M1 muscarinic receptor is a key target of neuroprotection, neuroregeneration and memory recovery by i-Extract from Withania somnifera.

Memory loss is one of the most tragic symptoms of Alzheimer's disease. Our laboratory has recently demonstrated that 'i-Extract' of Ashwagandha (Withania somnifera) restores memory loss in scopolamine (SC)-induced mice. The prime target of i-Extract is obscure. We hypothesize that i-Extract may primarily target muscarinic subtype acetylcholine receptors that regulate memory processes. The present study elucidates key target(s) of i-Extract via cellular, biochemical, and molecular techniques in a relevant amnesia mouse model and primary hippocampal neuronal cultures. Wild type Swiss albino mice were fed i-Extract, and hippocampal cells from naïve mice were treated with i-Extract, followed by muscarinic antagonist (dicyclomine) and agonist (pilocarpine) treatments. We measured dendritic formation and growth by immunocytochemistry, kallikrein 8 (KLK8) mRNA by reverse transcription polymerase chain reaction (RT-PCR), and levels of KLK8 and microtubule-associated protein 2, c isoform (MAP2c) proteins by western blotting. We performed muscarinic receptor radioligand binding. i-Extract stimulated an increase in dendrite growth markers, KLK8 and MAP2. Scopolamine-mediated reduction was significantly reversed by i-Extract in mouse cerebral cortex and hippocampus. Our study identified muscarinic receptor as a key target of i-Extract, providing mechanistic evidence for its clinical application in neurodegenerative cognitive disorders.

Alcoholic Extract of Ashwagandha Leaves Protects Against Amnesia by Regulation of Arc Function.

Our earlier report on scopolamine-induced amnesia and its improvement by pre-treatment with i-Extract (alcoholic extract of Ashwagandha leaf) suggested that the i-Extract mediated nootropic effect may involve neuronal immediate early gene, Arc. With a hypothesis that the i-Extract induced expression of Arc protein may cause augmentation in Arc function, we examined the effect of i-extract on a major function of Arc protein, i.e. F-actin expansion, using Arc antisense oligodeoxynucleotides (ODN). Stereotaxic infusion of Arc antisense ODN in the CA1 region of hippocampus decreased the level of Arc protein as demonstrated by immunoblotting. However, this decrease was attenuated when treated with i-Extract prior to infusion of Arc antisense ODN. We noted a significant decrease in the polymerization of F-actin during scopolamine-induced amnesia as well as Arc antisense ODN infusion that was restored rather enhanced when pre-treated with i-Extract in both the cases. We also compared the corresponding changes between CA1 (the infusion site) and CA3 (neighbouring site of infusion) regions of hippocampus, and found more pronounced effects in CA1 than in the CA3 region. The extent of F-actin polymerization, as revealed by changes in the dendritic spine architecture through Golgi staining, showed that both scopolamine as well as Arc antisense ODN disrupted the spine density and mushroom-shaped morphology that was again regained if pre-treated with i-Extract. In conclusion, the findings reveal that the Arc helps in polymerization of F-actin and subsequent changes in the morphology of dendritic spines after pre-treatment with i-Extract in scopolamine-induced amnesic mice, suggesting an important role of Arc in scopolamine-induced amnesia and its recovery by i-Extract.

Involvement of hippocampal Arc in amnesia and its recovery by alcoholic extract of Ashwagandha leaves.

Arc (Activity-regulated cytoskeletal-associated protein) is a member of the immediate-early gene (IEG) family protein. Because of its critical role in learning and memory, it is widely considered to be an important protein in synaptic plasticity and related neurobiological functions. Alcoholic extract of Ashwagandha leaves (i-Extract) was recently shown to have preventive and therapeutic potential for scopolamine-induced amnesia and glutamate-induced excitotoxicity. In the present study, we investigated the involvement of Arc in scopolamine-induced amnesia and its recovery by i-Extract with particular focus to the changes in Arc expression in the hippocampus and cerebral cortex of mice. Morris water maze test showed that spatial learning and memory of mice were drastically reduced by scopolamine administration but improved with i-Extract treatment as compared to control and scopolamine-challenged mice. Molecular analysis revealed a remarkable decline in Arc expression in both hippocampus and cerebral cortex of amnesic mice, which was recovered after i-Extract treatment. Interestingly, Arc expression showed better recovery in the hippocampus than the cerebral cortex and the pre-treatment with i-Extract was more effective than the post-treatment. These findings suggest that Arc may be involved in i-Extract mediated recovery from amnesia.

Protective role of Ashwagandha leaf extract and its component withanone on scopolamine-induced changes in the brain and brain-derived cells.

BACKGROUND: Scopolamine is a well-known cholinergic antagonist that causes amnesia in human and animal models. Scopolamine-induced amnesia in rodent models has been widely used to understand the molecular, biochemical, behavioral changes, and to delineate therapeutic targets of memory impairment. Although this has been linked to the decrease in central cholinergic neuronal activity following the blockade of muscarinic receptors, the underlying molecular and cellular mechanism(s) particularly the effect on neuroplasticity remains elusive. In the present study, we have investigated (i) the effects of scopolamine on the molecules involved in neuronal and glial plasticity both in vivo and in vitro and (ii) their recovery by alcoholic extract of Ashwagandha leaves (i-Extract). METHODOLOGY/PRINCIPAL FINDINGS: As a drug model, scopolamine hydrobromide was administered intraperitoneally to mice and its effect on the brain function was determined by molecular analyses. The results showed that the scopolamine caused downregulation of the expression of BDNF and GFAP in dose and time dependent manner, and these effects were markedly attenuated in response to i-Extract treatment. Similar to our observations in animal model system, we found that the scopolamine induced cytotoxicity in IMR32 neuronal and C6 glioma cells. It was associated with downregulation of neuronal cell markers NF-H, MAP2, PSD-95, GAP-43 and glial cell marker GFAP and with upregulation of DNA damage--γH2AX and oxidative stress--ROS markers. Furthermore, these molecules showed recovery when cells were treated with i-Extract or its purified component, withanone. CONCLUSION: Our study suggested that besides cholinergic blockade, scopolamine-induced memory loss may be associated with oxidative stress and Ashwagandha i-Extract, and withanone may serve as potential preventive and therapeutic agents for neurodegenerative disorders and hence warrant further molecular analyses.