Central Injection Of Ghrelin Rats Feeding And Drinking

Objective:To investigate the effects of intracerebroventricular injections ghrelin on feeding dynamism; To explore the effects of ghrelin on both food and water intake during thirst condition.Method:Five injections of rat ghrelin or PBS were administered once per day (0.4μg), into lateral cerebral ventricle (ICV) of free feeding adult male rats. Body weight was obtained daily, while ending retroperitoneal (RP) and epididymal (EPI) white adipose tissue (WAT) contents as well as blood levels of leptin and insulin were measured. The rats were exposed to one of five dipsetic stimuli:(1)36-hr water deprivation,(2) replacement of drinking water with3.0%NaCl,(3) peripheral administration of hypertonic saline,(4) ICV injection of angiotensin Ⅱ (AngⅡ), or (5) the peripheral hypertonic saline+central AngⅡ. Rats then were given ICV injection of ghrelin (0.4μg), and subsequent food and water intakes were measured.Results:Results showed that in the first and the second30-min intervals number of approaches to food container were significantly increased already after the2nd ICV ghrelin application (p<0.05), by47.2%and63.8%respectively, in comparison with control rats. Centrally applied ghrelin increased body weight after the2nd injection till the end of treatment (p<0.05), which was followed by increased food and water intake (p<0.05). At the end of treatment, RP and EPI WAT contents were increased (p<0.01and p<0.05). Serum insulin levels were elevated (p<0.05) while serum leptin levels were decreased (p<0.05). Deprivation of36h water notably can increase food intake(p<0.05); drinking with hypertonic saline for36h followed by icv injection of ghrelin can significantly increase food intake (p<0.01); peripheral administration of saline with icv injection of ghrelin can increase food intake (p<0.01);Ghrelin also affected water intake(p<0.01);Icv injection of AngⅡ had no effect on food intake(P>0.05),but water intake increased obviously(p<0.01);Specifically, ghrelin attenuated water intake stimulated by acute injection of AngⅡ (P<0.01); peripheral administration of hypertonic saline and central administration of AngⅡ, ghrelin can significantly increase food intake(p<0.05).Conclusion:Repetitive subnanomolar doses of central ghrelin administration play essential role in food initiation and feeding dynamics in freely feeding adult male rats; the actions of ghrelin are not limited to food intake, but can also include alterations in water intake.