Spike-wave discharges and sleep spindles in rats

Sleep spindles and spike-wave discharges are thought to originate from the same thalamic pacemaker. In the present work it is investigated whether sleep spindles and spike-wave discharges are also sensitive for the same drugs. Adult male WAG/Rij rats were chronically implanted with frontal and occipital EEG electrode pairs. Rats were intraperitoneally injected with clonidine (0.00625 mg/kg), phenobarbital (20 mg/kg), flunitrazepam (0.188 mg/kg). Frontal and occipital sleep spindles and mainly frontal spike-wave discharges were seen in the electroencephalogram. Phenobarbital and flunitrazepam reduced the number of spike-wave discharges and enhanced frontal sleep spindles, while clonidine facilitated spike-wave discharges and reduced frontal sleep spindles. The results of these three drugs indicate a reciprocal relationship between the number of frontal sleep spindles and the number of spike-wave discharges. Only clonidine facilitated occipital sleep spindles without an effect on spike-wave discharges. It can be concluded that frontal and occipital sleep spindles have a different pharmacological profile. Furthermore, the inverse relationship between frontal sleep spindles and spike-wave discharges may suggest that sleep spindles and spike-wave discharges are controlled by a single controlling system. However, in order to explain the clonidine data on occipital sleep spindles another factor must be incorporated in properties of the mechanism(s) involved in EEG oscillations.