Undoubtedly, the SARS-CoV-2 has become a major concern for all societies due to its catastrophic effects on public health. In addition, mutations and changes in the structure of the virus make it difficult to design effective treatment. Moreover, the amino acid sequence of a protein is a major factor in the formation of the second and tertiary structure in a protein. Amino acid replacement can have noticeable effects on the folding of a protein, especially if an asymmetric change (substitution of polar residue with non-polar, charged with an uncharged, positive charge with a negative charge, or large residue with small residue) occurs. D614G as a spike mutant of SARS-CoV-2 previously identified as an associated risk factor with a high mortality rate of this virus. Using structural bioinformatics, our group determined that D614G mutation could cause extensive changes in SARS-CoV-2 behavior including the secondary structure, receptor binding pattern, 3D conformation, and stability of it.
ObjectivesPrevious studies have suggested antidepressant properties for modafinil; however, the underlying mechanisms mediating the antidepressant effect of modafinil have not been well recognized in clinical and animal studies. Nitric oxide (NO) is involved in the pathophysiology of depression. We attempted to investigate the possible role of NO in the antidepressant-like effect of modafinil in mouse forced swimming test (FST) and tail suspension test (TST).MethodsThe antidepressant-like effect of modafinil (25, 50 and 75 mg/kg), alone and in combination with l-arginine, l-arg, (100 mg/kg) and NG-l-arginine methyl ester, l-NAME (5 mg/kg), was evaluated using FST and TST. Following behavioral tests, the hippocampi were dissected out to measure nitrite levels.ResultsFindings suggested that administration of modafinil at doses of 50 and 75 mg/kg significantly reduced immobility time in the FST and TST. Furthermore, administration of l-arg and l-NAME increased and decreased, respectively, the immobility time in the FST and TST. We showed that co-administration of a sub-effective dose of modafinil (25 mg/kg) plus l-NAME potentiated the antidepressant-like effect of the sub-effective dose of modafinil. In addition, co-treatment of an effective dose of modafinil (75 mg/kg) with l-arg attenuated the antidepressant-like effect of the effective dose of modafinil. We showed that the antidepressant-like effect of modafinil is associated with decreased nitrite levels in the hippocampus.ConclusionsOur findings for the first time support that the modulation of NO, partially at least, is involved in the antidepressant-like effect of modafinil in mouse FST and TST.
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