Hypothesis

Aged brains show a shift from NMDA‑dependent LTP to NMDA‑independent VGCC‑LTP alongside chondroitin sulfate‑rich ECM stiffening, which together lock synaptic weights into a over‑consolidated state. We hypothesize that co‑administration of BPC-157 and TB-500 reverses this shift by (1) reducing ECM chondroitin‑6‑sulfation through upregulation of extracellular sulfatases, and (2) normalizing actin‑mediated spine motility, thereby restoring NMDA‑receptor dependence of LTP and cognitive flexibility.

Mechanistic Rationale

• BPC-157 activates ERK1/2 pathways that increase expression of arylsulfatase B and heparanase, enzymes known to desulfate chondroitin sulfate glycosaminoglycans (see its ECM remodeling activity in TBI models)[3]. Reduced sulfation loosens the perineuronal net, decreasing the physical barrier that favors VGCC‑mediated calcium influx.
• TB-500 sequesters G‑actin and promotes F‑actin polymerization, enhancing dendritic spine motility and the ability of synapses to undergo NMDA‑dependent calcium signaling[4]. Increased actin turnover counteracts the ECM‑induced cytoskeletal rigidity that sustains VGCC‑LTP.
• Together, these actions lower the threshold for NMDA receptor activation while limiting the compensatory VGCC pathway, moving the plasticity balance back toward Hebbian, input‑specific LTP.
• This mechanistic shift predicts a downstream decrease in NRSF/REST‑mediated transcriptional repression, as neuronal activity patterns normalize.[1]

Testable Predictions

1. Biochemical – Aged mice receiving BPC-157 + TB-500 will show reduced chondroitin‑6‑sulfation in hippocampal homogenates (measured by ELISA or LC‑MS) compared with vehicle controls.
2. Electrophysiological – Field recordings will reveal a higher NMDA‑LTP/VGCC‑LTP ratio in the CA1 region of treated animals, accompanied by a leftward shift in the input‑output curve.
3. Behavioral – Treated mice will outperform controls on surprise‑based learning tasks (e.g., reversal learning or oddball detection) that require updating of entrenched predictions, while showing no difference in simple motor assays.
4. Molecular – Western blots will show increased phospho‑ERK1/2, elevated F‑actin/G‑actin ratio, and decreased NRSF/REST protein levels in the hippocampus of treated mice.

Experimental Design (Falsifiable)

• Subjects: 24‑month-old C57BL/6J mice (n=12 per group).
• Groups: (1) Vehicle saline, (2) BPC-157 alone (10 µg/kg/day, i.p.), (3) TB-500 alone (2 mg/kg/day, i.p.), (4) BPC-157 + TB-500 (same doses). Treatment for 4 weeks.
• Outcomes: Biochemical ECM sulfation assay, ex vivo hippocampal slice electrophysiology (NMDA‑LTP via D‑APV sensitivity, VGCC‑LTP via nifedipine sensitivity), behavioral reversal learning in a water maze, and Western blot analysis of signaling markers.
• Falsification: If the combination does not reduce chondroitin‑6‑sulfation, fails to increase the NMDA‑LTP/VGCC‑LTP ratio, or does not improve surprise‑dependent learning relative to monotherapies or vehicle, the hypothesis is refuted.

This framework translates the over‑consolidation model of cognitive aging into a concrete, peptide‑based strategy that can be directly tested and either validated or rejected with existing preclinical techniques.