Azadirachta indica A. Juss Ameliorates Memory Deficits and Reduces Anxiety-Like Behavior by Modulating Cholinergic Neurotransmission in An Animal Model of Depression: In Silico and In Vivo Studies

Exposure to prolonged and severe stress can lead to negative effects on learning and memory, increased anxiety, reduced motivation, disturbed cholinergic activity, and hippocampal and prefrontal cortical neuronal damage. On the other hand, drugs from natural origin have a beneficial effect on neuronal structure and functions. Azadirachta indica (neem), belonging to the Meliaceae family, has been reported to exhibit beneficial effects in wound healing, diabetes management, and antibacterial properties. This study aimed to assess the impact of Azadirachta indica on chronic immobilization stress-induced memory impairment in rats. Chronic immobilization stress was induced in rats for 2 hours/day over 10 days. Following this, Azadirachta indica was administered at doses of 200, 400, and 600 mg/kg for 14 days. Twenty-four hours after the treatment, behavioral tests, including the novel object recognition test (NORT), T-maze, and elevated plus maze (EPM), were conducted to evaluate memory and anxiety-like behaviors. Acetylcholinesterase (AChE) activity was measured in the frontal cortex, hippocampus, and septum. Additionally, molecular docking studies were performed using Molegro Virtual Docker (MVD-2013, 6.0) to analyze the interaction of 19 active chemical constituents from aqueous neem extracts with various targets, including AChE, brain-derived neurotrophic factor (BDNF), N-methyl-D-aspartate(NMDA) receptors, and anti-cortisol Fab in complex with corticosterone. Azadirachta indica treatment significantly enhanced learning and memory in chronically stressed rats, as evidenced by improved performance in NORT and T-maze tests, along with reduced anxiety-like behavior in the EPM test. Treatment also restored AChE activity in the stressed animals. Molecular docking studies indicated that the active constituents of neem extract showed high docking scores to AChE, BDNF, NMDA receptors, and anti-cortisol Fab, correlating with the experimental findings. Azadirachta indica exhibited neuroprotective and cholinergic transmission modulation properties, which may underlie its memory-enhancing effects in chronically stressed rats. Treatment enhanced memory in NORT and T-maze test (p<0.001). Also, anxiety behavior was reduced in the EPM (p<0.001). The correlation between the in vitro experimental data and the in silico molecular docking results suggests that neem’s active compounds could be potential candidates for improving memory and managing stress-induced cognitive impairments.