Ghrelin is produced by the A-like cells of the stomach and mobilized by food deprivation. It was reported recently that acute psychological stress increases ghrelin gene expression in rat oxyntic mucosa. The aim of this study was to examine the effect of such stress on circulating ghrelin levels. To this end, we measured plasma ghrelin in Wistar Kyoto (WKY) rats (a high-anxiety strain) and Sprague-Dawley (SPD) rats (a lowanxiety strain), exposed to water avoidance stress for 60 min. Blood was collected before and after the stress. Acute stress increased the plasma ACTH concentration similar to 5-fold (p < 0.01) in both strains of rats, while plasma ghrelin increased by 85% (p < 0.01) in the SPD rats and by 40% (p < 0.001) in the WKY rats. Ghrelin levels after acute stress were higher (p < 0.05) in the SPD rats than in the WKY rats. Sham stress did not affect plasma ghrelin. We conclude that acute psychological stress mobilizes ghrelin and that the SPD rats respond with a higher plasma ghrelin concentration than the WKY rats. (c) 2006 Elsevier B.V. All rights reserved.