A series of new 10-methoxypyrazino [1, 2-a] indoles has been prepared and shown to be 5HT2C receptor ligands. The studied compounds 10a–j were found to act as partial agonists at the 5HT2C receptor, binding with high affinity and moderate selectivity versus 5HT1A and 5HT2A receptors, but inducing only a submaximal increase in phosphoinositol formation. Compound 10j was demonstrated to be active in animal models of obsessive-compulsive ...