Animal experiment:

Twelve male Wistar rats weighing 350 to 400 g at the time of surgery are used. SB-399885 hydrochloride 2.5, 5 and 10 mg/kg or vehicle (1% aqueous solution of Tween 80) (n=6) are administered intraperitoneally in animals adapted to a 12 h dark/12 h light cycle for 4 weeks, starting 2 h after the beginning of the dark period. Each animal receives all 12 treatments. Recordings are begun 15 min later and continued for 6 h. The control solution and SB-399885 hydrochloride are given at least three days apart[1].

SB-399885 hydrochloride is a 5-HT6 receptor antagonist.

Compare with the control vehicle SB-399885 hydrochloride 10 mg/kg significantly increases wakefulness (W) (F(3,15)=3.32, P<0.05) while slow wave sleep (SWS), rapid-eye-movement sleep (REMS) and the number of REM periods are reduced (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). Analysis of sleep variables in 2-h blocks shows that SB-399885 hydrochloride 10 mg/kg increases W (F(3,15)=5.48, P<0.01) and reduces SWS (F(3,15)=5.42, P<0.01) and REMS (F(3,15)= 4.05, P<0.01) during the first 2-h period. SB-399885 hydrochloride 5 and 10 mg/kg augment light sleep over the first (F(3,15)=3.46,P<0.01 and F(3,15)= 3.65, P<0.01, respectively) and the second (F(3,15)=3.23, P<0.05 and F(3,15)=3.08, P<0.05, respectively) 2-h recording periods. SB-399885 hydrochloride 10 mg/kg significantly increases REMS latency (F(3,15)=3.60, P<0.01) and reduces the number of REM periods during the first 2-h of recording (F(3,15)=3.88, P<0.01)[1].

References:
[1]. Monti JM, et al. Effects of the 5-HT6 receptor antagonists SB-399885 and RO-4368554 and of the 5-HT(2A) receptor antagonist EMD 281014 on sleep and wakefulness in the rat during both phases of the light-dark cycle. Behav Brain Res. 2011 Jan 1;216(1):381-8.