Ghrelin is a natural ligand for the growth hormone (GH) secretagogue
(GHS) receptor (GHS-R) 1a in vertebrates. This
hormone was first identified as a stimulator of GH release from
the pituitary, and further studies revealed that ghrelin is a regulator
of feeding behavior: central or peripheral injection of ghrelin
stimulates food intake in rats. Ghrelin-stimulated feeding
has also been demonstrated in goldfish