The orexigenic hormone ghrelin defends against depressive symptoms of chronic stress

Abstract
The peptide hormone ghrelin has previously been linked to the regulation of metabolism. This study in mice finds that increasing levels of ghrelin, either through subcutaneous injections or calorie restriction, has an anxiolytic and antidepressive effect. This reveals a previously unknown function for ghrelin. We found that increasing ghrelin levels, through subcutaneous injections or calorie restriction, produced anxiolytic- and antidepressant-like responses in the elevated plus maze and forced swim test. Moreover, chronic social defeat stress, a rodent model of depression, persistently increased ghrelin levels, whereas growth hormone secretagogue receptor (Ghsr) null mice showed increased deleterious effects of chronic defeat. Together, these findings demonstrate a previously unknown function for ghrelin in defending against depressive-like symptoms of chronic stress.