Differential effects of the 5-HT2 receptor antagonist on the anti-immobility effects of noradrenaline and serotonin reuptake inhibitors in the forced swimming test.

The effects of the 5-HT(2) receptor antagonist, LY 53857 on the effects of noradrenaline and serotonin reuptake inhibitors were investigated using the forced swimming test. LY 53857 enhanced anti-immobility effects of clomipramine and maprotiline, which can inhibit reuptake of noradrenaline. However, LY 53857 did not affect the immobility time of mice treated with the selective serotonin reuptake inhibitors (SSRIs) fluoxetine and fluvoxamine. These results suggest that antagonism of the 5-HT(2) receptor leads to potentiation of the antidepressant effects of noradrenaline reuptake inhibitors but not SSRIs and that LY 53857 may modify the activity of noradrenergic neurons.