Emotional stress enhanced ghrelin secretion from the stomach

Ghrelin, a novel growth hormone releasing peptide, has been reported to accelerate food intake and gastrointestinal motility. The relationship between ghrelin secretion and emotional stress remains unknown. The present study was designed to investigate ghrelin dynamics in mice after the application of the emotional stress. To apply emotional stress in the mouse model, the communication box paradigm was used. Just after the communication box protocol, the mice were examined. The plasma and gastric ghrelin levels were measured by enzyme immunoassay and radioimmunoassay. Ghrelin immunohistochemistry and quantitative RT-PCR of preproghrelin mRNA in the stomach were performed. The plasma ghrelin levels were significantly increased in the stress-applied mice. Gastric ghrelin levels and the density of ghrelin-immunoreactive cells in the stress-applied mice tended to be decreased as compared with that in the control mice, but the difference was not statistically significant. There was no significant difference in the preproghrelin mRNA expression levels between the stress-applied mice and the control mice. The present study demonstrated for the first time that the plasma level of ghrelin increased in the association emotional stress.