Galanin

What is Galanin?

Galanin is an endogenous neuropeptide first isolated and sequenced in 1983 by Kazuhiko Tatemoto and colleagues at the Karolinska Institute, who purified it from porcine intestine using the same C-terminal-amide detection method that had previously yielded peptide YY and neuropeptide Y. It is 29 amino acids long in most mammalian species (pig, rat, mouse, sheep) and 30 amino acids long in humans, with the N-terminal 1-15 sequence highly conserved across vertebrates and responsible for receptor binding. The name comes from the N-terminal glycine and C-terminal alanine that bracket the molecule. Galanin signals through three G-protein-coupled receptor subtypes — GAL1, GAL2, and GAL3 (encoded by GALR1, GALR2, GALR3) — cloned between 1994 and 1997, each with distinct anatomical distributions and downstream signaling. Galanin and a related peptide, galanin-like peptide (GALP), make up the galanin family, which evolutionary studies have linked to spexin and kisspeptin through ancestral gene duplication. Galanin is widely distributed in the central and peripheral nervous systems, with prominent expression in the hypothalamus, locus coeruleus, basal forebrain, dorsal root ganglia, and enteric neurons, and it is co-released with classical neurotransmitters including norepinephrine, acetylcholine, and serotonin. It is studied for diverse roles in feeding (orexigenic, with a notable preference for fat intake), mood (anxiolytic and antidepressant-like effects in animal models), nociception, seizure modulation (anticonvulsant), and Alzheimer's disease, where galanin-containing fibers hypertrophy and hyperinnervate the surviving basal forebrain cholinergic neurons in late-stage disease. Galanin itself is not an approved therapeutic — clinical interest centers on subtype-selective galanin receptor agonists and antagonists in development for epilepsy, depression, and addiction.

What Galanin Is Investigated For

Galanin is an endogenous-biology and drug-target topic, not a peptide consumers take. Its scientific footprint is broad: feeding (intracerebral galanin in rodents drives intake with a fat-preference signature, established by Kyrkouli, Stanley, and Leibowitz at Rockefeller in 1986), seizure modulation (galanin and selective GAL1/GAL2 agonists are robustly anticonvulsant in animal models, with adeno-associated-virus galanin gene therapy explored as an experimental epilepsy strategy), mood (GAL2 agonism produces antidepressant-like behavioral effects, and GAL3 antagonism produces anxiolytic and antidepressant signals), and Alzheimer's disease (galanin-containing fibers hypertrophy and hyperinnervate surviving basal forebrain cholinergic neurons in late-stage AD, with no measurable change through mild cognitive impairment or early AD — a finding extensively characterized by Mufson, Counts, and colleagues, with ongoing debate over whether the upregulation is neuroprotective, maladaptive, or epiphenomenal). The translational story has been slow: despite three cloned receptor subtypes, well-defined anatomy, and strong preclinical efficacy in seizure and mood paradigms, no galanin-receptor-targeted drug has reached approval. Two 2026 developments have partially reshaped the picture. Paslawski and colleagues (Neuropsychopharmacology 2026), working out of Svenningsson's and Hökfelt's group at the Karolinska Institute where galanin was first isolated in 1983, reported that psilocybin therapy in a randomized MDD trial selectively lowered CSF galanin and noradrenaline — which the authors interpret as a key pharmacodynamic signature of the drug. It is the strongest human data point the field has produced — and it is still a short secondary biomarker analysis that does not show the size of the galanin change tracking the size of the symptom improvement. In parallel, Yue and colleagues (Front Psychiatry 2026) identified a GalR2–mitochondrial (PINK1/Parkin) axis in the ventral hippocampus that mediates depression-like phenotypes after prenatal stress, with intranasal AR-M1896 (a GalR2 agonist) rescuing the phenotype and providing a concrete new mechanism for the antidepressant candidacy of GAL2 agonism. The honest framing is that galanin is one of the most thoroughly mapped neuropeptide systems in modern neuroscience and remains a credible target for future epilepsy and depression therapeutics — and after two decades of slow translation, the CSF biomarker and mechanistic advances of 2026 mark the first time the depression chapter has meaningfully advanced beyond animal-model efficacy.

History & Discovery

Galanin was isolated and sequenced in 1983 by Kazuhiko Tatemoto, Ake Rokaeus, Hans Jornvall, T.J. McDonald, and Viktor Mutt at the Karolinska Institute in Stockholm, working in the same laboratory and with the same chemical detection method that had earlier yielded peptide YY and neuropeptide Y. The team purified a 29-amino-acid peptide from porcine intestine using a C-terminal-amide-targeting strategy and named it 'galanin' for the N-terminal glycine and C-terminal alanine residues that bracket the molecule. The 1983 FEBS Letters paper founded the galanin field. The human form, identified later, is one residue longer at 30 amino acids — a small structural difference with no obvious functional consequence. The receptor pharmacology unfolded over the following decade and a half. Habert-Ortoli, Amiranoff, Laburthe, and Mayaux cloned the first human galanin receptor (GAL1/GALR1) in 1994 (PNAS), demonstrating Gi/o coupling and inhibition of adenylate cyclase. GAL2/GALR2 followed soon after from multiple laboratories, with Gq/11 coupling and a distinct hippocampal-enriched distribution. GAL3/GALR3 was cloned by Wang and colleagues in 1997 (Journal of Biological Chemistry), with restricted distribution and Gi/o coupling similar to GAL1. The three-subtype framework, completed by 1997, became the foundation for subtype-selective medicinal chemistry. The functional story developed in parallel. Hypothalamic feeding effects were established by Sahar Kyrkouli, B. Glenn Stanley, and Sarah Leibowitz at Rockefeller University in the mid-1980s, with the 1986 European Journal of Pharmacology paper showing that medial-hypothalamic galanin injection drives food intake. Subsequent work characterized the selective fat-preference signature. The anticonvulsant story emerged from Andrey Mazarati, Claude Wasterlain, and colleagues, with the 1998 Journal of Neuroscience paper establishing galanin's seizure-modulating role and the reciprocal regulation of hippocampal galanin by seizure activity. The Alzheimer's disease connection was developed by Elliott Mufson, Scott Counts, and collaborators at Rush University Medical Center, with two decades of postmortem and transgenic-mouse work characterizing galanin fiber hypertrophy over surviving basal forebrain cholinergic neurons in late-stage AD — the definitive 2001 CNS Drug Reviews paper laid out the case for galanin as a candidate AD therapeutic target. The galanin family was further extended by the discovery of galanin-like peptide (GALP) in 1999 and by evolutionary work placing galanin, GALP, spexin, and kisspeptin in a common ancestral lineage — the 2014 Kim and colleagues Endocrinology paper showed that spexin activates GAL2 and GAL3, formally placing it in the galanin family. The clinical translation of galanin pharmacology has been slow. Adeno-associated-virus galanin gene therapy for epilepsy has been explored in preclinical and limited translational settings (Riban, During, and colleagues). Subtype-selective small-molecule agonists and antagonists at GAL1, GAL2, and GAL3 have been developed and tested in mood, seizure, and addiction models, with GAL3 antagonists drawing particular interest for alcohol use disorder — although the knockout-mouse phenotype reported by the Kofler and Djouma laboratories, in which GAL3-null mice drink more alcohol rather than less, sits awkwardly against the antagonist pharmacology and remains unexplained. As of 2026, no galanin-receptor-targeted drug has reached approval for any indication.

How It Works

Galanin is a small protein that nerve cells release as a chemical messenger. It does not have one job — it has many. Released in the hypothalamus, it makes you eat more, especially fat. Released in the hippocampus, it dampens seizure activity. Released in the amygdala, it lowers anxiety in animal studies. Released in the basal forebrain, it gets dramatically increased in Alzheimer's disease, though scientists still debate whether that helps or hurts. Galanin works by docking onto three different receptors on nearby cells (GAL1, GAL2, GAL3), each of which sends a different downstream signal — which is why the same peptide can have so many different effects depending on where in the brain it is acting.

Galanin is a 29- or 30-amino-acid peptide (29 in most mammals, 30 in humans) produced by processing of the GAL gene preprogalanin precursor. The N-terminal 1-15 sequence is highly conserved across vertebrates and contains the receptor-binding pharmacophore. Galanin signals through three G-protein-coupled receptors of the rhodopsin family: GAL1 (GALR1), GAL2 (GALR2), and GAL3 (GALR3), cloned between 1994 (Habert-Ortoli human GAL1 in PNAS) and 1997 (Wang et al. GAL3 in JBC). Receptor coupling differs by subtype. GAL1 signals predominantly through Gi/o, inhibiting adenylate cyclase and lowering cAMP, with downstream activation of inwardly rectifying potassium channels and inhibition of voltage-gated calcium channels — a hyperpolarizing, inhibitory signaling profile that underlies many of galanin's modulatory effects on neuronal firing. GAL2 couples to Gq/11, activating phospholipase C and mobilizing intracellular calcium, with additional Gi/o coupling depending on cellular context — this dual-coupling profile is associated with GAL2's distinctive antidepressant-like and anticonvulsant effects. GAL3 couples to Gi/o similarly to GAL1, but with a more restricted anatomical distribution that has positioned it as a target for addiction and mood pharmacology. Anatomical distribution is broad and partially subtype-specific. GAL1 is densely expressed in the hypothalamus, amygdala, hippocampus, locus coeruleus, dorsal root ganglia, and spinal cord. GAL2 is enriched in hippocampus, hypothalamus, and dorsal root ganglia. GAL3 has the most restricted distribution: the 1997 cloning paper detected it only in heart, spleen, and testis, with no GAL3 signal detectable in brain on Northern blot, and later more sensitive in-situ work found only low-abundance message in hypothalamic and periventricular regions. Its scarcity in brain tissue is part of why GAL3 pharmacology has been harder to pin down than GAL1 or GAL2. Galanin itself is co-expressed with classical neurotransmitters in many systems — with norepinephrine in the locus coeruleus, with serotonin in the dorsal raphe, with acetylcholine in basal forebrain cholinergic neurons, and with NPY in arcuate-nucleus feeding-related circuits — and is co-released during high-frequency activity, providing peptidergic modulation that complements fast classical transmission. Functionally, hypothalamic galanin acting at GAL1/GAL2 receptors stimulates feeding with a fat-preference bias (Kyrkouli, Stanley, Leibowitz). Hippocampal galanin acts presynaptically through GAL1 to inhibit glutamate release, providing the cellular substrate for galanin's anticonvulsant action — selectively engaged by GAL1 and GAL2 agonists in animal models of status epilepticus and limbic seizure (Mazarati and colleagues). Galanin-containing fibers in the basal forebrain hypertrophy and hyperinnervate the surviving cholinergic neurons of the nucleus basalis in late-stage Alzheimer's disease — not in the prodromal or early-AD window — where they may act as a compensatory neuroprotective signal, a contributor to cholinergic hypofunction, or a marker of cellular stress (Mufson, Counts). GAL2 agonism produces antidepressant-like behavioral effects, while GAL3 antagonism produces both anxiolytic and antidepressant effects in rodent models, with GAL3 antagonists reducing alcohol self-administration in rodents — though GAL3 knockout mice paradoxically show an increased ethanol preference, a direction-of-effect conflict the field has not resolved.

Evidence Snapshot

Research Gaps & Open Questions

What the current literature has not yet settled about Galanin:

• 01Why pharmacological GAL3 antagonism and genetic GAL3 deletion produce opposite drinking phenotypes — antagonists reduce alcohol self-administration in rodents while GAL3-knockout mice show an increased ethanol preference and increased operant responding for ethanol, with no difference in ethanol metabolism, saccharin preference, sucrose preference or high-fat-diet preference to explain it. Until that contradiction is resolved, the GAL3-for-addiction rationale rests on an unexplained inconsistency.
• 02Whether galanin's role in tumour immunosuppression makes GALR3 antagonism an oncology strategy rather than a neuropsychiatric one. Glioblastoma cells secrete galanin that acts on GALR3 on monocytic myeloid-derived suppressor cells to drive infiltration and ferroptosis resistance, and blocking that axis alongside anti-PD1 produced durable complete regressions in about 60% of treated mice — a far stronger preclinical signal than the CNS indications the field has pursued for thirty years.
• 03Whether the elevated circulating galanin reported in type 2 diabetes is causal, compensatory, or an artefact of a thin evidence base — the 2026 meta-analysis found a large effect (SMD 1.35, 95% CI 1.02–1.68) but rests on only four studies and 343 participants, and the authors themselves rate the certainty of evidence as very low.
• 04Whether peripherally restricted GALR2 agonists can deliver analgesia without central exposure. The stabilized spexin analogue LIT-01-144 showed no evidence of central nervous system penetration yet attenuated pain behaviour in persistent inflammatory pain through GALR2 and independently of opioid receptors — which, if it holds, would sidestep the blood-brain-barrier problem that has blocked galanin drug development rather than trying to solve it.
• 05Whether basal-forebrain galanin fiber hyperinnervation in late-stage Alzheimer's disease is neuroprotective, contributory to cholinergic dysfunction, or epiphenomenal — this directional question has been unresolved for two decades and determines whether AD therapeutics should target galanin agonism or antagonism.
• 06Whether subtype-selective galanin receptor ligands (GAL1, GAL2, or GAL3) can achieve adequate central nervous system exposure with small molecules to deliver the preclinical efficacy seen with peptide agonists in animal seizure, depression, and addiction models.
• 07The clinical viability of adeno-associated-virus galanin gene therapy for focal epilepsy — preclinical efficacy is robust, but translational evidence in humans remains very limited.
• 08Whether GAL3 antagonism is a viable strategy for alcohol use disorder in humans — knockout-mouse data and selective-antagonist preclinical results are encouraging, but no clinical trial has yet validated the approach.
• 09The role of galanin in human feeding behavior versus the rodent fat-preference paradigm — whether galanin meaningfully drives macronutrient selection in humans, and whether human galanin polymorphisms influence dietary patterns or obesity risk.
• 10The functional significance of the human-specific 30-residue galanin sequence (versus the 29-residue rodent form) — whether the additional residue alters receptor selectivity, signaling efficacy, or proteolytic stability in ways that complicate translation from animal models.
• 11Whether spexin, the recently characterized GAL2/GAL3-active galanin family member, plays a parallel or distinct role in human feeding and energy balance, and whether spexin pharmacology represents a more tractable therapeutic angle than galanin itself.

Forms & Administration

Galanin is not formulated or approved as a therapeutic in any jurisdiction. Research applications use synthetic galanin (1-29 in animals, 1-30 in human studies) for in vitro receptor binding and signaling assays, ex vivo tissue pharmacology, intracerebroventricular or intrathecal administration in animal models, and a small number of human investigative infusion studies under research protocols. Subtype-selective galanin receptor agonists and antagonists exist as research tools, none of which has entered a registered clinical trial for epilepsy, depression, or addiction — a search of ClinicalTrials.gov returns no interventional study of galanin or any galanin-receptor ligand in any indication. Compounded galanin from peptide marketplaces has no validated clinical use.

Common Questions

Who Galanin Is NOT For

Drug & Supplement Interactions

There is no validated human drug-interaction profile for galanin because no galanin product has been clinically developed. Theoretical interactions follow from galanin's known signaling: at GAL1/GAL2 receptors, galanin agonism modulates seizure threshold and could in principle interact with antiseizure medications (carbamazepine, valproate, lamotrigine, levetiracetam) by altering hippocampal excitability. At GAL2 and GAL3 receptors, galanin modulates depression- and anxiety-relevant circuits with potential interaction with selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants, and benzodiazepines. Locus coeruleus galanin co-released with norepinephrine could theoretically modulate effects of noradrenergic agents (alpha-2 agonists, beta-blockers, atomoxetine), and basal-forebrain galanin co-released with acetylcholine could in principle interact with cholinesterase inhibitors used in Alzheimer's disease (donepezil, rivastigmine, galantamine) — particularly relevant given galanin's documented overexpression in AD cholinergic neurons. None of these interactions has been characterized in controlled human studies; they are mechanistic possibilities that argue against casual exogenous galanin exposure rather than documented clinical events.

Safety Profile

Legal Status

Regulatory status changes over time. Verify current local rules with a qualified professional.

Myths & Misconceptions