Ghrelin is an endogenous gastrointestinal hormone and neuropeptide that binds to the growth hormone (GH) secretagogue receptor (GHS-R). It increases intracellular calcium in CHO cells expressing rat GHS-R (EC50 = 2.5 nM) and induces GH release from primary rat pituitary cells (EC50 = 2.1 nM). Ghrelin (10 nM) also reduces glucose-, arginine-, and carbachol-induced insulin release and arginine-induced somatostatin release from perfused rat pancreas. It increases GH plasma levels in anesthetized rats, but does not affect follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin, thyroid-stimulating hormone (TSH), or adrenocorticotropic hormone (ACTH) levels when administered at a dose of 10 μg per animal. Ghrelin increases gastric motility in rats in a dose-dependent manner when administered intracranially into the lateral septum and increases food intake and body weight when administered intracerebroventricularly at a dose of 1 μg per animal.