Galanin is a peptide hormone that controls various biological activities [ PUBMED:1710578 ]. Galanin-like immuno-reactivity has been found in the central and peripheral nervous systems of mammals, with high concentrations demonstrated in discrete regions of the central nervous system, including the median eminence, hypothalamus … expand

Galanin is a peptide hormone that controls various biological activities [ PUBMED:1710578 ]. Galanin-like immuno-reactivity has been found in the central and peripheral nervous systems of mammals, with high concentrations demonstrated in discrete regions of the central nervous system, including the median eminence, hypothalamus, arcuate nucleus, septum, neuro-intermediate lobe of the pituitary, and the spinal cord. Its localisation within neurosecretory granules suggests that galanin may function as a neurotransmitter, and it has been shown to coexist with a variety of other peptide and amine neurotransmitters within individual neurons [ PUBMED:2448788 ].

Although the precise physiological role of galanin is uncertain, it has a number of pharmacological properties: it stimulates food intake, when injected into the third ventricle of rats; it increases levels of plasma growth hormone and prolactin, and decreases dopamine levels in the median eminence [ PUBMED:2448788 ]; and infusion into humans results in hyperglycemia and glucose intolerance, and inhibits pancreatic release of insulin, somatostatin and pancreatic peptide. Galanin also modulates smooth muscle contractility within the gastro-intestinal and genito-urinary tracts, all such activities suggesting that the hormone may play an important role in the nervous modulation of endocrine and smooth muscle function [ PUBMED:2448788 ].

This family represents the 124 amino acid precursor protein to galanin. The precursor includes a signal peptide, galanin (29 amino acids), and a 60-amino acid galanin mRNA-associated peptide. In the precursor, galanin includes a C-terminal glycine and is flanked on each side by dibasic tryptic cleavage sites. The deduced amino acid sequence of rat galanin is 90% similar to porcine galanin, with all three amino acid differences in the C-terminal heptapeptide. The predicted galanin mRNA-associated peptide includes a 35-amino acid sequence that is 78% similar to the previously reported porcine analogue. This sequence is set off by a single basic tryptic cleavage site and includes a 17-amino acid region that is nearly identical to the porcine counterpart. The high interspecies conservation suggests a biological role for this putative peptide.