FG-5803

Comparative studies of the 1-piperazinecarboxamide derivative 4-[3-(4-fluorobenzoyl)propyl]-N-cyclohexyl-1-piperazinecarboxamide hydrochloride (FG5803) were made with clozapine and haloperidol. Receptor studies revealed that FG5803 potently and selectively bound to the serotonin type 2A receptors (Ki = 13 nM). FG5803 inhibited 5-hydroxytrophan- and 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane-induced head twitches, which indicated potent in vivo serotonin type 2A receptor antagonism. FG5803 caused an acute activation of the tuberoinfundibular dopamine neurons and produced only a transient rise in plasma prolactin. In behavioral studies in rats, FG5803 showed strong antagonistic action on presynaptic dopaminergic autoreceptors but only weak postsynaptic dopamine D2 blockade. FG5803 was not cataleptogenic and did not antagonize amphetamine-induced stereotypies. FG5803 was active in the reduction of aggressive behavior and spontaneous exploratory behavior in mice and rats. Therefore, FG5803 is expected to constitute a promising approach in the search for a novel class of antipsychotic drugs that have a broader spectrum of activity and fewer adverse effects than the conventional, antidopaminergic antipsychotics.