Isobolographic analysis of the antidepressant interaction in two-drug combinations of citalopram, bupropion, and scopolamine in mice

The additive effect between bupropion and citicoline upon induction of anti-nociceptive effect in nerve-ligated mice

OBJECTIVES

Bupropion is an atypical antidepressant that shows robust efficacy in the regulation of neuropathic pain. Citicoline is a dietary supplement which is used as a neuroprotective agent for central nervous system (CNS) disorders. The probable interaction between bupropion and citicoline on neuropathic pain was assessed in male mice.

METHODS

Neuropathic pain was induced by sciatic nerve ligation. Neuropathic pain was examined in nerve-ligated mice using tail-flick and hot-plate tests.

RESULTS

The results indicated that intraperitoneal (i.p.) administration of citicoline (50 and 100 mg/kg) induced an anti-nociceptive effect in nerve-ligated animals. Similarly, i.p. injection of bupropion (2.5 and 5 mg/kg) induced anti-nociceptive effects in nerve-ligated mice. Co-administration of different doses of bupropion (2.5 and 5 mg/kg) along with a low dose of citicoline (25 mg/kg) caused an anti-nociceptive effect by enhancement of tail-flick and hot plate latencies. Interestingly, there is an additive effect between bupropion and citicoline upon the induction of the anti-nociceptive effect.

CONCLUSIONS

Based on these results, it can be concluded that there is an interaction between bupropion and citicoline upon induction of an anti-nociceptive effect in nerve-ligated mice.

Synergistic antidepressant-like effect of xylopic acid co-administered with selected antidepressants

Background

Xylopic acid (XA), a kaurene diterpene from the dried fruits of Xylopia aethiopica, has anxiolytic- and antidepressant-like activity in mice and zebrafish. We aimed to assess the potential synergistic antidepressant-like effects of XA when combined with selected antidepressants in the mouse forced-swim test.

Materials and methods

The antidepressant-like effect of xylopic acid (XA) (10, 30, 100 mgkg-1), fluoxetine (Flx) (3, 10, 30 mgkg-1), sertraline (Sert) (3, 10, 30 mgkg-1), imipramine (Imi) (10, 30, 100 mgkg-1) and ketamine (Ket) (0.1, 0.3, 1.0 mgkg-1), was evaluated in forced swim test. The dose (ED50) that achieved a 50% reduction in immobility time was determined from the respective log-dose response curves. XA and the selected antidepressants were co-administered in fixed-dose ratio combinations (1/2:1/2, 1/4:1/4, 1/8:1/8) of the ED50 to identify the experimental ED50 (ED50mix). The theoretical ED50(ED50add), of all combinations was determined using isobolograms and compared with the ED50mix to identify the nature of the interaction. The effect of dose combinations on general locomotor activity was assessed in the open-field test.

Results

The interaction index (γ) for the following XA combinations, XA/Flx, XA/Sert, XA/Imi and XA/Ket were 0.42, 0.41, 0.31 and 0.34. An independent sample t-test revealed that the experimental ED50 (ED50mix) was significantly lower than the theoretical ED50 (ED50add) in all combinations of XA, indicative of a synergistic antidepressant-like effect. However, combinations of XA with ketamine significantly reduced general locomotor activity at all dose combinations.

Conclusion

The co-administration of xylopic acid and fluoxetine, imipramine, sertraline and ketamine produces a synergistic antidepressant-like effect in mice.