Indole derivatives and their use as ligands of serotonin receptor.

A compound of the formula: wherein each of R1 and R2 is hydrogen, halo, cyano or methyl, the dotted line represents a double bond, where each of R4 and R5 is hydrogen, C1-6 alkyl, cyclopropyl or cyclopropyl -C1-6alkyl, n is 0 or 1, and R3 is -SR6, -SOR6, -SO2R6, -COR6, -CH2OH or -CONHR7, where R6 is C1-6 alkyl and R7 is hydrogen or C1- alkyl 6; with the proviso that one of R1 and R2 is hydrogen and the other is fluorine, each of R4 and R5 is hydrogen or C1-6 alkyl, n is 0, then R3 is not -COR6 or -CONHR7 it; or a salt thereof.