Interaction of zinc with antidepressants in the tail suspension test

The antidepressant-like effect of zinc has been shown in several animal models of depression. In this study, zinc chloride (ZnCl2) was given alone or in combination with different classes of antidepressants by oral route (p.o.) to mice and the behavioral response in the tail suspension test (TST), a predictive test of antidepressant action, was investigated. ZnCl2 at a dose of 10 and 30 mg/kg, p.o., reduced the immobility time in the TST, without affecting the locomotor activity in open-field test. The antidepressants fluoxetine, paroxetine, imipramine, desipramine and bupropion produced a significant reduction in the immobility time in TST at the doses of 10, 1, 1, 1 and 10 mg/kg, p.o., respectively. The combined treatment of sub-effective doses of ZnCl2 (1 mg/kg) with sub-effective doses of fluoxetine (5 mg/kg), paroxetine (0.1 mg/kg), desipramine (0.1 mg/kg), imipramine (0.1 mg/kg) or bupropion (1 mg/kg) induced a significant reduction in the immobility time in the TST when compared with the groups treated with ZnCl2 or with antidepressants alone. The treatment with sub-effective doses of ZnCl2 and antidepressants alone or in combination did not affect the locomotion in open-field test, except that desipramine alone reduced the ambulation. The results first indicate that ZnCl2 administered by p.o. route produces an antidepressant-like effect in the TST. Moreover, synergistic effects of zinc with antidepressants were shown in the TST, suggesting that an improvement in the response to the antidepressant therapy occurs when zinc is combined with different classes of antidepressants.