Synergistic Sedative Activity of Indirubin on Diazepam in Thiopental Sodium-induced Sleeping Mice: A Potential GABAergic Transmission.

Insomnia remains one of the most common sleep disorders and causes significant discomfort as well as impairment in social, interpersonal, and vocational aspects of life. This study focuses on assessing the sedative activity of indigo naturalis indirubin (IND) on thiopental sodium (TS)-induced sleeping mice and evaluating the underlying molecular mechanisms through an in silico study. The adult male Swiss albino mice were used and given IND (5 and 10 mg/kg, i.p.), and diazepam (DZP) (2 mg/kg) in the respective groups individually and in combination to investigate modulatory effects. After 30 min, the treated mice were given TS (20 mg/kg, i.p.) to promote sleep, and the latency and duration of sleep were recorded manually. The in vivo study revealed that a higher dose of test sample (IND-10 mg/kg) showed lower latency and higher sleeping duration than a lower dose. Furthermore, an in silico study was performed to predict the involvement of gamma-aminobutyric acid (GABA) receptors in the sleep mechanism and assess pharmacokinetics and toxicity. Findings revealed that IND increased the duration of sleeping and decreased the latency of sleep induction. Additionally. the combination therapy of IND and DZP demonstrated synergistic sedative activity, as indicated by a greater reduction in locomotor activity and increased duration of sedation compared to either drug alone. IND exhibited a higher binding affinity (-9.1 kcal/mol) than DZP (-8.3 kcal/mol) at the identical binding site in the in silico study. The pharmacokinetic analysis of IND indicated acceptable drug-likeness and good pharmacokinetic properties. In conclusion, IND produced a potent sedative effect in the mouse model, possibly through the GABA receptor interaction pathways.