BACKGROUND: Ghrelin, an orexigenic peptide, is secreted from endocrine cells in 
the gastric mucosa. Circulating levels rise in the preprandial phase, suggesting 
an anticipatory or cephalic phase of release, and decline in the postprandial 
phase, suggesting either the loss of a stimulatory factor or inhibition by 
factors released when nutrients enter the intestine. We hypothesized that vagal 
signals are not required for the (i) preprandial increase or (ii) postprandial 
suppression of ghrelin levels. Further, we wanted to investigate the hypothesis 
that (iii) glucagon-like peptide-1 might be implicated in the postprandial 
decline in ghrelin levels.
METHODS: We measured ghrelin levels in plasma from sham-feeding and meal studies 
carried out in vagotomized individuals and controls, and from a GLP-1 infusion 
study carried out in fasting healthy young individuals.
KEY RESULTS: We find that (i) ghrelin secretion is unchanged during indirect 
vagal stimulation as elicited by modified sham-feeding in vagotomized 
individuals and matched controls, (ii) ghrelin secretion is similarly suppressed 
after meal ingestion in vagotomized individuals and controls, and (iii) infusion 
of GLP-1 does not lower ghrelin levels.
CONCLUSIONS & INFERENCES: We conclude that for postprandial suppression of 
circulating ghrelin levels, a circulating factor (but not GLP-1) or short 
(duodeno-gastric) reflexes seem to be implicated.