N-(2-(5-ethylbenzo[b]thiophen-3-yl)ethyl)acetamide

S-22153 is a potent melatonin receptor antagonist with EC50 values of 19 nM, 4.6 nM for hMT1 and hMT2 melatonin receptor, respectively. S-22153 has Ki values of 8.6 nM (CHO cells) and 16.3 nM (HEK cells) for hMT1, and 6.0 nM (CHO cells) and 8.2 nM (HEK cells) for hMT2. S-22153 is a specific ligand of MT1 and MT2 melatonin receptors subtypes[1][2]. S-22153 sets the temperature and activity periods to approximately 24 hr and increase the circadian amplitude of both rhythms in mice, which exposed to continuous light[1] .

[1]. Li XM, et al. Circadian rhythm entrainment with melatonin, melatonin receptor antagonist S22153 or their combination in mice exposed to constant light. J Pineal Res. 2004;37(3):176-184. [2]. Audinot V, et al. New selective ligands of human cloned melatonin MT1 and MT2 receptors. Naunyn Schmiedebergs Arch Pharmacol. 2003;367(6):553-561.