Nootropics & cognitive
FGL(L)
A 15-amino-acid fragment of the neural cell adhesion molecule that activates FGFR1 in rodent brains — real synaptic-plasticity data, zero human trials.
Research chemical Nootropics & cognitive
- Full name
- FGL Peptide (NCAM-derived FG-Loop Peptide)
- Also known as
- FGL, FG-Loop peptide, FGLL, NCAM mimetic peptide FGL
- Regulatory status
- Unapproved research compound. No FDA/EMA approval, no clinical trials registered in humans as of 2026; all published work is in vitro or in rodent models.
Origin
FGL is a synthetic 15-amino-acid peptide (sequence EVYVVAENQQGKSKA) corresponding to the second fibronectin type III (F3) module of the neural cell adhesion molecule (NCAM), first described by Cambon et al. (2004). It is not naturally circulating — it's a lab-designed mimetic of a binding loop within a much larger cell-surface protein.
Mechanism
FGL binds and activates fibroblast growth factor receptor 1 (FGFR1), the same receptor NCAM engages via heterophilic interaction, without requiring the full NCAM protein. Downstream, this triggers PKC and CaMKII signaling that facilitates synaptic AMPA receptor delivery and NMDA-receptor-dependent long-term potentiation (LTP) in hippocampal neurons, and separately drives neurotrophic and anti-inflammatory effects (suppressing microglial activation via neuronal CD200 upregulation).
Research summary
Evidence
All evidence is preclinical — cell culture and rodent studies, no human data. In rats, systemic or intracerebroventricular FGL improved spatial and fear-conditioning memory consolidation, facilitated hippocampal LTP in the dentate gyrus, and reduced amyloid-beta-induced CA1 pyramidal cell loss with partial rescue of social recognition memory in an Alzheimer's-relevant lesion model. In vitro, FGL promoted synaptogenesis, enhanced presynaptic function, mobilized neural stem cells, and suppressed neuroinflammatory microglial activation in aged rats. One study also found FGL alone (without amyloid-beta) reduced CA1 pyramidal cell counts by 40%, a caution against assuming benign effects outside disease models.
Evidence tier: Research chemical — see the methodology note for how this is assessed.
Citations
- A synthetic neural cell adhesion molecule mimetic peptide promotes synaptogenesis, enhances presynaptic function, and facilitates memory consolidation — Cambon K, Hansen SM, Venero C, et al. (2004)
- A novel anti-inflammatory role of NCAM-derived mimetic peptide, FGL — Downer EJ, Cowley TR, Lyons A, et al. (2008)
- Amyloid-beta induced CA1 pyramidal cell loss in young adult rats is alleviated by systemic treatment with FGL, a neural cell adhesion molecule-derived mimetic peptide — Corbett NJ, Gabbott PL, Klementiev B, et al. (2013)
- Facilitation of AMPA receptor synaptic delivery as a molecular mechanism for cognitive enhancement — Knafo S, Venero C, Sánchez-Puelles C, et al. (2012)
- The neural cell adhesion molecule-derived peptide FGL facilitates long-term plasticity in the dentate gyrus in vivo — Dallérac G, Zerwas M, Novikova T, et al. (2011)
- The synthetic NCAM mimetic peptide FGL mobilizes neural stem cells in vitro and in vivo — Klein R, Blaschke S, Neumaier B, et al. (2014)
Reported benefits
- Enhanced spatial learning and memory consolidation (rodent studies)
- Facilitated hippocampal long-term potentiation (LTP)
- Partial protection against amyloid-beta-induced neuronal loss and memory deficits (rodent AD model)
- Anti-inflammatory / anti-microglial activation effects in aged rat brain
- Promoted synaptogenesis and neural stem cell mobilization in vitro
Dosing protocols reported in the literature & community
These are protocols reported by compounding pharmacies, published trials, or self-experimentation communities — not a prescription. Start low, especially for anything new.
| Route | Reported protocol |
|---|---|
| Subcutaneous (rodent research dose) | Published rat studies typically used single or repeated doses in the range of ~1-3 mg/kg systemically; no human dosing data exists. Self-experimentation reports describing human doses are anecdotal extrapolations, not validated protocols. |
| Intracerebroventricular (research only) | Used exclusively in animal studies (microgram-range local infusion) to demonstrate direct CNS mechanism — not a route relevant to human self-use. |
Side effects
- Unknown in humans — no human safety data exists
- In rats, FGL alone (without pathology present) was associated with a reduction in CA1 pyramidal neuron counts in one study, suggesting effects may not be uniformly beneficial in a healthy brain
- Theoretical concern: FGFR1 agonism is not tissue-restricted to brain — systemic off-target growth-factor signaling effects are unstudied
Safety notes
Community & reddit notes (anecdotal — not clinical evidence)
FGL circulates in nootropic/longevity peptide forums as a theoretical 'NCAM mimetic' for memory enhancement, usually referenced alongside other FGFR-pathway peptides. Discussion tends to lean heavily on the Cambon 2004 and Knafo 2012 papers while glossing over the mixed CA1-neuron finding; actual self-reported use logs are sparse compared to better-established nootropic peptides.