Behavioral profiles of SSRIs in animal models of depression, anxiety and aggression - Are they all alike?

The behavioral profiles of five clinically used selective serotonin reuptake inhibitors (SSRIs) citalopram, paroxetine, sertraline, fluvoxamine and fluoxetine, have been compared in animal models of antidepressant (mouse forced swim test), anxiolytic (exploration of black and white test box and footshock-induced ultrasonic vocalization in the rat) and antiaggressive (isolation-induced aggressive behavior in the mouse) activity. The results are discussed in relation to receptor binding data from the literature. Furthermore, affinities for the sigma(1) and sigma(2) binding sites are presented. Citalopram reversed the immobility induced by forced swimming with a potency similar to that of imipramine. Paroxetine, fluvoxamine and fluoxetine reversed swim-induced immobility less potently and with a maximum of 40-50% reversal. Citalopram produced a mixed anxiogenic-/anxiolytic-like response in rats tested in the two-compartment black and white box. Paroxetine induced an anxiogenic-like response at low doses and the other SSRIs were without major effects. Citalopram and paroxetine inhibited footshock-induced ultrasonic vocalization with high potencies. The dose-response curve was biphasic for citalopram with a maximum of 64% inhibition. Sertraline and fluvoxamine inhibited the vocalization less potently, and fluoxetine induced a weak inhibitory effect corresponding to a maximum of 32%. Sertraline, fluvoxamine and fluoxetine inhibited isolation-induced aggressive behavior, whereas citalopram and paroxetine were inactive. Both 5-HT1 and 5-HT2 receptors are involved, and there was a functional interaction between 5-HT1A and 5-HT2A or 5-HT2C receptors, as ritanserin potentiated the antiaggressive effect of 1,5-HTP as well as that of 8-OH-DPAT.