Fluvoxamine, a new antidepressant drug, fails to show antiserotonin activity

Fluvoxamine, (E)-5-methoxy-4'-(trifluoromethyl)valerophenone O-2(2-aminoethyl)oxime, a new antidepressant drug inhibiting serotonin (5-HT) uptake, was studied in rats and mice in order to check whether it has any central anti-5-HT activity, as do some tricyclic antidepressants, e.g. amitriptyline and doxepin. Fluvoxamine did not influence either the 5-hydroxytryptophan-induced head twitch response in mice or the tryptamine convulsions in rats. In the hind limb flexor reflex of the spinal rat the stimulation induced by fenfluramine was inhibited, that induced by LSD was not changed. Fluvoxamine also antagonized the hyperthermia (at ambient temperature of 28 degrees C), induced in rats by fenfluramine or p-chloroamphetamine. The hyperthermia caused by m-chlorophenylpiperazine was not inhibited. Fluvoxamine did not antagonize the 5-HT pressor effect in pithed rats. It has no effect on the immobility time in the behavioural despair test in rats. The results indicate that fluvoxamine fails to show anti-5-HT activity.