Galanin

Endogenous Hormone

Galanin is a neuropeptide found throughout the central and peripheral nervous systems and the gastrointestinal tract. In humans it is a 30-amino-acid peptide (29 amino acids in some other species), and it is notable for being one of the more broadly distributed neuropeptides in the brain, where it acts largely as a modulator — fine-tuning the activity of other neurotransmitter systems rather than acting as a simple on/off signal. First identified in the 1980s, galanin has since been implicated in a strikingly wide range of physiological processes, which has made it a persistent subject of neuroscience and metabolic research. Among galanin's best-studied roles is its involvement in feeding behavior. When injected into feeding-related regions of the hypothalamus in animal studies, galanin stimulates food intake and appears to have a particular association with the consumption of dietary fat, positioning it within the network of brain peptides that regulate appetite and macronutrient preference. Beyond feeding, galanin has been linked to the modulation of pain signaling (nociception), regulation of mood and responses to stress with possible relevance to depression and anxiety, control of neuronal excitability with anticonvulsant (anti-seizure) effects, and neuroprotection and nerve regeneration following injury. This breadth reflects galanin's role as a modulator that shapes how neural circuits respond under different conditions. Galanin exerts its effects through three G protein-coupled receptors — GAL1, GAL2, and GAL3 (also written GalR1, GalR2, GalR3) — which are distributed differently across tissues and couple to different intracellular signaling pathways. This receptor diversity is thought to underlie galanin's ability to produce distinct, sometimes opposing, effects in different circuits, and it is a major reason the system is attractive for drug discovery: subtype-selective agonists or antagonists could, in principle, target one function (for example, seizure control or pain) without engaging the others. Considerable preclinical effort has gone into exploring these possibilities. Galanin is an endogenous peptide produced by the body; it is not sold or administered as a drug, and there is currently no marketed medicine that is galanin or a galanin-receptor-targeting therapeutic. It should be understood as a research target rather than a treatment, and claims that galanin can be supplemented to control appetite, mood, or seizures are not supported by approved clinical evidence. For readers interested in appetite and neuropeptide biology, galanin is best studied alongside other feeding-related neuropeptides such as neuropeptide Y, with which it participates in the hypothalamic circuitry that governs hunger and energy balance.