Galanin

Where it comes from

Made in

Hypothalamus, locus coeruleus, dorsal root ganglia, pituitary, gut and pancreas

Sent out by

Fat intake, stress and nerve injury raise it

Acts on

• Hypothalamus (feeding, especially fat)
• Locus coeruleus (mood)
• Hippocampus (memory)
• Spinal cord (pain)
• Islets (insulin)

What it does

• Drives alcohol intake in rodents; its pull towards fat specifically failed to replicate in one laboratory ²
• Holds down seizures in the hippocampus; it cuts acetylcholine release in the ventral hippocampus, though what that does to memory is disputed ²
• Rises hugely in injured sensory neurons; in Alzheimer’s disease galanin fibres hyperinnervate the surviving cholinergic neurons, which now reads as protective ²

In medicine

• No medicine copies it or blocks it. Galanin is a research marker in nerve injury and a drug target in epilepsy and depression ²
• Its three receptors are the practical obstacle: GALR1, GALR2 and GALR3 do different things in the same brain, and no ligand selective enough to separate them has reached people ²

Beyond the body’s own use

• Stabilised galanin analogues reduced seizure severity in animal models of epilepsy, though not in every model; the best studied of them worked after injection into the bloodstream, which plain galanin does not, and none has reached people ³
• Variants of the galanin gene and of its GALR3 receptor were linked with alcohol dependence in two populations by one laboratory, and have not been replicated independently ²
• Nothing containing galanin is approved or obtainable outside the laboratory. What is being asked of it is whether a brake on seizures the brain already uses can be imitated by a molecule small enough to get in ³