Effects of 5-HT(2) receptor antagonists on the anti-immobility effects of imipramine in the forced swimming test with mice

The effects of 5-HT(2) receptor antagonists on antidepressant effects of imipramine were investigated in the forced swimming test. Imipramine induced anti-immobility effects in mice dose dependently. Pretreatment with the 5-HT(2A/2B/2C) receptor antagonist, 4-isopropyl-7-methyl-9-(2-hydroxy-1-methyl-propoxycarbonyl)-4,6A,7,8,9,10,10A-octahydro-indolo[4,3-FG]quinolone maleate (LY 53857) significantly enhanced the anti-immobility effects of imipramine. The 5-HT(2C/2B) receptor antagonist, N-3-pyridinyl-3,5-dihydro-5-methyl-benzo[1,2-b:4,5-b']dipyrrole-1(2H)-carboxamide (SB 206553), also enhanced, while the 5-HT(2A) receptor antagonist, ketanserin, was without effect. These results suggest that blockade of the 5-HT(2C/2B) receptor leads to potentiation of the antidepressant effects of imipramine.