This invention relates to a compound ##STR1## in which R.sub.1 representsa 1,2,3,6-tetrahydro-1-pyridyl radical substituted in the 4-position by (a) a phenyl radical, (b) a phenyl radical substituted by a halogen atom or an alkyl, hydroxy or alkoxy radical, (c) a 3-indolyl radical, (d) a 3-indolyl radical substituted on the nitrogen atom by an alkyl or alkylcarbonyl radical and/or in the 5-position by a halogen atom or (e) a 3-(5-hydroxyindolyl) radical.a 1-piperazinyl radical substituted in the 4-position by (a) a phenyl radical, (b) a phenyl radical substituted by an alkoxy, alkyl, hydroxy, nitro or amino radical or a halogen atom, (c) a 1,2-benzisothiazol-3-yl radical, (d) a 1,2-benzisoxazol-3-yl radical or (e) a 2-pyridyl radical.a piperidino radical substituted in the 4-position by (a) a phenyl radical, (b) a phenyl radical substituted by a halogen atom or a hydroxy, alkyl or alkoxy radical, (c) two phenyl radicals, (d) a bis(4-fluorophenyl)methylene radical, (e) a 4-fluorobenzoyl radical, (f) a 2-oxo-1-benzimidazolinyl radical, (g) a 2-oxo-1-benzimidazolinyl radical substituted in the 3-position by an alkylcarbonyl or benzoyl radical, (b) a hydroxy radical and a phenyl radical optionally substituted with an alkyl, alkoxy or hydroxy radical or a halogen atom, (i) a 3-indolyl radical, (j) a 3-indolyl radical substituted on the nitrogen atom by an alkyl or alkylcarbonyl radical and/or in the 5-position by a halogen atom or (k) a 3-(5-hydroxyindolyl) radical.either:R.sub.2 and R.sub.3, which are identical, represent a hydrogen or halogen atom and R.sub.4 represents a hydrogen atom orR.sub.2 and R.sub.4 represent a hydrogen atom and R.sub.3 represents a halogen atom or an acetylamino radical orR.sub.2 and R.sub.3 represent a hydrogen atom and R.sub.4 represents a halogen atom and R.sub.5 represents a --CH.dbd. group.or R.sub.2, R.sub.3 and R.sub.4 represent a hydrogen atom and R.sub.5 represents a nitrogen atom.R.sub.6 represents an alkylene chain containing 2 to 4 carbon atoms or a propylene chain substituted in the 1- or 3-position by an alkyl radical or in the 2-position by an alkyl, alkoxy, hydroxy, dialkylamino, piperidino, morpholino or thiomorpholino radical,with the reservation that when R.sub.6 represents a propylene radical substituted in the 2-position by a dialkylamino, piperidino, morpholino or thiomorpholino radical, R.sub.1 cannot be a radical containing a hydroxy radical, and their salts, are useful in therapy for their ability to block serotonin receptors.