OBJECTIVE: The purpose of this study was to investigate the impact of intracerebroventricular (ICV) injection of the two endogenous forms of acyl ghrelin, O-n-octanoylated ghrelin and des-Gln¹⁴-ghrelin, on feeding behavior, as well as their interactions with insulin, obestatin, and corticotropin-releasing factor receptor (CRF-R) antagonist in the forebrain to influence food intake. METHODS: We examined the food intake in conscious, freely fed rats, which were chronically implanted with ICV catheters. RESULTS: O-n-octanoylated ghrelin and des-Gln¹⁴-ghrelin (0.1 nmol/rat) were equally potent in stimulating food intake in freely fed rats, up to 8 h after ICV injection (P < 0.05). In contrast, ICV administration of insulin (8 mU/rat), obestatin (2 nmol/rat), and astressin (2 nmol/rat), a specific CRF-R antagonist, did not modify feeding in freely fed rats. Furthermore, pretreatment with ICV insulin (P < 0.01), but not obestatin or astressin, at the abovementioned dose, blocked central acyl-ghrelin-induced hyperphagic effects. CONCLUSION: ICV O-n-octanoylated ghrelin and its splice variant, des-Gln¹⁴-ghrelin, are equally potent to elicit food intake in freely fed rats, while these feeding-stimulating effects are opposed by insulin, but independent of obestatin and endogenous CRF-R in the forebrain.
OBJECTIVE: The purpose of this study was to investigate the impact of intracerebroventricular (ICV) injection of the two endogenous forms of acyl ghrelin, O-n-octanoylated ghrelin and des-Gln¹⁴-ghrelin, on feeding behavior, as well as their interactions with insulin, obestatin, and corticotropin-releasing factor receptor (CRF-R) antagonist in the forebrain to influence food intake. METHODS: We examined the food intake in conscious, freely fed rats, which were chronically implanted with ICV catheters. RESULTS: O-n-octanoylated ghrelin and des-Gln¹⁴-ghrelin (0.1 nmol/rat) were equally potent in stimulating food intake in freely fed rats, up to 8 h after ICV injection (P < 0.05). In contrast, ICV administration of insulin (8 mU/rat), obestatin (2 nmol/rat), and astressin (2 nmol/rat), a specific CRF-R antagonist, did not modify feeding in freely fed rats. Furthermore, pretreatment with ICV insulin (P < 0.01), but not obestatin or astressin, at the abovementioned dose, blocked central acyl-ghrelin-induced hyperphagic effects. CONCLUSION:ICV O-n-octanoylated ghrelin and its splice variant, des-Gln¹⁴-ghrelin, are equally potent to elicit food intake in freely fed rats, while these feeding-stimulating effects are opposed by insulin, but independent of obestatin and endogenous CRF-R in the forebrain.