Better antidepressant efficacy of mecamylamine in combination with L-NAME than with L-arginine

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

Depression and anxiety are psychiatric diseases that commonly occur together, and the patient burden and complexity increase when both are present. Comorbid anxiety and depression are often more resistant to common drug treatments such as antidepressants. Combination therapy is a suggested approach in treating these patients, where a decline of doses could reduce undesirable outcomes and still achieve optimal effects. We, therefore, conducted a preclinical study to assess the effect of two-drug combinations of citalopram, bupropion, and scopolamine on anxiety- and antidepressive-like behaviors in male NMRI mice and aimed to determine the nature of the interaction between components. Anxiety- or antidepressive-like activity of mice was assessed by the hole-board or forced swim test (FST), respectively. Our results revealed that citalopram (0.01-0.25 mg/kg; i.p.), bupropion (1-9 mg/kg; i.p.), or scopolamine (0.01-0.1 mg/kg; i.p.) diminished immobility time in the FST, suggesting an antidepressive-like effect. Citalopram decreased dead-dip counts in the hole-board, indicating an anxiogenic-like activity. All two-drug combinations, at inactive doses, exerted an antidepressive-like behavior. Only bupropion/scopolamine combination increased head-dip counts compared to the bupropion/saline group. Isobolographic analysis revealed an antidepressive synergy effect between citalopram plus bupropion, and an antidepressive additive impact between scopolamine plus citalopram or bupropion. It should be noted that the higher dose of each drug alone declined locomotor activity, while two-drug combinations did not affect this parameter. These results suggest a stronger antidepressive effect for citalopram/bupropion combination than other two-drug combinations.

Antidepressant-like Effect of Merazin Hydrate Depends on NO/ERK by Suppressing Its Downstream NF-κB or Nonactivating CREB/BDNF in Mouse Hippocampus

Merazin hydrate (MH), an essential ingredient of Fructus aurantii, has been identified to have an antidepressant-like effect. However, the molecular mechanisms of MH modulate depressive behavior are largely uncharacterized. Here, in lipopolysaccharide-induced mice, we identified that a single administration of MH recovered depressive behaviors and down-regulated the expressions of neuronal nitric oxide synthase (nNOS) in the hippocampus after 1 day. Activation of nNOS by l-arginine led to depressive behaviors, and inhibition of nNOS contributed to antidepressive behaviors. Notably, MH only reversed the expression of nNOS's downstream NF-κB and not the CREB/BDNF pathway in the hippocampus, and MH's antidepressant-like effects were prevented by Asatone (an agonist of NF-κB) and not H89 (an antagonist of CREB). MH also normalized the expressions of GFAP and IB-1 in dentate gyrus in the hippocampus and inflammatory factors such as IL-1β, IL-10, and TNF-α in serum. Overall, our studies reveal the molecular mechanisms of MH's antidepressant-like effect.