SB-399885 hydrochloride is an antagonist of 5-HT6 receptor.

SB-399885 hydrochloride, administered at a dose of 10 mg/kg, significantly enhances wakefulness (W) (F(3,15)=3.32, P<0.05) and decreases both slow wave sleep (SWS) and rapid-eye-movement sleep (REMS), as well as reducing the number of REM periods (F(3,15)=4.0, P<0.01; F(3,15)=3.14, P<0.05 and F(3,15)=2.62, P<0.05, respectively) compared to the control vehicle. Further analysis on 2-hour intervals revealed that this dose increased W (F(3,15)=5.48, P<0.01) and diminished SWS and REMS during the initial 2-hour period (F(3,15)=5.42, P<0.01 and F(3,15)= 4.05, P<0.01, respectively). Additionally, doses of 5 and 10 mg/kg were found to increase light sleep across the first and second 2-hour recording periods (F(3,15)=3.46,P<0.01 and F(3,15)= 3.65, P<0.01; and F(3,15)=3.23, P<0.05 and F(3,15)=3.08, P<0.05, respectively). The 10 mg/kg dose also notably prolonged REMS latency (F(3,15)=3.60, P<0.01) and decreased the number of REM periods within the first two hours of recording (F(3,15)=3.88, P<0.01).