galanin

Galanin is a neuropeptide that is widely expressed in the central and peripheral nervous systems. In humans and other mammals, the active form is produced from the GAL gene as part of a larger precursor called preprogalanin, which is proteolytically processed to generate galanin and a second peptide known as GMAP (galanin-derived GMAP). The peptide exists in multiple forms depending on species, but the 29–amino-acid form is the most commonly studied in humans.

Galanin signals through three G protein–coupled receptors, GALR1, GALR2, and GALR3. These receptors couple to different intracellular pathways (for example, GALR1 and GALR3 primarily engage Gi/o signaling, while GALR2 can activate Gq/11 pathways), leading to diverse physiological effects. Receptor distribution is broad, with high expression in brain regions such as the hypothalamus, amygdala, hippocampus, and brainstem, as well as in certain peripheral tissues including the gut and pancreas. Galanin-expressing neurons often co-localize with noradrenergic neurons in the locus coeruleus, suggesting roles in arousal, stress, and mood regulation.

Physiologically, galanin is involved in regulating feeding and energy balance, modulating nociception and pain pathways, and influencing mood, anxiety, learning, and memory. It also participates in neuroendocrine regulation and may affect insulin secretion and glucose metabolism. In the nervous system, it can contribute to neuroprotection and synaptic plasticity under certain conditions.

In research and clinical contexts, galanin is studied as a potential target for obesity treatments, analgesics, and mood disorders. Alterations in galanin signaling have been investigated in various neurodegenerative and neuropsychiatric conditions, and pharmacological tools targeting GAL receptors are used primarily in preclinical models to explore therapeutic possibilities.