Central injection of des-acyl chicken ghrelin does not affect food intake in chicks

In rodents and goldfish, ghrelin is well known as an orexigenic peptide, and des-acyl ghrelin, which is a ghrelin gene-derived peptide lacking Ser-3 acylation, affects feeding behavior when injected with or without ghrelin. Intracerebroventricular (ICV) injection of ghrelin inhibits food intake in chicks (Gallus gallus), but has the opposite effect in rodents and goldfish. The aim of the present study was to investigate the effect of chicken des-acyl ghrelin on feeding in chicks. ICV injection of des-acyl ghrelin alone at doses from 4 to 1000 pmol did not affect food intake in fed and 12-h fasted chicks. Co-injection of des-acyl ghrelin with ghrelin tended to attenuate ghrelin-induced anorexia. In an in vitro study, only the highest concentration (10−6 M) of des-acyl ghrelin increased intracellular calcium ion concentration in chicken GHS-R1a-expressing cells. Des-acyl ghrelin (10−6 M) slightly but significantly decreased intracellular calcium ion influx induced by 1 or 3 nM ghrelin. The present results demonstrate that des-acyl ghrelin is not positively involved in the central regulation of feeding in chicks. The feeding regulatory network between ghrelin and des-acyl ghrelin in chicks would be different from those in rodents and goldfish.

Research highlights
► Central administration of ghrelin inhibits feeding behavior in chicks.
► Central administration of des-acyl ghrelin does not affect feeding behavior.
► Des-acyl ghrelin tends to attenuate the effect of ghrelin.
► Ghrelin-related feeding regulation in chicks is unique comparing with mammals and fish.