Fananserin displaces [125I]AMIK from 5-HT2 receptors with an IC50 of 0.21 nM in rat frontal cortex. Fananserin shows moderate affinity for alpha 1-adrenoceptors in the rat thalamus (IC50 = 14 nM) and for histamine H1 receptors in the guinea-pig cerebellum (IC50 = 13 nM). Fananserin (0.5-4 mg/kg; p.o.) increases the duration of deep nonrapid eye movement (NREM) sleep at the expense of wakefulness in a dose-dependent manner.