What is PE-22-28?
PE-22-28 is a tiny synthetic peptide — just seven amino acids long — designed in the lab as a shorter, more potent version of a natural molecule called spadin.[4] Spadin itself comes from a much larger protein called sortilin, which the body naturally processes and trims into smaller pieces.[6] One of those pieces, spadin (also written PE 12-28), was discovered to have antidepressant properties. Researchers then went further, studying the breakdown products of spadin in the blood, and identified PE-22-28 as an even more powerful fragment.[4]
PE-22-28 is classified as a research compound. It has never been approved for human use by any regulatory body. Everything described here comes from preclinical laboratory and animal studies.
How PE-22-28 Works
Think of a neuron (brain cell) like a tiny rechargeable battery. To fire a signal, it needs to manage the flow of charged particles — including potassium ions — in and out through special doors called ion channels. One of these doors is called the TREK-1 potassium channel.
When TREK-1 is too open (too active), it acts like a leak in the battery — the neuron becomes harder to excite, which researchers link to depressive-like states.[3] PE-22-28 works by blocking TREK-1, essentially closing that leaky door so the neuron can fire more normally.[4]
What makes PE-22-28 especially interesting is its potency. Lab studies on human TREK-1 cells showed it blocks the channel at an IC50 (the concentration needed to block half the channels) of just 0.12 nM — compared to 40–60 nM for original spadin. In plain terms, it takes a far smaller amount to do the same job.[4] It also stays active in the body for up to 23 hours, versus only about 7 hours for spadin — a big improvement for research purposes.[4]
What the Research Shows
Antidepressant Effects in Animal Models
In preclinical behavioral tests — specifically the Forced Swim Test (FST) and Novelty Suppressed Feeding (NSF) test, which are standard ways researchers measure depressive-like behavior in mice — PE-22-28 showed significant effects after just 4 days of sub-chronic treatment.[4] That speed is notable: classical antidepressants like fluoxetine (Prozac) typically take 3–4 weeks to show effects in equivalent models.[3]
Neurogenesis and Synaptogenesis
Beyond mood-like behavior, PE-22-28 was found to stimulate neurogenesis — the growth of new brain cells — after just a 4-day treatment window.[4] It also boosted synaptogenesis (the formation of new connections between neurons), measured by increases in a protein called PSD-95 in mouse cortical neurons.[4] This mirrors what was seen with original spadin analogs, where neurogenesis and synaptogenesis were linked to lasting antidepressant-like effects.[3]
Stroke Recovery and Post-Stroke Depression
A 2019 study investigated mini-spadin (a closely related shortened analog) in a mouse model of focal ischemia (a type of stroke) and the depression that can follow it.[1] Researchers used a clever two-phase dosing strategy: a very low dose early after the stroke to activate TREK-1 and protect brain tissue, then a higher dose later to block TREK-1 and treat depressive-like symptoms.[1] The compound prevented weight loss, reduced dopaminergic cell loss in a brain region called the substantia nigra, and improved both motor and cognitive deficits caused by the stroke. It also prevented post-stroke depression as measured in the FST and NSF tests.[1]
The Sortilin Connection
To understand why PE-22-28 matters, it helps to know its origin story. Sortilin — the parent protein — physically interacts with TREK-1 channels at the surface of neurons.[6] Levels of sortilin-derived peptides in human blood have been found to differ in patients with major depressive disorder, suggesting this whole pathway may be relevant to real-world depression biology.[6] Earlier work on retro-inverso analogs of spadin (chemically mirrored versions that are harder for the body to break down) also confirmed the TREK-1 blocking approach can boost hippocampal neurogenesis in 4-day treatment windows without triggering side effects on pain, seizure, or cardiac function in animal tests.[5]
What PE-22-28 Is Being Studied For
- Rapid-acting antidepressant effects — blocking TREK-1 to improve depressive-like behavior in animal models[4]
- Neurogenesis — stimulating new brain cell growth[4]
- Post-stroke depression — addressing mood disorders that follow brain ischemia[1]
- Neuroprotection after stroke — low-dose TREK-1 activation in the acute phase[1]
- Synaptogenesis — promoting new neuron-to-neuron connections[4]
How PE-22-28 Is Dosed in Research
Dosing in animal studies has varied considerably depending on the research goal. The dosage chart on this page summarizes the three main dose ranges documented in published studies — covering neuroprotection after stroke, post-stroke depression treatment, and sub-chronic antidepressant/neurogenesis protocols.[1][4] Because PE-22-28 is active at very low nanogram-range doses, precise measurement is critical. Use the calculator on this page to help convert research doses accurately. These figures are for reference purposes only and relate strictly to animal research models.
Mixing and Storing PE-22-28
PE-22-28 typically arrives as a lyophilized powder (freeze-dried). To reconstitute it, researchers generally use sterile bacteriostatic water or a saline solution, adding the solvent slowly along the side of the vial and gently swirling — never shaking — to avoid damaging the peptide. Because PE-22-28 is active at extremely low concentrations, serial dilution using a calibrated pipette is recommended to reach the nanogram range needed for research dosing. Once reconstituted, the solution should be stored at 2–8°C (refrigerated) and used within a short window — typically a few days to a week — or divided into single-use aliquots and stored frozen at −20°C to preserve stability. Avoid repeated freeze-thaw cycles, which can degrade peptide integrity. Always work under sterile conditions and label vials clearly with the date of reconstitution.
Sources
- First evidence of protective effects on stroke recovery and post-stroke depression induced by sortilin-derived peptides. — Neuropharmacology, 2019. PMID 31325429.
- Sortilin derived propeptide regulation during adipocyte differentiation and inflammation. — Biochemical and biophysical research communications, 2017. PMID 27816451.
- Fighting against depression with TREK-1 blockers: Past and future. A focus on spadin. — Pharmacology & therapeutics, 2019. PMID 30291907.
- Shortened Spadin Analogs Display Better TREK-1 Inhibition, In Vivo Stability and Antidepressant Activity. — Frontiers in pharmacology, 2017. PMID 28955242.
- Retroinverso analogs of spadin display increased antidepressant effects. — Psychopharmacology, 2015. PMID 25080852.
- The Involvement of Sortilin/NTSR3 in Depression as the Progenitor of Spadin and Its Role in the Membrane Expression of TREK-1. — Frontiers in pharmacology, 2018. PMID 30670975.
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