Aims: 

Risperidone, an atypical antipsychotic agent with high affinity to several monoamine receptors including serotonin 5-HT2 and dopamine D2 receptors, was studied for its effects on vigilance states and EEG power spectra.

Methods: 

Polysomnographic recordings (EEG, EMG, motor activity) were performed in freely moving male Sprague-Dawley rats for 2 h after treatment with risperidone (0.03, 0.1 or 0.5 mg/kg i.p.) at light onset. Active and passive wake (AW, PW), light and deep slow wave sleep (SWS-1, SWS-2) and paradoxical sleep (PS) were studied.

Results: 

All doses decreased the time spent in PS. The highest dose of risperidone significantly increased and decreased the cumulative time of PW and SWS-2, respectively. The lowest dose of risperidone increased the EEG power at 4 Hz during PW, SWS-1 and SWS-2, furthermore, decreased the beta (13-30Hz) band during PW. An increase was noticeable in EEG power density at the 3-4 Hz and 6-8 Hz frequency ranges in SWS-1, and there was also an increase in the 2-5 Hz frequency ranges in SWS-2. Interestingly, 0.1 mg/kg dose of risperidone took effect only in SWS-1 (an increase at 7 Hz), and the highest dose had no effects on EEG power spectra.

Conclusion: 

Sleep pattern and EEG power spectra were affected most effectively by highest and lowest doses of risperidone, respectively. The strongest effects of this drug were a decrease in time spent in PS and an elevated EEG power at 4 Hz.

This work was supported by the 6th Framework Program of the EU, LSHM-CT-2004-503474.