Alarin is a 25
amino acid peptide that belongs to the
galanin peptide family. It is derived from the
galanin-like peptide gene by a splice variant, which excludes exon 3.
Alarin was first identified in gangliocytes of neuroblastic
tumors and later shown to have a vasoactive function in the skin. Recently,
alarin was demonstrated to stimulate food intake as well as the hypothalamic-pituitary-gonadal axis in rodents, suggesting that it might be a neuromodulatory
peptide in the brain. However, the individual neurons in the central nervous system that express
alarin have not been identified. Here, we determined the distribution of
alarin-like immunoreactivity (
alarin-LI) in the adult murine brain. The specificity of the antibody against
alarin was demonstrated by the absence of labeling after pre-absorption of the antiserum with synthetic
alarin peptide and in transgenic mouse brains lacking neurons expressing the GALP gene.
Alarin-LI was observed in different areas of the murine brain. A high intensity of
alarin-LI was detected in the accessory olfactory bulb, the medial preoptic area, the amygdala, different nuclei of the hypothalamus such as the arcuate nucleus and the ventromedial hypothalamic nucleus, the trigeminal complex, the locus coeruleus, the ventral chochlear nucleus, the facial nucleus, and the epithelial layer of the plexus choroideus. The distinct expression pattern of
alarin in the adult mouse brain suggests potential functions in reproduction and metabolism.