Agomelatine (S-20098) L(+)-Tartaric acid is a specific agonist of MT1 and MT2 receptors (Kis: 0.1, 0.06, 0.12, and 0.27 nM for CHO-hMT1, HEK-hMT1, CHO-hMT2, and HEK-hMT2). It also is a selective 5-HT2C receptor antagonist (pKis: 6.4 and 6.2 at native (porcine) and cloned (human) 5-HT2C receptors).

5-HT2C receptor (native porcine): pki： 6.4 , MT1 (human, CHO cells):ki:0.1 nM , MT2 (human, CHO cells):0.12 nM (ki), HEK-hMT2:0.27 nM (ki), 5-HT2C receptor (human):6.2 pki, HEK-hMT1:0.06 nM (ki)

Agomelatine acts as a full agonist of MT1 and MT2 receptors with EC50s of 1.6, 0.10 nM for CHO hMT1 CHO-hMT2 (hΜΤ1 and hΜΤ2 receptors expressed in CHO or HEK cell membranes) [1]. Agomelatine also interacts with h5-HT2B receptors, whereas it shows low affinity at native (rat)/cloned, human 5-HT2A (<5.0/5.3), and 5-HT1A (<5.0/5.2) receptors, and negligible (<5.0) affinity for other 5-HT receptors [2].

Agomelatine (25, 50, or 75 mg/kg; i.p.) has antioxidant activity in Strychnine (75 mg/kg, i.p.) or Pilocarpine (400 mg/kg, i.p.) induced seizure models in mice. Agomelatine does not have any antioxidant effects on parameters of oxidative stress produced by Pentylenetetrazole (PTZ) or Picrotoxin (PTX) induced seizure models when compared to controls [3].