Stimulation of food intake in rats by centrally administered hypothalamic growth hormone-releasing factor

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Abstract
Hypothalamic growth hormone-releasing factors (GRFs) have been purified recently from human pancreatic (hp) tumours1,2 and from rat hypothalamus (rh)3. GRF peptides have strong homology with peptides of the glucagon, vasoactive intestinal polypeptide and PHI-27 family. Aside from their potent actions on release of somatotropin, no other biological actions of GRFs have been reported. GRF has been localized in neurones bordering the ventromedial hypothalamic nucleus (refs 4, 5; L. Swanson and P. Sawchenko, manuscript in preparation), a region associated frequently with experimental analysis of feeding behaviour6. We now report that intracerebroventricularly (i.c.v.)-administered rhGRF and hpGRF(1–40) in doses of 0.2, 2.0 and 20.0 pmol, produced an increase in food intake in hungry rats. This effect seemed to be specific to GRF as i.c.v. injections of a structurally related but physiologically inactive peptide7 in the same doses had no effect on feeding. In addition, peripheral injections of rhGRF or growth hormone had no effect on food intake, suggesting that the present effects may be mediated centrally. Injections (i.c.v.) of rhGRF (0.2, 2.0 and 20.0 pmol) had no effect on general activity, suggesting that GRF does not produce nonspecific arousal.