The 5-HT2 receptor antagonist reduces immobility of mice treated with the atypical antidepressant mianserin in the forced swimming test.

Effects of co-administration with the 5-HT(2) receptor antagonist LY 53857 and the antidepressant mianserin on immobility time in the forced swimming test were investigated in mice. Mianserin did not affect the immobility time at ranges from 1-10 mg/kg, although it elicited anti-immobility effects at 20 mg/kg. Co-administration of the 5-HT(2) receptor antagonist LY 53857 and a subactive dose of mianserin induced apparent anti-immobility effects. Since mianserin facilitates noradrenaline (NA) release from nerve terminals via inhibition of alpha(2) receptors, the blockade of the 5-HT(2) receptor may increase the antidepressant effect of drugs modifying NA levels in the synaptic cleft.