SLEEP AND EEG POWER SPECTRUM EFFECTS OF THE 5-HT1A ANTAGONIST NAN-190ALONE AND IN COMBINATION WITH CITALOPRAM

The sleep and waking and EEG power spectrum effects of the putative 5- HT1A antagonist NAN-190 (0.5 mg/kg, i.p.) were studied alone and in co -administration with the selective serotonin re-uptake inhibitor cital opram (5.0 mg/kg, i.p.) in the rat. Citalopram, as in a prior dose-res ponse study, reduced REM sleep. In addition, a slight increase in NREM sleep was observed. Citalopram reduced NREM fronto-parietal (FP) EEG power density in the 5-20 Hz range. When administered alone, NAN-190 s uppressed REM sleep in the first 2 h, and reduced SWS-2 in the first 4 h after administration. NAN-190 also suppressed selectively NREM slee p slow-wave activity in both fronto-frontal (FF) and FP EEG power spec trum. When administrated in combination with citalopram, an attenuatio n of the power density I eduction in the 7-15 Hz range in the FF EEG o f citalopram alone, was observed. However, the EEG power spectral dens ity and REM sleep suppressive effects of NAN-190 were both augmented. The results are compatible with the notion that serotonin is involved in the modulation of the slow wave activity in the EEG during NREM sle ep. The results are cordant with other data suggesting that postsynapt ic 5-HT1A stimulation might increase slow wave activity in the NREM EE G, and that serotonergic stimulation of other receptor subtypes (possi bly 5-HT2) may decrease slow wave activity in the NREM EEG.