The originally described distinction between the two types of spike-wave discharges was mainly based on the shape, polarity and duration of the discharges. In the present study other characteristics such as the spatial and temporal distribution of the spike and wave components of the two discharges and frequency spectra were found to differ between the two types. In addition, a reciprocal regulation of the two types of spike-wave discharges by drugs affecting the dopaminergic system (haloperidol and apomorphine) was observed. The results convincingly demonstrate the difference between the two phenomena and warrant the search for neurobiological mechanisms underlying both types of spike-wave discharges.