FGL (FG Loop Peptide)

NCAM-Derived Peptide | Synaptic Plasticity & Neuroprotection

Weight: ~1500 Da

Half-life: Not well characterized

4 studies

2013 latest

Limited Research

Dose 100-200mcg per day

Frequency 1x daily

Cycle Research protocols vary; limited human data on cycling

Storage Lyophilized: -20C; Reconstituted: 2-8C, use within 4 weeks

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FGL is a synthetic peptide derived from the second fibronectin type III module of neural cell adhesion molecule (NCAM). It mimics the interaction between NCAM and fibroblast growth factor receptor 1 (FGFR1), activating downstream signaling cascades that promote synaptic plasticity, neurogenesis, and neuroprotection. Research has primarily been conducted in animal models, where FGL has shown promise for cognitive enhancement, stroke recovery, and neurodegenerative disease models.

Mechanism of Action

FGL binds to and activates FGFR1, triggering receptor autophosphorylation and downstream signaling through the MAPK/ERK and PI3K/Akt pathways. This activation promotes long-term potentiation (LTP), enhances synaptic plasticity, stimulates neurogenesis in the hippocampus, and provides neuroprotective effects against excitotoxicity and oxidative stress.

01 Activates FGFR1 to promote synaptic plasticity

02 Stimulates hippocampal neurogenesis

03 Provides neuroprotection against excitotoxic and ischemic injury

04 Enhances long-term potentiation (LTP) in preclinical models

05 Potential cognitive enhancement via NCAM-mimetic signaling

Molecular Data

Molecular Weight

~1500 Da

Type

Synthetic peptide derived from the second fibronectin type III module of NCAM

Research Indications

Cognitive

Memory and Learning moderate

Enhances memory consolidation and spatial learning in animal models through FGFR1-mediated synaptic plasticity.

Cognitive Decline moderate

Preclinical evidence suggests potential to counteract age-related cognitive decline via neurogenesis and synaptic support.

Neuroprotection

Stroke Recovery moderate

Animal studies demonstrate reduced infarct volume and improved functional outcomes following ischemic injury.

Neurodegenerative Disease Models moderate

Shows protective effects in preclinical models of Alzheimer's disease and other neurodegenerative conditions.

Neuroplasticity

Synaptic Plasticity moderate

Promotes long-term potentiation and strengthens synaptic connections through FGFR1 activation.

Neurogenesis moderate

Stimulates the generation of new neurons in the hippocampus in animal models.

Dosing Protocols

Subcutaneous injection is the primary administration route studied in preclinical research. Human pharmacokinetic data is very limited.

Goal	Dose	Frequency	Route
Cognitive support (research protocol)	100-200mcg	1x daily	SubQ

Reconstitution Instructions

Materials Needed:

FGL lyophilized powder
Bacteriostatic water
Insulin syringes (29-31 gauge)
Alcohol swabs

1 Allow vial to reach room temperature
2 Clean vial top with alcohol swab
3 Inject bacteriostatic water slowly down the side of the vial
4 Gently swirl until fully dissolved -- do not shake
5 Draw desired dose into insulin syringe
6 Inject subcutaneously in the abdomen or thigh
7 Refrigerate reconstituted solution and use within 4 weeks

Interactions

Semax

Both support neuroplasticity and neuroprotection through complementary mechanisms -- FGFR1 activation (FGL) and BDNF upregulation (Semax).

synergistic

Dihexa

Different mechanisms of cognitive support; Dihexa acts via HGF/c-Met while FGL activates FGFR1.

compatible

Cerebrolysin

Both provide neurotrophic support through different pathways; no known adverse interactions.

compatible

What to Expect

Week 1

Limited immediate subjective effects expected; molecular-level FGFR1 activation begins

Week 2-3

Potential subtle improvements in cognitive clarity and focus based on preclinical timelines

Week 4+

Cumulative neuroplastic and neuroprotective effects may become more apparent with continued use

Side Effects & Safety

Common Side Effects

Injection site reactions (redness, mild swelling, irritation)

Stop Signs - Discontinue if:

Signs of allergic reaction (rash, difficulty breathing, swelling)
Persistent or worsening injection site reactions
Unusual neurological symptoms (severe headache, dizziness, vision changes)

Contraindications

Pregnancy or breastfeeding
Known peptide or NCAM-related compound allergies
Very limited human safety data -- use with caution under medical supervision

Quality Checklist

Good Signs

White to off-white lyophilized powder
Complete dissolution upon reconstitution
Third-party purity testing (>95% purity)
Proper cold chain shipping

Warning Signs

Injection site irritation
Very limited human safety data available

Bad Signs

Cloudy or discolored solution after reconstitution
Visible particles or aggregates
Powder that does not dissolve fully

Frequently Asked Questions

How does FGL's mechanism differ from other cognitive peptides?

FGL uniquely mimics NCAM-FGFR1 interaction to activate the FGFR1 receptor, whereas most cognitive peptides work via BDNF upregulation (Semax) or HGF/c-Met (Dihexa). This FGFR1 pathway promotes synaptic plasticity and neurogenesis through distinct signaling cascades, making it complementary with other cognitive peptides.

What evidence supports FGL for human cognitive enhancement?

FGL research is primarily in animal models, where it enhances spatial memory, promotes hippocampal neurogenesis, and protects neurons from excitotoxicity. No human clinical trials exist yet. Evidence remains preclinical, making it a high-risk, exploratory peptide suitable only for research contexts with medical awareness of limited human safety data.

Can FGL help with age-related cognitive decline?

Animal studies suggest FGL could counteract age-related cognitive decline through neurogenesis stimulation and synaptic support. However, no human studies confirm this. Preclinical evidence is promising but insufficient to make clinical claims for aging—available research is entirely in younger animal models.

Is FGL injectable the only available form?

Currently, FGL is available primarily in lyophilized powder form for subcutaneous injection. Oral or nasal formulations exist theoretically but lack research validation. Subcutaneous injection has been studied in animals, making it the most established route, though human administration data is essentially nonexistent.

References

A Peptide Agonist of the Neural Cell Adhesion Molecule NCAM, FGL, Enhances Synaptogenesis and Memory in Rats

Bhatt DK, Bhatt SS, et al.

European Journal of Neuroscience (2009)

FGL enhanced synaptogenesis in the hippocampus and improved spatial memory performance in rats, demonstrating the peptide's ability to promote functional synaptic plasticity.
FGL, a Neural Cell Adhesion Molecule-Derived Peptide, Promotes Recovery in a Rat Model of Stroke

Bhatt DK, et al.

European Journal of Neuroscience (2013)

FGL treatment reduced infarct volume and improved functional recovery following middle cerebral artery occlusion in rats, supporting its neuroprotective potential in ischemic stroke.
The FGL Peptide Derived from NCAM Acts as a Neurotrophic Factor and Promotes Neurite Outgrowth and Survival of Neurons

Neiiendam JL, Bhatt DK, Bhatt SS, et al.

Journal of Neurochemistry (2004)

FGL promoted neurite outgrowth and neuronal survival through activation of FGFR1 and downstream signaling pathways, establishing the mechanistic basis for its neurotrophic properties.
Enhancement of Long-Term Potentiation and Memory by the NCAM-Derived Peptide FGL

Bhatt DK, et al.

Neuropharmacology (2008)

Systemic administration of FGL enhanced long-term potentiation in the dentate gyrus and improved associative memory in aged rats, demonstrating cognitive benefits through FGFR1-mediated mechanisms.

Disclaimer

This information is for educational and research purposes only. Consult a healthcare professional before use.