Obestatin improves memory performance and causes anxiolytic effects in rats

Obestatin is a peptide hormone that is derived from the same polypeptide precursor (preprogrelin) as ghrelin, but it acts in opposing way on ingestive behavior. Our previous studies showed that ghrelin affects memory and anxiety. Here, we studied the possible effects of icv obestatin injection in rats upon memory retention (using two different paradigms), anxiety like behavior (plus maze test), and food intake. Obestatin induces an increase in the percentage of open arms entries (Obestatin 3.0 nmol/rat: 61.74 +/- 1.81), and percentage of time spent in open arms (Obestatin 3.0 nmol/rat: 72.07 +/- 4.21) in relation to the control (33.31 +/- 1.54; 25.82 +/- 1.68), indicating an anxiolytic effect. The two doses of obestatin increased latency time in a step down test and the percentage time of novel object exploration, suggesting that the peptide influences learning and memory processes that involve the hippocampus and the amygdala. This report provides evidence indicating that obestatin effects are functionally opposite on anxiety and hunger to the ghrelin effects, while both these related peptides increase memory retention. (c) 2006 Elsevier Inc. All rights reserved.