We propose that chronic berberine treatment reduces age‑related neural over‑consolidation by activating AMPK in astrocytes, which in turn accelerates degradation of perineuronal nets (PNNs) and dampens complement‑mediated synaptic tagging. This mechanistic shift restores cortical and hippocampal plasticity without requiring neuronal replacement.

Mechanistic Rationale

AMPK activation in astrocytes enhances lysosomal biogenesis through FOXO3 phosphorylation, upregulating cathepsins and matrix metalloproteinases that chondroitin sulfate proteoglycans—the core of PNNs—are susceptible to. Simultaneously, AMPK suppresses NF‑κB signaling, lowering astrocytic production of C1q and other complement initiators that flag synapses for microglial phagocytosis. By decreasing both extracellular matrix rigidity and inappropriate synapse elimination, the circuit regains a lower threshold for updating predictive models, directly addressing the over‑consolidation hypothesis.

Predictions & Experimental Design

1. Structural: Aged mice (20‑24 mo) receiving berberine (200 mg/kg/day, oral) for 8 weeks will show a ≥30 % reduction in WFA‑labeled PNN density in hippocampal CA1 and prefrontal cortex compared with vehicle controls (measure via immunohistochemistry).
2. Molecular: Astrocytic isolates from treated mice will exhibit increased AMPK‑pThr172, elevated cathepsin B/L activity, and decreased C1q mRNA (qPCR) relative to controls.
3. Functional: Treated animals will outperform controls in reversal learning tasks (e.g., Morris water maze platform shift) and exhibit higher long‑term potentiation magnitude in acute slices, indicating restored plasticity.
4. Specificity: Co‑administration of the AMPK inhibitor compound C will abolish berberine‑induced PNN reduction and behavioral improvement, confirming pathway dependence.

Potential Confounds & Controls

Berberine’s peripheral metabolic effects could indirectly influence brain physiology via altered glucose or lipid availability. To isolate central actions, we will include a group receiving peripherally restricted berberine analogue (e.g., berberine‑sulfonate) that does not cross the blood‑brain barrier; lack of effect in this group would support a central mechanism. Additionally, we will monitor plasma AMPK activity to ensure peripheral changes do not correlate with central outcomes.

This hypothesis is testable with standard neuroanatomical, biochemical, and behavioral assays, and falsifiable if berberine fails to alter PNN density, complement signaling, or reversal learning despite confirmed AMPK activation in astrocytes.